Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=82df39738ba9e02c057fa99b7461a56117d36119
Commit:     82df39738ba9e02c057fa99b7461a56117d36119
Parent:     e629a7ddc0188e1bb9e956e698a9bd00c19c9854
Author:     Roland McGrath <[EMAIL PROTECTED]>
AuthorDate: Tue Oct 16 23:27:02 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Wed Oct 17 08:42:52 2007 -0700

    Add MMF_DUMP_ELF_HEADERS
    
    This adds the MMF_DUMP_ELF_HEADERS option to /proc/pid/coredump_filter.
    This dumps the first page (only) of a private file mapping if it appears to
    be a mapping of an ELF file.  Including these pages in the core dump may
    give sufficient identifying information to associate the original DSO and
    executable file images and their debugging information with a core file in
    a generic way just from its contents (e.g.  when those binaries were built
    with ld --build-id).  I expect this to become the default behavior
    eventually.  Existing versions of gdb can be confused by the core dumps it
    creates, so it won't enabled by default for some time to come.  Soon many
    people will have systems with a gdb that handle these dumps, so they can
    arrange to set the bit at boot and have it inherited system-wide.
    
    This also cleans up the checking of the MMF_DUMP_* flag bits, which did not
    need to be using atomic macros.
    
    Signed-off-by: Roland McGrath <[EMAIL PROTECTED]>
    Cc: Hidehiro Kawai <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 fs/binfmt_elf.c       |   78 +++++++++++++++++++++++++++++++++---------------
 include/linux/sched.h |    3 +-
 2 files changed, 55 insertions(+), 26 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 66cd711..4263326 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1201,35 +1201,68 @@ static int dump_seek(struct file *file, loff_t off)
 }
 
 /*
- * Decide whether a segment is worth dumping; default is yes to be
- * sure (missing info is worse than too much; etc).
- * Personally I'd include everything, and use the coredump limit...
- *
- * I think we should skip something. But I am not sure how. H.J.
+ * Decide what to dump of a segment, part, all or none.
  */
-static int maydump(struct vm_area_struct *vma, unsigned long mm_flags)
+static unsigned long vma_dump_size(struct vm_area_struct *vma,
+                                  unsigned long mm_flags)
 {
        /* The vma can be set up to tell us the answer directly.  */
        if (vma->vm_flags & VM_ALWAYSDUMP)
-               return 1;
+               goto whole;
 
        /* Do not dump I/O mapped devices or special mappings */
        if (vma->vm_flags & (VM_IO | VM_RESERVED))
                return 0;
 
+#define FILTER(type)   (mm_flags & (1UL << MMF_DUMP_##type))
+
        /* By default, dump shared memory if mapped from an anonymous file. */
        if (vma->vm_flags & VM_SHARED) {
-               if (vma->vm_file->f_path.dentry->d_inode->i_nlink == 0)
-                       return test_bit(MMF_DUMP_ANON_SHARED, &mm_flags);
-               else
-                       return test_bit(MMF_DUMP_MAPPED_SHARED, &mm_flags);
+               if (vma->vm_file->f_path.dentry->d_inode->i_nlink == 0 ?
+                   FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
+                       goto whole;
+               return 0;
        }
 
-       /* By default, if it hasn't been written to, don't write it out. */
-       if (!vma->anon_vma)
-               return test_bit(MMF_DUMP_MAPPED_PRIVATE, &mm_flags);
+       /* Dump segments that have been written to.  */
+       if (vma->anon_vma && FILTER(ANON_PRIVATE))
+               goto whole;
+       if (vma->vm_file == NULL)
+               return 0;
 
-       return test_bit(MMF_DUMP_ANON_PRIVATE, &mm_flags);
+       if (FILTER(MAPPED_PRIVATE))
+               goto whole;
+
+       /*
+        * If this looks like the beginning of a DSO or executable mapping,
+        * check for an ELF header.  If we find one, dump the first page to
+        * aid in determining what was mapped here.
+        */
+       if (FILTER(ELF_HEADERS) && vma->vm_file != NULL && vma->vm_pgoff == 0) {
+               u32 __user *header = (u32 __user *) vma->vm_start;
+               u32 word;
+               /*
+                * Doing it this way gets the constant folded by GCC.
+                */
+               union {
+                       u32 cmp;
+                       char elfmag[SELFMAG];
+               } magic;
+               BUILD_BUG_ON(SELFMAG != sizeof word);
+               magic.elfmag[EI_MAG0] = ELFMAG0;
+               magic.elfmag[EI_MAG1] = ELFMAG1;
+               magic.elfmag[EI_MAG2] = ELFMAG2;
+               magic.elfmag[EI_MAG3] = ELFMAG3;
+               if (get_user(word, header) == 0 && word == magic.cmp)
+                       return PAGE_SIZE;
+       }
+
+#undef FILTER
+
+       return 0;
+
+whole:
+       return vma->vm_end - vma->vm_start;
 }
 
 /* An ELF note in memory */
@@ -1669,16 +1702,13 @@ static int elf_core_dump(long signr, struct pt_regs 
*regs, struct file *file, un
        for (vma = first_vma(current, gate_vma); vma != NULL;
                        vma = next_vma(vma, gate_vma)) {
                struct elf_phdr phdr;
-               size_t sz;
-
-               sz = vma->vm_end - vma->vm_start;
 
                phdr.p_type = PT_LOAD;
                phdr.p_offset = offset;
                phdr.p_vaddr = vma->vm_start;
                phdr.p_paddr = 0;
-               phdr.p_filesz = maydump(vma, mm_flags) ? sz : 0;
-               phdr.p_memsz = sz;
+               phdr.p_filesz = vma_dump_size(vma, mm_flags);
+               phdr.p_memsz = vma->vm_end - vma->vm_start;
                offset += phdr.p_filesz;
                phdr.p_flags = vma->vm_flags & VM_READ ? PF_R : 0;
                if (vma->vm_flags & VM_WRITE)
@@ -1718,13 +1748,11 @@ static int elf_core_dump(long signr, struct pt_regs 
*regs, struct file *file, un
        for (vma = first_vma(current, gate_vma); vma != NULL;
                        vma = next_vma(vma, gate_vma)) {
                unsigned long addr;
+               unsigned long end;
 
-               if (!maydump(vma, mm_flags))
-                       continue;
+               end = vma->vm_start + vma_dump_size(vma, mm_flags);
 
-               for (addr = vma->vm_start;
-                    addr < vma->vm_end;
-                    addr += PAGE_SIZE) {
+               for (addr = vma->vm_start; addr < end; addr += PAGE_SIZE) {
                        struct page *page;
                        struct vm_area_struct *vma;
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index e643357..cb952bc 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -359,8 +359,9 @@ extern int get_dumpable(struct mm_struct *mm);
 #define MMF_DUMP_ANON_SHARED   3
 #define MMF_DUMP_MAPPED_PRIVATE        4
 #define MMF_DUMP_MAPPED_SHARED 5
+#define MMF_DUMP_ELF_HEADERS   6
 #define MMF_DUMP_FILTER_SHIFT  MMF_DUMPABLE_BITS
-#define MMF_DUMP_FILTER_BITS   4
+#define MMF_DUMP_FILTER_BITS   5
 #define MMF_DUMP_FILTER_MASK \
        (((1 << MMF_DUMP_FILTER_BITS) - 1) << MMF_DUMP_FILTER_SHIFT)
 #define MMF_DUMP_FILTER_DEFAULT \
-
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