[Crash-utility] [PATCH 11/16] MIPS64: Fixes for the gathering of the active task registers for the 'bt' command
Youling Tang
tangyouling at loongson.cn
Tue Jan 26 11:18:42 UTC 2021
dumpfiles:
(1) If ELF notes are not available, read them from the kernel's
crash_notes.
(2) If an online CPUs did not save its ELF notes, then adjust
the mapping of each ELF note to its CPU accordingly.
E.g. With this patch:
crash> bt
PID: 4768 TASK: 9800000243bcf200 CPU: 3 COMMAND: "bash"
#0 [980000024291f930] __crash_kexec at ffffffff802fff84
#1 [980000024291faa0] panic at ffffffff80248cac
#2 [980000024291fb40] die at ffffffff8021b338
#3 [980000024291fb70] do_page_fault at ffffffff802315e0
#4 [980000024291fbd0] tlb_do_page_fault_1 at ffffffff80239388
#5 [980000024291fd00] sysrq_handle_crash at ffffffff8085d308
#6 [980000024291fd10] __handle_sysrq at ffffffff8085d9e0
#7 [980000024291fd60] write_sysrq_trigger at ffffffff8085e020
#8 [980000024291fd80] proc_reg_write at ffffffff804762f0
#9 [980000024291fda0] __vfs_write at ffffffff803f3138
Signed-off-by: Huacai Chen <chenhuacai at loongson.cn>
Signed-off-by: Youling Tang <tangyouling at loongson.cn>
---
mips64.c | 203 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 202 insertions(+), 1 deletion(-)
diff --git a/mips64.c b/mips64.c
index 57a7f41..d949af4 100644
--- a/mips64.c
+++ b/mips64.c
@@ -42,7 +42,9 @@ static void mips64_get_stack_frame(struct bt_info *bt, ulong *pcp, ulong *spp);
static int mips64_get_dumpfile_stack_frame(struct bt_info *bt,
ulong *nip, ulong *ksp);
static int mips64_get_frame(struct bt_info *bt, ulong *pcp, ulong *spp);
-
+static int mips64_init_active_task_regs(void);
+static int mips64_get_crash_notes(void);
+static int mips64_get_elf_notes(void);
/*
* 3 Levels paging PAGE_SIZE=16KB
@@ -806,6 +808,192 @@ mips64_get_frame(struct bt_info *bt, ulong *pcp, ulong *spp)
return TRUE;
}
+static int
+mips64_init_active_task_regs(void)
+{
+ int retval;
+
+ retval = mips64_get_crash_notes();
+ if (retval == TRUE)
+ return retval;
+
+ return mips64_get_elf_notes();
+}
+
+/*
+ * Retrieve task registers for the time of the crash.
+ */
+static int
+mips64_get_crash_notes(void)
+{
+ struct machine_specific *ms = machdep->machspec;
+ ulong crash_notes;
+ Elf64_Nhdr *note;
+ ulong offset;
+ char *buf, *p;
+ ulong *notes_ptrs;
+ ulong i;
+
+ /*
+ * crash_notes contains per cpu memory for storing cpu states
+ * in case of system crash.
+ */
+ if (!symbol_exists("crash_notes"))
+ return FALSE;
+
+ crash_notes = symbol_value("crash_notes");
+
+ notes_ptrs = (ulong *)GETBUF(kt->cpus*sizeof(notes_ptrs[0]));
+
+ /*
+ * Read crash_notes for the first CPU. crash_notes are in standard ELF
+ * note format.
+ */
+ if (!readmem(crash_notes, KVADDR, ¬es_ptrs[kt->cpus-1],
+ sizeof(notes_ptrs[kt->cpus-1]), "crash_notes",
+ RETURN_ON_ERROR)) {
+ error(WARNING, "cannot read crash_notes\n");
+ FREEBUF(notes_ptrs);
+ return FALSE;
+ }
+
+ 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];
+ }
+
+ buf = GETBUF(SIZE(note_buf));
+
+ 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++) {
+
+ if (!readmem(notes_ptrs[i], KVADDR, buf, SIZE(note_buf), "note_buf_t",
+ RETURN_ON_ERROR)) {
+ error(WARNING,
+ "cannot find NT_PRSTATUS note for cpu: %d\n", i);
+ goto fail;
+ }
+
+ /*
+ * Do some sanity checks for this note before reading registers from it.
+ */
+ note = (Elf64_Nhdr *)buf;
+ p = buf + sizeof(Elf64_Nhdr);
+
+ /*
+ * dumpfiles created with qemu won't have crash_notes, but there will
+ * be elf notes; dumpfiles created by kdump do not create notes for
+ * offline cpus.
