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From c05db8d7d83389a342664073547bd29eda900158 Mon Sep 17 00:00:00 2001
From: Hong YANG <hong.yang3@nio.com>
Date: Mon, 15 Nov 2021 15:41:01 +0800
Subject: [PATCH 1/2] arm64: Support overflow stack panic
Kernel commit <872d8327ce89> ("arm64: add VMAP_STACK overflow detection")
has supported the overflow stack exception handling. Without the patch, the
"bt" command will make crash generate a core dump because of segmentation
fault. With the patch, the "bt" command can display the overflow stack.
Before:
crash> bt
PID: 3607 TASK: ffffffcbf9a4da00 CPU: 2 COMMAND: "sh"
Segmentation fault (core dumped)
After:
crash> bt
PID: 3607 TASK: ffffffcbf9a4da00 CPU: 2 COMMAND: "sh"
#0 [ffffffccbfd85f50] __delay at ffffff8008ceded8
...
#5 [ffffffccbfd85fd0] emergency_restart at ffffff80080d49fc
#6 [ffffffccbfd86140] panic at ffffff80080af4c0
#7 [ffffffccbfd86150] nmi_panic at ffffff80080af150
#8 [ffffffccbfd86190] handle_bad_stack at ffffff800808b0b8
#9 [ffffffccbfd862d0] __bad_stack at ffffff800808285c
PC: ffffff8008082e80 [el1_sync]
LR: ffffff8000d6c214 [stack_overflow_demo+84]
SP: ffffff1a79930070 PSTATE: 204003c5
X29: ffffff8011b03d00 X28: ffffffcbf9a4da00 X27: ffffff8008e02000
X26: 0000000000000040 X25: 0000000000000124 X24: ffffffcbf9a4da00
X23: 0000007daec2e288 X22: ffffffcbfe03b800 X21: 0000007daec2e288
X20: 0000000000000002 X19: 0000000000000002 X18: 0000000000000002
X17: 00000000000003e7 X16: 0000000000000000 X15: 0000000000000000
X14: ffffffcc17facb00 X13: ffffffccb4c25c00 X12: 0000000000000000
X11: ffffffcc17fad660 X10: 0000000000000af0 X9: 0000000000000000
X8: ffffff1a799334f0 X7: 0000000000000000 X6: 000000000000003f
X5: 0000000000000040 X4: 0000000000000010 X3: 00000065981d07f0
X2: 00000065981d07f0 X1: 0000000000000000 X0: ffffff1a799334f0
Signed-off-by: Hong YANG <hong.yang3@nio.com>
---
arm64.c | 169 ++++++++++++++++++++++++++++++++++++++++++++++++++------
defs.h | 6 ++
2 files changed, 159 insertions(+), 16 deletions(-)
diff --git a/arm64.c b/arm64.c
index 94681d1a37db..23c3d75d85aa 100644
--- a/arm64.c
+++ b/arm64.c
@@ -45,6 +45,7 @@ static int arm64_vtop_3level_4k(ulong, ulong, physaddr_t *, int);
static int arm64_vtop_4level_4k(ulong, ulong, physaddr_t *, int);
static ulong arm64_get_task_pgd(ulong);
static void arm64_irq_stack_init(void);
+static void arm64_overflow_stack_init(void);
static void arm64_stackframe_init(void);
static int arm64_eframe_search(struct bt_info *);
static int arm64_is_kernel_exception_frame(struct bt_info *, ulong);
@@ -63,6 +64,7 @@ static int arm64_get_dumpfile_stackframe(struct bt_info *, struct arm64_stackfra
static int arm64_in_kdump_text(struct bt_info *, struct arm64_stackframe *);
static int arm64_in_kdump_text_on_irq_stack(struct bt_info *);
static int arm64_switch_stack(struct bt_info *, struct arm64_stackframe *, FILE *);
+static int arm64_switch_stack_from_overflow(struct bt_info *, struct arm64_stackframe *, FILE *);
static int arm64_get_stackframe(struct bt_info *, struct arm64_stackframe *);
static void arm64_get_stack_frame(struct bt_info *, ulong *, ulong *);
static void arm64_gen_hidden_frame(struct bt_info *bt, ulong, struct arm64_stackframe *);
@@ -78,8 +80,11 @@ static int arm64_get_smp_cpus(void);
static void arm64_clear_machdep_cache(void);
static int arm64_on_process_stack(struct bt_info *, ulong);
static int arm64_in_alternate_stack(int, ulong);
+static int arm64_in_alternate_stackv(int cpu, ulong stkptr, ulong *stacks, ulong stack_size);
static int arm64_on_irq_stack(int, ulong);
+static int arm64_on_overflow_stack(int, ulong);
static void arm64_set_irq_stack(struct bt_info *);
+static void arm64_set_overflow_stack(struct bt_info *);
static void arm64_set_process_stack(struct bt_info *);
static int arm64_get_kvaddr_ranges(struct vaddr_range *);
static void arm64_get_crash_notes(void);
@@ -463,6 +468,7 @@ arm64_init(int when)
machdep->hz = 100;
arm64_irq_stack_init();
+ arm64_overflow_stack_init();
arm64_stackframe_init();
break;
@@ -1715,6 +1721,49 @@ arm64_irq_stack_init(void)
}
}
+/*
+ * Gather Overflow stack values.
