From 909af768e88867016f427264ae39d27a57b6a8ed Mon Sep 17 00:00:00 2001 From: Jason Baron Date: Fri, 23 Mar 2012 15:02:51 -0700 Subject: coredump: remove VM_ALWAYSDUMP flag The motivation for this patchset was that I was looking at a way for a qemu-kvm process, to exclude the guest memory from its core dump, which can be quite large. There are already a number of filter flags in /proc//coredump_filter, however, these allow one to specify 'types' of kernel memory, not specific address ranges (which is needed in this case). Since there are no more vma flags available, the first patch eliminates the need for the 'VM_ALWAYSDUMP' flag. The flag is used internally by the kernel to mark vdso and vsyscall pages. However, it is simple enough to check if a vma covers a vdso or vsyscall page without the need for this flag. The second patch then replaces the 'VM_ALWAYSDUMP' flag with a new 'VM_NODUMP' flag, which can be set by userspace using new madvise flags: 'MADV_DONTDUMP', and unset via 'MADV_DODUMP'. The core dump filters continue to work the same as before unless 'MADV_DONTDUMP' is set on the region. The qemu code which implements this features is at: http://people.redhat.com/~jbaron/qemu-dump/qemu-dump.patch In my testing the qemu core dump shrunk from 383MB -> 13MB with this patch. I also believe that the 'MADV_DONTDUMP' flag might be useful for security sensitive apps, which might want to select which areas are dumped. This patch: The VM_ALWAYSDUMP flag is currently used by the coredump code to indicate that a vma is part of a vsyscall or vdso section. However, we can determine if a vma is in one these sections by checking it against the gate_vma and checking for a non-NULL return value from arch_vma_name(). Thus, freeing a valuable vma bit. Signed-off-by: Jason Baron Acked-by: Roland McGrath Cc: Chris Metcalf Cc: Avi Kivity Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index c2ae3cd..219e4ef 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -533,8 +533,7 @@ int vectors_user_mapping(void) struct mm_struct *mm = current->mm; return install_special_mapping(mm, 0xffff0000, PAGE_SIZE, VM_READ | VM_EXEC | - VM_MAYREAD | VM_MAYEXEC | - VM_ALWAYSDUMP | VM_RESERVED, + VM_MAYREAD | VM_MAYEXEC | VM_RESERVED, NULL); } diff --git a/arch/hexagon/kernel/vdso.c b/arch/hexagon/kernel/vdso.c index 16277c3..f212a45 100644 --- a/arch/hexagon/kernel/vdso.c +++ b/arch/hexagon/kernel/vdso.c @@ -78,8 +78,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) /* MAYWRITE to allow gdb to COW and set breakpoints. */ ret = install_special_mapping(mm, vdso_base, PAGE_SIZE, VM_READ|VM_EXEC| - VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| - VM_ALWAYSDUMP, + VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, &vdso_page); if (ret) diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c index e5cdfd6..0f1af58 100644 --- a/arch/mips/kernel/vdso.c +++ b/arch/mips/kernel/vdso.c @@ -88,8 +88,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) ret = install_special_mapping(mm, addr, PAGE_SIZE, VM_READ|VM_EXEC| - VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| - VM_ALWAYSDUMP, + VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, &vdso_page); if (ret) diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c index 7d14bb69..d36ee10 100644 --- a/arch/powerpc/kernel/vdso.c +++ b/arch/powerpc/kernel/vdso.c @@ -263,17 +263,11 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) * the "data" page of the vDSO or you'll stop getting kernel updates * and your nice userland gettimeofday will be totally dead. * It's fine to use that for setting breakpoints in the vDSO code - * pages though - * - * 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. + * pages though. */ rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT, VM_READ|VM_EXEC| - VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| - VM_ALWAYSDUMP, + VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, vdso_pagelist); if (rc) { current->mm->context.vdso_base = 0; diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c index e704a99..9c80138 100644 --- a/arch/s390/kernel/vdso.c +++ b/arch/s390/kernel/vdso.c @@ -241,17 +241,11 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) * on the "data" page of the vDSO or you'll stop getting kernel * updates and your nice userland gettimeofday will be totally dead. * It's fine to use that for setting breakpoints in the vDSO code - * pages though - * - * 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. + * pages though. */ rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT, VM_READ|VM_EXEC| - VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| - VM_ALWAYSDUMP, + VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, vdso_pagelist); if (rc) current->mm->context.vdso_base = 0; diff --git a/arch/sh/kernel/vsyscall/vsyscall.c b/arch/sh/kernel/vsyscall/vsyscall.c index 1d6d51a..5ca5797 100644 --- a/arch/sh/kernel/vsyscall/vsyscall.c +++ b/arch/sh/kernel/vsyscall/vsyscall.c @@ -73,8 +73,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) ret = install_special_mapping(mm, addr, PAGE_SIZE, VM_READ | VM_EXEC | - VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC | - VM_ALWAYSDUMP, + VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, syscall_pages); if (unlikely(ret)) goto up_fail; diff --git a/arch/tile/mm/elf.c b/arch/tile/mm/elf.c index 55e58e9..1a00fb6 100644 --- a/arch/tile/mm/elf.c +++ b/arch/tile/mm/elf.c @@ -117,17 +117,11 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, /* * MAYWRITE to allow gdb to COW and set breakpoints - * - * 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. */ vdso_base = VDSO_BASE; retval = install_special_mapping(mm, vdso_base, PAGE_SIZE, VM_READ|VM_EXEC| - VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| - VM_ALWAYSDUMP, + VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, vdso_pages); #ifndef __tilegx__ diff --git a/arch/unicore32/kernel/process.c b/arch/unicore32/kernel/process.c index 52edc2b..432b429 100644 --- a/arch/unicore32/kernel/process.c +++ b/arch/unicore32/kernel/process.c @@ -381,7 +381,7 @@ int vectors_user_mapping(void) return install_special_mapping(mm, 0xffff0000, PAGE_SIZE, VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYEXEC | - VM_ALWAYSDUMP | VM_RESERVED, + VM_RESERVED, NULL); } diff --git a/arch/x86/um/mem_32.c b/arch/x86/um/mem_32.c index 639900a..f40281e 100644 --- a/arch/x86/um/mem_32.c +++ b/arch/x86/um/mem_32.c @@ -23,14 +23,6 @@ static int __init gate_vma_init(void) 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); diff --git a/arch/x86/um/vdso/vma.c b/arch/x86/um/vdso/vma.c index 91f4ec9..af91901 100644 --- a/arch/x86/um/vdso/vma.c +++ b/arch/x86/um/vdso/vma.c @@ -64,8 +64,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) err = install_special_mapping(mm, um_vdso_addr, PAGE_SIZE, VM_READ|VM_EXEC| - VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| - VM_ALWAYSDUMP, + VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, vdsop); up_write(&mm->mmap_sem); diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c index 468d591..a944020 100644 --- a/arch/x86/vdso/vdso32-setup.c +++ b/arch/x86/vdso/vdso32-setup.c @@ -250,13 +250,7 @@ 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; } @@ -343,17 +337,10 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) if (compat_uses_vma || !compat) { /* * MAYWRITE to allow gdb to COW and set breakpoints - * - * 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. */ ret = install_special_mapping(mm, addr, PAGE_SIZE, VM_READ|VM_EXEC| - VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| - VM_ALWAYSDUMP, + VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, vdso32_pages); if (ret) diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c index 153407c..17e1827 100644 --- a/arch/x86/vdso/vma.c +++ b/arch/x86/vdso/vma.c @@ -124,8 +124,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) ret = install_special_mapping(mm, addr, vdso_size, VM_READ|VM_EXEC| - VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| - VM_ALWAYSDUMP, + VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, vdso_pages); if (ret) { current->mm->context.vdso = NULL; diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 81878b7..b64be5b 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1093,6 +1093,29 @@ out: */ /* + * The purpose of always_dump_vma() is to make sure that special kernel mappings + * that are useful for post-mortem analysis are included in every core dump. + * In that way we ensure that the core dump is fully interpretable later + * without matching up the same kernel and hardware config to see what PC values + * meant. These special mappings include - vDSO, vsyscall, and other + * architecture specific mappings + */ +static bool always_dump_vma(struct vm_area_struct *vma) +{ + /* Any vsyscall mappings? */ + if (vma == get_gate_vma(vma->vm_mm)) + return true; + /* + * arch_vma_name() returns non-NULL for special architecture mappings, + * such as vDSO sections. + */ + if (arch_vma_name(vma)) + return true; + + return false; +} + +/* * Decide what to dump of a segment, part, all or none. */ static unsigned long vma_dump_size(struct vm_area_struct *vma, @@ -1100,8 +1123,8 @@ static unsigned long vma_dump_size(struct vm_area_struct *vma, { #define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type)) - /* The vma can be set up to tell us the answer directly. */ - if (vma->vm_flags & VM_ALWAYSDUMP) + /* always dump the vdso and vsyscall sections */ + if (always_dump_vma(vma)) goto whole; /* Hugetlb memory check */ diff --git a/include/linux/mm.h b/include/linux/mm.h index 7330742..2de2ddb 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -111,7 +111,6 @@ extern unsigned int kobjsize(const void *objp); #define VM_HUGEPAGE 0x01000000 /* MADV_HUGEPAGE marked this vma */ #endif #define VM_INSERTPAGE 0x02000000 /* The vma has had "vm_insert_page()" done on it */ -#define VM_ALWAYSDUMP 0x04000000 /* Always include in core dumps */ #define VM_CAN_NONLINEAR 0x08000000 /* Has ->fault & does nonlinear pages */ #define VM_MIXEDMAP 0x10000000 /* Can contain "struct page" and pure PFN pages */ diff --git a/mm/memory.c b/mm/memory.c index 3416b6e..6105f47 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3623,13 +3623,7 @@ 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); -- cgit v0.10.2