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Subject[PATCH 3/4] coredump: ELF-FDPIC: enable to omit anonymous shared memory
This patch enables to omit anonymous shared memory from an ELF-FDPIC
formatted core file when it is generated.

The debug messages from maydump() in fs/binfmt_elf_fdpic.c are changed
appropriately so that we can know what kind of memory segments are
dumped or not.

Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
---
fs/binfmt_elf_fdpic.c | 37 +++++++++++++++++++++++++------------
1 files changed, 25 insertions(+), 12 deletions(-)

Index: linux-2.6.20-mm1/fs/binfmt_elf_fdpic.c
===================================================================
--- linux-2.6.20-mm1.orig/fs/binfmt_elf_fdpic.c
+++ linux-2.6.20-mm1/fs/binfmt_elf_fdpic.c
@@ -1168,7 +1168,7 @@ static int dump_seek(struct file *file,
*
* I think we should skip something. But I am not sure how. H.J.
*/
-static int maydump(struct vm_area_struct *vma)
+static int maydump(struct vm_area_struct *vma, unsigned int omit_anon_shared)
{
/* Do not dump I/O mapped devices or special mappings */
if (vma->vm_flags & (VM_IO | VM_RESERVED)) {
@@ -1184,15 +1184,22 @@ static int maydump(struct vm_area_struct
return 0;
}

- /* Dump shared memory only if mapped from an anonymous file. */
+ /*
+ * Dump shared memory only if mapped from an anonymous file and
+ * /proc/<pid>/coredump_omit_anonymous_shared flag is not set.
+ */
if (vma->vm_flags & VM_SHARED) {
- if (vma->vm_file->f_path.dentry->d_inode->i_nlink == 0) {
+ if (vma->vm_file->f_path.dentry->d_inode->i_nlink) {
kdcore("%08lx: %08lx: no (share)", vma->vm_start, vma->vm_flags);
+ return 0;
+ }
+ if (omit_anon_shared) {
+ kdcore("%08lx: %08lx: no (anon-share)", vma->vm_start, vma->vm_flags);
+ return 0;
+ } else {
+ kdcore("%08lx: %08lx: yes (anon-share)", vma->vm_start, vma->vm_flags);
return 1;
}
-
- kdcore("%08lx: %08lx: no (share)", vma->vm_start, vma->vm_flags);
- return 0;
}

#ifdef CONFIG_MMU
@@ -1444,14 +1451,15 @@ static int elf_dump_thread_status(long s
*/
#ifdef CONFIG_MMU
static int elf_fdpic_dump_segments(struct file *file, struct mm_struct *mm,
- size_t *size, unsigned long *limit)
+ size_t *size, unsigned long *limit,
+ unsigned int omit_anon_shared)
{
struct vm_area_struct *vma;

for (vma = current->mm->mmap; vma; vma = vma->vm_next) {
unsigned long addr;

- if (!maydump(vma))
+ if (!maydump(vma, omit_anon_shared))
continue;

for (addr = vma->vm_start;
@@ -1499,14 +1507,15 @@ end_coredump:
*/
#ifndef CONFIG_MMU
static int elf_fdpic_dump_segments(struct file *file, struct mm_struct *mm,
- size_t *size, unsigned long *limit)
+ size_t *size, unsigned long *limit,
+ unsigned int omit_anon_shared)
{
struct vm_list_struct *vml;

for (vml = current->mm->context.vmlist; vml; vml = vml->next) {
struct vm_area_struct *vma = vml->vma;

- if (!maydump(vma))
+ if (!maydump(vma, omit_anon_shared))
continue;

if ((*size += PAGE_SIZE) > *limit)
@@ -1557,6 +1566,7 @@ static int elf_fdpic_core_dump(long sign
struct vm_list_struct *vml;
#endif
elf_addr_t *auxv;
+ unsigned int omit_anon_shared = 0;

/*
* We no longer stop all VM operations.
@@ -1694,6 +1704,8 @@ static int elf_fdpic_core_dump(long sign
/* Page-align dumped data */
dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);

+ omit_anon_shared = current->mm->coredump_omit_anon_shared;
+
/* write program headers for segments dump */
for (
#ifdef CONFIG_MMU
@@ -1715,7 +1727,7 @@ static int elf_fdpic_core_dump(long sign
phdr.p_offset = offset;
phdr.p_vaddr = vma->vm_start;
phdr.p_paddr = 0;
- phdr.p_filesz = maydump(vma) ? sz : 0;
+ phdr.p_filesz = maydump(vma, omit_anon_shared) ? sz : 0;
phdr.p_memsz = sz;
offset += phdr.p_filesz;
phdr.p_flags = vma->vm_flags & VM_READ ? PF_R : 0;
@@ -1749,7 +1761,8 @@ static int elf_fdpic_core_dump(long sign

DUMP_SEEK(dataoff);

- if (elf_fdpic_dump_segments(file, current->mm, &size, &limit) < 0)
+ if (elf_fdpic_dump_segments(file, current->mm, &size, &limit,
+ omit_anon_shared) < 0)
goto end_coredump;

#ifdef ELF_CORE_WRITE_EXTRA_DATA

-
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