Date: Fri, 09 Mar 2018 11:22:19 -0800 From: John Baldwin <jhb@freebsd.org> To: Andriy Gapon <avg@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r330338 - head/sys/amd64/amd64 Message-ID: <2557369.6nFzd3kAUm@ralph.baldwin.cx> In-Reply-To: <201803031510.w23FAbeC065867@repo.freebsd.org> References: <201803031510.w23FAbeC065867@repo.freebsd.org>
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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
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