[Crash-utility] [PATCH 10/16] MIPS64: Add basic support for the 'bt' command
Youling Tang
tangyouling at loongson.cn
Tue Jan 26 11:17:32 UTC 2021
Add basic support for the 'bt' command, refer to the implementation
of mips.c.
E.g. With this patch:
crash> bt
PID: 4768 TASK: 9800000243bcf200 CPU: 3 COMMAND: "bash"
bt: WARNING: cannot determine starting stack frame for task 9800000243bcf200
Signed-off-by: Huacai Chen <chenhuacai at loongson.cn>
Signed-off-by: Youling Tang <tangyouling at loongson.cn>
---
mips64.c | 427 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 426 insertions(+), 1 deletion(-)
diff --git a/mips64.c b/mips64.c
index 18e763d..57a7f41 100644
--- a/mips64.c
+++ b/mips64.c
@@ -28,6 +28,21 @@ static int mips64_kvtop(struct task_context *tc, ulong kvaddr,
physaddr_t *paddr, int verbose);
static void mips64_cmd_mach(void);
static void mips64_display_machine_stats(void);
+static void mips64_back_trace_cmd(struct bt_info *bt);
+static void mips64_analyze_function(ulong start, ulong offset,
+ struct mips64_unwind_frame *current,
+ struct mips64_unwind_frame *previous);
+static void mips64_dump_backtrace_entry(struct bt_info *bt,
+ struct syment *sym, struct mips64_unwind_frame *current,
+ struct mips64_unwind_frame *previous, int level);
+static void mips64_dump_exception_stack(struct bt_info *bt, char *pt_regs);
+static int mips64_is_exception_entry(struct syment *sym);
+static void mips64_stackframe_init(void);
+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);
+
/*
* 3 Levels paging PAGE_SIZE=16KB
@@ -385,6 +400,413 @@ mips64_display_machine_stats(void)
}
/*
+ * Unroll a kernel stack.
+ */
+static void
+mips64_back_trace_cmd(struct bt_info *bt)
+{
+ struct mips64_unwind_frame current, previous;
+ struct mips64_register *regs;
+ struct mips64_pt_regs_main *mains;
+ struct mips64_pt_regs_cp0 *cp0;
+ char pt_regs[SIZE(pt_regs)];
+ int level = 0;
+ int invalid_ok = 1;
+
+ if (bt->flags & BT_REGS_NOT_FOUND)
+ return;
+
+ previous.sp = previous.pc = previous.ra = 0;
+
+ current.pc = bt->instptr;
+ current.sp = bt->stkptr;
+ current.ra = 0;
+
+ if (!INSTACK(current.sp, bt))
+ return;
+
+ if (bt->machdep) {
+ regs = bt->machdep;
+ previous.pc = current.ra = regs->regs[MIPS64_EF_R31];
+ }
+
+ while (current.sp <= bt->stacktop - 32 - SIZE(pt_regs)) {
+ struct syment *symbol = NULL;
+ ulong offset;
+
+ if (CRASHDEBUG(8))
+ fprintf(fp, "level %d pc %#lx ra %#lx sp %lx\n",
+ level, current.pc, current.ra, current.sp);
+
+ if (!IS_KVADDR(current.pc) && !invalid_ok)
+ return;
+
+ symbol = value_search(current.pc, &offset);
+ if (!symbol && !invalid_ok) {
+ error(FATAL, "PC is unknown symbol (%lx)", current.pc);
+ return;
+ }
+ invalid_ok = 0;
+
+ /*
+ * If we get an address which points to the start of a
+ * function, then it could one of the following:
+ *
+ * - we are dealing with a noreturn function. The last call
+ * from a noreturn function has an ra which points to the
+ * start of the function after it. This is common in the
+ * oops callchain because of die() which is annotated as
+ * noreturn.
+ *
+ * - we have taken an exception at the start of this function.
+ * In this case we already have the RA in current.ra.
