[PATCH v2] Extend core dump note section to contain file names of mapped files

Denys Vlasenko
2012-07-12T19:42:10Z

This note has the following format:

long count -- how many files are mapped
long page_size -- units for file_ofs
array of [COUNT] elements of
long start
long end
long file_ofs
followed by COUNT filenames in ASCII: "FILE1" NUL "FILE2" NUL...

Compared to previous version, code is simplified
as suggested by Oleg Nesterov.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 1b52956..8e60c38 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1372,6 +1372,72 @@ static void fill_auxv_note(struct memelfnote *note, struct mm_struct *mm)
fill_note(note, "CORE", NT_AUXV, i * sizeof(elf_addr_t), auxv);
}

+#define MAX_FILE_NOTE_SIZE (4*1024*1024)
+
+static void fill_files_note(struct memelfnote *note)
+{
+ struct vm_area_struct *vma;
+ struct file *file;
+ unsigned count, word_count, size, remaining;
+ long *data;
+ long *start_end_ofs;
+ char *name;
+
+ count = 0;
+ for (vma = current->mm->mmap; vma != NULL; vma = vma->vm_next) {
+ file = vma->vm_file;
+ if (!file)
+ continue;
+ count++;
+ }
+
+ size = count * 64;
+ word_count = 2 + 3 * count;
+ alloc:
+ if (size >= MAX_FILE_NOTE_SIZE) /* paranoia check */
+ goto err;
+ size = round_up(size, PAGE_SIZE);
+ data = vmalloc(size);
+ if (!data)
+ goto err;
+
+ start_end_ofs = data;
+ name = (void*)&start_end_ofs[word_count];
+ remaining = size - word_count * sizeof(long);
+
+ *start_end_ofs++ = count;
+ *start_end_ofs++ = PAGE_SIZE;
+ for (vma = current->mm->mmap; vma != NULL; vma = vma->vm_next) {
+ const char *filename;
+
+ file = vma->vm_file;
+ if (!file)
+ continue;
+ filename = d_path(&file->f_path, name, remaining);
+ if (IS_ERR(filename)) {
+ if (PTR_ERR(filename) == -ENAMETOOLONG) {
+ vfree(data);
+ size = size * 5 / 4;
+ goto alloc;
+ }
+ /* continue; - WRONG, we must have COUNT elements */
+ filename = "";
+ }
+ /* d_path() fills at the end, move it to front */
+ do
+ remaining--;
+ while ((*name++ = *filename++) != '\0');
+
+ *start_end_ofs++ = vma->vm_start;
+ *start_end_ofs++ = vma->vm_end;
+ *start_end_ofs++ = vma->vm_pgoff;
+ }
+
+ size = name - (char*)data;
+ fill_note(note, "CORE", NT_FILE, size, data);
+ err: ;
+}
+
#ifdef CORE_DUMP_USE_REGSET
#include <linux/regset.h>

@@ -1386,6 +1452,7 @@ struct elf_note_info {
struct elf_thread_core_info *thread;
struct memelfnote psinfo;
struct memelfnote auxv;
+ struct memelfnote files;
size_t size;
int thread_notes;
};
@@ -1562,6 +1629,9 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
fill_auxv_note(&info->auxv, current->mm);
info->size += notesize(&info->auxv);

+ fill_files_note(&info->files);
+ info->size += notesize(&info->files);
+
return 1;
}

@@ -1590,6 +1660,8 @@ static int write_note_info(struct elf_note_info *info,
return 0;
if (first && !writenote(&info->auxv, file, foffset))
return 0;
+ if (first && !writenote(&info->files, file, foffset))
+ return 0;

for (i = 1; i < info->thread_notes; ++i)
if (t->notes[i].data &&
@@ -1616,6 +1688,7 @@ static void free_note_info(struct elf_note_info *info)
kfree(t);
}
kfree(info->psinfo.data);
+ vfree(info->files.data);
}

#else
diff --git a/include/linux/elf.h b/include/linux/elf.h
index 999b4f5..5e6c08f 100644
--- a/include/linux/elf.h
+++ b/include/linux/elf.h
@@ -372,6 +372,7 @@ typedef struct elf64_shdr {
#define NT_PRPSINFO 3
#define NT_TASKSTRUCT 4
#define NT_AUXV 6
+#define NT_FILE 0x46494c45
#define NT_PRXFPREG 0x46e62b7f /* copied from gdb5.1/include/elf/common.h */
#define NT_PPC_VMX 0x100 /* PowerPC Altivec/VMX registers */
#define NT_PPC_SPE 0x101 /* PowerPC SPE/EVR registers */