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License cleanup: add SPDX GPL-2.0 license identifier to files with no license Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-01 08:07:57 -06:00
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
*/
#include <linux/sched/debug.h>
#include <linux/kallsyms.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>
#include <linux/kdebug.h>
#include <linux/export.h>
#include <linux/ptrace.h>
#include <linux/kexec.h>
#include <linux/sysfs.h>
#include <linux/bug.h>
#include <linux/nmi.h>
#include <asm/cpu_entry_area.h>
#include <asm/stacktrace.h>
x86/exceptions: Split debug IST stack The debug IST stack is actually two separate debug stacks to handle #DB recursion. This is required because the CPU starts always at top of stack on exception entry, which means on #DB recursion the second #DB would overwrite the stack of the first. The low level entry code therefore adjusts the top of stack on entry so a secondary #DB starts from a different stack page. But the stack pages are adjacent without a guard page between them. Split the debug stack into 3 stacks which are separated by guard pages. The 3rd stack is never mapped into the cpu_entry_area and is only there to catch triple #DB nesting: --- top of DB_stack <- Initial stack --- end of DB_stack guard page --- top of DB1_stack <- Top of stack after entering first #DB --- end of DB1_stack guard page --- top of DB2_stack <- Top of stack after entering second #DB --- end of DB2_stack guard page If DB2 would not act as the final guard hole, a second #DB would point the top of #DB stack to the stack below #DB1 which would be valid and not catch the not so desired triple nesting. The backing store does not allocate any memory for DB2 and its guard page as it is not going to be mapped into the cpu_entry_area. - Adjust the low level entry code so it adjusts top of #DB with the offset between the stacks instead of exception stack size. - Make the dumpstack code aware of the new stacks. - Adjust the in_debug_stack() implementation and move it into the NMI code where it belongs. As this is NMI hotpath code, it just checks the full area between top of DB_stack and bottom of DB1_stack without checking for the guard page. That's correct because the NMI cannot hit a stackpointer pointing to the guard page between DB and DB1 stack. Even if it would, then the NMI operation still is unaffected, but the resume of the debug exception on the topmost DB stack will crash by touching the guard page. [ bp: Make exception_stack_names static const char * const ] Suggested-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Baoquan He <bhe@redhat.com> Cc: "Chang S. Bae" <chang.seok.bae@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Joerg Roedel <jroedel@suse.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: linux-doc@vger.kernel.org Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Qian Cai <cai@lca.pw> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.439944544@linutronix.de
2019-04-14 09:59:57 -06:00
static const char * const exception_stack_names[] = {
[ ESTACK_DF ] = "#DF",
[ ESTACK_NMI ] = "NMI",
x86/exceptions: Split debug IST stack The debug IST stack is actually two separate debug stacks to handle #DB recursion. This is required because the CPU starts always at top of stack on exception entry, which means on #DB recursion the second #DB would overwrite the stack of the first. The low level entry code therefore adjusts the top of stack on entry so a secondary #DB starts from a different stack page. But the stack pages are adjacent without a guard page between them. Split the debug stack into 3 stacks which are separated by guard pages. The 3rd stack is never mapped into the cpu_entry_area and is only there to catch triple #DB nesting: --- top of DB_stack <- Initial stack --- end of DB_stack guard page --- top of DB1_stack <- Top of stack after entering first #DB --- end of DB1_stack guard page --- top of DB2_stack <- Top of stack after entering second #DB --- end of DB2_stack guard page If DB2 would not act as the final guard hole, a second #DB would point the top of #DB stack to the stack below #DB1 which would be valid and not catch the not so desired triple nesting. The backing store does not allocate any memory for DB2 and its guard page as it is not going to be mapped into the cpu_entry_area. - Adjust the low level entry code so it adjusts top of #DB with the offset between the stacks instead of exception stack size. - Make the dumpstack code aware of the new stacks. - Adjust the in_debug_stack() implementation and move it into the NMI code where it belongs. As this is NMI hotpath code, it just checks the full area between top of DB_stack and bottom of DB1_stack without checking for the guard page. That's correct because the NMI cannot hit a stackpointer pointing to the guard page between DB and DB1 stack. Even if it would, then the NMI operation still is unaffected, but the resume of the debug exception on the topmost DB stack will crash by touching the guard page. [ bp: Make exception_stack_names static const char * const ] Suggested-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Baoquan He <bhe@redhat.com> Cc: "Chang S. Bae" <chang.seok.bae@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Joerg Roedel <jroedel@suse.