+ */
+ if (note->n_namesz == 0 && (DISKDUMP_DUMPFILE() || KDUMP_DUMPFILE())) {
+ if (DISKDUMP_DUMPFILE())
+ note = diskdump_get_prstatus_percpu(i);
+ else if (KDUMP_DUMPFILE())
+ note = netdump_get_prstatus_percpu(i);
+ if (note) {
+ /*
+ * SIZE(note_buf) accounts for a "final note", which is a
+ * trailing empty elf note header.
+ */
+ long notesz = SIZE(note_buf) - sizeof(Elf64_Nhdr);
+
+ if (sizeof(Elf64_Nhdr) + roundup(note->n_namesz, 4) +
+ note->n_descsz == notesz)
+ BCOPY((char *)note, buf, notesz);
+ } else {
+ error(WARNING,
+ "cannot find NT_PRSTATUS note for cpu: %d\n", i);
+ continue;
+ }
+ }
+
+ /*
+ * Check the sanity of NT_PRSTATUS note only for each online cpu.
+ */
+ if (note->n_type != NT_PRSTATUS) {
+ error(WARNING, "invalid NT_PRSTATUS note (n_type != NT_PRSTATUS)\n");
+ goto fail;
+ }
+ if (!STRNEQ(p, "CORE")) {
+ error(WARNING, "invalid NT_PRSTATUS note (name != \"CORE\"\n");
+ goto fail;
+ }
+
+ /*
+ * Find correct location of note data. This contains elf_prstatus
+ * structure which has registers etc. for the crashed task.
+ */
+ offset = sizeof(Elf64_Nhdr);
+ offset = roundup(offset + note->n_namesz, 4);
+ p = buf + offset; /* start of elf_prstatus */
+
+ BCOPY(p + OFFSET(elf_prstatus_pr_reg), &panic_task_regs[i],
+ sizeof(panic_task_regs[i]));
+ }
+
+ /*
+ * And finally we have the registers for the crashed task. This is
+ * used later on when dumping backtrace.
+ */
+ ms->crash_task_regs = panic_task_regs;
+
+ FREEBUF(buf);
+ FREEBUF(notes_ptrs);
+ return TRUE;
+
+fail:
+ FREEBUF(buf);
+ FREEBUF(notes_ptrs);
+ free(panic_task_regs);
+ return FALSE;
+}
+
+static int
+mips64_get_elf_notes(void)
+{
+ struct machine_specific *ms = machdep->machspec;
+ int i;
+
+ if (!DISKDUMP_DUMPFILE() && !KDUMP_DUMPFILE())
+ return FALSE;
+
+ panic_task_regs = calloc(kt->cpus, sizeof(*panic_task_regs));
+ if (!panic_task_regs)
+ error(FATAL, "cannot calloc panic_task_regs space\n");
+
+ for (i = 0; i < kt->cpus; i++) {
+ Elf64_Nhdr *note = NULL;
+ size_t len;
+
+ if (DISKDUMP_DUMPFILE())
+ note = diskdump_get_prstatus_percpu(i);
+ else if (KDUMP_DUMPFILE())
+ note = netdump_get_prstatus_percpu(i);
+
+ if (!note) {
+ error(WARNING,
+ "cannot find NT_PRSTATUS note for cpu: %d\n", i);
+ continue;
+ }
+
+ len = sizeof(Elf64_Nhdr);
+ len = roundup(len + note->n_namesz, 4);
+
+ BCOPY((char *)note + len + OFFSET(elf_prstatus_pr_reg),
+ &panic_task_regs[i], sizeof(panic_task_regs[i]));
+ }
+
+ ms->crash_task_regs = panic_task_regs;
+
+ return TRUE;
+}
+
/*
* Accept or reject a symbol from the kernel namelist.
*/
@@ -959,9 +1147,22 @@ mips64_init(int when)
mips64_stackframe_init();
if (!machdep->hz)
machdep->hz = 250;
+ MEMBER_OFFSET_INIT(elf_prstatus_pr_reg, "elf_prstatus",
+ "pr_reg");
+ STRUCT_SIZE_INIT(note_buf, "note_buf_t");
break;
case POST_VM:
+ /*
+ * crash_notes contains machine specific information about the
+ * crash. In particular, it contains CPU registers at the time
+ * of the crash. We need this information to extract correct
+ * backtraces from the panic task.
+ */
+ if (!ACTIVE() && !mips64_init_active_task_regs())
+ error(WARNING,
+ "cannot retrieve registers for active task%s\n\n",
+ kt->cpus > 1 ? "s" : "");
break;
}
}
--
2.1.0
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