+ *
+ * Overflow stack supported since 4.14, in commit 872d8327c
+ */
+static void
+arm64_overflow_stack_init(void)
+{
+ int i;
+ struct syment *sp;
+ struct gnu_request request, *req;
+ struct machine_specific *ms = machdep->machspec;
+ req = &request;
+
+ if (symbol_exists("overflow_stack") &&
+ (sp = per_cpu_symbol_search("overflow_stack")) &&
+ get_symbol_type("overflow_stack", NULL, req)) {
+ if (CRASHDEBUG(1)) {
+ fprintf(fp, "overflow_stack: \n");
+ fprintf(fp, " type: %x, %s\n",
+ (int)req->typecode,
+ (req->typecode == TYPE_CODE_ARRAY) ?
+ "TYPE_CODE_ARRAY" : "other");
+ fprintf(fp, " target_typecode: %x, %s\n",
+ (int)req->target_typecode,
+ req->target_typecode == TYPE_CODE_INT ?
+ "TYPE_CODE_INT" : "other");
+ fprintf(fp, " target_length: %ld\n",
+ req->target_length);
+ fprintf(fp, " length: %ld\n", req->length);
+ }
+
+ if (!(ms->overflow_stacks = (ulong *)malloc((size_t)(kt->cpus * sizeof(ulong)))))
+ error(FATAL, "cannot malloc overflow_stack addresses\n");
+
+ ms->overflow_stack_size = ARM64_OVERFLOW_STACK_SIZE;
+ machdep->flags |= OVERFLOW_STACKS;
+
+ for (i = 0; i < kt->cpus; i++)
+ ms->overflow_stacks[i] = kt->__per_cpu_offset[i] + sp->value;
+ }
+}
+
/*
* Gather and verify all of the backtrace requirements.
*/
@@ -1960,6 +2009,7 @@ static char *arm64_exception_functions[] = {
"do_mem_abort",
"do_el0_irq_bp_hardening",
"do_sp_pc_abort",
+ "handle_bad_stack",
NULL
};
@@ -1978,7 +2028,10 @@ arm64_in_exception_text(ulong ptr)
if ((ptr >= ms->__exception_text_start) &&
(ptr < ms->__exception_text_end))
return TRUE;
- } else if ((name = closest_symbol(ptr))) { /* Linux 5.5 and later */
+ }
+
+ name = closest_symbol(ptr);
+ if (name != NULL) { /* Linux 5.5 and later */
for (func = &arm64_exception_functions[0]; *func; func++) {
if (STREQ(name, *func))
return TRUE;
@@ -2252,15 +2305,14 @@ arm64_unwind_frame(struct bt_info *bt, struct arm64_stackframe *frame)
if ((frame->fp == 0) && (frame->pc == 0))
return FALSE;
- if (!(machdep->flags & IRQ_STACKS))
- return TRUE;
-
- if (!(machdep->flags & IRQ_STACKS))
+ if (!(machdep->flags & (IRQ_STACKS | OVERFLOW_STACKS)))
return TRUE;
if (machdep->flags & UNW_4_14) {
- if ((bt->flags & BT_IRQSTACK) &&
- !arm64_on_irq_stack(bt->tc->processor, frame->fp)) {
+ if (((bt->flags & BT_IRQSTACK) &&
+ !arm64_on_irq_stack(bt->tc->processor, frame->fp)) ||
+ ((bt->flags & BT_OVERFLOW_STACK) &&
+ !arm64_on_overflow_stack(bt->tc->processor, frame->fp))) {
if (arm64_on_process_stack(bt, frame->fp)) {
arm64_set_process_stack(bt);
@@ -2677,6 +2729,9 @@ arm64_back_trace_cmd(struct bt_info *bt)
if (arm64_on_irq_stack(bt->tc->processor, bt->frameptr)) {
arm64_set_irq_stack(bt);
bt->flags |= BT_IRQSTACK;
+ } else if (arm64_on_overflow_stack(bt->tc->processor, bt->frameptr)) {
