public inbox for libc-ports@sourceware.org
 help / color / mirror / Atom feed
From: Richard Henderson <rth@twiddle.net>
To: libc-ports@sourceware.org
Cc: alpha@gentoo.org,	mattst88@gmail.com
Subject: [COMMITTED] alpha: Fix signal thunk unwind info
Date: Sat, 16 Nov 2013 11:06:00 -0000	[thread overview]
Message-ID: <1384564284-27834-1-git-send-email-rth@twiddle.net> (raw)

---
I'm still testing this same patch applied to 2.18.  I don't plan on
backporting it further.  Gentoo can do that if it wishes, but I hope
most of their users will update all the way to the most recent.


r~


 ports/ChangeLog.alpha                              |  5 +++++
 ports/sysdeps/unix/sysv/linux/alpha/rt_sigaction.S | 18 ++++++++++++++----
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/ports/ChangeLog.alpha b/ports/ChangeLog.alpha
index 07f5dfb..8f97951 100644
--- a/ports/ChangeLog.alpha
+++ b/ports/ChangeLog.alpha
@@ -1,3 +1,8 @@
+2013-11-16  Richard Henderson  <rth@redhat.com>
+
+	* sysdeps/unix/sysv/linux/alpha/rt_sigaction.S: Include a nop
+	before each signal thunk.
+
 2013-10-30  Mike Frysinger  <vapier@gentoo.org>
 
 	* sysdeps/alpha/configure.in: Moved to ...
diff --git a/ports/sysdeps/unix/sysv/linux/alpha/rt_sigaction.S b/ports/sysdeps/unix/sysv/linux/alpha/rt_sigaction.S
index 3d291fd..6efa738 100644
--- a/ports/sysdeps/unix/sysv/linux/alpha/rt_sigaction.S
+++ b/ports/sysdeps/unix/sysv/linux/alpha/rt_sigaction.S
@@ -83,14 +83,21 @@ PSEUDO_END(__syscall_rt_sigaction)
 	cfi_offset (64, \base + 2 * 8)
 	.endm
 
-	.align	4
-
 	cfi_startproc
 	cfi_return_column (64)
 	.cfi_signal_frame
 	SIGCONTEXT_REGS -648
-
 	cfi_def_cfa_offset (648)
+
+	/* While this frame is marked as a signal frame, that only applies
+	   to how this return address is handled for the outer frame.
+	   The return address that arrived here, from the inner frame, is
+	   not marked as a signal frame and so the unwinder still tries to
+	   subtract 1 to examine the presumed call insn.  Thus we must
+	   extend the unwind info to a nop before the start.  */
+	nop
+	.align 4
+
 __syscall_sigreturn:
 	mov	sp, a0
 	ldi	v0, __NR_sigreturn
@@ -98,8 +105,11 @@ __syscall_sigreturn:
 	.size	__syscall_sigreturn, .-__syscall_sigreturn
 	.type	__syscall_sigreturn, @function
 
-	.align 4
+	/* See above wrt including the nop.  */
 	cfi_def_cfa_offset (176 + 648)
+	nop
+	.align 4
+
 __syscall_rt_sigreturn:
 	mov	sp,a0
 	ldi	v0,__NR_rt_sigreturn
-- 
1.8.3.1

                 reply	other threads:[~2013-11-16  1:11 UTC|newest]

Thread overview: [no followups] expand[flat|nested]  mbox.gz  Atom feed

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1384564284-27834-1-git-send-email-rth@twiddle.net \
    --to=rth@twiddle.net \
    --cc=alpha@gentoo.org \
    --cc=libc-ports@sourceware.org \
    --cc=mattst88@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).