svn commit: r330338 - head/sys/amd64/amd64
Andriy Gapon
avg at FreeBSD.org
Mon Mar 12 07:52:31 UTC 2018
On 09/03/2018 21:22, John Baldwin wrote:
> On Saturday, March 03, 2018 03:10:37 PM Andriy Gapon wrote:
>> Author: avg
>> Date: Sat Mar 3 15:10:37 2018
>> New Revision: 330338
>> URL: https://svnweb.freebsd.org/changeset/base/330338
>>
>> Log:
>> db_nextframe/amd64: catch up with r328083 to recognize fast_syscall_common
>>
>> Since that change the system call stack traces look like this:
>> ...
>> sys___sysctl() at sys___sysctl+0x5f/frame 0xfffffe0028e13ac0
>> amd64_syscall() at amd64_syscall+0x79b/frame 0xfffffe0028e13bf0
>> fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe0028e13bf0
>> So, db_nextframe() stopped recognizing the system call frame.
>> This commit should fix that.
>>
>> Reviewed by: kib
>> MFC after: 4 days
>>
>> Modified:
>> head/sys/amd64/amd64/db_trace.c
>>
>> Modified: head/sys/amd64/amd64/db_trace.c
>> ==============================================================================
>> --- head/sys/amd64/amd64/db_trace.c Sat Mar 3 13:20:44 2018 (r330337)
>> +++ head/sys/amd64/amd64/db_trace.c Sat Mar 3 15:10:37 2018 (r330338)
>> @@ -212,7 +212,9 @@ db_nextframe(struct amd64_frame **fp, db_addr_t *ip, s
>> strcmp(name, "Xcpususpend") == 0 ||
>> strcmp(name, "Xrendezvous") == 0)
>> frame_type = INTERRUPT;
>> - else if (strcmp(name, "Xfast_syscall") == 0)
>> + else if (strcmp(name, "Xfast_syscall") == 0 ||
>> + strcmp(name, "Xfast_syscall_pti") == 0 ||
>> + strcmp(name, "fast_syscall_common") == 0)
>> frame_type = SYSCALL;
>
> I think you actually just want to replace Xfast_syscall with
> fast_syscall_common. Neither Xfast_syscall nor Xfast_syscall_pti call any
> functions before jumping to the common label, so when unwinding from a system
> call you should always get the common label. (That is, I think we should
> remove Xfast_syscall and Xfast_syscall_pti here. Any stack trace that
> happens to find those symbols during unwinding won't have a valid SYSCALL
> frame to unwind.)
>
I kept / added those to, sort of, decouple db_nextframe from the current
implementation details. I hope that the extra code does not create too much
overhead.
--
Andriy Gapon
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