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: linux-doc@vger.kernel.org Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Qian Cai <cai@lca.pw> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.439944544@linutronix.de
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[ ESTACK_DB2 ] = "#DB2",
[ ESTACK_DB1 ] = "#DB1",
[ ESTACK_DB ] = "#DB",
[ ESTACK_MCE ] = "#MC",
};
const char *stack_type_name(enum stack_type type)
{
x86/exceptions: Split debug IST stack The debug IST stack is actually two separate debug stacks to handle #DB recursion. This is required because the CPU starts always at top of stack on exception entry, which means on #DB recursion the second #DB would overwrite the stack of the first. The low level entry code therefore adjusts the top of stack on entry so a secondary #DB starts from a different stack page. But the stack pages are adjacent without a guard page between them. Split the debug stack into 3 stacks which are separated by guard pages. The 3rd stack is never mapped into the cpu_entry_area and is only there to catch triple #DB nesting: --- top of DB_stack <- Initial stack --- end of DB_stack guard page --- top of DB1_stack <- Top of stack after entering first #DB --- end of DB1_stack guard page --- top of DB2_stack <- Top of stack after entering second #DB --- end of DB2_stack guard page If DB2 would not act as the final guard hole, a second #DB would point the top of #DB stack to the stack below #DB1 which would be valid and not catch the not so desired triple nesting. The backing store does not allocate any memory for DB2 and its guard page as it is not going to be mapped into the cpu_entry_area. - Adjust the low level entry code so it adjusts top of #DB with the offset between the stacks instead of exception stack size. - Make the dumpstack code aware of the new stacks. - Adjust the in_debug_stack() implementation and move it into the NMI code where it belongs. As this is NMI hotpath code, it just checks the full area between top of DB_stack and bottom of DB1_stack without checking for the guard page. That's correct because the NMI cannot hit a stackpointer pointing to the guard page between DB and DB1 stack. Even if it would, then the NMI operation still is unaffected, but the resume of the debug exception on the topmost DB stack will crash by touching the guard page. [ bp: Make exception_stack_names static const char * const ] Suggested-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Baoquan He <bhe@redhat.com> Cc: "Chang S. Bae" <chang.seok.bae@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Joerg Roedel <jroedel@suse.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: linux-doc@vger.kernel.org Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Qian Cai <cai@lca.pw> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.439944544@linutronix.de
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BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
if (type == STACK_TYPE_IRQ)
return "IRQ";
if (type == STACK_TYPE_ENTRY) {
/*
* On 64-bit, we have a generic entry stack that we
* use for all the kernel entry points, including
* SYSENTER.
*/
return "ENTRY_TRAMPOLINE";
}
x86/dumpstack: Add get_stack_info() support for the SYSENTER stack get_stack_info() doesn't currently know about the SYSENTER stack, so unwinding will fail if we entered the kernel on the SYSENTER stack and haven't fully switched off. Teach get_stack_info() about the SYSENTER stack. With future patches applied that run part of the entry code on the SYSENTER stack and introduce an intentional BUG(), I would get: PANIC: double fault, error_code: 0x0 ... RIP: 0010:do_error_trap+0x33/0x1c0 ... Call Trace: Code: ... With this patch, I get: PANIC: double fault, error_code: 0x0 ... Call Trace: <SYSENTER> ? async_page_fault+0x36/0x60 ? invalid_op+0x22/0x40 ? async_page_fault+0x36/0x60 ? sync_regs+0x3c/0x40 ? sync_regs+0x2e/0x40 ? error_entry+0x6c/0xd0 ? async_page_fault+0x36/0x60 </SYSENTER> Code: ... which is a lot more informative. Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Borislav Petkov <bp@suse.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bpetkov@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Laight <David.Laight@aculab.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Eduardo Valentin <eduval@amazon.com> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Will Deacon <will.deacon@arm.com> Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Link: https://lkml.kernel.org/r/20171204150605.392711508@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-12-04 07:07:13 -07:00
