[RFC PATCH] powerpc: show registers when unwinding interrupt frames
Michael Ellerman
mpe at ellerman.id.au
Wed Dec 2 17:03:34 AEDT 2020
Christophe Leroy <christophe.leroy at csgroup.eu> writes:
> Le 07/11/2020 à 03:33, Nicholas Piggin a écrit :
>> It's often useful to know the register state for interrupts in
>> the stack frame. In the below example (with this patch applied),
>> the important information is the state of the page fault.
>>
>> A blatant case like this probably rather should have the page
>> fault regs passed down to the warning, but quite often there are
>> less obvious cases where an interrupt shows up that might give
>> some more clues.
>>
>> The downside is longer and more complex bug output.
>
> Do we want all interrupts, including system call ?
I think we do.
> I don't find the dump of the syscall interrupt so usefull, do you ?
Yes :)
Because it's consistent, ie. we always show the full chain back to
userspace.
I think it's also helpful for folks who are less familiar with how
things work to show all the pieces, rather than hiding syscalls or
treating them specially.
Also I'm pretty sure I've had occasions where I've been debugging and
wanted to see the values that came in from userspace.
cheers
> See below an (unexpected?) KUAP warning due to an expected NULL pointer dereference in
> copy_from_kernel_nofault() called from kthread_probe_data()
>
>
> [ 1117.202054] ------------[ cut here ]------------
> [ 1117.202102] Bug: fault blocked by AP register !
> [ 1117.202261] WARNING: CPU: 0 PID: 377 at arch/powerpc/include/asm/nohash/32/kup-8xx.h:66
> do_page_fault+0x4a8/0x5ec
> [ 1117.202310] Modules linked in:
> [ 1117.202428] CPU: 0 PID: 377 Comm: sh Tainted: G W
> 5.10.0-rc5-s3k-dev-01340-g83f53be2de31-dirty #4175
> [ 1117.202499] NIP: c0012048 LR: c0012048 CTR: 00000000
> [ 1117.202573] REGS: cacdbb88 TRAP: 0700 Tainted: G W
> (5.10.0-rc5-s3k-dev-01340-g83f53be2de31-dirty)
> [ 1117.202625] MSR: 00021032 <ME,IR,DR,RI> CR: 24082222 XER: 20000000
> [ 1117.202899]
> [ 1117.202899] GPR00: c0012048 cacdbc40 c2929290 00000023 c092e554 00000001 c09865e8 c092e640
> [ 1117.202899] GPR08: 00001032 00000000 00000000 00014efc 28082224 100d166a 100a0920 00000000
> [ 1117.202899] GPR16: 100cac0c 100b0000 1080c3fc 1080d685 100d0000 100d0000 00000000 100a0900
> [ 1117.202899] GPR24: 100d0000 c07892ec 00000000 c0921510 c21f4440 0000005c c0000000 cacdbc80
> [ 1117.204362] NIP [c0012048] do_page_fault+0x4a8/0x5ec
> [ 1117.204461] LR [c0012048] do_page_fault+0x4a8/0x5ec
> [ 1117.204509] Call Trace:
> [ 1117.204609] [cacdbc40] [c0012048] do_page_fault+0x4a8/0x5ec (unreliable)
> [ 1117.204771] [cacdbc70] [c00112f0] handle_page_fault+0x8/0x34
> [ 1117.204911] --- interrupt: 301 at copy_from_kernel_nofault+0x70/0x1c0
> [ 1117.204979] NIP: c010dbec LR: c010dbac CTR: 00000001
> [ 1117.205053] REGS: cacdbc80 TRAP: 0301 Tainted: G W
> (5.10.0-rc5-s3k-dev-01340-g83f53be2de31-dirty)
> [ 1117.205104] MSR: 00009032 <EE,ME,IR,DR,RI> CR: 28082224 XER: 00000000
> [ 1117.205416] DAR: 0000005c DSISR: c0000000
> [ 1117.205416] GPR00: c0045948 cacdbd38 c2929290 00000001 00000017 00000017 00000027 0000000f
> [ 1117.205416] GPR08: c09926ec 00000000 00000000 3ffff000 24082224
> [ 1117.206106] NIP [c010dbec] copy_from_kernel_nofault+0x70/0x1c0
> [ 1117.206202] LR [c010dbac] copy_from_kernel_nofault+0x30/0x1c0
