[ARM] 5559/1: Limit the stack unwinding caused by a kthread exit
When a kthread function returns, it branches to do_exit(). However, the
unwinding information isn't valid anymore and any stack trace caused by
do_exit() may be incorrect. This patch adds a kernel_thread_exit()
function and annotated with '.cantunwind' so that the unwinder stops
when reaching it.
Tested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 1585423..56820cc 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -352,6 +352,23 @@
" .size kernel_thread_helper, . - kernel_thread_helper\n"
" .previous");
+#ifdef CONFIG_ARM_UNWIND
+extern void kernel_thread_exit(long code);
+asm( ".section .text\n"
+" .align\n"
+" .type kernel_thread_exit, #function\n"
+"kernel_thread_exit:\n"
+" .fnstart\n"
+" .cantunwind\n"
+" bl do_exit\n"
+" nop\n"
+" .fnend\n"
+" .size kernel_thread_exit, . - kernel_thread_exit\n"
+" .previous");
+#else
+#define kernel_thread_exit do_exit
+#endif
+
/*
* Create a kernel thread.
*/
@@ -363,7 +380,7 @@
regs.ARM_r1 = (unsigned long)arg;
regs.ARM_r2 = (unsigned long)fn;
- regs.ARM_r3 = (unsigned long)do_exit;
+ regs.ARM_r3 = (unsigned long)kernel_thread_exit;
regs.ARM_pc = (unsigned long)kernel_thread_helper;
regs.ARM_cpsr = SVC_MODE | PSR_ENDSTATE;