From 90cc414a34a8065d0d5e95a44587f7e84da5ef70 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] arm64: Support overflow stack panic

Overflow stack supported since kernel 4.14 in commit 872d8327ce8,
without this patch, bt command trigger a SIGSEGV fault due the SP
pointed to the overflow stack which not yet loaded by crash.

Before:

      KERNEL: ../vmlinux
    DUMPFILE: la_guestdump.gcore
        CPUS: 8
        DATE: Tue Jul 13 19:59:44 CST 2021
      UPTIME: 00:00:42
LOAD AVERAGE: 3.99, 1.13, 0.39
       TASKS: 1925
    NODENAME: localhost
     RELEASE: 4.14.156+
     VERSION: #1 SMP PREEMPT Tue Jul 13 10:37:23 UTC 2021
     MACHINE: aarch64  (unknown Mhz)
      MEMORY: 8.7 GB
       PANIC: "Kernel panic - not syncing: kernel stack overflow"
         PID: 1969
     COMMAND: "irq/139-0-0024"
        TASK: ffffffcc1a230000  [THREAD_INFO: ffffffcc1a230000]
         CPU: 0
       STATE: TASK_RUNNING (PANIC)

crash-7.3.0> bt
PID: 1969   TASK: ffffffcc1a230000  CPU: 0   COMMAND: "irq/139-0-0024"
Segmentation fault (core dumped)

After:

crash> bt
PID: 1969   TASK: ffffffcc1a230000  CPU: 0   COMMAND: "irq/139-0-0024"
  #0 [ffffffcc7fd5cf50] __delay at ffffff8008c80774
  #1 [ffffffcc7fd5cf60] __const_udelay at ffffff8008c80864
  #2 [ffffffcc7fd5cf80] msm_trigger_wdog_bite at ffffff80084e9430
  #3 [ffffffcc7fd5cfa0] do_vm_restart at ffffff80087bc974
  #4 [ffffffcc7fd5cfc0] machine_restart at ffffff80080856fc
  #5 [ffffffcc7fd5cfd0] emergency_restart at ffffff80080d49bc
  #6 [ffffffcc7fd5d140] panic at ffffff80080af4c0
  #7 [ffffffcc7fd5d150] nmi_panic at ffffff80080af150
  #8 [ffffffcc7fd5d190] handle_bad_stack at ffffff800808b0b8
  #9 [ffffffcc7fd5d2d0] __bad_stack at ffffff800808285c
--- <IRQ stack> ---
 #10 [ffffff801187bc60] el1_error_invalid at ffffff8008082e7c
 #11 [ffffff801187bcc0] cyttsp6_mt_attention at ffffff8000e8498c [cyttsp6]
 #12 [ffffff801187bd20] call_atten_cb at ffffff8000e82030 [cyttsp6]
 #13 [ffffff801187bdc0] cyttsp6_irq at ffffff8000e81e34 [cyttsp6]
 #14 [ffffff801187bdf0] irq_thread_fn at ffffff8008128dd8
 #15 [ffffff801187be50] irq_thread at ffffff8008128ca4
 #16 [ffffff801187beb0] kthread at ffffff80080d2fc4
crash>

Signed-off-by: Hong YANG <hong.yang3@nio.com>
---
 arm64.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++----
 defs.h  |  6 ++++
 2 files changed, 92 insertions(+), 6 deletions(-)

diff --git a/arm64.c b/arm64.c
index 94681d1..403fcc2 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);
@@ -78,8 +79,11 @@ 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 +467,7 @@ arm64_init(int when)
 			machdep->hz = 100;
 
 		arm64_irq_stack_init();
+		arm64_overflow_stack_init();
 		arm64_stackframe_init();
 		break;
 
@@ -1715,6 +1720,49 @@ 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_PTR) ?
+						"TYPE_CODE_PTR" : "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->irq_stacks[i] = kt->__per_cpu_offset[i] + sp->value;
+	}
+}
+
 /*
  *  Gather and verify all of the backtrace requirements.
  */
@@ -2673,6 +2721,12 @@ arm64_back_trace_cmd(struct bt_info *bt)
 			bt->hp->eip : GET_STACK_ULONG(bt->hp->esp);
 		stackframe.sp = bt->hp->esp + 8;
 		bt->flags &= ~BT_REGS_NOT_FOUND;
+	} 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;
+		stackframe.fp = bt->frameptr;
 	} else {
 		if (arm64_on_irq_stack(bt->tc->processor, bt->frameptr)) {
 			arm64_set_irq_stack(bt);
@@ -3881,20 +3935,36 @@ arm64_on_irq_stack(int cpu, ulong stkptr)
 }
 
 static int
-arm64_in_alternate_stack(int cpu, ulong stkptr)
+arm64_in_alternate_stackv(int cpu, ulong stkptr, ulong *stacks, ulong stack_size)
 {
-	struct machine_specific *ms = machdep->machspec;
-
-	if (!ms->irq_stack_size || (cpu >= kt->cpus))
+	if (!stack_size || (cpu >= kt->cpus))
 		return FALSE;
 
-	if ((stkptr >= ms->irq_stacks[cpu]) &&
-	    (stkptr < (ms->irq_stacks[cpu] + ms->irq_stack_size)))
+	if ((stkptr >= stacks[cpu]) &&
+	    (stkptr < (stacks[cpu] + stack_size)))
 		return TRUE;
 
 	return FALSE;
 }
 
+static int
+arm64_in_alternate_stack(int cpu, ulong stkptr)
+{
+	struct machine_specific *ms = machdep->machspec;
+
+	return arm64_in_alternate_stackv(cpu, stkptr,
+			ms->irq_stacks, ms->irq_stack_size);
+}
+
+static int
+arm64_on_overflow_stack(int cpu, ulong stkptr)
+{
+	struct machine_specific *ms = machdep->machspec;
+
+	return arm64_in_alternate_stackv(cpu, stkptr,
+			ms->overflow_stacks, ms->overflow_stack_size);
+}
+
 static void
 arm64_set_irq_stack(struct bt_info *bt)
 {
@@ -3905,6 +3975,16 @@ 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 a2f3085..7e2a16e 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;
@@ -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)
-- 
2.25.1

