![Arnd Bergmann](/assets/img/avatar_default.png)
Looking at functions with large stack frames across all architectures led me discovering that BUG() suffers from the same problem as fortify_panic(), which I've added a workaround for already. In short, variables that go out of scope by calling a noreturn function or __builtin_unreachable() keep using stack space in functions afterwards. A workaround that was identified is to insert an empty assembler statement just before calling the function that doesn't return. I'm adding a macro "barrier_before_unreachable()" to document this, and insert calls to that in all instances of BUG() that currently suffer from this problem. The files that saw the largest change from this had these frame sizes before, and much less with my patch: fs/ext4/inode.c:82:1: warning: the frame size of 1672 bytes is larger than 800 bytes [-Wframe-larger-than=] fs/ext4/namei.c:434:1: warning: the frame size of 904 bytes is larger than 800 bytes [-Wframe-larger-than=] fs/ext4/super.c:2279:1: warning: the frame size of 1160 bytes is larger than 800 bytes [-Wframe-larger-than=] fs/ext4/xattr.c:146:1: warning: the frame size of 1168 bytes is larger than 800 bytes [-Wframe-larger-than=] fs/f2fs/inode.c:152:1: warning: the frame size of 1424 bytes is larger than 800 bytes [-Wframe-larger-than=] net/netfilter/ipvs/ip_vs_core.c:1195:1: warning: the frame size of 1068 bytes is larger than 800 bytes [-Wframe-larger-than=] net/netfilter/ipvs/ip_vs_core.c:395:1: warning: the frame size of 1084 bytes is larger than 800 bytes [-Wframe-larger-than=] net/netfilter/ipvs/ip_vs_ftp.c:298:1: warning: the frame size of 928 bytes is larger than 800 bytes [-Wframe-larger-than=] net/netfilter/ipvs/ip_vs_ftp.c:418:1: warning: the frame size of 908 bytes is larger than 800 bytes [-Wframe-larger-than=] net/netfilter/ipvs/ip_vs_lblcr.c:718:1: warning: the frame size of 960 bytes is larger than 800 bytes [-Wframe-larger-than=] drivers/net/xen-netback/netback.c:1500:1: warning: the frame size of 1088 bytes is larger than 800 bytes [-Wframe-larger-than=] In case of ARC and CRIS, it turns out that the BUG() implementation actually does return (or at least the compiler thinks it does), resulting in lots of warnings about uninitialized variable use and leaving noreturn functions, such as: block/cfq-iosched.c: In function 'cfq_async_queue_prio': block/cfq-iosched.c:3804:1: error: control reaches end of non-void function [-Werror=return-type] include/linux/dmaengine.h: In function 'dma_maxpq': include/linux/dmaengine.h:1123:1: error: control reaches end of non-void function [-Werror=return-type] This makes them call __builtin_trap() instead, which should normally dump the stack and kill the current process, like some of the other architectures already do. I tried adding barrier_before_unreachable() to panic() and fortify_panic() as well, but that had very little effect, so I'm not submitting that patch. Vineet said: : For ARC, it is double win. : : 1. Fixes 3 -Wreturn-type warnings : : | ../net/core/ethtool.c:311:1: warning: control reaches end of non-void function : [-Wreturn-type] : | ../kernel/sched/core.c:3246:1: warning: control reaches end of non-void function : [-Wreturn-type] : | ../include/linux/sunrpc/svc_xprt.h:180:1: warning: control reaches end of : non-void function [-Wreturn-type] : : 2. bloat-o-meter reports code size improvements as gcc elides the : generated code for stack return. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365 Link: http://lkml.kernel.org/r/20171219114112.939391-1-arnd@arndb.de Signed-off-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Vineet Gupta <vgupta@synopsys.com> [arch/arc] Tested-by: Vineet Gupta <vgupta@synopsys.com> [arch/arc] Cc: Mikael Starvik <starvik@axis.com> Cc: Jesper Nilsson <jesper.nilsson@axis.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Christopher Li <sparse@chrisli.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Kees Cook <keescook@chromium.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Will Deacon <will.deacon@arm.com> Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org> Cc: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
346 lines
10 KiB
C
346 lines
10 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef __LINUX_COMPILER_H
|
|
#define __LINUX_COMPILER_H
|
|
|
|
#include <linux/compiler_types.h>
|
|
|
|
#ifndef __ASSEMBLY__
|
|
|
|
#ifdef __KERNEL__
|
|
|
|
/*
|
|
* Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
|
|
* to disable branch tracing on a per file basis.
