On 2021/9/15 下午11:17, Peter Zijlstra wrote:
> On Wed, Sep 15, 2021 at 09:51:57AM +0800, 王贇 wrote:
>
>>> +
>>> + if (in_exception_stack_guard((void *)address))
>>> + pr_emerg("PANIC: exception stack guard: 0x%lx\n", address);
>>> #endif
>>>
>>> pr_emerg("PANIC: double fault, error_code: 0x%lx\n", error_code);
>>>
>>
>> The panic triggered as below after the stack size recovered, I found this info
>> could be helpful, maybe we should keep it?
>
> Could you please test this?
It seems like not working properly, we get very long trace ending as below:
Regards,
Michael Wang
[ 34.662432][ C0] BUG: unable to handle page fault for address: fffffe0000008ff0
[ 34.662435][ C0] #PF: supervisor read access in kernel mode
[ 34.662438][ C0] #PF: error_code(0x0000) - not-present page
[ 34.662442][ C0] PGD 13ffef067 P4D 13ffef067 PUD 13ffed067 PMD 13ffec067 PTE 0
[ 34.662455][ C0] Oops: 0000 [#11] SMP PTI
[ 34.662459][ C0] CPU: 0 PID: 713 Comm: a.out Not tainted 5.14.0-next-20210913+ #530
[ 34.662465][ C0] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[ 34.662468][ C0] RIP: 0010:get_stack_info_noinstr+0x8d/0xf0
[ 34.662474][ C0] Code: 40 82 66 85 c9 74 33 8b 34 d5 40 6d 40 82 0f b7 14 d5 46 6d 40 82 48 01 f0 41 89 14 24 48 01 c1 49 89 44 24 08 49 89 4c 24 10 <48> 8b 41 f0 49 89 44 24 18 b8 01 00 00 00 eb 87 65 48 8b 05 43 c5
[ 34.662485][ C0] RSP: 0018:fffffe0000009bb0 EFLAGS: 00010086
[ 34.662490][ C0] RAX: fffffe0000008000 RBX: ffff888107422180 RCX: fffffe0000009000
[ 34.662494][ C0] RDX: 0000000000000085 RSI: 0000000000000000 RDI: fffffe0000008f30
[ 34.662498][ C0] RBP: fffffe0000008f30 R08: ffffffff82754eff R09: fffffe0000009b78
[ 34.662502][ C0] R10: 0000000000000000 R11: 0000000000000006 R12: fffffe0000009c28
[ 34.662506][ C0] R13: 0000000000000000 R14: ffff888107422180 R15: fffffe0000009c48
[ 34.662510][ C0] FS: 00007f5298fe2740(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000
[ 34.662516][ C0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 34.662520][ C0] CR2: fffffe0000008ff0 CR3: 0000000109b5a005 CR4: 00000000003606f0
[ 34.662524][ C0] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 34.662528][ C0] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 34.662532][ C0] Call Trace:
[ 34.662534][ C0] <#DF>
[ 34.662542][ C0] get_stack_info+0x30/0xb0
[ 34.662556][ C0] show_trace_log_lvl+0xf9/0x410
[ 34.662571][ C0] ? sprint_symbol_build_id+0x30/0x30
[ 34.662605][ C0] ? 0xffffffffa0106083
[ 34.662628][ C0] __die_body+0x1a/0x60
[ 34.662641][ C0] page_fault_oops+0xe8/0x560
[ 34.662671][ C0] kernelmode_fixup_or_oops+0x107/0x120
[ 34.662687][ C0] __bad_area_nosemaphore+0x1b8/0x280
[ 34.662707][ C0] do_kern_addr_fault+0x57/0xc0
[ 34.662719][ C0] exc_page_fault+0x1c1/0x300
[ 34.662735][ C0] asm_exc_page_fault+0x1e/0x30
[ 34.662742][ C0] RIP: 0010:get_stack_info_noinstr+0x8d/0xf0
[ 34.662749][ C0] Code: 40 82 66 85 c9 74 33 8b 34 d5 40 6d 40 82 0f b7 14 d5 46 6d 40 82 48 01 f0 41 89 14 24 48 01 c1 49 89 44 24 08 49 89 4c 24 10 <48> 8b 41 f0 49 89 44 24 18 b8 01 00 00 00 eb 87 65 48 8b 05 43 c5
