Re: [Crash-utility] [PATCH v2] Fix kmem failing to print task context when address is vmalloced stack

Hi, Tao Thank you for the fix. On Thu, Aug 25, 2022 at 8:00 PM <crash-utility-request(a)redhat.com&gt; wrote: > > Date: Thu, 25 Aug 2022 14:42:45 +0800 > From: Tao Liu <ltao(a)redhat.com&gt; > To: crash-utility(a)redhat.com > Subject: [Crash-utility] [PATCH v2] Fix kmem failing to print task > context when address is vmalloced stack > Message-ID: <20220825064243.71447-1-ltao(a)redhat.com&gt; > Content-Type: text/plain; charset="US-ASCII"; x-default=true > > When kernel enabled CONFIG_VMAP_STACK, stack can be allocated to > vmalloced area. Currently crash didn't handle the case, as a result, > kmem will not print the task context as expected. This patch fix the > bug by checking if the address is a vmalloced stack first. > > Before: > crash> kmem ffffb7efce9bbe28 > VMAP_AREA VM_STRUCT ADDRESS RANGE SIZE > ffff94eb9102c640 ffff94eb9102b140 ffffb7efce9b8000 - ffffb7efce9bd000 20480 > > PAGE PHYSICAL MAPPING INDEX CNT FLAGS > ffffdd28220dc000 1883700000 0 0 1 50000000000000 > > After: > crash> kmem ffffb7efce9bbe28 > PID: 847 > COMMAND: "khungtaskd" > TASK: ffff94f8038f4000 [THREAD_INFO: ffff94f8038f4000] > CPU: 72 > STATE: TASK_RUNNING (PANIC) > > VMAP_AREA VM_STRUCT ADDRESS RANGE SIZE > ffff94eb9102c640 ffff94eb9102b140 ffffb7efce9b8000 - ffffb7efce9bd000 20480 > I have one question: If the given physical address falls in the vmalloc area, it won't print the task context, is that expected? For example:

[1] Before this patch: the "kmem + physical/virtual address" has the same output asbelow. crash> kmem ffffb7efce9bbe28 VMAP_AREA VM_STRUCT ADDRESS RANGE SIZE ffff94eb9102c640 ffff94eb9102b140 ffffb7efce9b8000 - ffffb7efce9bd000 20480 PAGE PHYSICAL MAPPING INDEX CNT FLAGS ffffdd28220dc000 1883700000 0 0 1 50000000000000 crash> kmem 1883700e28 <----- vtop ffffb7efce9bbe28 VMAP_AREA VM_STRUCT ADDRESS RANGE SIZE ffff94eb9102c640 ffff94eb9102b140 ffffb7efce9b8000 - ffffb7efce9bd000 20480 PAGE PHYSICAL MAPPING INDEX CNT FLAGS ffffdd28220dc000 1883700000 0 0 1 50000000000000 [2] After this patch: the "kmem + physical/virtual address" has different output asbelow. crash> kmem ffffb7efce9bbe28 PID: 847 COMMAND: "khungtaskd" TASK: ffff94f8038f4000 [THREAD_INFO: ffff94f8038f4000] CPU: 72 STATE: TASK_RUNNING (PANIC) VMAP_AREA VM_STRUCT ADDRESS RANGE SIZE ffff94eb9102c640 ffff94eb9102b140 ffffb7efce9b8000 - ffffb7efce9bd000 20480 PAGE PHYSICAL MAPPING INDEX CNT FLAGS ffffdd28220dc000 1883700000 0 0 1 50000000000000 crash> kmem 1883700e28 <----- vtop ffffb7efce9bbe28 VMAP_AREA VM_STRUCT ADDRESS RANGE SIZE ffff94eb9102c640 ffff94eb9102b140 ffffb7efce9b8000 - ffffb7efce9bd000 20480 PAGE PHYSICAL MAPPING INDEX CNT FLAGS ffffdd28220dc000 1883700000 0 0 1 50000000000000 Thanks. Lianbo > PAGE PHYSICAL MAPPING INDEX CNT FLAGS > ffffdd28220dc000 1883700000 0 0 1 50000000000000 > > Signed-off-by: Tao Liu <ltao(a)redhat.com&gt; > --- > > v1 -> v2: 1) Remove goto to print task context and vmlist. > 2) Update commit log to show the change. > > --- > memory.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/memory.c b/memory.c > index 7339f0c..9ab5781 100644 > --- a/memory.c > +++ b/memory.c > @@ -13477,6 +13477,10 @@ kmem_search(struct meminfo *mi) > * Check for a valid mapped address. > */ > if ((mi->memtype == KVADDR) && IS_VMALLOC_ADDR(mi->spec_addr)) { > + if ((task = stkptr_to_task(vaddr)) && (tc = task_to_context(task))) { > + show_context(tc); > + fprintf(fp, "\n"); > + } > if (kvtop(NULL, mi->spec_addr, &paddr, 0)) { > mi->flags = orig_flags | VMLIST_VERIFY; > dump_vmlist(mi); > -- > 2.33.1 > > > > ------------------------------ > > Subject: Digest Footer > > -- > Crash-utility mailing list > Crash-utility(a)redhat.com > https://listman.redhat.com/mailman/listinfo/crash-utility > > > ------------------------------ > > End of Crash-utility Digest, Vol 203, Issue 41 > ********************************************** >