arm64: unwind: strip PAC from kernel addresses

When we enable pointer authentication in the kernel, LR values saved to
the stack will have a PAC which we must strip in order to retrieve the
real return address.

Strip PACs when unwinding the stack in order to account for this.

When function graph tracer is used with patchable-function-entry then
return_to_handler will also have pac bits so strip it too.

Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
[Amit: Re-position ptrauth_strip_insn_pac, comment]
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index a336cb124320f789b35ec778a73e8bc6791b8177..139679c745bf78ac7946aabf528205f9525d4477 100644 (file)
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -14,6 +14,7 @@
 #include <linux/stacktrace.h>
 
 #include <asm/irq.h>
+#include <asm/pointer_auth.h>
 #include <asm/stack_pointer.h>
 #include <asm/stacktrace.h>
 
@@ -86,7 +87,7 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
        if (tsk->ret_stack &&
-                       (frame->pc == (unsigned long)return_to_handler)) {
+               (ptrauth_strip_insn_pac(frame->pc) == (unsigned long)return_to_handler)) {
                struct ftrace_ret_stack *ret_stack;
                /*
                 * This is a case where function graph tracer has
@@ -101,6 +102,8 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
        }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 
+       frame->pc = ptrauth_strip_insn_pac(frame->pc);
+
        /*
         * Frames created upon entry from EL0 have NULL FP and PC values, so
         * don't bother reporting these. Frames created by __noreturn functions