+ *
+ * - we are in one of these routines which appear with zero
+ * offset in manually-constructed stack frames:
+ *
+ * * ret_from_exception
+ * * ret_from_irq
+ * * ret_from_fork
+ * * ret_from_kernel_thread
+ */
+ if (symbol && !STRNEQ(symbol->name, "ret_from") && !offset &&
+ !current.ra && current.sp < bt->stacktop - 32 - SIZE(pt_regs)) {
+ if (CRASHDEBUG(8))
+ fprintf(fp, "zero offset at %s, try previous symbol\n",
+ symbol->name);
+
+ symbol = value_search(current.pc - 4, &offset);
+ if (!symbol) {
+ error(FATAL, "PC is unknown symbol (%lx)", current.pc);
+ return;
+ }
+ }
+
+ if (symbol && mips64_is_exception_entry(symbol)) {
+
+ mains = (struct mips64_pt_regs_main *) \
+ (pt_regs + OFFSET(pt_regs_regs));
+ cp0 = (struct mips64_pt_regs_cp0 *) \
+ (pt_regs + OFFSET(pt_regs_cp0_badvaddr));
+
+ GET_STACK_DATA(current.sp, pt_regs, sizeof(pt_regs));
+
+ previous.ra = mains->regs[31];
+ previous.sp = mains->regs[29];
+ current.ra = cp0->cp0_epc;
+
+ if (CRASHDEBUG(8))
+ fprintf(fp, "exception pc %#lx ra %#lx sp %lx\n",
+ previous.pc, previous.ra, previous.sp);
+
+ /* The PC causing the exception may have been invalid */
+ invalid_ok = 1;
+ } else if (symbol) {
+ mips64_analyze_function(symbol->value, offset, ¤t, &previous);
+ } else {
+ /*
+ * The current PC is invalid. Assume that the code
+ * jumped through a invalid pointer and that the SP has
+ * not been adjusted.
+ */
+ previous.sp = current.sp;
+ }
+
+ mips64_dump_backtrace_entry(bt, symbol, ¤t, &previous, level++);
+
+ current.pc = current.ra;
+ current.sp = previous.sp;
+ current.ra = previous.ra;
+
+ if (CRASHDEBUG(8))
+ fprintf(fp, "next %d pc %#lx ra %#lx sp %lx\n",
+ level, current.pc, current.ra, current.sp);
+
+ previous.sp = previous.pc = previous.ra = 0;
+ }
+}
+
+static void
+mips64_analyze_function(ulong start, ulong offset,
+ struct mips64_unwind_frame *current,
+ struct mips64_unwind_frame *previous)
+{
+ ulong i, reg;
+ ulong rapos = 0;
+ ulong spadjust = 0;
+ uint32_t *funcbuf, *ip;
+
+ if (CRASHDEBUG(8))
+ fprintf(fp, "%s: start %#lx offset %#lx\n",
+ __func__, start, offset);
+
+ if (!offset) {
+ previous->sp = current->sp;
+ return;
+ }
+
+ ip = funcbuf = (uint32_t *)GETBUF(offset);
+ if (!readmem(start, KVADDR, funcbuf, offset,
+ "mips64_analyze_function", RETURN_ON_ERROR)) {
+ FREEBUF(funcbuf);
+ error(WARNING, "Cannot read function at %16lx\n", start);
+ return;
+ }
+
+ for (i = 0; i < offset; i += 4) {
+ ulong insn = *ip & 0xffffffff;
+ ulong high = (insn >> 16) & 0xffff;
+ ulong low = insn & 0xffff;
+
+ if (CRASHDEBUG(8))
+ fprintf(fp, "insn @ %#lx = %#lx\n", start + i, insn);
+
+ if (high == 0x27bd || high == 0x67bd) { /* ADDIU/DADDIU sp, sp, imm */
+ if (!(low & 0x8000))
+ break;
+
+ spadjust += 0x10000 - low;
+ if (CRASHDEBUG(8))
+ fprintf(fp, "spadjust = %lu\n", spadjust);
+ } else if (high == 0xafbf) { /* SW RA, imm(SP) */
+ rapos = current->sp + low;
+ if (CRASHDEBUG(8))
+ fprintf(fp, "rapos %lx\n", rapos);
+ break;
+ } else if (high == 0xffbf) { /* SD RA, imm(SP) */
+ rapos = current->sp + low;
+ if (CRASHDEBUG(8))
+ fprintf(fp, "rapos %lx\n", rapos);
+ break;
+ } else if ((insn & 0xffe08020) == 0xeba00020) { /* GSSQ reg, reg, offset(SP) */
+ reg = (insn >> 16) & 0x1f;
+ if (reg == 31) {
+ low = ((((insn >> 6) & 0x1ff) ^ 0x100) - 0x100) << 4;
+ rapos = current->sp + low;
+ if (CRASHDEBUG(8))
+ fprintf(fp, "rapos %lx\n", rapos);
+ break;
+ }
+ reg = insn & 0x1f;
+ if (reg == 31) {
+ low = (((((insn >> 6) & 0x1ff) ^ 0x100) - 0x100) << 4) + 8;
