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authorMarc Zyngier <marc.zyngier@arm.com>2016-07-21 09:44:17 +0100
committerAlex Shi <alex.shi@linaro.org>2016-10-20 15:38:13 +0800
commita5d55dd10f2a061849e7a665aa4b16bf258d9d0a (patch)
tree1793b968dfc363f5a370ac75b9a16f823063bf97
parent71b5200f5f0c1e9966dd7d238526e85f4fbf8089 (diff)
downloadlinux-linaro-stable-a5d55dd10f2a061849e7a665aa4b16bf258d9d0a.tar.gz
arm64: kprobes: Cleanup jprobe_return
commit 3b7d14e9f3f1efd4c4348800e977fd1ce4ca660e upstream. jprobe_return seems to have aged badly. Comments referring to non-existent behaviours, and a dangerous habit of messing with registers without telling the compiler. This patches applies the following remedies: - Fix the comments to describe the actual behaviour - Tidy up the asm sequence to directly assign the stack pointer without clobbering extra registers - Mark the rest of the function as unreachable() so that the compiler knows that there is no need for an epilogue - Stop making jprobe_return_break a global function (you really don't want to call that guy, and it isn't even a function). Tested with tcp_probe. Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: David A. Long <dave.long@linaro.org>
-rw-r--r--arch/arm64/kernel/probes/kprobes.c22
1 files changed, 10 insertions, 12 deletions
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index b1189741dbb0..235455412caa 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -34,8 +34,6 @@
#include "decode-insn.h"
-void jprobe_return_break(void);
-
DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@@ -513,18 +511,17 @@ void __kprobes jprobe_return(void)
/*
* Jprobe handler return by entering break exception,
* encoded same as kprobe, but with following conditions
- * -a magic number in x0 to identify from rest of other kprobes.
+ * -a special PC to identify it from the other kprobes.
* -restore stack addr to original saved pt_regs
*/
- asm volatile ("ldr x0, [%0]\n\t"
- "mov sp, x0\n\t"
- ".globl jprobe_return_break\n\t"
- "jprobe_return_break:\n\t"
- "brk %1\n\t"
- :
- : "r"(&kcb->jprobe_saved_regs.sp),
- "I"(BRK64_ESR_KPROBES)
- : "memory");
+ asm volatile(" mov sp, %0 \n"
+ "jprobe_return_break: brk %1 \n"
+ :
+ : "r" (kcb->jprobe_saved_regs.sp),
+ "I" (BRK64_ESR_KPROBES)
+ : "memory");
+
+ unreachable();
}
int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
@@ -533,6 +530,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
long stack_addr = kcb->jprobe_saved_regs.sp;
long orig_sp = kernel_stack_pointer(regs);
struct jprobe *jp = container_of(p, struct jprobe, kp);
+ extern const char jprobe_return_break[];
if (instruction_pointer(regs) != (u64) jprobe_return_break)
return 0;