[PATCH v2] Fix kmem failing to print task context when address is vmalloced stack

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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

	  PAGE         PHYSICAL      MAPPING       INDEX CNT FLAGS
    ffffdd28220dc000 1883700000                0        0  1 50000000000000

Signed-off-by: Tao Liu <ltao@xxxxxxxxxx>
---

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

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