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arm64: Support overflow stack panic
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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 <[email protected]>
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@yangh @lian-bo
yangh authored and lian-bo committed Dec 1, 2021
1 parent d9b11dd commit 995db8a
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Showing 2 changed files with 159 additions and 16 deletions.
169 changes: 153 additions & 16 deletions arm64.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand All @@ -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 *);
Expand All @@ -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);
Expand Down Expand Up @@ -463,6 +468,7 @@ arm64_init(int when)
machdep->hz = 100;

arm64_irq_stack_init();
arm64_overflow_stack_init();
arm64_stackframe_init();
break;

Expand Down Expand Up @@ -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.
*/
Expand Down Expand Up @@ -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
};

Expand All @@ -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;
Expand Down Expand Up @@ -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);

Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand All @@ -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++;
}
Expand Down Expand Up @@ -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)
{
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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
Expand All @@ -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)
{
Expand Down
6 changes: 6 additions & 0 deletions defs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -5770,6 +5775,7 @@ 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)
Expand Down

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