if (type >= STACK_TYPE_EXCEPTION && type <= STACK_TYPE_EXCEPTION_LAST)
return exception_stack_names[type - STACK_TYPE_EXCEPTION];
return NULL;
}
x86/dumpstack/64: Speedup in_exception_stack() The current implementation of in_exception_stack() iterates over the exception stacks array. Most of the time this is an useless exercise, but even for the actual use cases (perf and ftrace) it takes at least 2 iterations to get to the NMI stack. As the exception stacks and the guard pages are page aligned the loop can be avoided completely. Add a initial check whether the stack pointer is inside the full exception stack area and leave early if not. Create a lookup table which describes the stack area. The table index is the page offset from the beginning of the exception stacks. So for any given stack pointer the page offset is computed and a lookup in the description table is performed. If it is inside a guard page, return. If not, use the descriptor to fill in the info structure. The table is filled at compile time and for the !KASAN case the interesting page descriptors exactly fit into a single cache line. Just the last guard page descriptor is in the next cacheline, but that should not be accessed in the regular case. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.543320386@linutronix.de
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/**
* struct estack_pages - Page descriptor for exception stacks
* @offs: Offset from the start of the exception stack area
* @size: Size of the exception stack
* @type: Type to store in the stack_info struct
*/
struct estack_pages {
u32 offs;
u16 size;
u16 type;
};
x86/dumpstack/64: Speedup in_exception_stack() The current implementation of in_exception_stack() iterates over the exception stacks array. Most of the time this is an useless exercise, but even for the actual use cases (perf and ftrace) it takes at least 2 iterations to get to the NMI stack. As the exception stacks and the guard pages are page aligned the loop can be avoided completely. Add a initial check whether the stack pointer is inside the full exception stack area and leave early if not. Create a lookup table which describes the stack area. The table index is the page offset from the beginning of the exception stacks. So for any given stack pointer the page offset is computed and a lookup in the description table is performed. If it is inside a guard page, return. If not, use the descriptor to fill in the info structure. The table is filled at compile time and for the !KASAN case the interesting page descriptors exactly fit into a single cache line. Just the last guard page descriptor is in the next cacheline, but that should not be accessed in the regular case. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.543320386@linutronix.de
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#define EPAGERANGE(st) \
[PFN_DOWN(CEA_ESTACK_OFFS(st)) ... \
PFN_DOWN(CEA_ESTACK_OFFS(st) + CEA_ESTACK_SIZE(st) - 1)] = { \
.offs = CEA_ESTACK_OFFS(st), \
.size = CEA_ESTACK_SIZE(st), \
.type = STACK_TYPE_EXCEPTION + ESTACK_ ##st, }
x86/dumpstack/64: Speedup in_exception_stack() The current implementation of in_exception_stack() iterates over the exception stacks array. Most of the time this is an useless exercise, but even for the actual use cases (perf and ftrace) it takes at least 2 iterations to get to the NMI stack. As the exception stacks and the guard pages are page aligned the loop can be avoided completely. Add a initial check whether the stack pointer is inside the full exception stack area and leave early if not. Create a lookup table which describes the stack area. The table index is the page offset from the beginning of the exception stacks. So for any given stack pointer the page offset is computed and a lookup in the description table is performed. If it is inside a guard page, return. If not, use the descriptor to fill in the info structure. The table is filled at compile time and for the !KASAN case the interesting page descriptors exactly fit into a single cache line. Just the last guard page descriptor is in the next cacheline, but that should not be accessed in the regular case. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.543320386@linutronix.de
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/*
* Array of exception stack page descriptors. If the stack is larger than
* PAGE_SIZE, all pages covering a particular stack will have the same
* info. The guard pages including the not mapped DB2 stack are zeroed
* out.
