[Crash-utility] [PATCH] Bugfix and optimization for ARM64 getting crash notes

[qiwuchen55 at gmail.com]

From: chenqiwu <chenqiwu at xiaomi.com>

1) ARM64 call arm64_get_crash_notes() to retrieve active task
registers when POST_VM before calling map_cpus_to_prstatus()
to remap the NT_PRSTATUS elf notes to the online cpus. It's
better to call arm64_get_crash_notes() when POST_INIT.
2) arm64_get_crash_notes() check the sanity of NT_PRSTATUS notes
only for online cpus. If one cpu contains invalid note, it's
better to continue finding the crash notes for other online cpus.
So we can extract the backtraces for the online cpus which contain
valid note by using command "bt -a".
3) map_cpus_to_prstatus() remap the NT_PRSTATUS notes only to the
online cpus. Make sure there must be a one-to-one relationship
between the number of online cpus and the number of notes.

Signed-off-by: chenqiwu <chenqiwu at xiaomi.com>
---
 arm64.c    | 49 +++++++++++++++++++++++++++++--------------------
 diskdump.c |  9 +++------
 netdump.c  |  4 ++--
 3 files changed, 34 insertions(+), 28 deletions(-)

diff --git a/arm64.c b/arm64.c
index 233029d..cbad461 100644
--- a/arm64.c
+++ b/arm64.c
@@ -458,7 +458,7 @@ arm64_init(int when)
 		arm64_stackframe_init();
 		break;
 
-	case POST_VM:
+	case POST_INIT:
 		/*
 		 * crash_notes contains machine specific information about the
 		 * crash. In particular, it contains CPU registers at the time
@@ -3587,7 +3587,7 @@ arm64_get_crash_notes(void)
 	ulong offset;
 	char *buf, *p;
 	ulong *notes_ptrs;
-	ulong i;
+	ulong i, j;
 
 	if (!symbol_exists("crash_notes"))
 		return FALSE;
@@ -3620,12 +3620,12 @@ arm64_get_crash_notes(void)
 	if (!(ms->panic_task_regs = calloc((size_t)kt->cpus, sizeof(struct arm64_pt_regs))))
 		error(FATAL, "cannot calloc panic_task_regs space\n");
 	
-	for  (i = 0; i < kt->cpus; i++) {
-
+	for  (i = 0, j = 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: failed to read note_buf_t\n", i);
+			++j;
+			continue;
 		}
 
 		/*
@@ -3655,19 +3655,29 @@ arm64_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);
+				if (CRASHDEBUG(1))
+					error(WARNING,
+						"cpu#%d: cannot find NT_PRSTATUS note\n", i);
+				++j;
 				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 note (n_type != NT_PRSTATUS)\n", i);
+			++j;
+			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 note (name != \"CORE\")\n", i);
+			++j;
+			continue;
 		}
 
 		/*
@@ -3684,14 +3694,13 @@ arm64_get_crash_notes(void)
 
 	FREEBUF(buf);
 	FREEBUF(notes_ptrs);
-	return TRUE;
 
-fail:
-	FREEBUF(buf);
-	FREEBUF(notes_ptrs);
-	free(ms->panic_task_regs);
-	ms->panic_task_regs = NULL;
-	return FALSE;
+	if (j == kt->cpus) {
+		free(ms->panic_task_regs);
+		ms->panic_task_regs = NULL;
+		return FALSE;
+	}
+	return TRUE;
 }
 
 static void
diff --git a/diskdump.c b/diskdump.c
index e88243e..12d8e9c 100644
--- a/diskdump.c
+++ b/diskdump.c
@@ -130,12 +130,9 @@ map_cpus_to_prstatus_kdump_cmprs(void)
 	 */
 	nrcpus = (kt->kernel_NR_CPUS ? kt->kernel_NR_CPUS : NR_CPUS);
 
-	for (i = 0, j = 0; i < nrcpus; i++) {
-		if (in_cpu_map(ONLINE_MAP, i)) {
-			dd->nt_prstatus_percpu[i] = nt_ptr[j++];
-			dd->num_prstatus_notes = 
-				MAX(dd->num_prstatus_notes, i+1);
-		}
+	for (i = 0; i < nrcpus; i++) {
+		if (in_cpu_map(ONLINE_MAP, i))
+			dd->nt_prstatus_percpu[i] = nt_ptr[i];
 	}
 
 	FREEBUF(nt_ptr);
diff --git a/netdump.c b/netdump.c
index 406416a..849638a 100644
--- a/netdump.c
+++ b/netdump.c
@@ -97,9 +97,9 @@ map_cpus_to_prstatus(void)
 	 */
 	nrcpus = (kt->kernel_NR_CPUS ? kt->kernel_NR_CPUS : NR_CPUS);
 
-	for (i = 0, j = 0; i < nrcpus; i++) {
+	for (i = 0; i < nrcpus; i++) {
 		if (in_cpu_map(ONLINE_MAP, i))
-			nd->nt_prstatus_percpu[i] = nt_ptr[j++];
+			nd->nt_prstatus_percpu[i] = nt_ptr[i];
 	}
 
 	FREEBUF(nt_ptr);
-- 
1.9.1