path: root/arch/arm64
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authorMark Rutland <mark.rutland@arm.com>2018-12-07 18:39:27 +0000
committerWill Deacon <will.deacon@arm.com>2018-12-13 16:42:46 +0000
commitccc43810827f9feb5e588e4b7098dc55b1d972f8 (patch)
treeda4af8576de9d0a0d470a6ec31331f4909667070 /arch/arm64
parentarm64: expose user PAC bit positions via ptrace (diff)
arm64: perf: strip PAC when unwinding userspace
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> Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to '')
2 files changed, 12 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index 2a22c03c1540..5ccf49b4dac3 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -69,6 +69,12 @@ static inline void ptrauth_keys_switch(struct ptrauth_keys *keys)
#define ptrauth_user_pac_mask() GENMASK(54, vabits_user)
+/* Only valid for EL0 TTBR0 instruction pointers */
+static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
+ return ptr & ~ptrauth_user_pac_mask();
#define ptrauth_thread_init_user(tsk) \
do { \
struct task_struct *__ptiu_tsk = (tsk); \
@@ -80,6 +86,7 @@ do { \
#else /* CONFIG_ARM64_PTR_AUTH */
+#define ptrauth_strip_insn_pac(lr) (lr)
#define ptrauth_thread_init_user(tsk)
#define ptrauth_thread_switch(tsk)
#endif /* CONFIG_ARM64_PTR_AUTH */
diff --git a/arch/arm64/kernel/perf_callchain.c b/arch/arm64/kernel/perf_callchain.c
index bcafd7dcfe8b..94754f07f67a 100644
--- a/arch/arm64/kernel/perf_callchain.c
+++ b/arch/arm64/kernel/perf_callchain.c
@@ -18,6 +18,7 @@
#include <linux/perf_event.h>
#include <linux/uaccess.h>
+#include <asm/pointer_auth.h>
#include <asm/stacktrace.h>
struct frame_tail {
@@ -35,6 +36,7 @@ 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 +49,9 @@ 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