svn commit: r330338 - head/sys/amd64/amd64

[John Baldwin]

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.)

-- 
John Baldwin