[Bug binutils/19147] New: readelf -n does not print all NT_FILE notes (off by one)

[ppluzhnikov at google dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=19147

            Bug ID: 19147
           Summary: readelf -n does not print all NT_FILE notes (off by
                    one)
           Product: binutils
           Version: 2.26 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: binutils
          Assignee: unassigned at sourceware dot org
          Reporter: ppluzhnikov at google dot com
  Target Milestone: ---

Test:

cat t.c
#include <stdlib.h>
int main() { abort(); }

gcc -static t.c && gdb -q ./a.out

(gdb) r
Starting program: /tmp/a.out

Program received signal SIGABRT, Aborted.
0x0000000000444749 in raise ()
(gdb) info proc map
process 133253
Mapped address spaces:

          Start Addr           End Addr       Size     Offset objfile
            0x400000           0x4bf000    0xbf000        0x0 /tmp/a.out
            0x6be000           0x6c1000     0x3000    0xbe000 /tmp/a.out
            0x6c1000           0x6e7000    0x26000        0x0 [heap]
      0x7ffff7ffd000     0x7ffff7fff000     0x2000        0x0 [vdso]
      0x7ffffffde000     0x7ffffffff000    0x21000        0x0 [stack]
  0xffffffffff600000 0xffffffffff601000     0x1000        0x0 [vsyscall]

Note that there are two mappings, and when the kernel saves a core dump, the
file count is 2.

Yet 'readelf -n /tmp/core.133445' prints only one of them:

Displaying notes found at file offset 0x00000200 with length 0x000009b8:
  Owner                 Data size       Description
  CORE                 0x00000150       NT_PRSTATUS (prstatus structure)
  CORE                 0x00000088       NT_PRPSINFO (prpsinfo structure)
  CORE                 0x00000080       NT_SIGINFO (siginfo_t data)
  CORE                 0x00000130       NT_AUXV (auxiliary vector)
  CORE                 0x00000064       NT_FILE (mapped files)
    Page size: 4096
                 Start                 End         Page Offset
    0x0000000000400000  0x00000000004bf000  0x0000000000000000
        /tmp/a.out
  CORE                 0x00000200       NT_FPREGSET (floating point registers)
  LINUX                0x00000340       NT_X86_XSTATE (x86 XSAVE extended
state)


The fix is trivial:

diff --git a/binutils/readelf.c b/binutils/readelf.c
index e8c215d..22cec2c 100644
--- a/binutils/readelf.c
+++ b/binutils/readelf.c
@@ -15151,7 +15151,7 @@ print_core_note (Elf_Internal_Note *pnote)
          (int) (4 + 2 * addr_size), _("End"),
          (int) (4 + 2 * addr_size), _("Page Offset"));
   filenames = descdata + count * 3 * addr_size;
-  while (--count > 0)
+  while (count-- > 0)
     {
       bfd_vma start, end, file_ofs;


With the fix:

build/binutils/readelf -n /tmp/core.133445

Displaying notes found at file offset 0x00000200 with length 0x000009b8:
  Owner                 Data size       Description
  CORE                 0x00000150       NT_PRSTATUS (prstatus structure)
  CORE                 0x00000088       NT_PRPSINFO (prpsinfo structure)
  CORE                 0x00000080       NT_SIGINFO (siginfo_t data)
  CORE                 0x00000130       NT_AUXV (auxiliary vector)
  CORE                 0x00000064       NT_FILE (mapped files)
    Page size: 4096
                 Start                 End         Page Offset
    0x0000000000400000  0x00000000004bf000  0x0000000000000000
        /tmp/a.out
    0x00000000006be000  0x00000000006c1000  0x00000000000000be
        /tmp/a.out
  CORE                 0x00000200       NT_FPREGSET (floating point registers)
  LINUX                0x00000340       NT_X86_XSTATE (x86 XSAVE extended
state)

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