From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Mark Brown <broonie@kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Mark Rutland <mark.rutland@arm.com>,
Julien Thierry <jthierry@redhat.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, James Morris <jmorris@namei.org>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
live-patching@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH v3 2/4] arm64: Check the return PC against unreliable code sections
Date: Wed, 5 May 2021 15:00:43 -0500 [thread overview]
Message-ID: <587e0d68-48fd-6920-d803-2346ec00517b@linux.microsoft.com> (raw)
In-Reply-To: <CAMj1kXGcv3+=sXUswSFvhm1K2PZj+qVSSa7XBte9NqxeBNn5dA@mail.gmail.com>
OK. I will make all the changes you suggested.
Thanks!
Madhavan
On 5/5/21 2:30 PM, Ard Biesheuvel wrote:
> On Mon, 3 May 2021 at 19:38, <madvenka@linux.microsoft.com> wrote:
>>
>> From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
>>
>> Create a sym_code_ranges[] array to cover the following text sections that
>> contain functions defined as SYM_CODE_*(). These functions are low-level
>> functions (and do not have a proper frame pointer prolog and epilog). So,
>> they are inherently unreliable from a stack unwinding perspective.
>>
>> .entry.text
>> .idmap.text
>> .hyp.idmap.text
>> .hyp.text
>> .hibernate_exit.text
>> .entry.tramp.text
>>
>> If a return PC falls in any of these, mark the stack trace unreliable.
>>
>> The only exception to this is - if the unwinder has reached the last
>> frame already, it will not mark the stack trace unreliable since there
>> is no more unwinding to do. E.g.,
>>
>> - ret_from_fork() occurs at the end of the stack trace of
>> kernel tasks.
>>
>> - el0_*() functions occur at the end of EL0 exception stack
>> traces. This covers all user task entries into the kernel.
>>
>> NOTE:
>> - EL1 exception handlers are in .entry.text. So, stack traces that
>> contain those functions will be marked not reliable. This covers
>> interrupts, exceptions and breakpoints encountered while executing
>> in the kernel.
>>
>> - At the end of an interrupt, the kernel can preempt the current
>> task if required. So, the stack traces of all preempted tasks will
>> show the interrupt frame and will be considered unreliable.
>>
>> Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
>> ---
>> arch/arm64/kernel/stacktrace.c | 54 ++++++++++++++++++++++++++++++++++
>> 1 file changed, 54 insertions(+)
>>
>> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
>> index c21a1bca28f3..1ff14615a55a 100644
>> --- a/arch/arm64/kernel/stacktrace.c
>> +++ b/arch/arm64/kernel/stacktrace.c
>> @@ -15,9 +15,48 @@
>>
>> #include <asm/irq.h>
>> #include <asm/pointer_auth.h>
>> +#include <asm/sections.h>
>> #include <asm/stack_pointer.h>
>> #include <asm/stacktrace.h>
>>
>> +struct code_range {
>> + unsigned long start;
>> + unsigned long end;
>> +};
>> +
>> +struct code_range sym_code_ranges[] =
>
> This should be static and const
>
>> +{
>> + /* non-unwindable ranges */
>> + { (unsigned long)__entry_text_start,
>> + (unsigned long)__entry_text_end },
>> + { (unsigned long)__idmap_text_start,
>> + (unsigned long)__idmap_text_end },
>> + { (unsigned long)__hyp_idmap_text_start,
>> + (unsigned long)__hyp_idmap_text_end },
>> + { (unsigned long)__hyp_text_start,
>> + (unsigned long)__hyp_text_end },
>> +#ifdef CONFIG_HIBERNATION
>> + { (unsigned long)__hibernate_exit_text_start,
>> + (unsigned long)__hibernate_exit_text_end },
>> +#endif
>> +#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
>> + { (unsigned long)__entry_tramp_text_start,
>> + (unsigned long)__entry_tramp_text_end },
>> +#endif
>> + { /* sentinel */ }
>> +};
>> +
>> +static struct code_range *lookup_range(unsigned long pc)
>
> const struct code_range *
>
>> +{
>> + struct code_range *range;
>
> const struct code_range *
>
>> +
>> + for (range = sym_code_ranges; range->start; range++) {
>> + if (pc >= range->start && pc < range->end)
>> + return range;
>> + }
>> + return range;
>> +}
>> +
>> /*
>> * AArch64 PCS assigns the frame pointer to x29.
>> *
>> @@ -43,6 +82,7 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
>> {
>> unsigned long fp = frame->fp;
>> struct stack_info info;
>> + struct code_range *range;
>
> const struct code_range *
>
>>
>> frame->reliable = true;
>>
>> @@ -103,6 +143,8 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
>> return 0;
>> }
>>
>> + range = lookup_range(frame->pc);
>> +
>> #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>> if (tsk->ret_stack &&
>> frame->pc == (unsigned long)return_to_handler) {
>> @@ -118,9 +160,21 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
>> return -EINVAL;
>> frame->pc = ret_stack->ret;
>> frame->pc = ptrauth_strip_insn_pac(frame->pc);
>> + return 0;
>> }
>> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
>>
>> + if (!range->start)
>> + return 0;
>> +
>> + /*
>> + * The return PC falls in an unreliable function. If the final frame
>> + * has been reached, no more unwinding is needed. Otherwise, mark the
>> + * stack trace not reliable.
>> + */
>> + if (frame->fp)
>> + frame->reliable = false;
>> +
>> return 0;
>> }
>> NOKPROBE_SYMBOL(unwind_frame);
>> --
>> 2.25.1
>>
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-05-05 20:00 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
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 [this message]
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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