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Commit f47aef55 authored by Roland McGrath's avatar Roland McGrath Committed by Linus Torvalds
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[PATCH] i386 vDSO: use VM_ALWAYSDUMP 



This patch fixes core dumps to include the vDSO vma, which is left out now.
It removes the special-case core writing macros, which were not doing the
right thing for the vDSO vma anyway.  Instead, it uses VM_ALWAYSDUMP in the
vma; there is no need for the fixmap page to be installed.  It handles the
CONFIG_COMPAT_VDSO case by making elf_core_dump use the fake vma from
get_gate_vma after real vmas in the same way the /proc/PID/maps code does.

This changes core dumps so they no longer include the non-PT_LOAD phdrs from
the vDSO.  I made the change to add them in the first place, but in turned out
that nothing ever wanted them there since the advent of NT_AUXV.  It's cleaner
to leave them out, and just let the phdrs inside the vDSO image speak for
themselves.

Signed-off-by: default avatarRoland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e5b97dde

arch/i386/kernel/sysenter.c

+7 −5
Original line number Diff line number Diff line
@@ -79,11 +79,6 @@ int __init sysenter_setup(void) 
#ifdef CONFIG_COMPAT_VDSO

	__set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_READONLY);

	printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));

#else

	/*

	 * In the non-compat case the ELF coredumping code needs the fixmap:

	 */

	__set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_KERNEL_RO);

#endif



	if (!boot_cpu_has(X86_FEATURE_SEP)) {
@@ -147,6 +142,13 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack) 
	vma->vm_end = addr + PAGE_SIZE;

	/* MAYWRITE to allow gdb to COW and set breakpoints */

	vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE;

	/*

	 * Make sure the vDSO gets into every core dump.

	 * Dumping its contents makes post-mortem fully interpretable later

	 * without matching up the same kernel and hardware config to see

	 * what PC values meant.

	 */

	vma->vm_flags |= VM_ALWAYSDUMP;

	vma->vm_flags |= mm->def_flags;

	vma->vm_page_prot = protection_map[vma->vm_flags & 7];

	vma->vm_ops = &syscall_vm_ops;

fs/binfmt_elf.c

+35 −3
Original line number Diff line number Diff line
@@ -1428,6 +1428,32 @@ static int elf_dump_thread_status(long signr, struct elf_thread_status *t) 
	return sz;

}



static struct vm_area_struct *first_vma(struct task_struct *tsk,

					struct vm_area_struct *gate_vma)

{

	struct vm_area_struct *ret = tsk->mm->mmap;



	if (ret)

		return ret;

	return gate_vma;

}

/*

 * Helper function for iterating across a vma list.  It ensures that the caller

 * will visit `gate_vma' prior to terminating the search.

 */

static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,

					struct vm_area_struct *gate_vma)

{

	struct vm_area_struct *ret;



	ret = this_vma->vm_next;

	if (ret)

		return ret;

	if (this_vma == gate_vma)

		return NULL;

	return gate_vma;

}



/*

 * Actual dumper

 *
@@ -1443,7 +1469,7 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file) 
	int segs;

	size_t size = 0;

	int i;

	struct vm_area_struct *vma;

	struct vm_area_struct *vma, *gate_vma;

	struct elfhdr *elf = NULL;

	loff_t offset = 0, dataoff, foffset;

	unsigned long limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
@@ -1529,6 +1555,10 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file) 
	segs += ELF_CORE_EXTRA_PHDRS;

#endif



	gate_vma = get_gate_vma(current);

	if (gate_vma != NULL)

		segs++;



	/* Set up header */

	fill_elf_header(elf, segs + 1);	/* including notes section */
@@ -1596,7 +1626,8 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file) 
	dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);



	/* Write program headers for segments dump */

	for (vma = current->mm->mmap; vma != NULL; vma = vma->vm_next) {

	for (vma = first_vma(current, gate_vma); vma != NULL;

			vma = next_vma(vma, gate_vma)) {

		struct elf_phdr phdr;

		size_t sz;
@@ -1645,7 +1676,8 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file) 
	/* Align to page */

	DUMP_SEEK(dataoff - foffset);



	for (vma = current->mm->mmap; vma != NULL; vma = vma->vm_next) {

	for (vma = first_vma(current, gate_vma); vma != NULL;

			vma = next_vma(vma, gate_vma)) {

		unsigned long addr;



		if (!maydump(vma))

include/asm-i386/elf.h

+0 −44
Original line number Diff line number Diff line
@@ -168,50 +168,6 @@ do if (vdso_enabled) { \ 
		NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_COMPAT_BASE);	\

} while (0)



/*

 * These macros parameterize elf_core_dump in fs/binfmt_elf.c to write out

 * extra segments containing the vsyscall DSO contents.  Dumping its

 * contents makes post-mortem fully interpretable later without matching up

 * the same kernel and hardware config to see what PC values meant.

 * Dumping its extra ELF program headers includes all the other information

 * a debugger needs to easily find how the vsyscall DSO was being used.

 */

#define ELF_CORE_EXTRA_PHDRS		(VDSO_HIGH_EHDR->e_phnum)

#define ELF_CORE_WRITE_EXTRA_PHDRS					      \

do {									      \

	const struct elf_phdr *const vsyscall_phdrs =			      \

		(const struct elf_phdr *) (VDSO_HIGH_BASE		      \

					   + VDSO_HIGH_EHDR->e_phoff);    \

	int i;								      \

	Elf32_Off ofs = 0;						      \

	for (i = 0; i < VDSO_HIGH_EHDR->e_phnum; ++i) {		      \

		struct elf_phdr phdr = vsyscall_phdrs[i];		      \

		if (phdr.p_type == PT_LOAD) {				      \

			BUG_ON(ofs != 0);				      \

			ofs = phdr.p_offset = offset;			      \

			phdr.p_memsz = PAGE_ALIGN(phdr.p_memsz);	      \

			phdr.p_filesz = phdr.p_memsz;			      \

			offset += phdr.p_filesz;			      \

		}							      \

		else							      \

			phdr.p_offset += ofs;				      \

		phdr.p_paddr = 0; /* match other core phdrs */		      \

		DUMP_WRITE(&phdr, sizeof(phdr));			      \

	}								      \

} while (0)

#define ELF_CORE_WRITE_EXTRA_DATA					      \

do {									      \

	const struct elf_phdr *const vsyscall_phdrs =			      \

		(const struct elf_phdr *) (VDSO_HIGH_BASE		      \

					   + VDSO_HIGH_EHDR->e_phoff);    \

	int i;								      \

	for (i = 0; i < VDSO_HIGH_EHDR->e_phnum; ++i) {		      \

		if (vsyscall_phdrs[i].p_type == PT_LOAD)		      \

			DUMP_WRITE((void *) vsyscall_phdrs[i].p_vaddr,	      \

				   PAGE_ALIGN(vsyscall_phdrs[i].p_memsz));    \

	}								      \

} while (0)



#endif



#endif

mm/memory.c

+7 −0
Original line number Diff line number Diff line
@@ -2608,6 +2608,13 @@ static int __init gate_vma_init(void) 
	gate_vma.vm_end = FIXADDR_USER_END;

	gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;

	gate_vma.vm_page_prot = __P101;

	/*

	 * Make sure the vDSO gets into every core dump.

	 * Dumping its contents makes post-mortem fully interpretable later

	 * without matching up the same kernel and hardware config to see

	 * what PC values meant.

	 */

	gate_vma.vm_flags |= VM_ALWAYSDUMP;

	return 0;

}

__initcall(gate_vma_init);