From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
To: Mark Brown <broonie@kernel.org>
Cc: jpoimboe@redhat.com, mark.rutland@arm.com, jthierry@redhat.com,
catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org,
pasha.tatashin@soleen.com, linux-arm-kernel@lists.infradead.org,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v3 1/4] arm64: Introduce stack trace reliability checks in the unwinder
Date: Tue, 4 May 2021 14:14:19 -0500 [thread overview]
Message-ID: <66680284-8c80-1434-6c49-d86a47767168@linux.microsoft.com> (raw)
In-Reply-To: <20210504155056.GB7094@sirena.org.uk>
On 5/4/21 10:50 AM, Mark Brown wrote:
> On Mon, May 03, 2021 at 12:36:12PM -0500, madvenka@linux.microsoft.com wrote:
>
>> + /*
>> + * First, make sure that the return address is a proper kernel text
>> + * address. A NULL or invalid return address probably means there's
>> + * some generated code which __kernel_text_address() doesn't know
>> + * about. Mark the stack trace as not reliable.
>> + */
>> + if (!__kernel_text_address(frame->pc)) {
>> + frame->reliable = false;
>> + return 0;
>> + }
>
> Do we want the return here? It means that...
>
>> +
>> #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>> if (tsk->ret_stack &&
>> - (ptrauth_strip_insn_pac(frame->pc) == (unsigned long)return_to_handler)) {
>> + frame->pc == (unsigned long)return_to_handler) {
>> struct ftrace_ret_stack *ret_stack;
>> /*
>> * This is a case where function graph tracer has
>> @@ -103,11 +117,10 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
>> if (WARN_ON_ONCE(!ret_stack))
>> return -EINVAL;
>> frame->pc = ret_stack->ret;
>> + frame->pc = ptrauth_strip_insn_pac(frame->pc);
>> }
>
> ...we skip this handling in the case where we're not in kernel code. I
> don't know off hand if that's a case that can happen right now but it
> seems more robust to run through this and anything else we add later,
> even if it's not relevant now changes either in the unwinder itself or
> resulting from some future work elsewhere may mean it later becomes
> important. Skipping futher reliability checks is obviously fine if
> we've already decided things aren't reliable but this is more than just
> a reliability check.
>
AFAICT, currently, all the functions that the unwinder checks do have
valid kernel text addresses. However, I don't think there is any harm
in letting it fall through and make all the checks. So, I will remove the
return statement.
Thanks!
Madhavan
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next prev parent reply other threads:[~2021-05-04 19:16 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <65cf4dfbc439b010b50a0c46ec500432acde86d6>
2021-05-03 17:36 ` [RFC PATCH v3 0/4] arm64: Stack trace reliability checks in the unwinder madvenka
2021-05-03 17:36 ` [RFC PATCH v3 1/4] arm64: Introduce stack " madvenka
2021-05-04 15:50 ` Mark Brown
2021-05-04 19:14 ` Madhavan T. Venkataraman [this message]
2021-05-04 21:52 ` Josh Poimboeuf
2021-05-04 23:13 ` Madhavan T. Venkataraman
2021-05-05 0:07 ` Josh Poimboeuf
2021-05-05 0:21 ` Madhavan T. Venkataraman
2021-05-03 17:36 ` [RFC PATCH v3 2/4] arm64: Check the return PC against unreliable code sections madvenka
2021-05-04 16:05 ` Mark Brown
2021-05-04 19:03 ` Madhavan T. Venkataraman
2021-05-04 19:32 ` Madhavan T. Venkataraman
2021-05-05 16:46 ` Mark Brown
2021-05-05 18:48 ` Madhavan T. Venkataraman
2021-05-05 18:50 ` Madhavan T. Venkataraman
2021-05-06 13:45 ` Mark Brown
2021-05-06 15:21 ` Madhavan T. Venkataraman
2021-05-05 16:34 ` Mark Brown
2021-05-05 17:51 ` Madhavan T. Venkataraman
2021-05-05 19:30 ` Ard Biesheuvel
2021-05-05 20:00 ` Madhavan T. Venkataraman
2021-05-03 17:36 ` [RFC PATCH v3 3/4] arm64: Handle miscellaneous functions in .text and .init.text madvenka
2021-05-06 14:12 ` Mark Brown
2021-05-06 15:30 ` Madhavan T. Venkataraman
2021-05-06 15:32 ` Madhavan T. Venkataraman
2021-05-06 15:44 ` Mark Brown
2021-05-06 15:56 ` Madhavan T. Venkataraman
2021-05-06 15:37 ` Mark Brown
2021-05-06 15:57 ` Madhavan T. Venkataraman
2021-05-03 17:36 ` [RFC PATCH v3 4/4] arm64: Handle funtion graph tracer better in the unwinder madvenka
2021-05-06 14:43 ` Mark Brown
2021-05-06 15:20 ` Madhavan T. Venkataraman
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