+ rapos = current->sp + low;
+ if (CRASHDEBUG(8))
+ fprintf(fp, "rapos %lx\n", rapos);
+ break;
+ }
+ }
+
+ ip++;
+ }
+
+ FREEBUF(funcbuf);
+
+ previous->sp = current->sp + spadjust;
+
+ if (rapos && !readmem(rapos, KVADDR, ¤t->ra,
+ sizeof(current->ra), "RA from stack",
+ RETURN_ON_ERROR)) {
+ error(FATAL, "Cannot read RA from stack %lx", rapos);
+ return;
+ }
+}
+
+static void
+mips64_dump_backtrace_entry(struct bt_info *bt, struct syment *sym,
+ struct mips64_unwind_frame *current,
+ struct mips64_unwind_frame *previous, int level)
+{
+ const char *name = sym ? sym->name : "(invalid)";
+ struct load_module *lm;
+ char *name_plus_offset = NULL;
+ struct syment *symp;
+ ulong symbol_offset;
+ char buf[BUFSIZE];
+ char pt_regs[SIZE(pt_regs)];
+
+ if (bt->flags & BT_SYMBOL_OFFSET) {
+ symp = value_search(current->pc, &symbol_offset);
+
+ if (symp && symbol_offset)
+ name_plus_offset =
+ value_to_symstr(current->pc, buf, bt->radix);
+ }
+
+ fprintf(fp, "%s#%d [%016lx] %s at %016lx", level < 10 ? " " : "", level,
+ current->sp, name_plus_offset ? name_plus_offset : name,
+ current->pc);
+
+ if (module_symbol(current->pc, NULL, &lm, NULL, 0))
+ fprintf(fp, " [%s]", lm->mod_name);
+
+ fprintf(fp, "\n");
+
+ if (sym && mips64_is_exception_entry(sym)) {
+ GET_STACK_DATA(current->sp, &pt_regs, SIZE(pt_regs));
+ mips64_dump_exception_stack(bt, pt_regs);
+ }
+}
+
+static void
+mips64_dump_exception_stack(struct bt_info *bt, char *pt_regs)
+{
+ struct mips64_pt_regs_main *mains;
+ struct mips64_pt_regs_cp0 *cp0;
+ int i;
+ char buf[BUFSIZE];
+
+ mains = (struct mips64_pt_regs_main *) (pt_regs + OFFSET(pt_regs_regs));
+ cp0 = (struct mips64_pt_regs_cp0 *) \
+ (pt_regs + OFFSET(pt_regs_cp0_badvaddr));
+
+ for (i = 0; i < 32; i += 4) {
+ fprintf(fp, " $%2d : %016lx %016lx %016lx %016lx\n",
+ i, mains->regs[i], mains->regs[i+1],
+ mains->regs[i+2], mains->regs[i+3]);
+ }
+ fprintf(fp, " Hi : %016lx\n", mains->hi);
+ fprintf(fp, " Lo : %016lx\n", mains->lo);
+
+ value_to_symstr(cp0->cp0_epc, buf, 16);
+ fprintf(fp, " epc : %016lx %s\n", cp0->cp0_epc, buf);
+
+ value_to_symstr(mains->regs[31], buf, 16);
+ fprintf(fp, " ra : %016lx %s\n", mains->regs[31], buf);
+
+ fprintf(fp, " Status: %016lx\n", mains->cp0_status);
+ fprintf(fp, " Cause : %016lx\n", cp0->cp0_cause);
+ fprintf(fp, " BadVA : %016lx\n", cp0->cp0_badvaddr);
+}
+
+static int
+mips64_is_exception_entry(struct syment *sym)
+{
+ return STREQ(sym->name, "ret_from_exception") ||
+ STREQ(sym->name, "ret_from_irq") ||
+ STREQ(sym->name, "work_resched") ||
+ STREQ(sym->name, "handle_sys") ||
+ STREQ(sym->name, "handle_sysn32") ||
+ STREQ(sym->name, "handle_sys64");
+}
+
+static void
+mips64_stackframe_init(void)
+{
+ long task_struct_thread = MEMBER_OFFSET("task_struct", "thread");
+ long thread_reg29 = MEMBER_OFFSET("thread_struct", "reg29");
+ long thread_reg31 = MEMBER_OFFSET("thread_struct", "reg31");
+
+ if ((task_struct_thread == INVALID_OFFSET) ||
+ (thread_reg29 == INVALID_OFFSET) ||
+ (thread_reg31 == INVALID_OFFSET)) {
+ error(FATAL,
+ "cannot determine thread_struct offsets\n");
+ return;
+ }
+
+ ASSIGN_OFFSET(task_struct_thread_reg29) =
+ task_struct_thread + thread_reg29;
+ ASSIGN_OFFSET(task_struct_thread_reg31) =
+ task_struct_thread + thread_reg31;
+
+ STRUCT_SIZE_INIT(pt_regs, "pt_regs");
+ MEMBER_OFFSET_INIT(pt_regs_regs, "pt_regs", "regs");
+ MEMBER_OFFSET_INIT(pt_regs_cp0_badvaddr, "pt_regs", "cp0_badvaddr");
+}
+
+/*
+ * Get a stack frame combination of pc and ra from the most relevant spot.