*/
static const
struct estack_pages estack_pages[CEA_ESTACK_PAGES] ____cacheline_aligned = {
EPAGERANGE(DF),
EPAGERANGE(NMI),
EPAGERANGE(DB1),
EPAGERANGE(DB),
EPAGERANGE(MCE),
};
static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
{
x86/dumpstack/64: Speedup in_exception_stack() The current implementation of in_exception_stack() iterates over the exception stacks array. Most of the time this is an useless exercise, but even for the actual use cases (perf and ftrace) it takes at least 2 iterations to get to the NMI stack. As the exception stacks and the guard pages are page aligned the loop can be avoided completely. Add a initial check whether the stack pointer is inside the full exception stack area and leave early if not. Create a lookup table which describes the stack area. The table index is the page offset from the beginning of the exception stacks. So for any given stack pointer the page offset is computed and a lookup in the description table is performed. If it is inside a guard page, return. If not, use the descriptor to fill in the info structure. The table is filled at compile time and for the !KASAN case the interesting page descriptors exactly fit into a single cache line. Just the last guard page descriptor is in the next cacheline, but that should not be accessed in the regular case. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.543320386@linutronix.de
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unsigned long begin, end, stk = (unsigned long)stack;
const struct estack_pages *ep;
struct pt_regs *regs;
unsigned int k;
x86/exceptions: Split debug IST stack The debug IST stack is actually two separate debug stacks to handle #DB recursion. This is required because the CPU starts always at top of stack on exception entry, which means on #DB recursion the second #DB would overwrite the stack of the first. The low level entry code therefore adjusts the top of stack on entry so a secondary #DB starts from a different stack page. But the stack pages are adjacent without a guard page between them. Split the debug stack into 3 stacks which are separated by guard pages. The 3rd stack is never mapped into the cpu_entry_area and is only there to catch triple #DB nesting: --- top of DB_stack <- Initial stack --- end of DB_stack guard page --- top of DB1_stack <- Top of stack after entering first #DB --- end of DB1_stack guard page --- top of DB2_stack <- Top of stack after entering second #DB --- end of DB2_stack guard page If DB2 would not act as the final guard hole, a second #DB would point the top of #DB stack to the stack below #DB1 which would be valid and not catch the not so desired triple nesting. The backing store does not allocate any memory for DB2 and its guard page as it is not going to be mapped into the cpu_entry_area. - Adjust the low level entry code so it adjusts top of #DB with the offset between the stacks instead of exception stack size. - Make the dumpstack code aware of the new stacks. - Adjust the in_debug_stack() implementation and move it into the NMI code where it belongs. As this is NMI hotpath code, it just checks the full area between top of DB_stack and bottom of DB1_stack without checking for the guard page. That's correct because the NMI cannot hit a stackpointer pointing to the guard page between DB and DB1 stack. Even if it would, then the NMI operation still is unaffected, but the resume of the debug exception on the topmost DB stack will crash by touching the guard page. [ bp: Make exception_stack_names static const char * const ] Suggested-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Baoquan He <bhe@redhat.com> Cc: "Chang S. Bae" <chang.seok.bae@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Joerg Roedel <jroedel@suse.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: linux-doc@vger.kernel.org Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Qian Cai <cai@lca.pw> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.439944544@linutronix.de
2019-04-14 09:59:57 -06:00
BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
x86/dumpstack/64: Speedup in_exception_stack() The current implementation of in_exception_stack() iterates over the exception stacks array. Most of the time this is an useless exercise, but even for the actual use cases (perf and ftrace) it takes at least 2 iterations to get to the NMI stack. As the exception stacks and the guard pages are page aligned the loop can be avoided completely. Add a initial check whether the stack pointer is inside the full exception stack area and leave early if not. Create a lookup table which describes the stack area. The table index is the page offset from the beginning of the exception stacks. So for any given stack pointer the page offset is computed and a lookup in the description table is performed. If it is inside a guard page, return. If not, use the descriptor to fill in the info structure. The table is filled at compile time and for the !KASAN case the interesting page descriptors exactly fit into a single cache line. Just the last guard page descriptor is in the next cacheline, but that should not be accessed in the regular case. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.543320386@linutronix.de
2019-04-14 09:59:58 -06:00
begin = (unsigned long)__this_cpu_read(cea_exception_stacks);
/*
* Handle the case where stack trace is collected _before_
* cea_exception_stacks had been initialized.
