Hi lianbo attached pacth v3.
> Can you help double check if a sanity check needs to be added? I saw the
value 'pc|mask' is always checked in crash code as below:
> ...
> LR = regs->regs[30];
> if (is_kernel_text (LR | ms->CONFIG_ARM64_KERNELPACMASK))
> LR |= ms->CONFIG_ARM64_KERNELPACMASK;
> ...
> if yes, the value pc can be passed as an argument in
crash_get_kernel_pac_mask(), and then deal with this one.
/* arm64 kernel lr maybe has patuh */
void crash_decode_ptrauth_pc(ulong *pc);
void crash_decode_ptrauth_pc(ulong *pc)
{
#ifdef ARM64
struct machine_specific *ms = machdep->machspec;
if (is_kernel_text(*pc | ms->CONFIG_ARM64_KERNELPACMASK))
*pc |= ms->CONFIG_ARM64_KERNELPACMASK;
#endif /* !ARM64 */
}
Guanyou Chen <chenguanyou9...@gmail.com> 于2025年1月15日周三 17:55写道：
> Hi lianbo
>
> attach patch v2.
>
> lijiang <liji...@redhat.com> 于2025年1月15日周三 16:42写道：
>
>> Thank you for the patch, Guanyou.
>>
>> On Tue, Dec 31, 2024 at 7:22 PM <
>> devel-requ...@lists.crash-utility.osci.io> wrote:
>>
>>> Date: Thu, 26 Dec 2024 00:08:50 +0800
>>> From: Guanyou Chen <chenguanyou9...@gmail.com>
>>> Subject: [Crash-utility] [PATCH] arm64: add pac mask to better support
>>> gdb stack unwind
>>> To: Lianbo <liji...@redhat.com>, Tao Liu <l...@redhat.com>,
>>> devel@lists.crash-utility.osci.io
>>> Message-ID:
>>> <
>>> cahs3rmxjg6oxb_zmgnr60kripoxo9tnb_63k+rjjhfk1t7a...@mail.gmail.com>
>>> Content-Type: multipart/mixed; boundary="0000000000009f35d6062a1a727c"
>>>
>>> --0000000000009f35d6062a1a727c
>>> Content-Type: multipart/alternative;
>>> boundary="0000000000009f35d5062a1a727a"
>>>
>>> --0000000000009f35d5062a1a727a
>>> Content-Type: text/plain; charset="UTF-8"
>>>
>>> Hi Lianbo & Tao
>>>
>>> Currently, gdb passthroughs of 'bt', 'frame', 'up', 'down',
>>> 'info, locals' don't work on arm64 machine enabled pauth.
>>> This is due to gdb not knowing the lr register real values
>>> to unwind the stack frames.
>>>
>>> ----------------------------
>>> gdb passthrough (eg. "bt") | |
>>> crash -------------------------> | |
>>> | gdb_interface |
>>> | |
>>> | |
>>> | ---------------------- |
>>> get_kernel_pac_mask | | | |
>>> crash_target<-------------------------+--| gdb | |
>>> --------------------------+->| | |
>>> arm64: CONFIG_ARM64_KERNELPACMASK| | | |
>>> other: ~0UL | | | |
>>> | ---------------------- |
>>> ----------------------------
>>>
>>> With the patch:
>>> crash> gdb bt
>>> #0 __switch_to (prev=prev@entry=0xffffff8001af92c0,
>>> next=next@entry=0xffffff889da7a580)
>>> at /proc/self/cwd/common/arch/arm64/kernel/process.c:569
>>> #1 0xffffffd3602132c0 in context_switch (rq=0xffffff8a7295a080,
>>> prev=0xffffff8001af92c0, next=0xffffff889da7a580, rf=<optimized out>) at
>>> /proc/self/cwd/common/kernel/sched/core.c:5515
>>> #2 __schedule (sched_mode=<optimized out>, sched_mode@entry
>>> =2147859424)
>>> at /proc/self/cwd/common/kernel/sched/core.c:6843
>>> #3 0xffffffd3602136d8 in schedule () at
>>> /proc/self/cwd/common/kernel/sched/core.c:6917
>>> ...
