[PATCH 3/4] coredump: ELF-FDPIC: enable to omit anonymous shared memory

["Kawai, Hidehiro" <hidehiro.kawai.ez@hitachi.com>]

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