|
|
*/
|
|
#if defined(CONFIG_TRACE_BRANCH_PROFILING) \
|
|
&& !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
|
|
void ftrace_likely_update(struct ftrace_likely_data *f, int val,
|
|
int expect, int is_constant);
|
|
|
|
#define likely_notrace(x) __builtin_expect(!!(x), 1)
|
|
#define unlikely_notrace(x) __builtin_expect(!!(x), 0)
|
|
|
|
#define __branch_check__(x, expect, is_constant) ({ \
|
|
int ______r; \
|
|
static struct ftrace_likely_data \
|
|
__attribute__((__aligned__(4))) \
|
|
__attribute__((section("_ftrace_annotated_branch"))) \
|
|
______f = { \
|
|
.data.func = __func__, \
|
|
.data.file = __FILE__, \
|
|
.data.line = __LINE__, \
|
|
}; \
|
|
______r = __builtin_expect(!!(x), expect); \
|
|
ftrace_likely_update(&______f, ______r, \
|
|
expect, is_constant); \
|
|
______r; \
|
|
})
|
|
|
|
/*
|
|
* Using __builtin_constant_p(x) to ignore cases where the return
|
|
* value is always the same. This idea is taken from a similar patch
|
|
* written by Daniel Walker.
|
|
*/
|
|
# ifndef likely
|
|
# define likely(x) (__branch_check__(x, 1, __builtin_constant_p(x)))
|
|
# endif
|
|
# ifndef unlikely
|
|
# define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x)))
|
|
# endif
|
|
|
|
#ifdef CONFIG_PROFILE_ALL_BRANCHES
|
|
/*
|
|
* "Define 'is'", Bill Clinton
|
|
* "Define 'if'", Steven Rostedt
|
|
*/
|
|
#define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
|
|
#define __trace_if(cond) \
|
|
if (__builtin_constant_p(!!(cond)) ? !!(cond) : \
|
|
({ \
|
|
int ______r; \
|
|
static struct ftrace_branch_data \
|
|
__attribute__((__aligned__(4))) \
|
|
__attribute__((section("_ftrace_branch"))) \
|
|
______f = { \
|
|
.func = __func__, \
|
|
.file = __FILE__, \
|
|
.line = __LINE__, \
|
|
}; \
|
|
______r = !!(cond); \
|
|
______f.miss_hit[______r]++; \
|
|
______r; \
|
|
}))
|
|
#endif /* CONFIG_PROFILE_ALL_BRANCHES */
|
|
|
|
#else
|
|
# define likely(x) __builtin_expect(!!(x), 1)
|
|
# define unlikely(x) __builtin_expect(!!(x), 0)
|
|
#endif
|
|
|
|
/* Optimization barrier */
|
|
#ifndef barrier
|
|
# define barrier() __memory_barrier()
|
|
#endif
|
|
|
|
#ifndef barrier_data
|
|
# define barrier_data(ptr) barrier()
|
|
#endif
|
|
|
|
/* workaround for GCC PR82365 if needed */
|
|
#ifndef barrier_before_unreachable
|
|
# define barrier_before_unreachable() do { } while (0)
|
|
#endif
|
|
|
|
/* Unreachable code */
|
|
#ifdef CONFIG_STACK_VALIDATION
|
|
/*
|
|
* These macros help objtool understand GCC code flow for unreachable code.
|
|
* The __COUNTER__ based labels are a hack to make each instance of the macros
|
|
* unique, to convince GCC not to merge duplicate inline asm statements.