> [ 1117.206258] --- interrupt: 301
> [ 1117.206372] [cacdbd38] [c004bbb0] kthread_probe_data+0x44/0x70 (unreliable)
> [ 1117.206561] [cacdbd58] [c0045948] print_worker_info+0xe0/0x194
> [ 1117.206717] [cacdbdb8] [c00548ac] sched_show_task+0x134/0x168
> [ 1117.206851] [cacdbdd8] [c005a268] show_state_filter+0x70/0x100
> [ 1117.206989] [cacdbe08] [c039baa0] sysrq_handle_showstate+0x14/0x24
> [ 1117.207122] [cacdbe18] [c039bf18] __handle_sysrq+0xac/0x1d0
> [ 1117.207257] [cacdbe48] [c039c0c0] write_sysrq_trigger+0x4c/0x74
> [ 1117.207407] [cacdbe68] [c01fba48] proc_reg_write+0xb4/0x114
> [ 1117.207550] [cacdbe88] [c0179968] vfs_write+0x12c/0x478
> [ 1117.207686] [cacdbf08] [c0179e60] ksys_write+0x78/0x128
> [ 1117.207826] [cacdbf38] [c00110d0] ret_from_syscall+0x0/0x34
> [ 1117.207938] --- interrupt: c01 at 0xfd4e784
> [ 1117.208008] NIP: 0fd4e784 LR: 0fe0f244 CTR: 10048d38
> [ 1117.208083] REGS: cacdbf48 TRAP: 0c01 Tainted: G W
> (5.10.0-rc5-s3k-dev-01340-g83f53be2de31-dirty)
> [ 1117.208134] MSR: 0000d032 <EE,PR,ME,IR,DR,RI> CR: 44002222 XER: 00000000
> [ 1117.208470]
> [ 1117.208470] GPR00: 00000004 7fc34090 77bfb4e0 00000001 1080fa40 00000002 7400000f fefefeff
> [ 1117.208470] GPR08: 7f7f7f7f 10048d38 1080c414 7fc343c0 00000000
> [ 1117.209104] NIP [0fd4e784] 0xfd4e784
> [ 1117.209180] LR [0fe0f244] 0xfe0f244
> [ 1117.209236] --- interrupt: c01
> [ 1117.209274] Instruction dump:
> [ 1117.209353] 714a4000 418200f0 73ca0001 40820084 73ca0032 408200f8 73c90040 4082ff60
> [ 1117.209727] 0fe00000 3c60c082 386399f4 48013b65 <0fe00000> 80010034 3860000b 7c0803a6
> [ 1117.210102] ---[ end trace 1927c0323393af3e ]---
>
> Christophe
>
>
>>
>> Bug: Write fault blocked by AMR!
>> WARNING: CPU: 0 PID: 72 at arch/powerpc/include/asm/book3s/64/kup-radix.h:164 __do_page_fault+0x880/0xa90
>> Modules linked in:
>> CPU: 0 PID: 72 Comm: systemd-gpt-aut Not tainted
>> NIP: c00000000006e2f0 LR: c00000000006e2ec CTR: 0000000000000000
>> REGS: c00000000a4f3420 TRAP: 0700
>> MSR: 8000000000021033 <SF,ME,IR,DR,RI,LE> CR: 28002840 XER: 20040000
>> CFAR: c000000000128be0 IRQMASK: 3
>> GPR00: c00000000006e2ec c00000000a4f36c0 c0000000014f0700 0000000000000020
>> GPR04: 0000000000000001 c000000001290f50 0000000000000001 c000000001290f80
>> GPR08: c000000001612b08 0000000000000000 0000000000000000 00000000ffffe0f7
>> GPR12: 0000000048002840 c0000000016e0000 c00c000000021c80 c000000000fd6f60
>> GPR16: 0000000000000000 c00000000a104698 0000000000000003 c0000000087f0000
>> GPR20: 0000000000000100 c0000000070330b8 0000000000000000 0000000000000004
>> GPR24: 0000000002000000 0000000000000300 0000000002000000 c00000000a5b0c00
>> GPR28: 0000000000000000 000000000a000000 00007fffb2a90038 c00000000a4f3820
>> NIP [c00000000006e2f0] __do_page_fault+0x880/0xa90
>> LR [c00000000006e2ec] __do_page_fault+0x87c/0xa90
>> Call Trace:
>> [c00000000a4f36c0] [c00000000006e2ec] __do_page_fault+0x87c/0xa90 (unreliable)
>> [c00000000a4f3780] [c000000000e1c034] do_page_fault+0x34/0x90
>> [c00000000a4f37b0] [c000000000008908] data_access_common_virt+0x158/0x1b0
>> --- interrupt: 300 at __copy_tofrom_user_base+0x9c/0x5a4
>> NIP: c00000000009b028 LR: c000000000802978 CTR: 0000000000000800
>> REGS: c00000000a4f3820 TRAP: 0300
>> MSR: 800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 24004840 XER: 00000000