[ 34.662754][ C0] RSP: 0018:fffffe0000009ee8 EFLAGS: 00010086
[ 34.662759][ C0] RAX: fffffe0000008000 RBX: ffff888107422180 RCX: fffffe0000009000
[ 34.662763][ C0] RDX: 0000000000000085 RSI: 0000000000000000 RDI: fffffe0000008f28
[ 34.662767][ C0] RBP: fffffe0000008f28 R08: 0000000000000000 R09: 0000000000000000
[ 34.662771][ C0] R10: 0000000000000000 R11: 0000000000000000 R12: fffffe0000009f08
[ 34.662775][ C0] R13: fffffe0000008f28 R14: 0000000109b5a005 R15: 0000000000000000
[ 34.662816][ C0] ? get_stack_info_noinstr+0x12/0xf0
[ 34.662828][ C0] exc_double_fault+0x138/0x1a0
[ 34.662851][ C0] asm_exc_double_fault+0x1e/0x30
[ 34.662858][ C0] RIP: 0010:perf_ftrace_function_call+0x26/0x2e0
[ 34.662866][ C0] Code: 5b 5d c3 90 55 48 89 e5 41 57 41 56 41 55 41 54 49 89 f5 53 49 89 fc 48 89 d3 48 81 ec d0 00 00 00 65 48 8b 04 25 28 00 00 00 <48> 89 45 d0 31 c0 e8 9f 69 fa ff e8 2a 4a f1 ff 84 c0 74 14 e8 91
[ 34.662872][ C0] RSP: 0018:fffffe0000008f30 EFLAGS: 00010086
[ 34.662877][ C0] RAX: 0c14fdf027d1e500 RBX: ffff8881002f99f0 RCX: fffffe0000009038
[ 34.662881][ C0] RDX: ffff8881002f99f0 RSI: ffffffff817cd61f RDI: ffffffff811cc7b0
[ 34.662884][ C0] RBP: fffffe0000009028 R08: ffffffff82754ed9 R09: fffffe00000095d0
[ 34.662888][ C0] R10: fffffe00000095e8 R11: 0000000020455450 R12: ffffffff811cc7b0
[ 34.662892][ C0] R13: ffffffff817cd61f R14: ffff0a00ffffff05 R15: ffffffff81edac2d
[ 34.662896][ C0] ? get_stack_info_noinstr+0x8d/0xf0
[ 34.662904][ C0] ? symbol_string+0xbf/0x160
[ 34.662911][ C0] ? sprint_symbol_build_id+0x30/0x30
[ 34.662935][ C0] ? symbol_string+0xbf/0x160
[ 34.662942][ C0] ? sprint_symbol_build_id+0x30/0x30
[ 34.662959][ C0] </#DF>
[ 34.662964][ C0] BUG: unable to handle page fault for address: fffffe0000008ff0
[ 34.662966][ C0] #PF: supervisor read access in kernel mode
[ 34.662970][ C0] #PF: error_code(0x0000) - not-present page
[ 34.662973][ C0] PGD 13ffef067 P4D 13ffef067 PUD 13ffed067 PMD 13ffec067 PTE 0
[ 34.662986][ C0] Oops: 0000 [#12] SMP PTI
[ 34.662991][ C0] CPU: 0 PID: 713 Comm: a.out Not tainted 5.14.0-next-20210913+ #530
[ 34.662996][ C0] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
>
> ---
> Subject: x86/dumpstack/64: Add guard pages to stack_info
> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Date: Wed Sep 15 17:12:59 CEST 2021
>
> Explicitly add the exception stack guard pages to stack_info and
> report on them from #DF.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> ---
> arch/x86/include/asm/cpu_entry_area.h | 3 +++
> arch/x86/include/asm/stacktrace.h | 3 ++-
> arch/x86/kernel/dumpstack_64.c | 17 ++++++++++++++++-
> arch/x86/kernel/traps.c | 17 ++++++++++++++++-
> 4 files changed, 37 insertions(+), 3 deletions(-)
>
> --- a/arch/x86/include/asm/cpu_entry_area.h
> +++ b/arch/x86/include/asm/cpu_entry_area.h
> @@ -61,6 +61,9 @@ enum exception_stack_ordering {
> #define CEA_ESTACK_OFFS(st) \
> offsetof(struct cea_exception_stacks, st## _stack)
>
> +#define CEA_EGUARD_OFFS(st) \
> + offsetof(struct cea_exception_stacks, st## _stack_guard)
> +
> #define CEA_ESTACK_PAGES \
> (sizeof(struct cea_exception_stacks) / PAGE_SIZE)