*/
if (!begin)
return false;
x86/dumpstack/64: Speedup in_exception_stack() The current implementation of in_exception_stack() iterates over the exception stacks array. Most of the time this is an useless exercise, but even for the actual use cases (perf and ftrace) it takes at least 2 iterations to get to the NMI stack. As the exception stacks and the guard pages are page aligned the loop can be avoided completely. Add a initial check whether the stack pointer is inside the full exception stack area and leave early if not. Create a lookup table which describes the stack area. The table index is the page offset from the beginning of the exception stacks. So for any given stack pointer the page offset is computed and a lookup in the description table is performed. If it is inside a guard page, return. If not, use the descriptor to fill in the info structure. The table is filled at compile time and for the !KASAN case the interesting page descriptors exactly fit into a single cache line. Just the last guard page descriptor is in the next cacheline, but that should not be accessed in the regular case. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.543320386@linutronix.de
2019-04-14 09:59:58 -06:00
end = begin + sizeof(struct cea_exception_stacks);
/* Bail if @stack is outside the exception stack area. */
if (stk < begin || stk >= end)
return false;
x86/dumpstack/64: Speedup in_exception_stack() The current implementation of in_exception_stack() iterates over the exception stacks array. Most of the time this is an useless exercise, but even for the actual use cases (perf and ftrace) it takes at least 2 iterations to get to the NMI stack. As the exception stacks and the guard pages are page aligned the loop can be avoided completely. Add a initial check whether the stack pointer is inside the full exception stack area and leave early if not. Create a lookup table which describes the stack area. The table index is the page offset from the beginning of the exception stacks. So for any given stack pointer the page offset is computed and a lookup in the description table is performed. If it is inside a guard page, return. If not, use the descriptor to fill in the info structure. The table is filled at compile time and for the !KASAN case the interesting page descriptors exactly fit into a single cache line. Just the last guard page descriptor is in the next cacheline, but that should not be accessed in the regular case. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.543320386@linutronix.de
2019-04-14 09:59:58 -06:00
/* Calc page offset from start of exception stacks */
k = (stk - begin) >> PAGE_SHIFT;
/* Lookup the page descriptor */
ep = &estack_pages[k];
/* Guard page? */
if (!ep->size)
return false;
x86/dumpstack/64: Speedup in_exception_stack() The current implementation of in_exception_stack() iterates over the exception stacks array. Most of the time this is an useless exercise, but even for the actual use cases (perf and ftrace) it takes at least 2 iterations to get to the NMI stack. As the exception stacks and the guard pages are page aligned the loop can be avoided completely. Add a initial check whether the stack pointer is inside the full exception stack area and leave early if not. Create a lookup table which describes the stack area. The table index is the page offset from the beginning of the exception stacks. So for any given stack pointer the page offset is computed and a lookup in the description table is performed. If it is inside a guard page, return. If not, use the descriptor to fill in the info structure. The table is filled at compile time and for the !KASAN case the interesting page descriptors exactly fit into a single cache line. Just the last guard page descriptor is in the next cacheline, but that should not be accessed in the regular case. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.543320386@linutronix.de
2019-04-14 09:59:58 -06:00
begin += (unsigned long)ep->offs;
end = begin + (unsigned long)ep->size;
regs = (struct pt_regs *)end - 1;
x86/dumpstack/64: Speedup in_exception_stack() The current implementation of in_exception_stack() iterates over the exception stacks array. Most of the time this is an useless exercise, but even for the actual use cases (perf and ftrace) it takes at least 2 iterations to get to the NMI stack. As the exception stacks and the guard pages are page aligned the loop can be avoided completely. Add a initial check whether the stack pointer is inside the full exception stack area and leave early if not. Create a lookup table which describes the stack area. The table index is the page offset from the beginning of the exception stacks. So for any given stack pointer the page offset is computed and a lookup in the description table is performed. If it is inside a guard page, return. If not, use the descriptor to fill in the info structure. The table is filled at compile time and for the !KASAN case the interesting page descriptors exactly fit into a single cache line. Just the last guard page descriptor is in the next cacheline, but that should not be accessed in the regular case. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190414160145.543320386@linutronix.de
