From 831701099a7097662ddec9de464131ad50c7134b Mon Sep 17 00:00:00 2001
From: wonderzyp <wonderzyp@qq.com>
Date: Wed, 17 Jul 2024 11:02:06 +0800
Subject: [PATCH] A segfault issue was observed on KASAN enabled arm64 kernel
 due to the incorrect irq_stack_size, see the following stack trace: > (gdb)
 bt > #0  0x00005635ac2b166b in arm64_unwind_frame (frame=0x7ffdaf35cb70,
 bt=0x7ffdaf35d430) >     at arm64.c:2821 > #1  arm64_back_trace_cmd
 (bt=0x7ffdaf35d430) at arm64.c:3306 > #2  0x00005635ac27b108 in back_trace
 (bt=bt@entry=0x7ffdaf35d430) at kernel.c:3239 > #3  0x00005635ac2880ae in
 cmd_bt () at kernel.c:2863 > #4  0x00005635ac1f16dc in exec_command () at
 main.c:893 > #5  0x00005635ac1f192a in main_loop () at main.c:840 > #6 
 0x00005635ac50df81 in captured_main (data=<optimized out>) at main.c:1284 >
 #7  gdb_main (args=<optimized out>) at main.c:1313 > #8  0x00005635ac50e000
 in gdb_main_entry (argc=<optimized out>, argv=<optimized out>) >     at
 main.c:1338 > #9  0x00005635ac1ea2a5 in main (argc=5, argv=0x7ffdaf35dde8) at
 main.c:721

The issue was caused by not setting irq_stack_size correctly, and this patch will fix the issue by two ways:
1. if CONFIG_IKCONFIG is set, calculate the irq_stack_size according to kernel source code
2. if CONFIG_IKCONFIG is not set, get THREAD_SHIFT value by disassembling the tbnz instruction to calculate the irq_stack_size

Signed-off-by: Yeping.Zheng <yeping.zheng@nio.com>
---
 arm64.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 84 insertions(+), 2 deletions(-)

diff --git a/arm64.c b/arm64.c
index b3040d7..8347ba1 100644
--- a/arm64.c
+++ b/arm64.c
@@ -93,6 +93,7 @@ static void arm64_calc_VA_BITS(void);
 static int arm64_is_uvaddr(ulong, struct task_context *);
 static void arm64_calc_KERNELPACMASK(void);
 static int arm64_get_vmcoreinfo(unsigned long *vaddr, const char *label, int base);
+static ulong arm64_set_irq_stack_size(struct machine_specific *ms);
 
 struct kernel_range {
 	unsigned long modules_vaddr, modules_end;
@@ -2223,8 +2224,10 @@ arm64_irq_stack_init(void)
 		if (MEMBER_EXISTS("thread_union", "stack")) { 
 			if ((sz = MEMBER_SIZE("thread_union", "stack")) > 0)
 				ms->irq_stack_size = sz;
-		} else
-			ms->irq_stack_size = ARM64_IRQ_STACK_SIZE;
+		} else {
+			ulong res = arm64_set_irq_stack_size(ms);
+			ms->irq_stack_size = (res > 0) ? res : ARM64_IRQ_STACK_SIZE;
+		}
 
 		machdep->flags |= IRQ_STACKS;
 
@@ -4921,6 +4924,85 @@ static void arm64_calc_KERNELPACMASK(void)
 	}
 }
 
+static ulong arm64_set_irq_stack_size(struct machine_specific *ms)
+{
+	char *string;
+	int ret;
+	int kasan_thread_shift = 0;
+	int min_thread_shift;
+	ulong arm64_page_shift;
+	ulong thread_shift = 0;
+	ulong thread_size;
+	struct syment *sp;
+	const char* tbnz_str = "tbnz";
+	
+	if (kt->ikconfig_flags & IKCONFIG_AVAIL) {
+		if ((ret = get_kernel_config("CONFIG_KASAN_GENERIC", NULL) == IKCONFIG_Y) ||
+			(ret = get_kernel_config("CONFIG_KASAN_SW_TAGS", NULL) == IKCONFIG_Y)) {
+				kasan_thread_shift = 1;
+			}
+		min_thread_shift = 14 + kasan_thread_shift;
+
+		if ((ret = get_kernel_config("CONFIG_VMAP_STACK", NULL)) == IKCONFIG_Y){
+			if ((ret = get_kernel_config("CONFIG_ARM64_PAGE_SHIFT", &string)) == IKCONFIG_STR){
+				arm64_page_shift = atol(string);
+			}
+			if (min_thread_shift < arm64_page_shift){
+				thread_shift = arm64_page_shift;
+			} else {
+				thread_shift = min_thread_shift;
+			}
+		}	
+	} else {
+
+		if (!(sp = symbol_search("vectors"))) {
+			return -1;
+		}
+
+		const char* tbnz_str = "tbnz";
+		struct gnu_request *req;
+		req = (struct gnu_request *)GETBUF(sizeof(struct gnu_request));
+		req->command = GNU_PASS_THROUGH;
+		req->buf = GETBUF(BUFSIZE);
+		strcat(req->buf, "x/1024i ");
+
+		char tmp[100];
+		sprintf(tmp, "0x%lx", sp->value);
+		strcat(req->buf, tmp);
+		req->flags = (GNU_RETURN_ON_ERROR);
+		open_tmpfile();
+		req->fp = pc->tmpfile;
+		gdb_interface(req);
+
+
+		rewind(pc->tmpfile);
+		char line[BUFSIZE];
+		while (fgets(line, BUFSIZE, pc->tmpfile) != NULL) {
+			// printf("the buffer is not null\n");
+			char* tbnz_pos = strstr(line, tbnz_str);
+			if (tbnz_pos != NULL) {
+				char* thread_shift_pos = strstr(tbnz_pos, "#");
+				if (sscanf(thread_shift_pos + 1, "%ld", &thread_shift) == 1) {
+					if (CRASHDEBUG(1)){
+						error(INFO, "Detect thread shift via tbnz %ld\n", thread_shift);
+					}
+					break;
+				}
+			}
+    	}
+		close_tmpfile();
+		FREEBUF(req->buf);
+		FREEBUF(req);
+	}
+
+	if (thread_shift == 0) {
+		return -1;
+	}
+
+	thread_size = ((1UL) << thread_shift);
+	return thread_size;
+}
+
 #endif  /* ARM64 */
 
 
-- 
2.25.1