>
> --- a/arch/x86/include/asm/stacktrace.h
> +++ b/arch/x86/include/asm/stacktrace.h
> @@ -14,13 +14,14 @@
> #include <asm/switch_to.h>
>
> enum stack_type {
> - STACK_TYPE_UNKNOWN,
> + STACK_TYPE_UNKNOWN = 0,
> STACK_TYPE_TASK,
> STACK_TYPE_IRQ,
> STACK_TYPE_SOFTIRQ,
> STACK_TYPE_ENTRY,
> STACK_TYPE_EXCEPTION,
> STACK_TYPE_EXCEPTION_LAST = STACK_TYPE_EXCEPTION + N_EXCEPTION_STACKS-1,
> + STACK_TYPE_GUARD = 0x80,
> };
>
> struct stack_info {
> --- a/arch/x86/kernel/dumpstack_64.c
> +++ b/arch/x86/kernel/dumpstack_64.c
> @@ -32,9 +32,15 @@ const char *stack_type_name(enum stack_t
> {
> BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
>
> + if (type == STACK_TYPE_TASK)
> + return "TASK";
> +
> if (type == STACK_TYPE_IRQ)
> return "IRQ";
>
> + if (type == STACK_TYPE_SOFTIRQ)
> + return "SOFTIRQ";
> +
> if (type == STACK_TYPE_ENTRY) {
> /*
> * On 64-bit, we have a generic entry stack that we
> @@ -63,6 +69,11 @@ struct estack_pages {
> };
>
> #define EPAGERANGE(st) \
> + [PFN_DOWN(CEA_EGUARD_OFFS(st))] = { \
> + .offs = CEA_EGUARD_OFFS(st), \
> + .size = PAGE_SIZE, \
> + .type = STACK_TYPE_GUARD + \
> + STACK_TYPE_EXCEPTION + ESTACK_ ##st, }, \
> [PFN_DOWN(CEA_ESTACK_OFFS(st)) ... \
> PFN_DOWN(CEA_ESTACK_OFFS(st) + CEA_ESTACK_SIZE(st) - 1)] = { \
> .offs = CEA_ESTACK_OFFS(st), \
> @@ -111,10 +122,11 @@ static __always_inline bool in_exception
> k = (stk - begin) >> PAGE_SHIFT;
> /* Lookup the page descriptor */
> ep = &estack_pages[k];
> - /* Guard page? */
> + /* unknown entry */
> if (!ep->size)
> return false;
>
> +
> begin += (unsigned long)ep->offs;
> end = begin + (unsigned long)ep->size;
> regs = (struct pt_regs *)end - 1;
> @@ -193,6 +205,9 @@ int get_stack_info(unsigned long *stack,
> if (!get_stack_info_noinstr(stack, task, info))
> goto unknown;
>
> + if (info->type & STACK_TYPE_GUARD)
> + goto unknown;
> +
> /*
> * Make sure we don't iterate through any given stack more than once.
> * If it comes up a second time then there's something wrong going on:
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -461,6 +461,19 @@ DEFINE_IDTENTRY_DF(exc_double_fault)
> }
> #endif
>
> +#ifdef CONFIG_X86_64
> + {
> + struct stack_info info;
> +
> + if (get_stack_info_noinstr((void *)address, current, &info) &&
> + info.type & STACK_TYPE_GUARD) {
> + const char *name = stack_type_name(info.type & ~STACK_TYPE_GUARD);
> + pr_emerg("BUG: %s stack guard hit at %p (stack is %p..%p)\n",
> + name, (void *)address, info.begin, info.end);
> + }
> + }
> +#endif
> +
> pr_emerg("PANIC: double fault, error_code: 0x%lx\n", error_code);
> die("double fault", regs, error_code);
> panic("Machine halted.");
> @@ -708,7 +721,9 @@ asmlinkage __visible noinstr struct pt_r
> sp = regs->sp;
> stack = (unsigned long *)sp;
>
> - if (!get_stack_info_noinstr(stack, current, &info) || info.type == STACK_TYPE_ENTRY ||
> + if (!get_stack_info_noinstr(stack, current, &info) ||
> + info.type & STACK_TYPE_GUARD ||
> + info.type == STACK_TYPE_ENTRY ||
> info.type >= STACK_TYPE_EXCEPTION_LAST)
> sp = __this_cpu_ist_top_va(VC2);
>
>
