Subject: Re: [PATCH] x86/dumpstack/64: Add guard pages to stack_info

From: Peter Zijlstra <[email-masked]>
Date: Sat, 18 Sep 2021 08:56:50 +0200

On Sat, Sep 18, 2021 at 10:30:42AM +0800, 王贇 wrote:
> > Andy suggested something like this.
> 
> Now it seem like working well :-)

Thanks for sticking with it and testing all that over and over!

> [  193.100475][    C0] BUG: NMI stack guard page was hit at 0000000085fd977b (stack is 000000003a55b09e..00000000d8cce1a5)
> [  193.100493][    C0] stack guard page: 0000 [#1] SMP PTI
> [  193.100499][    C0] CPU: 0 PID: 968 Comm: a.out Not tainted 5.14.0-next-20210913+ #548
> [  193.100506][    C0] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
> [  193.100510][    C0] RIP: 0010:perf_swevent_get_recursion_context+0x0/0x70
> [  193.100523][    C0] Code: 48 03 43 28 48 8b 0c 24 bb 01 00 00 00 4c 29 f0 48 39 c8 48 0f 47 c1 49 89 45 08 e9 48 ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 <55> 53 e8 09 20 f2 ff 48 c7 c2 20 4d 03 00 65 48 03 15 5a 3b d2 7e
> [  193.100529][    C0] RSP: 0018:fffffe000000b000 EFLAGS: 00010046
> [  193.100535][    C0] RAX: 0000000080120006 RBX: fffffe000000b050 RCX: 0000000000000000
> [  193.100540][    C0] RDX: ffff88810de82180 RSI: ffffffff81269031 RDI: 000000000000001c
> [  193.100544][    C0] RBP: 000000000000001c R08: 0000000000000001 R09: 0000000000000000
> [  193.100548][    C0] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> [  193.100551][    C0] R13: fffffe000000b044 R14: 0000000000000001 R15: 0000000000000009
> [  193.100556][    C0] FS:  00007fa18c42d740(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000
> [  193.100562][    C0] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  193.100566][    C0] CR2: fffffe000000aff8 CR3: 00000001160ac005 CR4: 00000000003606f0
> [  193.100570][    C0] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [  193.100574][    C0] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [  193.100578][    C0] Call Trace:
> [  193.100581][    C0]  <NMI>
> [  193.100584][    C0]  perf_trace_buf_alloc+0x26/0xd0
> [  193.100597][    C0]  ? is_prefetch.isra.25+0x260/0x260
> [  193.100605][    C0]  ? __bad_area_nosemaphore+0x1b8/0x280
> [  193.100611][    C0]  perf_ftrace_function_call+0x18f/0x2e0
> 
> 
> Tested-by: Michael Wang <[email-masked]>
> 
> BTW, would you like to apply the other patch which increasing exception
> stack size after this one?

Yes, I have that queued behind it :-)