|
|
*/
|
|
#define annotate_reachable() ({ \
|
|
asm volatile("%c0:\n\t" \
|
|
".pushsection .discard.reachable\n\t" \
|
|
".long %c0b - .\n\t" \
|
|
".popsection\n\t" : : "i" (__COUNTER__)); \
|
|
})
|
|
#define annotate_unreachable() ({ \
|
|
asm volatile("%c0:\n\t" \
|
|
".pushsection .discard.unreachable\n\t" \
|
|
".long %c0b - .\n\t" \
|
|
".popsection\n\t" : : "i" (__COUNTER__)); \
|
|
})
|
|
#define ASM_UNREACHABLE \
|
|
"999:\n\t" \
|
|
".pushsection .discard.unreachable\n\t" \
|
|
".long 999b - .\n\t" \
|
|
".popsection\n\t"
|
|
#else
|
|
#define annotate_reachable()
|
|
#define annotate_unreachable()
|
|
#endif
|
|
|
|
#ifndef ASM_UNREACHABLE
|
|
# define ASM_UNREACHABLE
|
|
#endif
|
|
#ifndef unreachable
|
|
# define unreachable() do { annotate_reachable(); do { } while (1); } while (0)
|
|
#endif
|
|
|
|
/*
|
|
* KENTRY - kernel entry point
|
|
* This can be used to annotate symbols (functions or data) that are used
|
|
* without their linker symbol being referenced explicitly. For example,
|
|
* interrupt vector handlers, or functions in the kernel image that are found
|
|
* programatically.
|
|
*
|
|
* Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
|
|
* are handled in their own way (with KEEP() in linker scripts).
|
|
*
|
|
* KENTRY can be avoided if the symbols in question are marked as KEEP() in the
|
|
* linker script. For example an architecture could KEEP() its entire
|
|
* boot/exception vector code rather than annotate each function and data.
|
|
*/
|
|
#ifndef KENTRY
|
|
# define KENTRY(sym) \
|
|
extern typeof(sym) sym; \
|
|
static const unsigned long __kentry_##sym \
|
|
__used \
|
|
__attribute__((section("___kentry" "+" #sym ), used)) \
|
|
= (unsigned long)&sym;
|
|
#endif
|
|
|
|
#ifndef RELOC_HIDE
|
|
# define RELOC_HIDE(ptr, off) \
|
|
({ unsigned long __ptr; \
|
|
__ptr = (unsigned long) (ptr); \
|
|
(typeof(ptr)) (__ptr + (off)); })
|
|
#endif
|
|
|
|
#ifndef OPTIMIZER_HIDE_VAR
|
|
#define OPTIMIZER_HIDE_VAR(var) barrier()
|
|
#endif
|
|
|
|
/* Not-quite-unique ID. */
|
|
#ifndef __UNIQUE_ID
|
|
# define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
|
|
#endif
|
|
|
|
#include <uapi/linux/types.h>
|
|
|
|
#define __READ_ONCE_SIZE \
|
|
({ \
|
|
switch (size) { \
|
|
case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \
|
|
case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \
|
|
case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \
|
|
case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \
|
|
default: \
|
|
barrier(); \
|
|
__builtin_memcpy((void *)res, (const void *)p, size); \
|
|
barrier(); \
|
|
} \
|
|
})
|
|
|
|
static __always_inline
|
|
void __read_once_size(const volatile void *p, void *res, int size)
|
|
{
|
|
__READ_ONCE_SIZE;
|
|
}
|
|
|
|
#ifdef CONFIG_KASAN
|
|
/*
|
|
* We can't declare function 'inline' because __no_sanitize_address confilcts
|
|
* with inlining. Attempt to inline it may cause a build failure.
|
|
* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
|
|
* '__maybe_unused' allows us to avoid defined-but-not-used warnings.
|
|
*/
|
|
# define __no_kasan_or_inline __no_sanitize_address __maybe_unused
|
|
#else
|
|
# define __no_kasan_or_inline __always_inline
|
|
#endif
|
|
|
|
static __no_kasan_or_inline
|
|
void __read_once_size_nocheck(const volatile void *p, void *res, int size)
|
|
{
|
|
__READ_ONCE_SIZE;
|
|
}
|
|
|
|
static __always_inline void __write_once_size(volatile void *p, void *res, int size)
|
|
{
|
|
switch (size) {
|
|
case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
|
|
case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
|
|
case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
|
|
case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
|
|
default:
|
|
barrier();
|
|
__builtin_memcpy((void *)p, (const void *)res, size);
|
|
barrier();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Prevent the compiler from merging or refetching reads or writes. The
|
|
* compiler is also forbidden from reordering successive instances of
|
|
* READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
|
|
* particular ordering. One way to make the compiler aware of ordering is to
|
|
* put the two invocations of READ_ONCE or WRITE_ONCE in different C
|
|
* statements.
|
|
*
|
|
* These two macros will also work on aggregate data types like structs or
|
|
* unions. If the size of the accessed data type exceeds the word size of
|
|
* the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
|
|
* fall back to memcpy(). There's at least two memcpy()s: one for the
|
|
* __builtin_memcpy() and then one for the macro doing the copy of variable
|
|
* - '__u' allocated on the stack.
