* [PATCH] fix x86_64 sigreturn call so gdb recognizes it
@ 2016-11-12 17:07 Szabolcs Nagy
2016-11-13 0:12 ` [PATCH v2] fix x86_64 sigreturn trampoline " Szabolcs Nagy
0 siblings, 1 reply; 3+ messages in thread
From: Szabolcs Nagy @ 2016-11-12 17:07 UTC (permalink / raw)
To: musl
gdb cannot unwind across signal handlers if __restore{_rt} is not aligned.
---
other targets may be affected as well, i only tried x86_64 and i386.
src/signal/x86_64/restore.s | 1 +
1 file changed, 1 insertion(+)
diff --git a/src/signal/x86_64/restore.s b/src/signal/x86_64/restore.s
index 682af2d..179f3ef 100644
--- a/src/signal/x86_64/restore.s
+++ b/src/signal/x86_64/restore.s
@@ -1,3 +1,4 @@
+.align 16
.global __restore_rt
.global __restore
.type __restore_rt,@function
--
2.10.2
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH v2] fix x86_64 sigreturn trampoline so gdb recognizes it
2016-11-12 17:07 [PATCH] fix x86_64 sigreturn call so gdb recognizes it Szabolcs Nagy
@ 2016-11-13 0:12 ` Szabolcs Nagy
2016-11-13 2:46 ` Rich Felker
0 siblings, 1 reply; 3+ messages in thread
From: Szabolcs Nagy @ 2016-11-13 0:12 UTC (permalink / raw)
To: musl
gdb can only unwind across signal handlers if it recognizes the trampoline.
on x86_64 this means the pc must be in a function called __restore_rt or
if gdb cannot determine the symbol name the instruction sequence must match
to what gdb expects.
a nop is added before __restore_rt, the __restore alias is removed and
size annotation is added to make sure gdb maps any pc value within
__restore_rt unambigously to the __restore_rt symbol name.
and the instruction sequence got fixed to match what gdb expects.
---
arch/x86_64/ksigaction.h | 9 +++++++++
src/signal/x86_64/restore.s | 7 +++----
2 files changed, 12 insertions(+), 4 deletions(-)
create mode 100644 arch/x86_64/ksigaction.h
diff --git a/arch/x86_64/ksigaction.h b/arch/x86_64/ksigaction.h
new file mode 100644
index 0000000..7743c5c
--- /dev/null
+++ b/arch/x86_64/ksigaction.h
@@ -0,0 +1,9 @@
+struct k_sigaction {
+ void (*handler)(int);
+ unsigned long flags;
+ void (*restorer)(void);
+ unsigned mask[2];
+};
+
+void __restore_rt();
+#define __restore __restore_rt
diff --git a/src/signal/x86_64/restore.s b/src/signal/x86_64/restore.s
index 682af2d..b5c6e37 100644
--- a/src/signal/x86_64/restore.s
+++ b/src/signal/x86_64/restore.s
@@ -1,8 +1,7 @@
+ nop
.global __restore_rt
-.global __restore
.type __restore_rt,@function
-.type __restore,@function
__restore_rt:
-__restore:
- movl $15, %eax
+ mov $15, %rax
syscall
+.size __restore_rt,.-__restore_rt
--
2.10.2
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] fix x86_64 sigreturn trampoline so gdb recognizes it
2016-11-13 0:12 ` [PATCH v2] fix x86_64 sigreturn trampoline " Szabolcs Nagy
@ 2016-11-13 2:46 ` Rich Felker
0 siblings, 0 replies; 3+ messages in thread
From: Rich Felker @ 2016-11-13 2:46 UTC (permalink / raw)
To: musl
On Sun, Nov 13, 2016 at 01:12:05AM +0100, Szabolcs Nagy wrote:
> gdb can only unwind across signal handlers if it recognizes the trampoline.
> on x86_64 this means the pc must be in a function called __restore_rt or
> if gdb cannot determine the symbol name the instruction sequence must match
> to what gdb expects.
>
> a nop is added before __restore_rt, the __restore alias is removed and
> size annotation is added to make sure gdb maps any pc value within
> __restore_rt unambigously to the __restore_rt symbol name.
>
> and the instruction sequence got fixed to match what gdb expects.
Thanks! Committed a patch based on this as discussed on irc.
Rich
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2016-11-13 2:46 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2016-11-12 17:07 [PATCH] fix x86_64 sigreturn call so gdb recognizes it Szabolcs Nagy
2016-11-13 0:12 ` [PATCH v2] fix x86_64 sigreturn trampoline " Szabolcs Nagy
2016-11-13 2:46 ` Rich Felker
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