live-patching.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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

  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=587e0d68-48fd-6920-d803-2346ec00517b@linux.microsoft.com \
    --to=madvenka@linux.microsoft.com \
    --cc=ardb@kernel.org \
    --cc=broonie@kernel.org \
    --cc=catalin.marinas@arm.com \
    --cc=jmorris@namei.org \
    --cc=jpoimboe@redhat.com \
    --cc=jthierry@redhat.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=live-patching@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=pasha.tatashin@soleen.com \
    --cc=will@kernel.org \
    --subject='Re: [RFC PATCH v3 2/4] arm64: Check the return PC against unreliable code sections' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).