|
|
*
|
|
* Their two major use cases are: (1) Mediating communication between
|
|
* process-level code and irq/NMI handlers, all running on the same CPU,
|
|
* and (2) Ensuring that the compiler does not fold, spindle, or otherwise
|
|
* mutilate accesses that either do not require ordering or that interact
|
|
* with an explicit memory barrier or atomic instruction that provides the
|
|
* required ordering.
|
|
*/
|
|
#include <asm/barrier.h>
|
|
#include <linux/kasan-checks.h>
|
|
|
|
#define __READ_ONCE(x, check) \
|
|
({ \
|
|
union { typeof(x) __val; char __c[1]; } __u; \
|
|
if (check) \
|
|
__read_once_size(&(x), __u.__c, sizeof(x)); \
|
|
else \
|
|
__read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
|
|
smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
|
|
__u.__val; \
|
|
})
|
|
#define READ_ONCE(x) __READ_ONCE(x, 1)
|
|
|
|
/*
|
|
* Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
|
|
* to hide memory access from KASAN.
|
|
*/
|
|
#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
|
|
|
|
static __no_kasan_or_inline
|
|
unsigned long read_word_at_a_time(const void *addr)
|
|
{
|
|
kasan_check_read(addr, 1);
|
|
return *(unsigned long *)addr;
|
|
}
|
|
|
|
#define WRITE_ONCE(x, val) \
|
|
({ \
|
|
union { typeof(x) __val; char __c[1]; } __u = \
|
|
{ .__val = (__force typeof(x)) (val) }; \
|
|
__write_once_size(&(x), __u.__c, sizeof(x)); \
|
|
__u.__val; \
|
|
})
|
|
|
|
#endif /* __KERNEL__ */
|
|
|
|
#endif /* __ASSEMBLY__ */
|
|
|
|
#ifndef __optimize
|
|
# define __optimize(level)
|
|
#endif
|
|
|
|
/* Compile time object size, -1 for unknown */
|
|
#ifndef __compiletime_object_size
|
|
# define __compiletime_object_size(obj) -1
|
|
#endif
|
|
#ifndef __compiletime_warning
|
|
# define __compiletime_warning(message)
|
|
#endif
|
|
#ifndef __compiletime_error
|
|
# define __compiletime_error(message)
|
|
/*
|
|
* Sparse complains of variable sized arrays due to the temporary variable in
|
|
* __compiletime_assert. Unfortunately we can't just expand it out to make
|
|
* sparse see a constant array size without breaking compiletime_assert on old
|
|
* versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
|
|
*/
|
|
# ifndef __CHECKER__
|
|
# define __compiletime_error_fallback(condition) \
|
|
do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
|
|
# endif
|
|
#endif
|
|
#ifndef __compiletime_error_fallback
|
|
# define __compiletime_error_fallback(condition) do { } while (0)
|
|
#endif
|
|
|
|
#ifdef __OPTIMIZE__
|
|
# define __compiletime_assert(condition, msg, prefix, suffix) \
|
|
do { \
|
|
bool __cond = !(condition); \
|
|
extern void prefix ## suffix(void) __compiletime_error(msg); \
|
|
if (__cond) \
|
|
prefix ## suffix(); \
|
|
__compiletime_error_fallback(__cond); \
|
|
} while (0)
|
|
#else
|
|
# define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
|
|
#endif
|
|
|
|
#define _compiletime_assert(condition, msg, prefix, suffix) \
|
|
__compiletime_assert(condition, msg, prefix, suffix)
|
|
|
|
/**
|
|
* compiletime_assert - break build and emit msg if condition is false
|
|
* @condition: a compile-time constant condition to check
|
|
* @msg: a message to emit if condition is false
|
|
*
|
|
* In tradition of POSIX assert, this macro will break the build if the
|
|
* supplied condition is *false*, emitting the supplied error message if the
|
|
* compiler has support to do so.
|
|
*/
|
|
#define compiletime_assert(condition, msg) \
|
|
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
|
|
|
|
#define compiletime_assert_atomic_type(t) \
|
|
compiletime_assert(__native_word(t), \
|
|
"Need native word sized stores/loads for atomicity.")
|
|
|
|
#endif /* __LINUX_COMPILER_H */
|