2019-04-14 09:59:58 -06:00
info->type = ep->type;
info->begin = (unsigned long *)begin;
info->end = (unsigned long *)end;
info->next_sp = (unsigned long *)regs->sp;
return true;
}
static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
x86: Fixup wrong irq frame link in stacktraces When we enter in irq, two things can happen to preserve the link to the previous frame pointer: - If we were in an irq already, we don't switch to the irq stack as we are inside. We just need to save the previous frame pointer and to link the new one to the previous. - Otherwise we need another level of indirection. We enter the irq with the previous stack. We save the previous bp inside and make bp pointing to its saved address. Then we switch to the irq stack and push bp another time but to the new stack. This makes two levels to dereference instead of one. In the second case, the current stacktrace code omits the second level and loses the frame pointer accuracy. The stack that follows will then be considered as unreliable. Handling that makes the perf callchain happier. Before: 43.94% [k] _raw_read_lock | --- _read_lock | |--60.53%-- send_sigio | __kill_fasync | kill_fasync | evdev_pass_event | evdev_event | input_pass_event | input_handle_event | input_event | synaptics_process_byte | psmouse_handle_byte | psmouse_interrupt | serio_interrupt | i8042_interrupt | handle_IRQ_event | handle_edge_irq | handle_irq | __irqentry_text_start | ret_from_intr | | | |--30.43%-- __select | | | |--17.39%-- 0x454f15 | | | |--13.04%-- __read | | | |--13.04%-- vread_hpet | | | |--13.04%-- _xcb_lock_io | | | --13.04%-- 0x7f630878ce8 After: 50.00% [k] _raw_read_lock | --- _read_lock | |--98.97%-- send_sigio | __kill_fasync | kill_fasync | evdev_pass_event | evdev_event | input_pass_event | input_handle_event | input_event | | | |--96.88%-- synaptics_process_byte | | psmouse_handle_byte | | psmouse_interrupt | | serio_interrupt | | i8042_interrupt | | handle_IRQ_event | | handle_edge_irq | | handle_irq | | __irqentry_text_start | | ret_from_intr | | | | | |--39.78%-- __const_udelay | | | | | | | |--91.89%-- ath5k_hw_register_timeout | | | | ath5k_hw_noise_floor_calibration | | | | ath5k_hw_reset | | | | ath5k_reset | | | | ath5k_config | | | | ieee80211_hw_config | | | | | | | | | |--88.24%-- ieee80211_scan_work | | | | | worker_thread | | | | | kthread | | | | | child_rip | | | | | | | | | --11.76%-- ieee80211_scan_completed | | | | ieee80211_scan_work | | | | worker_thread | | | | kthread | | | | child_rip | | | | | | | --8.11%-- ath5k_hw_noise_floor_calibration | | | ath5k_hw_reset | | | ath5k_reset | | | ath5k_config Note: This does not only affect perf events but also x86-64 stacktraces. They were considered as unreliable once we quit the irq stack frame. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "K. Prasad" <prasad@linux.vnet.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com>
2009-12-05 21:34:27 -07:00
{
unsigned long *end = (unsigned long *)this_cpu_read(hardirq_stack_ptr);
unsigned long *begin = end - (IRQ_STACK_SIZE / sizeof(long));
x86: Fixup wrong irq frame link in stacktraces When we enter in irq, two things can happen to preserve the link to the previous frame pointer: - If we were in an irq already, we don't switch to the irq stack as we are inside. We just need to save the previous frame pointer and to link the new one to the previous. - Otherwise we need another level of indirection. We enter the irq with the previous stack. We save the previous bp inside and make bp pointing to its saved address. Then we switch to the irq stack and push bp another time but to the new stack. This makes two levels to dereference instead of one. In the second case, the current stacktrace code omits the second level and loses the frame pointer accuracy. The stack that follows will then be considered as unreliable. Handling that makes the perf callchain happier. Before: 43.94% [k] _raw_read_lock | --- _read_lock | |--60.53%-- send_sigio | __kill_fasync | kill_fasync | evdev_pass_event | evdev_event | input_pass_event | input_handle_event | input_event | synaptics_process_byte | psmouse_handle_byte | psmouse_interrupt | serio_interrupt | i8042_interrupt | handle_IRQ_event | handle_edge_irq | handle_irq | __irqentry_text_start | ret_from_intr | | | |--30.43%-- __select | | | |--17.39%-- 0x454f15 | | | |--13.04%-- __read | | | |--13.04%-- vread_hpet | | | |--13.04%-- _xcb_lock_io | | | --13.04%-- 0x7f630878ce8 After: 50.00% [k] _raw_read_lock | --- _read_lock | |--98.97%-- send_sigio | __kill_fasync | kill_fasync | evdev_pass_event | evdev_event | input_pass_event | input_handle_event | input_event | | | |--96.88%-- synaptics_process_byte | | psmouse_handle_byte | | psmouse_interrupt | | serio_interrupt | | i8042_interrupt | | handle_IRQ_event | | handle_edge_irq | | handle_irq | | __irqentry_text_start | | ret_from_intr | | | | | |--39.78%-- __const_udelay | | | | | | | |--91.89%-- ath5k_hw_register_timeout | | | | ath5k_hw_noise_floor_calibration | | | | ath5k_hw_reset | | | | ath5k_reset | | | | ath5k_config | | | | ieee80211_hw_config | | | | | | | | | |--88.24%-- ieee80211_scan_work | | | | | worker_thread | | | | | kthread | | | | | child_rip | | | | | | | | | --11.76%-- ieee80211_scan_completed | | | | ieee80211_scan_work | | | | worker_thread | | | | kthread | | | | child_rip | | | | | | | --8.11%-- ath5k_hw_noise_floor_calibration | | | ath5k_hw_reset | | | ath5k_reset | | | ath5k_config Note: This does not only affect perf events but also x86-64 stacktraces. They were considered as unreliable once we quit the irq stack frame. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: "K. Prasad" <prasad@linux.vnet.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com>
2009-12-05 21:34:27 -07:00
x86/dumpstack: Add support for unwinding empty IRQ stacks When an interrupt happens in entry code while running on a software IRQ stack, and the IRQ stack was empty, regs->sp will contain the stack end address (e.g., irq_stack_ptr). If the regs are passed to dump_trace(), get_stack_info() will report STACK_TYPE_UNKNOWN, causing dump_trace() to return prematurely without trying to go to the next stack. Update the bounds checking for software interrupt stacks so that the ending address is now considered part of the stack. This means that it's now possible for the 'walk_stack' callbacks -- print_context_stack() and print_context_stack_bp() -- to be called with an empty stack. But that's fine; they're already prepared to deal with that due to their on_stack() checks. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Byungchul Park <byungchul.park@lge.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nilay Vaish <nilayvaish@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/5a5e5de92dcf11e8dc6b6e8e50ad7639d067830b.1473905218.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-09-14 20:07:43 -06:00
/*
* This is a software stack, so 'end' can be a valid stack pointer.
* It just means the stack is empty.
*/
if (stack < begin || stack >= end)
return false;
info->type = STACK_TYPE_IRQ;
info->begin = begin;
info->end = end;
/*
* The next stack pointer is the first thing pushed by the entry code
* after switching to the irq stack.
*/
info->next_sp = (unsigned long *)*(end - 1);
return true;
}
int get_stack_info(unsigned long *stack, struct task_struct *task,
struct stack_info *info, unsigned long *visit_mask)
{
if (!stack)
goto unknown;
task = task ? : current;
if (in_task_stack(stack, task, info))
goto recursion_check;
if (task != current)
goto unknown;
if (in_exception_stack(stack, info))
goto recursion_check;
if (in_irq_stack(stack, info))
goto recursion_check;
if (in_entry_stack(stack, info))
x86/dumpstack: Add get_stack_info() support for the SYSENTER stack get_stack_info() doesn't currently know about the SYSENTER stack, so unwinding will fail if we entered the kernel on the SYSENTER stack and haven't fully switched off. Teach get_stack_info() about the SYSENTER stack. With future patches applied that run part of the entry code on the SYSENTER stack and introduce an intentional BUG(), I would get: PANIC: double fault, error_code: 0x0 ... RIP: 0010:do_error_trap+0x33/0x1c0 ... Call Trace: Code: ... With this patch, I get: PANIC: double fault, error_code: 0x0 ... Call Trace: <SYSENTER> ? async_page_fault+0x36/0x60 ? invalid_op+0x22/0x40 ? async_page_fault+0x36/0x60 ? sync_regs+0x3c/0x40 ? sync_regs+0x2e/0x40 ? error_entry+0x6c/0xd0 ? async_page_fault+0x36/0x60 </SYSENTER> Code: ... which is a lot more informative. Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Borislav Petkov <bp@suse.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bpetkov@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Laight <David.Laight@aculab.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Eduardo Valentin <eduval@amazon.com> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Will Deacon <will.deacon@arm.com> Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Link: https://lkml.kernel.org/r/20171204150605.392711508@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-12-04 07:07:13 -07:00
goto recursion_check;
goto unknown;
recursion_check:
/*
* Make sure we don't iterate through any given stack more than once.
* If it comes up a second time then there's something wrong going on:
* just break out and report an unknown stack type.
*/
if (visit_mask) {
if (*visit_mask & (1UL << info->type)) {
printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n", info->type);
goto unknown;
}
*visit_mask |= 1UL << info->type;
}
return 0;
unknown:
info->type = STACK_TYPE_UNKNOWN;
return -EINVAL;
}