+ */
+static void
+mips64_get_stack_frame(struct bt_info *bt, ulong *pcp, ulong *spp)
+{
+ ulong ksp, nip;
+ int ret = 0;
+
+ nip = ksp = 0;
+ bt->machdep = NULL;
+
+ if (DUMPFILE() && is_task_active(bt->task))
+ ret = mips64_get_dumpfile_stack_frame(bt, &nip, &ksp);
+ else
+ ret = mips64_get_frame(bt, &nip, &ksp);
+
+ if (!ret)
+ error(WARNING, "cannot determine starting stack frame for task %lx\n",
+ bt->task);
+
+ if (pcp)
+ *pcp = nip;
+ if (spp)
+ *spp = ksp;
+}
+
+/*
+ * Get the starting point for the active cpu in a diskdump.
+ */
+static int
+mips64_get_dumpfile_stack_frame(struct bt_info *bt, ulong *nip, ulong *ksp)
+{
+ const struct machine_specific *ms = machdep->machspec;
+ struct mips64_register *regs;
+ ulong epc, r29;
+
+ if (!ms->crash_task_regs) {
+ bt->flags |= BT_REGS_NOT_FOUND;
+ return FALSE;
+ }
+
+ /*
+ * We got registers for panic task from crash_notes. Just return them.
+ */
+ regs = &ms->crash_task_regs[bt->tc->processor];
+ epc = regs->regs[MIPS64_EF_CP0_EPC];
+ r29 = regs->regs[MIPS64_EF_R29];
+
+ if (!epc && !r29) {
+ bt->flags |= BT_REGS_NOT_FOUND;
+ return FALSE;
+ }
+
+ if (nip)
+ *nip = epc;
+ if (ksp)
+ *ksp = r29;
+
+ bt->machdep = regs;
+
+ return TRUE;
+}
+
+/*
+ * Do the work for mips64_get_stack_frame() for non-active tasks.
+ * Get SP and PC values for idle tasks.
+ */
+static int
+mips64_get_frame(struct bt_info *bt, ulong *pcp, ulong *spp)
+{
+ if (!bt->tc || !(tt->flags & THREAD_INFO))
+ return FALSE;
+
+ if (!readmem(bt->task + OFFSET(task_struct_thread_reg31),
+ KVADDR, pcp, sizeof(*pcp),
+ "thread_struct.regs31",
+ RETURN_ON_ERROR)) {
+ return FALSE;
+ }
+
+ if (!readmem(bt->task + OFFSET(task_struct_thread_reg29),
+ KVADDR, spp, sizeof(*spp),
+ "thread_struct.regs29",
+ RETURN_ON_ERROR)) {
+ return FALSE;
+ }
+
+ return TRUE;
+}
+
+/*
* Accept or reject a symbol from the kernel namelist.
*/
static int
@@ -414,7 +836,7 @@ mips64_get_page_size(void)
static ulong
mips64_vmalloc_start(void)
{
- return 0;
+ return first_vmalloc_address();
}
/*
@@ -515,6 +937,8 @@ mips64_init(int when)
machdep->uvtop = mips64_uvtop;
machdep->kvtop = mips64_kvtop;
machdep->cmd_mach = mips64_cmd_mach;
+ machdep->back_trace = mips64_back_trace_cmd;
+ machdep->get_stack_frame = mips64_get_stack_frame;
machdep->vmalloc_start = mips64_vmalloc_start;
machdep->processor_speed = mips64_processor_speed;
machdep->get_stackbase = generic_get_stackbase;
@@ -532,6 +956,7 @@ mips64_init(int when)
mips64_init_page_flags();
machdep->section_size_bits = _SECTION_SIZE_BITS;
machdep->max_physmem_bits = _MAX_PHYSMEM_BITS;
+ mips64_stackframe_init();
if (!machdep->hz)
machdep->hz = 250;
break;
--
2.1.0
More information about the Crash-utility
mailing list