![Andy Lutomirski](/assets/img/avatar_default.png)
The core mm code will provide a default gate area based on FIXADDR_USER_START and FIXADDR_USER_END if !defined(__HAVE_ARCH_GATE_AREA) && defined(AT_SYSINFO_EHDR). This default is only useful for ia64. arm64, ppc, s390, sh, tile, 64-bit UML, and x86_32 have their own code just to disable it. arm, 32-bit UML, and x86_64 have gate areas, but they have their own implementations. This gets rid of the default and moves the code into ia64. This should save some code on architectures without a gate area: it's now possible to inline the gate_area functions in the default case. Signed-off-by: Andy Lutomirski <luto@amacapital.net> Acked-by: Nathan Lynch <nathan_lynch@mentor.com> Acked-by: H. Peter Anvin <hpa@linux.intel.com> Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> [in principle] Acked-by: Richard Weinberger <richard@nod.at> [for um] Acked-by: Will Deacon <will.deacon@arm.com> [for arm64] Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Jeff Dike <jdike@addtoit.com> Cc: Richard Weinberger <richard@nod.at> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Nathan Lynch <Nathan_Lynch@mentor.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
198 lines
4.8 KiB
C
198 lines
4.8 KiB
C
/*
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* Copyright 2012 Tilera Corporation. All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation, version 2.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for
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* more details.
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*/
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#include <linux/binfmts.h>
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#include <linux/compat.h>
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#include <linux/elf.h>
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#include <linux/mm.h>
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#include <linux/pagemap.h>
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#include <asm/vdso.h>
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#include <asm/mman.h>
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#include <asm/sections.h>
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#include <arch/sim.h>
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/* The alignment of the vDSO. */
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#define VDSO_ALIGNMENT PAGE_SIZE
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static unsigned int vdso_pages;
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static struct page **vdso_pagelist;
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#ifdef CONFIG_COMPAT
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static unsigned int vdso32_pages;
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static struct page **vdso32_pagelist;
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#endif
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static int vdso_ready;
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/*
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* The vdso data page.
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*/
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static union {
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struct vdso_data data;
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u8 page[PAGE_SIZE];
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} vdso_data_store __page_aligned_data;
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struct vdso_data *vdso_data = &vdso_data_store.data;
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static unsigned int __read_mostly vdso_enabled = 1;
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static struct page **vdso_setup(void *vdso_kbase, unsigned int pages)
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{
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int i;
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struct page **pagelist;
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pagelist = kzalloc(sizeof(struct page *) * (pages + 1), GFP_KERNEL);
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BUG_ON(pagelist == NULL);
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for (i = 0; i < pages - 1; i++) {
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struct page *pg = virt_to_page(vdso_kbase + i*PAGE_SIZE);
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ClearPageReserved(pg);
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pagelist[i] = pg;
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}
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pagelist[pages - 1] = virt_to_page(vdso_data);
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pagelist[pages] = NULL;
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return pagelist;
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}
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static int __init vdso_init(void)
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{
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int data_pages = sizeof(vdso_data_store) >> PAGE_SHIFT;
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/*
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* We can disable vDSO support generally, but we need to retain
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* one page to support the two-bundle (16-byte) rt_sigreturn path.
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*/
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if (!vdso_enabled) {
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size_t offset = (unsigned long)&__vdso_rt_sigreturn;
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static struct page *sigret_page;
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sigret_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
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BUG_ON(sigret_page == NULL);
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vdso_pagelist = &sigret_page;
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vdso_pages = 1;
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BUG_ON(offset >= PAGE_SIZE);
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memcpy(page_address(sigret_page) + offset,
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vdso_start + offset, 16);
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#ifdef CONFIG_COMPAT
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vdso32_pages = vdso_pages;
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vdso32_pagelist = vdso_pagelist;
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#endif
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vdso_ready = 1;
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return 0;
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}
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vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
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vdso_pages += data_pages;
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vdso_pagelist = vdso_setup(vdso_start, vdso_pages);
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#ifdef CONFIG_COMPAT
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vdso32_pages = (vdso32_end - vdso32_start) >> PAGE_SHIFT;
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vdso32_pages += data_pages;
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vdso32_pagelist = vdso_setup(vdso32_start, vdso32_pages);
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#endif
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smp_wmb();
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vdso_ready = 1;
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return 0;
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}
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arch_initcall(vdso_init);
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const char *arch_vma_name(struct vm_area_struct *vma)
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{
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if (vma->vm_mm && vma->vm_start == VDSO_BASE)
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return "[vdso]";
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#ifndef __tilegx__
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if (vma->vm_start == MEM_USER_INTRPT)
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return "[intrpt]";
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#endif
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return NULL;
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}
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int setup_vdso_pages(void)
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{
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struct page **pagelist;
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unsigned long pages;
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struct mm_struct *mm = current->mm;
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unsigned long vdso_base = 0;
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int retval = 0;
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if (!vdso_ready)
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return 0;
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mm->context.vdso_base = 0;
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pagelist = vdso_pagelist;
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pages = vdso_pages;
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#ifdef CONFIG_COMPAT
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if (is_compat_task()) {
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pagelist = vdso32_pagelist;
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pages = vdso32_pages;
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}
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#endif
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/*
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* vDSO has a problem and was disabled, just don't "enable" it for the
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* process.
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*/
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if (pages == 0)
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return 0;
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vdso_base = get_unmapped_area(NULL, vdso_base,
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(pages << PAGE_SHIFT) +
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((VDSO_ALIGNMENT - 1) & PAGE_MASK),
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0, 0);
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if (IS_ERR_VALUE(vdso_base)) {
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retval = vdso_base;
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return retval;
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}
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/* Add required alignment. */
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vdso_base = ALIGN(vdso_base, VDSO_ALIGNMENT);
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/*
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* Put vDSO base into mm struct. We need to do this before calling
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* install_special_mapping or the perf counter mmap tracking code
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* will fail to recognise it as a vDSO (since arch_vma_name fails).
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*/
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mm->context.vdso_base = vdso_base;
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/*
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* our vma flags don't have VM_WRITE so by default, the process isn't
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* allowed to write those pages.
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* gdb can break that with ptrace interface, and thus trigger COW on
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* those pages but it's then your responsibility to never do that on
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* the "data" page of the vDSO or you'll stop getting kernel updates
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* and your nice userland gettimeofday will be totally dead.
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* It's fine to use that for setting breakpoints in the vDSO code
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* pages though
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*/
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retval = install_special_mapping(mm, vdso_base,
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pages << PAGE_SHIFT,
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VM_READ|VM_EXEC |
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VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
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pagelist);
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if (retval)
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mm->context.vdso_base = 0;
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return retval;
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}
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static __init int vdso_func(char *s)
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{
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return kstrtouint(s, 0, &vdso_enabled);
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}
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__setup("vdso=", vdso_func);
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