arm64: Get CPU registers from ELF notes even without crash_notes symbol

Currently arm64 crash retrieves the CPU registers from crash_notes symbol
or ELF notes only when the symbol exists, but there are dumpfiles which
have the registers in ELF notes without the symbol.

With the patch, crash can retrieve the registers from ELF notes without
the crash_notes symbol.

Signed-off-by: James Hsu <james.hsu@mediatek.com>
Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>

arm64.c

@@ -3698,14 +3698,48 @@ arm64_get_crash_notes(void)
 {
 	struct machine_specific *ms = machdep->machspec;
 	ulong crash_notes;
-	Elf64_Nhdr *note;
+	Elf64_Nhdr *note = NULL;
 	ulong offset;
 	char *buf, *p;
 	ulong *notes_ptrs;
 	ulong i, found;
 
-	if (!symbol_exists("crash_notes"))
+	if (!symbol_exists("crash_notes")) {
+		if (DISKDUMP_DUMPFILE() || KDUMP_DUMPFILE()) {
+			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 = found = 0; i < kt->cpus; i++) {
+				if (DISKDUMP_DUMPFILE())
+					note = diskdump_get_prstatus_percpu(i);
+				else if (KDUMP_DUMPFILE())
+					note = netdump_get_prstatus_percpu(i);
+
+				if (!note) {
+					error(WARNING, "cpu %d: cannot find NT_PRSTATUS note\n", i);
+					continue;
+				}
+
+				/*
+				 * 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 = (char *)note + offset; /* start of elf_prstatus */
+
+				BCOPY(p + OFFSET(elf_prstatus_pr_reg), &ms->panic_task_regs[i],
+				      sizeof(struct arm64_pt_regs));
+
+				found++;
+			}
+			if (!found) {
+				free(ms->panic_task_regs);
+				ms->panic_task_regs = NULL;
+			}
+		}
 		return;
+	}
 
 	crash_notes = symbol_value("crash_notes");