[ARM] 3262/4: allow ptraced syscalls to be overriden
Patch from Nicolas Pitre
This is needed by strace to properly handle the tracing of some system
calls. It could be useful for other applications as well.
Based on an earlier patch from Daniel Jacobowitz.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Daniel Jacobowitz <dan@debian.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 8826d98..2b92ce8 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -214,11 +214,13 @@
* context switches, and waiting for our parent to respond.
*/
__sys_trace:
+ mov r2, scno
add r1, sp, #S_OFF
mov r0, #0 @ trace entry [IP = 0]
bl syscall_trace
adr lr, __sys_trace_return @ return address
+ mov scno, r0 @ syscall number (possibly new)
add r1, sp, #S_R0 + S_OFF @ pointer to regs
cmp scno, #NR_syscalls @ check upper syscall limit
ldmccia r1, {r0 - r3} @ have to reload r0 - r3
@@ -227,6 +229,7 @@
__sys_trace_return:
str r0, [sp, #S_R0 + S_OFF]! @ save returned r0
+ mov r2, scno
mov r1, sp
mov r0, #1 @ trace exit [IP = 1]
bl syscall_trace
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index e591f72b..7b6256b 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -766,6 +766,11 @@
(unsigned long __user *) data);
break;
+ case PTRACE_SET_SYSCALL:
+ ret = 0;
+ child->ptrace_message = data;
+ break;
+
default:
ret = ptrace_request(child, request, addr, data);
break;
@@ -774,14 +779,14 @@
return ret;
}
-asmlinkage void syscall_trace(int why, struct pt_regs *regs)
+asmlinkage int syscall_trace(int why, struct pt_regs *regs, int scno)
{
unsigned long ip;
if (!test_thread_flag(TIF_SYSCALL_TRACE))
- return;
+ return scno;
if (!(current->ptrace & PT_PTRACED))
- return;
+ return scno;
/*
* Save IP. IP is used to denote syscall entry/exit:
@@ -790,6 +795,8 @@
ip = regs->ARM_ip;
regs->ARM_ip = why;
+ current->ptrace_message = scno;
+
/* the 0x80 provides a way for the tracing parent to distinguish
between a syscall stop and SIGTRAP delivery */
ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
@@ -804,4 +811,6 @@
current->exit_code = 0;
}
regs->ARM_ip = ip;
+
+ return current->ptrace_message;
}