ptrace still broken- PTRACE_CONT trap flag, and debug state

Hello,

main(){
__asm__("pushf\r\n"
              "popf\r\n"
             );
}

Single stepping through the "pushf" instruction and then attempting to
PTRACE_CONT will generate SIGTRAPs at each instruction. Although the
trap flag appears to not be set according to GETREG values, the pushf
will push a value with the TF bit on, which is then restored with
popf...

Here's an example of single stepping on a 2.6.8 and the trap flag
(uppercase letter means enabled):

8048351: push %ecx.
 eax=bffff7cc ebx=40146adc ecx=bffff740 edx=00000001
 esi=bffff7c4 edi=bffff750 ebp=bffff728 esp=bffff724
 flags= [c] [P] [a] [z] [S] [T] [I] [df] [id]

8048352: pushf .
 eax=bffff7cc ebx=40146adc ecx=bffff740 edx=00000001
 esi=bffff7c4 edi=bffff750 ebp=bffff728 esp=bffff720
 flags= [c] [P] [a] [z] [S] [T] [I] [df] [id]

8048353: popf .
 eax=bffff7cc ebx=40146adc ecx=bffff740 edx=00000001
 esi=bffff7c4 edi=bffff750 ebp=bffff728 esp=bffff724
 flags= [c] [P] [a] [z] [S] [T] [I] [df] [id]

8048354: pop %ecx.
 eax=bffff7cc ebx=40146adc ecx=bffff740 edx=00000001
 esi=bffff7c4 edi=bffff750 ebp=bffff728 esp=bffff728
 flags= [c] [P] [a] [z] [S] [T] [I] [df] [id]



and a 2.6.20



8048351: push %ecx.
 eax=bfcff654 ebx=b7f52ff4 ecx=bfcff5d0 edx=00000001
 esi=b7f80ce0 edi=00000000 ebp=bfcff5b8 esp=bfcff5b4
 flags= [c] [P] [a] [z] [S] [t] [I] [df] [id] 286

8048352: pushf .
 eax=bfcff654 ebx=b7f52ff4 ecx=bfcff5d0 edx=00000001
 esi=b7f80ce0 edi=00000000 ebp=bfcff5b8 esp=bfcff5b0
 flags= [c] [P] [a] [z] [S] [t] [I] [df] [id] 286

8048353: popf .
 eax=bfcff654 ebx=b7f52ff4 ecx=bfcff5d0 edx=00000001
 esi=b7f80ce0 edi=00000000 ebp=bfcff5b8 esp=bfcff5b4
 flags= [c] [P] [a] [z] [S] [T] [I] [df] [id] 386

8048354: pop %ecx.
 eax=bfcff654 ebx=b7f52ff4 ecx=bfcff5d0 edx=00000001
 esi=b7f80ce0 edi=00000000 ebp=bfcff5b8 esp=bfcff5b8
 flags= [c] [P] [a] [z] [S] [T] [I] [df] [id] 386



I'm not sure where along the line this was broken but it looks like
there were more than a few changes...
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

---

• Prev by Date: Re: [RFC] [PATCH 0/3] Add group fairness to CFS
• Next by Date: Re: [PATCH] libata: always use polling SETXFER
• Previous by thread: INTERNODE_CACHE_SHIFT redefinition for hot spot data alignment
• Next by thread: Re: [PATCH] libata: always use polling SETXFER
• Index(es):
  • Date
  • Thread

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]