From: madvenka@linux.microsoft.com
To: broonie@kernel.org, mark.rutland@arm.com, jpoimboe@redhat.com,
ardb@kernel.org, nobuta.keiya@fujitsu.com,
sjitindarsingh@gmail.com, catalin.marinas@arm.com,
will@kernel.org, jmorris@namei.org, pasha.tatashin@soleen.com,
jthierry@redhat.com, linux-arm-kernel@lists.infradead.org,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org,
madvenka@linux.microsoft.com
Subject: [RFC PATCH v6 2/3] arm64: Introduce stack trace reliability checks in the unwinder
Date: Wed, 30 Jun 2021 17:33:55 -0500 [thread overview]
Message-ID: <20210630223356.58714-3-madvenka@linux.microsoft.com> (raw)
In-Reply-To: <20210630223356.58714-1-madvenka@linux.microsoft.com>
From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
The unwinder should check for the presence of various features and
conditions that can render the stack trace unreliable. Introduce a
function unwind_check_frame() for this purpose.
Introduce the first reliability check in unwind_check_frame() - If
a return PC is not a valid kernel text address, consider the stack
trace unreliable. It could be some generated code.
Other reliability checks will be added in the future.
If a reliability check fails, it is a non-fatal error. Introduce a new
return code, UNWIND_CONTINUE_WITH_RISK, for non-fatal errors.
Call unwind_check_frame() from unwind_frame(). Also, call it from
start_backtrace() to remove the current assumption that the starting
frame is reliable.
Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
---
arch/arm64/include/asm/stacktrace.h | 4 +++-
arch/arm64/kernel/stacktrace.c | 17 ++++++++++++++++-
2 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 6fcd58553fb1..d1625d55b980 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -32,6 +32,7 @@ struct stack_info {
enum unwind_rc {
UNWIND_CONTINUE, /* No errors encountered */
+ UNWIND_CONTINUE_WITH_RISK, /* Non-fatal errors encountered */
UNWIND_ABORT, /* Fatal errors encountered */
UNWIND_FINISH, /* End of stack reached successfully */
};
@@ -73,6 +74,7 @@ extern void walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
bool (*fn)(void *, unsigned long), void *data);
extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
const char *loglvl);
+extern enum unwind_rc unwind_check_frame(struct stackframe *frame);
DECLARE_PER_CPU(unsigned long *, irq_stack_ptr);
@@ -176,7 +178,7 @@ static inline enum unwind_rc start_backtrace(struct stackframe *frame,
bitmap_zero(frame->stacks_done, __NR_STACK_TYPES);
frame->prev_fp = 0;
frame->prev_type = STACK_TYPE_UNKNOWN;
- return UNWIND_CONTINUE;
+ return unwind_check_frame(frame);
}
#endif /* __ASM_STACKTRACE_H */
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index e9c2c1fa9dde..ba7b97b119e4 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -18,6 +18,21 @@
#include <asm/stack_pointer.h>
#include <asm/stacktrace.h>
+/*
+ * Check the stack frame for conditions that make unwinding unreliable.
+ */
+enum unwind_rc unwind_check_frame(struct stackframe *frame)
+{
+ /*
+ * If the PC is not a known kernel text address, then we cannot
+ * be sure that a subsequent unwind will be reliable, as we
+ * don't know that the code follows our unwind requirements.
+ */
+ if (!__kernel_text_address(frame->pc))
+ return UNWIND_CONTINUE_WITH_RISK;
+ return UNWIND_CONTINUE;
+}
+
/*
* AArch64 PCS assigns the frame pointer to x29.
*
@@ -109,7 +124,7 @@ enum unwind_rc notrace unwind_frame(struct task_struct *tsk,
frame->pc = ptrauth_strip_insn_pac(frame->pc);
- return UNWIND_CONTINUE;
+ return unwind_check_frame(frame);
}
NOKPROBE_SYMBOL(unwind_frame);
--
2.25.1
next prev parent reply other threads:[~2021-06-30 22:34 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <3f2aab69a35c243c5e97f47c4ad84046355f5b90>
2021-06-30 22:33 ` [RFC PATCH v6 0/3] arm64: Implement stack trace reliability checks madvenka
2021-06-30 22:33 ` [RFC PATCH v6 1/3] arm64: Improve the unwinder return value madvenka
2021-07-28 16:56 ` Mark Rutland
2021-07-29 13:54 ` Madhavan T. Venkataraman
2021-06-30 22:33 ` madvenka [this message]
2021-06-30 22:33 ` [RFC PATCH v6 3/3] arm64: Create a list of SYM_CODE functions, check return PC against list madvenka
2021-07-28 17:25 ` Mark Rutland
2021-07-29 14:06 ` Madhavan T. Venkataraman
2021-07-29 14:52 ` Mark Brown
2021-07-29 17:07 ` Madhavan T. Venkataraman
2021-07-29 15:48 ` Mark Rutland
2021-07-29 16:27 ` Mark Brown
2021-07-29 17:09 ` Madhavan T. Venkataraman
2021-07-26 13:49 ` [RFC PATCH v6 0/3] arm64: Implement stack trace reliability checks Madhavan T. Venkataraman
2021-08-12 13:24 ` [RFC PATCH v7 0/4] arm64: Reorganize the unwinder and implement " madvenka
2021-08-12 13:24 ` [RFC PATCH v7 1/4] arm64: Make all stack walking functions use arch_stack_walk() madvenka
2021-08-12 15:23 ` Mark Brown
2021-08-12 16:30 ` Madhavan T. Venkataraman
2021-08-12 13:24 ` [RFC PATCH v7 2/4] arm64: Reorganize the unwinder code for better consistency and maintenance madvenka
2021-08-12 13:24 ` [RFC PATCH v7 3/4] arm64: Introduce stack trace reliability checks in the unwinder madvenka
2021-08-12 13:24 ` [RFC PATCH v7 4/4] arm64: Create a list of SYM_CODE functions, check return PC against list madvenka
2021-08-12 18:31 ` [RFC PATCH v7 0/4] arm64: Reorganize the unwinder and implement stack trace reliability checks Madhavan T. Venkataraman
2021-08-12 18:45 ` Madhavan T. Venkataraman
2021-08-12 18:35 ` madvenka
2021-08-12 18:35 ` [RFC PATCH v7 1/4] arm64: Make all stack walking functions use arch_stack_walk() madvenka
2021-08-12 18:35 ` [RFC PATCH v7 2/4] arm64: Reorganize the unwinder code for better consistency and maintenance madvenka
2021-08-12 18:35 ` [RFC PATCH v7 3/4] arm64: Introduce stack trace reliability checks in the unwinder madvenka
2021-08-12 18:35 ` [RFC PATCH v7 4/4] arm64: Create a list of SYM_CODE functions, check return PC against list madvenka
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