@@ -79,6 +79,12 @@ static inline void ptrauth_keys_dup(struct ptrauth_keys *old,
*/
#define ptrauth_pac_mask() GENMASK(54, VA_BITS)
+/* Only valid for EL0 TTBR0 instruction pointers */
+static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
+{
+ return ptr & ~ptrauth_pac_mask();
+}
+
#define mm_ctx_ptrauth_init(ctx) \
ptrauth_keys_init(&(ctx)->ptrauth_keys)
@@ -89,6 +95,7 @@ static inline void ptrauth_keys_dup(struct ptrauth_keys *old,
ptrauth_keys_dup(&(oldctx)->ptrauth_keys, &(newctx)->ptrauth_keys)
#else
+#define ptrauth_strip_insn_pac(lr) (lr)
#define mm_ctx_ptrauth_init(ctx)
#define mm_ctx_ptrauth_switch(ctx)
#define mm_ctx_ptrauth_dup(oldctx, newctx)
@@ -35,6 +35,7 @@ user_backtrace(struct frame_tail __user *tail,
{
struct frame_tail buftail;
unsigned long err;
+ unsigned long lr;
/* Also check accessibility of one struct frame_tail beyond */
if (!access_ok(VERIFY_READ, tail, sizeof(buftail)))
@@ -47,7 +48,9 @@ user_backtrace(struct frame_tail __user *tail,
if (err)
return NULL;
- perf_callchain_store(entry, buftail.lr);
+ lr = ptrauth_strip_insn_pac(buftail.lr);
+
+ perf_callchain_store(entry, lr);
/*
* Frame pointers should strictly progress back up the stack
When the kernel is unwinding userspace callchains, we can't expect that the userspace consumer of these callchains has the data necessary to strip the PAC from the stored LR. This patch has the kernel strip the PAC from user stackframes when the in-kernel unwinder is used. This only affects the LR value, and not the FP. This only affects the in-kernel unwinder. When userspace performs unwinding, it is up to userspace to strip PACs as necessary (which can be determined from DWARF information). Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Yao Qi <yao.qi@arm.com> --- arch/arm64/include/asm/pointer_auth.h | 7 +++++++ arch/arm64/kernel/perf_callchain.c | 5 ++++- 2 files changed, 11 insertions(+), 1 deletion(-)