>>>
>>> Without the patch:
>>> crash> gdb bt
>>> #0 __switch_to (prev=0xffffff8001af92c0, next=0xffffff889da7a580) at
>>> /proc/self/cwd/common/arch/arm64/kernel/process.c:569
>>> #1 0x9fc5c5d3602132c0 in ?? ()
>>> Backtrace stopped: previous frame identical to this frame (corrupt
>>> stack?)
>>>
>>> Signed-off-by: Guanyou.Chen <chenguan...@xiaomi.com>
>>> ---
>>> gdb-10.2.patch | 24 ++++++++++++++++++++++++
>>> gdb_interface.c | 11 +++++++++++
>>> 2 files changed, 35 insertions(+)
>>>
>>> diff --git a/gdb-10.2.patch b/gdb-10.2.patch
>>> index c867660..4c13a6b 100644
>>> --- a/gdb-10.2.patch
>>> +++ b/gdb-10.2.patch
>>> @@ -16216,3 +16216,27 @@ exit 0
>>> printf_filtered (_("Backtrace stopped: %s\n"),
>>> frame_stop_reason_string (trailing));
>>> }
>>> +--- gdb-10.2/gdb/frame.c.orig
>>> ++++ gdb-10.2/gdb/frame.c
>>> +@@ -944,6 +944,10 @@ frame_find_by_id (struct frame_id id)
>>> + return NULL;
>>> + }
>>> +
>>> ++#ifdef CRASH_MERGE
>>> ++extern "C" unsigned long crash_get_kernel_pac_mask(void);
>>> ++#endif
>>> ++
>>> + static CORE_ADDR
>>> + frame_unwind_pc (frame_info_ptr this_frame)
>>> + {
>>> +@@ -974,6 +978,10 @@ frame_unwind_pc (struct frame_info_ptr *this_frame)
>>> + try
>>> + {
>>> + pc = gdbarch_unwind_pc (prev_gdbarch, this_frame);
>>> ++#ifdef CRASH_MERGE
>>> ++ CORE_ADDR mask = crash_get_kernel_pac_mask();
>>> ++ pc |= mask;
>>>
>>
>> Can you help double check if a sanity check needs to be added? I saw the
>> value 'pc|mask' is always checked in crash code as below:
>> ...
>> LR = regs->regs[30];
>> if (is_kernel_text (LR | ms->CONFIG_ARM64_KERNELPACMASK))
>> LR |= ms->CONFIG_ARM64_KERNELPACMASK;
>> ...
>> if yes, the value pc can be passed as an argument in
>> crash_get_kernel_pac_mask(), and then deal with this one.
>>
>>
>>> ++#endif
>>> + pc_p = true;
>>> + }
>>> + catch (const gdb_exception_error &ex)
>>> diff --git a/gdb_interface.c b/gdb_interface.c
>>> index 315711e..765dafe 100644
>>> --- a/gdb_interface.c
>>> +++ b/gdb_interface.c
>>> @@ -1083,3 +1083,14 @@ int crash_get_current_task_reg (int regno, const
>>> char *regname,
>>> return machdep->get_current_task_reg(regno, regname, regsize, value);
>>> }
>>>
>>> +/* arm64 kernel lr pac mask */
>>> +unsigned long crash_get_kernel_pac_mask(void);
>>> +unsigned long crash_get_kernel_pac_mask(void)
>>> +{
>>> +#ifdef ARM64
>>> + struct machine_specific *ms = machdep->machspec;
>>> + return ms->CONFIG_ARM64_KERNELPACMASK;
>>> +#else
>>> + return ~0UL;
>>>
>>
>> The "~0UL" is 0xFFFFFFFFFFFFFFFF, is this expected? Or do you want it to
>> overflow?
>> ++ pc |= mask;
>>
>> It probably has the same result, but the "return 0UL" should be more
>> readable. Please see kernel code:
>> vmcoreinfo_append_str("NUMBER(KERNELPACMASK)=0x%llx\n",
>>
>> system_supports_address_auth() ?
>> ptrauth_kernel_pac_mask()
>> : 0);
>>
>>
>> BTW: I cannot apply your patch with git command, and ran into some
>> issues, probably it is a coding issue.
>>
>> Thanks
>> Lianbo
>>
>>
>>> +#endif /* !ARM64 */
>>> +}
>>> --
>>> 2.34.1
>>>
>>> Thanks,
>>> Guanyou
>>>
>>
0001-arm64-add-pac-mask-to-better-support-gdb-stack-unwin.patch.v3
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