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When accessing the 32-bit ARM kernel's "crash_notes" array, continue

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to read the per-cpu NT_PRSTATUS note contents if an invalid note is
encountered.  Without the patch, if an invalid note is found, all
other notes were ignored, and subsequent "bt" attempts on the active
tasks would fail.
(chenqiwu@xiaomi.com, anderson@redhat.com)
This commit is contained in:
Dave Anderson 2019-12-16 11:28:46 -05:00
parent c408862daf
commit 63df9c067d
1 changed files with 27 additions and 29 deletions
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56
arm.c
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@ -26,7 +26,7 @@
#include "defs.h"
static void arm_parse_cmdline_args(void);
static int arm_get_crash_notes(void);
static void arm_get_crash_notes(void);
static int arm_verify_symbol(const char *, ulong, char);
static int arm_is_module_addr(ulong);
static int arm_is_kvaddr(ulong);
@ -348,10 +348,8 @@ arm_init(int when)
* of the crash. We need this information to extract correct
* backtraces from the panic task.
*/
if (!ACTIVE() && !arm_get_crash_notes())
error(WARNING,
"cannot retrieve registers for active task%s\n\n",
kt->cpus > 1 ? "s" : "");
if (!ACTIVE())
arm_get_crash_notes();
if (init_unwind_tables()) {
if (CRASHDEBUG(1))
@ -543,7 +541,7 @@ arm_parse_cmdline_args(void)
/*
* Retrieve task registers for the time of the crash.
*/
static int
static void
arm_get_crash_notes(void)
{
struct machine_specific *ms = machdep->machspec;
@ -552,10 +550,10 @@ arm_get_crash_notes(void)
ulong offset;
char *buf, *p;
ulong *notes_ptrs;
ulong i;
ulong i, found;
if (!symbol_exists("crash_notes"))
return FALSE;
return;
crash_notes = symbol_value("crash_notes");
@ -570,11 +568,10 @@ arm_get_crash_notes(void)
RETURN_ON_ERROR)) {
error(WARNING, "cannot read crash_notes\n");
FREEBUF(notes_ptrs);
return FALSE;
return;
}
if (symbol_exists("__per_cpu_offset")) {
/* Add __per_cpu_offset for each cpu to form the pointer to the notes */
for (i = 0; i<kt->cpus; i++)
notes_ptrs[i] = notes_ptrs[kt->cpus-1] + kt->__per_cpu_offset[i];
@ -585,12 +582,11 @@ arm_get_crash_notes(void)
if (!(panic_task_regs = calloc((size_t)kt->cpus, sizeof(*panic_task_regs))))
error(FATAL, "cannot calloc panic_task_regs space\n");
for (i=0;i<kt->cpus;i++) {
for (i = found = 0; i<kt->cpus; i++) {
if (!readmem(notes_ptrs[i], KVADDR, buf, SIZE(note_buf), "note_buf_t",
RETURN_ON_ERROR)) {
error(WARNING, "failed to read note_buf_t\n");
goto fail;
error(WARNING, "cpu %d: cannot read NT_PRSTATUS note\n", i);
continue;
}
/*
@ -620,19 +616,23 @@ arm_get_crash_notes(void)
note->n_descsz == notesz)
BCOPY((char *)note, buf, notesz);
} else {
error(WARNING,
"cannot find NT_PRSTATUS note for cpu: %d\n", i);
error(WARNING, "cpu %d: cannot find NT_PRSTATUS note\n", i);
continue;
}
}
/*
* Check the sanity of NT_PRSTATUS note only for each online cpu.
* If this cpu has invalid note, continue to find the crash notes
* for other online cpus.
*/
if (note->n_type != NT_PRSTATUS) {
error(WARNING, "invalid note (n_type != NT_PRSTATUS)\n");
goto fail;
error(WARNING, "cpu %d: invalid NT_PRSTATUS note (n_type != NT_PRSTATUS)\n", i);
continue;
}
if (p[0] != 'C' || p[1] != 'O' || p[2] != 'R' || p[3] != 'E') {
error(WARNING, "invalid note (name != \"CORE\"\n");
goto fail;
if (!STRNEQ(p, "CORE")) {
error(WARNING, "cpu %d: invalid NT_PRSTATUS note (name != \"CORE\")\n", i);
continue;
}
/*
@ -646,6 +646,7 @@ arm_get_crash_notes(void)
BCOPY(p + OFFSET(elf_prstatus_pr_reg), &panic_task_regs[i],
sizeof(panic_task_regs[i]));
found++;
}
/*
@ -656,13 +657,10 @@ arm_get_crash_notes(void)
FREEBUF(buf);
FREEBUF(notes_ptrs);
return TRUE;
fail:
FREEBUF(buf);
FREEBUF(notes_ptrs);
free(panic_task_regs);
return FALSE;
if (!found) {
free(panic_task_regs);
ms->crash_task_regs = NULL;
}
}
/*