+ arm64_set_overflow_stack(bt);
+ bt->flags |= BT_OVERFLOW_STACK;
}
stackframe.sp = bt->stkptr;
stackframe.pc = bt->instptr;
@@ -2731,7 +2786,9 @@ arm64_back_trace_cmd(struct bt_info *bt)
break;
if (arm64_in_exception_text(bt->instptr) && INSTACK(stackframe.fp, bt)) {
- if (!(bt->flags & BT_IRQSTACK) ||
+ if (bt->flags & BT_OVERFLOW_STACK) {
+ exception_frame = stackframe.fp - KERN_EFRAME_OFFSET;
+ } else if (!(bt->flags & BT_IRQSTACK) ||
((stackframe.sp + SIZE(pt_regs)) < bt->stacktop)) {
if (arm64_is_kernel_exception_frame(bt, stackframe.fp - KERN_EFRAME_OFFSET))
exception_frame = stackframe.fp - KERN_EFRAME_OFFSET;
@@ -2745,6 +2802,12 @@ arm64_back_trace_cmd(struct bt_info *bt)
break;
}
+ if ((bt->flags & BT_OVERFLOW_STACK) &&
+ !arm64_on_overflow_stack(bt->tc->processor, stackframe.fp)) {
+ bt->flags &= ~BT_OVERFLOW_STACK;
+ if (arm64_switch_stack_from_overflow(bt, &stackframe, ofp) == USER_MODE)
+ break;
+ }
level++;
}
@@ -3131,6 +3194,43 @@ arm64_switch_stack(struct bt_info *bt, struct arm64_stackframe *frame, FILE *ofp
return KERNEL_MODE;
}
+static int
+arm64_switch_stack_from_overflow(struct bt_info *bt, struct arm64_stackframe *frame, FILE *ofp)
+{
+ int i;
+ ulong stacktop, words, addr;
+ ulong *stackbuf;
+ char buf[BUFSIZE];
+ struct machine_specific *ms = machdep->machspec;
+
+ if (bt->flags & BT_FULL) {
+ stacktop = ms->overflow_stacks[bt->tc->processor] + ms->overflow_stack_size;
+ words = (stacktop - bt->bptr) / sizeof(ulong);
+ stackbuf = (ulong *)GETBUF(words * sizeof(ulong));
+ readmem(bt->bptr, KVADDR, stackbuf, words * sizeof(long),
+ "top of overflow stack", FAULT_ON_ERROR);
+
+ addr = bt->bptr;
+ for (i = 0; i < words; i++) {
+ if (!(i & 1))
+ fprintf(ofp, "%s %lx: ", i ? "\n" : "", addr);
+ fprintf(ofp, "%s ", format_stack_entry(bt, buf, stackbuf[i], 0));
+ addr += sizeof(ulong);
+ }
+ fprintf(ofp, "\n");
+ FREEBUF(stackbuf);
+ }
+ fprintf(ofp, "--- <Overflow stack> ---\n");
+
+ if (frame->fp == 0)
+ return USER_MODE;
+
+ if (!(machdep->flags & UNW_4_14))
+ arm64_print_exception_frame(bt, frame->sp, KERNEL_MODE, ofp);
+
+ return KERNEL_MODE;
+}
+
static int
arm64_get_dumpfile_stackframe(struct bt_info *bt, struct arm64_stackframe *frame)
{
@@ -3682,6 +3782,16 @@ arm64_display_machine_stats(void)
machdep->machspec->irq_stacks[i]);
}
}
+ if (machdep->machspec->overflow_stack_size) {
+ fprintf(fp, "OVERFLOW STACK SIZE: %ld\n",
+ machdep->machspec->overflow_stack_size);
+ fprintf(fp, " OVERFLOW STACKS:\n");
+ for (i = 0; i < kt->cpus; i++) {
+ pad = (i < 10) ? 3 : (i < 100) ? 2 : (i < 1000) ? 1 : 0;
+ fprintf(fp, "%s CPU %d: %lx\n", space(pad), i,
+ machdep->machspec->overflow_stacks[i]);
+ }
+ }
}
static int
@@ -3875,24 +3985,41 @@ arm64_on_process_stack(struct bt_info *bt, ulong stkptr)