>> CFAR: c00000000009aff4 DAR: 00007fffb2a90038 DSISR: 0a000000 IRQMASK: 0
>> GPR00: 0000000000000000 c00000000a4f3ac0 c0000000014f0700 00007fffb2a90028
>> GPR04: c000000008720010 0000000000010000 0000000000000000 0000000000000000
>> GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000001
>> GPR12: 0000000000004000 c0000000016e0000 c00c000000021c80 c000000000fd6f60
>> GPR16: 0000000000000000 c00000000a104698 0000000000000003 c0000000087f0000
>> GPR20: 0000000000000100 c0000000070330b8 0000000000000000 0000000000000004
>> GPR24: c00000000a4f3c80 c000000008720000 0000000000010000 0000000000000000
>> GPR28: 0000000000010000 0000000008720000 0000000000010000 c000000001515b98
>> NIP [c00000000009b028] __copy_tofrom_user_base+0x9c/0x5a4
>> LR [c000000000802978] copyout+0x68/0xc0
>> --- interrupt: 300
>> [c00000000a4f3af0] [c0000000008074b8] copy_page_to_iter+0x188/0x540
>> [c00000000a4f3b50] [c00000000035c678] generic_file_buffered_read+0x358/0xd80
>> [c00000000a4f3c40] [c0000000004c1e90] blkdev_read_iter+0x50/0x80
>> [c00000000a4f3c60] [c00000000045733c] new_sync_read+0x12c/0x1c0
>> [c00000000a4f3d00] [c00000000045a1f0] vfs_read+0x1d0/0x240
>> [c00000000a4f3d50] [c00000000045a7f4] ksys_read+0x84/0x140
>> [c00000000a4f3da0] [c000000000033a60] system_call_exception+0x100/0x280
>> [c00000000a4f3e10] [c00000000000c508] system_call_common+0xf8/0x2f8
>> Instruction dump:
>> eae10078 3be0000b 4bfff890 60420000 792917e1 4182ff18 3c82ffab 3884a5e0
>> 3c62ffab 3863a6e8 480ba891 60000000 <0fe00000> 3be0000b 4bfff860 e93c0938
>>
>> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
>> ---
>> arch/powerpc/kernel/process.c | 20 ++++++++++++++------
>> 1 file changed, 14 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
>> index ea36a29c8b01..799f00b32f74 100644
>> --- a/arch/powerpc/kernel/process.c
>> +++ b/arch/powerpc/kernel/process.c
>> @@ -1475,12 +1475,10 @@ static void print_msr_bits(unsigned long val)
>> #define LAST_VOLATILE 12
>> #endif
>>
>> -void show_regs(struct pt_regs * regs)
>> +static void __show_regs(struct pt_regs *regs)
>> {
>> int i, trap;
>>
>> - show_regs_print_info(KERN_DEFAULT);
>> -
>> printk("NIP: "REG" LR: "REG" CTR: "REG"\n",
>> regs->nip, regs->link, regs->ctr);
>> printk("REGS: %px TRAP: %04lx %s (%s)\n",
>> @@ -1522,6 +1520,12 @@ void show_regs(struct pt_regs * regs)
>> printk("NIP ["REG"] %pS\n", regs->nip, (void *)regs->nip);
>> printk("LR ["REG"] %pS\n", regs->link, (void *)regs->link);
>> }
>> +}
>> +
>> +void show_regs(struct pt_regs *regs)
>> +{
>> + show_regs_print_info(KERN_DEFAULT);
>> + __show_regs(regs);
>> show_stack(current, (unsigned long *) regs->gpr[1], KERN_DEFAULT);
>> if (!user_mode(regs))
>> show_instructions(regs);
>> @@ -2192,10 +2196,14 @@ void show_stack(struct task_struct *tsk, unsigned long *stack,
>> && stack[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
>> struct pt_regs *regs = (struct pt_regs *)
>> (sp + STACK_FRAME_OVERHEAD);
>> +
>> lr = regs->link;
>> - printk("%s--- interrupt: %lx at %pS\n LR = %pS\n",
>> - loglvl, regs->trap,
>> - (void *)regs->nip, (void *)lr);
>> + printk("%s--- interrupt: %lx at %pS\n",
>> + loglvl, regs->trap, (void *)regs->nip);
>> + __show_regs(regs);
>> + printk("%s--- interrupt: %lx\n",
>> + loglvl, regs->trap);
>> +
>> firstframe = 1;
>> }
>>
>>
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