Re: [PATCH, MIPS] Extract PID from core dump file

["Maciej W. Rozycki" <macro at imgtec dot com>]

Hi Djordje,

 Apologies for the long RTT.  Cc-ing `gdb' as this affects GDB processing.

> On MIPS platforms, PID information was not correctly propagated from core dump
> file to internal GDB structures. This patch fixes that behavior.
> 
> The bug was found while trying to read TLS variable from core dump file on
> MIPS platforms, but it was not able because GDB needs correct PID information
> in order to do that.

 Would you be able to give me a recipe to reproduce a scenario where the 
effect of actions taken is not as expected?  I'd like to have it covered 
by a GDB test suite case if possible.

> This change is tested on MIPS64R2 board with o32, n32 and n64 executables.
> Test program is forced to crash in order to generate core file. Core file is
> loaded into GDB and bfd structure is checked if it has correct PID value, the
> same value executable had before crash.

 AFAICT however GDB prefers LWPID if available, so while I agree that 
technically we ought to retrieve PID as well, in reality it shouldn't 
really matter.  Having a test case demonstrating a user-visible effect 
would indeed help.

> Currently I don't have copyright assignment. Couple a weeks ago my company
> initiated process of getting copyright assignment  but with no response so
> far.

 Any update on progress?  While I think your change can be considered 
small enough not to require a copyright assignment for acceptance, it 
would be preferable if you had it.

> diff --git a/bfd/elf32-mips.c b/bfd/elf32-mips.c
> index 8c1a68eb..9ec2818 100644
> --- a/bfd/elf32-mips.c
> +++ b/bfd/elf32-mips.c
> @@ -2353,6 +2353,8 @@ elf32_mips_grok_psinfo (bfd *abfd, Elf_Internal_Note
> *note)
>  	return FALSE;
> 
>        case 128:		/* Linux/MIPS elf_prpsinfo */
> +	elf_tdata (abfd)->core->pid
> +	 = bfd_get_32 (abfd, note->descdata + 24);
>  	elf_tdata (abfd)->core->program
>  	 = _bfd_elfcore_strndup (abfd, note->descdata + 32, 16);
>  	elf_tdata (abfd)->core->command

 The offset isn't right however, you're fetching the process group ID 
rather than the process ID:

(gdb) ptype struct elf_prpsinfo
type = struct elf_prpsinfo {
    char pr_state;
    char pr_sname;
    char pr_zomb;
    char pr_nice;
    unsigned long pr_flag;
    __kernel_uid_t pr_uid;
    __kernel_gid_t pr_gid;
    pid_t pr_pid;
    pid_t pr_ppid;
    pid_t pr_pgrp;
    pid_t pr_sid;
    char pr_fname[16];
    char pr_psargs[80];
}
(gdb) print /d &((struct elf_prpsinfo *)0)->pr_pid
$1 = 16
(gdb) print /d &((struct elf_prpsinfo *)0)->pr_pgrp
$2 = 24
(gdb)

Same with n32.  The n64 variant is OK.

  Maciej