1 files changed, 55 insertions, 16 deletions

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index b6e046e4b289..fce99e249d61 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -809,7 +809,7 @@ void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
 	ri->fp = sara;
 
 	/* Replace the return addr with trampoline addr */
-	*sara = (unsigned long) &kretprobe_trampoline;
+	*sara = (unsigned long) &__kretprobe_trampoline;
 }
 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 
@@ -1019,52 +1019,91 @@ NOKPROBE_SYMBOL(kprobe_int3_handler);
  */
 asm(
 	".text\n"
-	".global kretprobe_trampoline\n"
-	".type kretprobe_trampoline, @function\n"
-	"kretprobe_trampoline:\n"
-	/* We don't bother saving the ss register */
+	".global __kretprobe_trampoline\n"
+	".type __kretprobe_trampoline, @function\n"
+	"__kretprobe_trampoline:\n"
 #ifdef CONFIG_X86_64
+	/* Push a fake return address to tell the unwinder it's a kretprobe. */
+	"	pushq $__kretprobe_trampoline\n"
+	UNWIND_HINT_FUNC
+	/* Save the 'sp - 8', this will be fixed later. */
 	"	pushq %rsp\n"
 	"	pushfq\n"
 	SAVE_REGS_STRING
 	"	movq %rsp, %rdi\n"
 	"	call trampoline_handler\n"
-	/* Replace saved sp with true return address. */
-	"	movq %rax, 19*8(%rsp)\n"
 	RESTORE_REGS_STRING
+	/* In trampoline_handler(), 'regs->flags' is copied to 'regs->sp'. */
+	"	addq $8, %rsp\n"
 	"	popfq\n"
 #else
+	/* Push a fake return address to tell the unwinder it's a kretprobe. */
+	"	pushl $__kretprobe_trampoline\n"
+	UNWIND_HINT_FUNC
+	/* Save the 'sp - 4', this will be fixed later. */
 	"	pushl %esp\n"
 	"	pushfl\n"
 	SAVE_REGS_STRING
 	"	movl %esp, %eax\n"
 	"	call trampoline_handler\n"
-	/* Replace saved sp with true return address. */
-	"	movl %eax, 15*4(%esp)\n"
 	RESTORE_REGS_STRING
+	/* In trampoline_handler(), 'regs->flags' is copied to 'regs->sp'. */
+	"	addl $4, %esp\n"
 	"	popfl\n"
 #endif
 	"	ret\n"
-	".size kretprobe_trampoline, .-kretprobe_trampoline\n"
+	".size __kretprobe_trampoline, .-__kretprobe_trampoline\n"
 );
-NOKPROBE_SYMBOL(kretprobe_trampoline);
-STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
+NOKPROBE_SYMBOL(__kretprobe_trampoline);
+/*
+ * __kretprobe_trampoline() skips updating frame pointer. The frame pointer
+ * saved in trampoline_handler() points to the real caller function's
+ * frame pointer. Thus the __kretprobe_trampoline() doesn't have a
+ * standard stack frame with CONFIG_FRAME_POINTER=y.
+ * Let's mark it non-standard function. Anyway, FP unwinder can correctly
+ * unwind without the hint.
+ */
+STACK_FRAME_NON_STANDARD_FP(__kretprobe_trampoline);
+
+/* This is called from kretprobe_trampoline_handler(). */
+void arch_kretprobe_fixup_return(struct pt_regs *regs,
+				 kprobe_opcode_t *correct_ret_addr)
+{
+	unsigned long *frame_pointer = &regs->sp + 1;
 
+	/* Replace fake return address with real one. */
+	*frame_pointer = (unsigned long)correct_ret_addr;
+}
 
 /*
- * Called from kretprobe_trampoline
+ * Called from __kretprobe_trampoline
  */
-__used __visible void *trampoline_handler(struct pt_regs *regs)
+__used __visible void trampoline_handler(struct pt_regs *regs)
 {
+	unsigned long *frame_pointer;
+
 	/* fixup registers */
 	regs->cs = __KERNEL_CS;
 #ifdef CONFIG_X86_32
 	regs->gs = 0;
 #endif
-	regs->ip = (unsigned long)&kretprobe_trampoline;
+	regs->ip = (unsigned long)&__kretprobe_trampoline;
 	regs->orig_ax = ~0UL;
+	regs->sp += sizeof(long);
+	frame_pointer = &regs->sp + 1;
 
-	return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline, &regs->sp);
+	/*
+	 * The return address at 'frame_pointer' is recovered by the
+	 * arch_kretprobe_fixup_return() which called from the
+	 * kretprobe_trampoline_handler().
+	 */
+	kretprobe_trampoline_handler(regs, frame_pointer);
+
+	/*
+	 * Copy FLAGS to 'pt_regs::sp' so that __kretprobe_trapmoline()
+	 * can do RET right after POPF.
+	 */
+	regs->sp = regs->flags;
 }
 NOKPROBE_SYMBOL(trampoline_handler);