}
static int
-arm64_on_irq_stack(int cpu, ulong stkptr)
+arm64_in_alternate_stackv(int cpu, ulong stkptr, ulong *stacks, ulong stack_size)
{
- return arm64_in_alternate_stack(cpu, stkptr);
+ if ((cpu >= kt->cpus) || (stacks == NULL) || !stack_size)
+ return FALSE;
+
+ if ((stkptr >= stacks[cpu]) &&
+ (stkptr < (stacks[cpu] + stack_size)))
+ return TRUE;
+
+ return FALSE;
}
static int
arm64_in_alternate_stack(int cpu, ulong stkptr)
+{
+ return (arm64_on_irq_stack(cpu, stkptr) ||
+ arm64_on_overflow_stack(cpu, stkptr));
+}
+
+static int
+arm64_on_irq_stack(int cpu, ulong stkptr)
{
struct machine_specific *ms = machdep->machspec;
- if (!ms->irq_stack_size || (cpu >= kt->cpus))
- return FALSE;
+ return arm64_in_alternate_stackv(cpu, stkptr,
+ ms->irq_stacks, ms->irq_stack_size);
+}
- if ((stkptr >= ms->irq_stacks[cpu]) &&
- (stkptr < (ms->irq_stacks[cpu] + ms->irq_stack_size)))
- return TRUE;
+static int
+arm64_on_overflow_stack(int cpu, ulong stkptr)
+{
+ struct machine_specific *ms = machdep->machspec;
- return FALSE;
+ return arm64_in_alternate_stackv(cpu, stkptr,
+ ms->overflow_stacks, ms->overflow_stack_size);
}
static void
@@ -3905,6 +4032,16 @@ arm64_set_irq_stack(struct bt_info *bt)
alter_stackbuf(bt);
}
+static void
+arm64_set_overflow_stack(struct bt_info *bt)
+{
+ struct machine_specific *ms = machdep->machspec;
+
+ bt->stackbase = ms->overflow_stacks[bt->tc->processor];
+ bt->stacktop = bt->stackbase + ms->overflow_stack_size;
+ alter_stackbuf(bt);
+}
+
static void
arm64_set_process_stack(struct bt_info *bt)
{
diff --git a/defs.h b/defs.h
index 43eff46b105d..caaa11e50c87 100644
--- a/defs.h
+++ b/defs.h
@@ -3218,6 +3218,7 @@ typedef signed int s32;
#define UNW_4_14 (0x200)
#define FLIPPED_VM (0x400)
#define HAS_PHYSVIRT_OFFSET (0x800)
+#define OVERFLOW_STACKS (0x1000)
/*
* Get kimage_voffset from /dev/crash
@@ -3260,6 +3261,7 @@ typedef signed int s32;
#define ARM64_STACK_SIZE (16384)
#define ARM64_IRQ_STACK_SIZE ARM64_STACK_SIZE
+#define ARM64_OVERFLOW_STACK_SIZE (4096)
#define _SECTION_SIZE_BITS 30
#define _SECTION_SIZE_BITS_5_12 27
@@ -3332,6 +3334,9 @@ struct machine_specific {
char *irq_stackbuf;
ulong __irqentry_text_start;
ulong __irqentry_text_end;
+ ulong overflow_stack_size;
+ ulong *overflow_stacks;
+ char *overflow_stackbuf;
/* for exception vector code */
ulong exp_entry1_start;
ulong exp_entry1_end;
@@ -5778,6 +5783,7 @@ ulong cpu_map_addr(const char *type);
#define BT_CPUMASK (0x1000000000000ULL)
#define BT_SHOW_ALL_REGS (0x2000000000000ULL)
#define BT_REGS_NOT_FOUND (0x4000000000000ULL)
+#define BT_OVERFLOW_STACK (0x8000000000000ULL)
#define BT_SYMBOL_OFFSET (BT_SYMBOLIC_ARGS)
#define BT_REF_HEXVAL (0x1)
--
2.30.2
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