Bug 290066

Got the same error ("Serious error when reading debug info...") with valgrind trunk (rev. 12379) on a PPC host (PPC440EPx, ELDK4.2).

No symbols get loaded.

Don't know if its a valgrind or a linker/toolchain/binutils error. It boils down to a loop in readelf.c:read_elf_debug_info(). There it is not able to detect a "RW Area".

The test statement is: "(phdr->p_flags & (PF_R | PF_W | PF_X)) == (PF_R | PF_W)". In this particular case the Read, Write AND Execute bits are set and the statement evaluates to false...

As a workaround i've applied this patch:

########################### snip ##########################

--- coregrind/m_debuginfo/readelf.c (Revision 12379)
+++ coregrind/m_debuginfo/readelf.c (Arbeitskopie)
@@ -1539,7 +1539,7 @@
                 && phdr->p_offset < di->fsm.rw_map_foff + di->fsm.rw_map_size
                 && phdr->p_offset + phdr->p_filesz
                    <= di->fsm.rw_map_foff + di->fsm.rw_map_size
-                && (phdr->p_flags & (PF_R | PF_W | PF_X)) == (PF_R | PF_W)) {
+                && (phdr->p_flags & (PF_R | PF_W | PF_X)) >= (PF_R | PF_W)) {
                if (n_rw == N_RX_RW_AREAS) {
                   ML_(symerr)(di, True,
                               "N_RX_RW_AREAS is too low; "

########################### snip ##########################

Valgrind is now able to read the symbols from the programms and libraries.

The relevant snippet from readelf output of the to-be-debuged program:

########################### snip ##########################
ELF Header:
  Magic:   7f 45 4c 46 01 02 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF32
  Data:                              2's complement, big endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           PowerPC
  Version:                           0x1
  Entry point address:               0x10000550
  Start of program headers:          52 (bytes into file)
  Start of section headers:          39416 (bytes into file)
  Flags:                             0x0
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         8
  Size of section headers:           40 (bytes)
  Number of section headers:         38
  Section header string table index: 35

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0  0
  [ 1] .interp           PROGBITS        10000134 000134 00000d 00   A  0   0  1
  [ 2] .note.ABI-tag     NOTE            10000144 000144 000020 00   A  0   0  4
  ...
  [19] .got2             PROGBITS        10041018 001018 000008 00  WA  0   0  1
  [20] .dynamic          DYNAMIC         10041020 001020 0000d8 08  WA  5   0  4
  [21] .data             PROGBITS        100410f8 0010f8 000008 00  WA  0   0  4
  [22] .got              PROGBITS        10041100 001100 000014 04 WAX  0   0  4
  [23] .sbss             NOBITS          10041114 001114 000006 00  WA  0   0  4
  ...
  [37] .strtab           STRTAB          00000000 00aca8 000950 00      0   0  1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings)
  I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)

There are no section groups in this file.

Program Headers:
  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  PHDR           0x000034 0x10000034 0x10000034 0x00100 0x00100 R E 0x4
  INTERP         0x000134 0x10000134 0x10000134 0x0000d 0x0000d R   0x1
      [Requesting program interpreter: /lib/ld.so.1]
  LOAD           0x000000 0x10000000 0x10000000 0x00f98 0x00f98 R E 0x40000
  LOAD           0x001000 0x10041000 0x10041000 0x00114 0x00204 RWE 0x40000
  DYNAMIC        0x001020 0x10041020 0x10041020 0x000d8 0x000d8 RW  0x4
  NOTE           0x000144 0x10000144 0x10000144 0x00020 0x00020 R   0x4
  GNU_EH_FRAME   0x000e78 0x10000e78 0x10000e78 0x0003c 0x0003c R   0x4
  GNU_STACK      0x000000 0x00000000 0x00000000 0x00000 0x00000 RW  0x4

########################### snip ##########################


As you can see, the program header 4 at position 0x001000 has the flags "RWE".

Let me know, if you need more info ...

I confirm the patch fixes the same bug I had using valgrind on a e300c3 (powerpc) compiler.

Can you try 3.8.0 and see if the problem still exists?  I believe this may have
been fixed with a more general patch in 3.8.0, but I am not sure.

Hi, does Valgrind 3.8.0 or 3.8.1 have this patch (I looked in release notes for both but didn't see anything that looked like solving this bug?)??

Otherwise, does anybody know if this problem occured first in 3.7.0 and didn't exist in earlier releases?

I have tested vanilla Valgrind 3.8.1 for e300c3 (powerpc) compiler and it works fine without any patch.

(In reply to comment #4)
> Hi, does Valgrind 3.8.0 or 3.8.1 have this patch (I looked in release notes
> for both but didn't see anything that looked like solving this bug?)??
> 
> Otherwise, does anybody know if this problem occured first in 3.7.0 and
> didn't exist in earlier releases?