* [PATCH][gdb/tdep, rs6000] Don't skip system call in skip_prologue
@ 2021-11-02 11:33 Tom de Vries
2021-11-02 16:26 ` Simon Marchi
2021-11-02 16:54 ` Kevin Buettner
0 siblings, 2 replies; 4+ messages in thread
From: Tom de Vries @ 2021-11-02 11:33 UTC (permalink / raw)
To: gdb-patches; +Cc: Ulrich Weigand, Kevin Buettner, Carl Love
Hi,
I ran into a case where a breakpoint on _exit never triggered, because it was
set past the end of the _exit prologue, past the end of the exit_group system
call (which does not return).
Fix this by treating system calls the same as branches in skip_prologue:
by default, don't skip.
Tested on ppc64le-linux, on a power 8 machine.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28527
Any comments?
Thanks,
- Tom
[gdb/tdep, rs6000] Don't skip system call in skip_prologue
---
gdb/rs6000-tdep.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c
index 78b4fd1a913..4830ed22593 100644
--- a/gdb/rs6000-tdep.c
+++ b/gdb/rs6000-tdep.c
@@ -2137,6 +2137,12 @@ skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc, CORE_ADDR lim_pc,
/* Never skip branches. */
break;
+ /* Test based on opcode and mask values of
+ powerpc_opcodes[svc..svcla] in opcodes/ppc-opc.c. */
+ if ((op & 0xffff0000) == 0x44000000)
+ /* Never skip system calls. */
+ break;
+
if (num_skip_non_prologue_insns++ > max_skip_non_prologue_insns)
/* Do not scan too many insns, scanning insns is expensive with
remote targets. */
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH][gdb/tdep, rs6000] Don't skip system call in skip_prologue
2021-11-02 11:33 [PATCH][gdb/tdep, rs6000] Don't skip system call in skip_prologue Tom de Vries
@ 2021-11-02 16:26 ` Simon Marchi
2021-11-02 18:13 ` Tom de Vries
2021-11-02 16:54 ` Kevin Buettner
1 sibling, 1 reply; 4+ messages in thread
From: Simon Marchi @ 2021-11-02 16:26 UTC (permalink / raw)
To: Tom de Vries, gdb-patches; +Cc: Ulrich Weigand
On 2021-11-02 7:33 a.m., Tom de Vries via Gdb-patches wrote:
> Hi,
>
> I ran into a case where a breakpoint on _exit never triggered, because it was
> set past the end of the _exit prologue, past the end of the exit_group system
> call (which does not return).
>
> Fix this by treating system calls the same as branches in skip_prologue:
> by default, don't skip.
>
> Tested on ppc64le-linux, on a power 8 machine.
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28527
>
> Any comments?
>
> Thanks,
> - Tom
>
> [gdb/tdep, rs6000] Don't skip system call in skip_prologue
>
> ---
> gdb/rs6000-tdep.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c
> index 78b4fd1a913..4830ed22593 100644
> --- a/gdb/rs6000-tdep.c
> +++ b/gdb/rs6000-tdep.c
> @@ -2137,6 +2137,12 @@ skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc, CORE_ADDR lim_pc,
> /* Never skip branches. */
> break;
>
> + /* Test based on opcode and mask values of
> + powerpc_opcodes[svc..svcla] in opcodes/ppc-opc.c. */
> + if ((op & 0xffff0000) == 0x44000000)
> + /* Never skip system calls. */
> + break;
> +
> if (num_skip_non_prologue_insns++ > max_skip_non_prologue_insns)
> /* Do not scan too many insns, scanning insns is expensive with
> remote targets. */
>
The explanation makes sense, but I think a powerpc maintainer should ack the
patch.
And I think it would be useful to paste the "disassembly /r" of the _exit
function in the commit message, showing where the breakpoint used to be
placed, and where it is placed now.
Simon
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH][gdb/tdep, rs6000] Don't skip system call in skip_prologue
2021-11-02 11:33 [PATCH][gdb/tdep, rs6000] Don't skip system call in skip_prologue Tom de Vries
2021-11-02 16:26 ` Simon Marchi
@ 2021-11-02 16:54 ` Kevin Buettner
1 sibling, 0 replies; 4+ messages in thread
From: Kevin Buettner @ 2021-11-02 16:54 UTC (permalink / raw)
To: Tom de Vries; +Cc: gdb-patches, Ulrich Weigand, Carl Love
On Tue, 2 Nov 2021 12:33:04 +0100
Tom de Vries <tdevries@suse.de> wrote:
> I ran into a case where a breakpoint on _exit never triggered, because it was
> set past the end of the _exit prologue, past the end of the exit_group system
> call (which does not return).
>
> Fix this by treating system calls the same as branches in skip_prologue:
> by default, don't skip.
LGTM.
Kevin
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH][gdb/tdep, rs6000] Don't skip system call in skip_prologue
2021-11-02 16:26 ` Simon Marchi
@ 2021-11-02 18:13 ` Tom de Vries
0 siblings, 0 replies; 4+ messages in thread
From: Tom de Vries @ 2021-11-02 18:13 UTC (permalink / raw)
To: Simon Marchi, gdb-patches; +Cc: Ulrich Weigand
On 11/2/21 5:26 PM, Simon Marchi wrote:
> On 2021-11-02 7:33 a.m., Tom de Vries via Gdb-patches wrote:
>> Hi,
>>
>> I ran into a case where a breakpoint on _exit never triggered, because it was
>> set past the end of the _exit prologue, past the end of the exit_group system
>> call (which does not return).
>>
>> Fix this by treating system calls the same as branches in skip_prologue:
>> by default, don't skip.
>>
>> Tested on ppc64le-linux, on a power 8 machine.
>>
>> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28527
>>
>> Any comments?
>>
>> Thanks,
>> - Tom
>>
>> [gdb/tdep, rs6000] Don't skip system call in skip_prologue
>>
>> ---
>> gdb/rs6000-tdep.c | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c
>> index 78b4fd1a913..4830ed22593 100644
>> --- a/gdb/rs6000-tdep.c
>> +++ b/gdb/rs6000-tdep.c
>> @@ -2137,6 +2137,12 @@ skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc, CORE_ADDR lim_pc,
>> /* Never skip branches. */
>> break;
>>
>> + /* Test based on opcode and mask values of
>> + powerpc_opcodes[svc..svcla] in opcodes/ppc-opc.c. */
>> + if ((op & 0xffff0000) == 0x44000000)
>> + /* Never skip system calls. */
>> + break;
>> +
>> if (num_skip_non_prologue_insns++ > max_skip_non_prologue_insns)
>> /* Do not scan too many insns, scanning insns is expensive with
>> remote targets. */
>>
>
>
> The explanation makes sense, but I think a powerpc maintainer should ack the
> patch.
>
The only mention I found in gdb/MAINTAINERS related to powerpc is Kevin,
and he approved it.
> And I think it would be useful to paste the "disassembly /r" of the _exit
> function in the commit message, showing where the breakpoint used to be
> placed, and where it is placed now.
Ack, good suggestion, done and committed.
Thanks,
- Tom
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-11-02 18:13 UTC | newest]
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2021-11-02 11:33 [PATCH][gdb/tdep, rs6000] Don't skip system call in skip_prologue Tom de Vries
2021-11-02 16:26 ` Simon Marchi
2021-11-02 18:13 ` Tom de Vries
2021-11-02 16:54 ` Kevin Buettner
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