Set SA_RESTORER in sigaction()
GDB looks for specific opcode sequences when trying to recognize a stack
frame as a signal trampoline. The sequences it looks for happen to be those
created when SA_RESTORER is set, since glibc always sets a restorer. This
patch does the same here, so that the trampolines can be correctly identified.
Change-Id: I0ac574a68818cb24d939c3527f3aaeb04b853d04
diff --git a/libc/arch-arm/bionic/__sig_restorer.S b/libc/arch-arm/bionic/__sig_restorer.S
new file mode 100644
index 0000000..3f6f284
--- /dev/null
+++ b/libc/arch-arm/bionic/__sig_restorer.S
@@ -0,0 +1,7 @@
+.global __sig_restorer
+
+/* This is the opcode sequence GDB looks for in order to recognize
+ this stack frame as a signal trampoline (see sigaction.c) */
+__sig_restorer:
+ mov r7, #119 /* __NR_sigreturn */
+ swi #0
diff --git a/libc/arch-arm/bionic/sigaction.c b/libc/arch-arm/bionic/sigaction.c
new file mode 100644
index 0000000..96ca7c6
--- /dev/null
+++ b/libc/arch-arm/bionic/sigaction.c
@@ -0,0 +1,29 @@
+#include <signal.h>
+
+extern int __sigaction(int signum, const struct sigaction *act, struct sigaction *oldact);
+extern void __sig_restorer();
+
+int sigaction(int signum, const struct sigaction *act, struct sigaction *oldact)
+{
+ struct sigaction real_act;
+
+ /* If the caller has not set a custom restorer, then set up a default one.
+ * The code will function properly without this, however GDB will not be
+ * able to recognize the stack frame as a signal trampoline, because it
+ * is hardcoded to look for the instruction sequence that glibc uses in
+ * its custom restorer. By creating our own restorer with the same
+ * sequence, we ensure that GDB correctly identifies this as a signal
+ * trampoline frame.
+ *
+ * See http://sourceware.org/ml/gdb/2010-01/msg00143.html for more
+ * information on this.*/
+ if(act && !(act->sa_flags & SA_RESTORER)) {
+ real_act = *act;
+ real_act.sa_flags |= SA_RESTORER;
+ real_act.sa_restorer = __sig_restorer;
+
+ act = &real_act;
+ }
+
+ return __sigaction(signum, act, oldact);
+}
diff --git a/libc/arch-arm/syscalls.mk b/libc/arch-arm/syscalls.mk
index 706cb0c..f4cb63a 100644
--- a/libc/arch-arm/syscalls.mk
+++ b/libc/arch-arm/syscalls.mk
@@ -120,13 +120,13 @@
syscall_src += arch-arm/syscalls/__timer_getoverrun.S
syscall_src += arch-arm/syscalls/__timer_delete.S
syscall_src += arch-arm/syscalls/utimes.S
-syscall_src += arch-arm/syscalls/sigaction.S
syscall_src += arch-arm/syscalls/sigprocmask.S
syscall_src += arch-arm/syscalls/__sigsuspend.S
syscall_src += arch-arm/syscalls/__rt_sigaction.S
syscall_src += arch-arm/syscalls/__rt_sigprocmask.S
syscall_src += arch-arm/syscalls/__rt_sigtimedwait.S
syscall_src += arch-arm/syscalls/sigpending.S
+syscall_src += arch-arm/syscalls/__sigaction.S
syscall_src += arch-arm/syscalls/socket.S
syscall_src += arch-arm/syscalls/socketpair.S
syscall_src += arch-arm/syscalls/bind.S
diff --git a/libc/arch-arm/syscalls/sigaction.S b/libc/arch-arm/syscalls/__sigaction.S
similarity index 81%
rename from libc/arch-arm/syscalls/sigaction.S
rename to libc/arch-arm/syscalls/__sigaction.S
index 2696f1e..aba44b8 100644
--- a/libc/arch-arm/syscalls/sigaction.S
+++ b/libc/arch-arm/syscalls/__sigaction.S
@@ -2,12 +2,12 @@
#include <sys/linux-syscalls.h>
.text
- .type sigaction, #function
- .globl sigaction
+ .type __sigaction, #function
+ .globl __sigaction
.align 4
.fnstart
-sigaction:
+__sigaction:
.save {r4, r7}
stmfd sp!, {r4, r7}
ldr r7, =__NR_sigaction