Thread (37 messages) 37 messages, 3 authors, 2021-09-18

Re: [PATCH] x86/dumpstack/64: Add guard pages to stack_info

From: 王贇 <hidden>
Date: 2021-09-18 02:38:18
Also in: bpf, linux-perf-users, lkml


On 2021/9/18 上午12:40, Peter Zijlstra wrote:
[snip]
-	printk(KERN_EMERG "BUG: stack guard page was hit at %p (stack is %p..%p)\n",
-		 (void *)fault_address, current->stack,
-		 (char *)current->stack + THREAD_SIZE - 1);
-	die(message, regs, 0);
+	const char *name = stack_type_name(info->type);
+
+	printk(KERN_EMERG "BUG: %s stack guard page was hit at %p (stack is %p..%p)\n",
+	       name, (void *)fault_address, info->begin, info->end);
Just found that the printed pointer address is not correct:
  BUG: NMI stack guard page was hit at 0000000085fd977b (stack is 000000003a55b09e..00000000d8cce1a5)

Maybe we could use %px instead?

Regards,
Michael Wang
quoted hunk ↗ jump to hunk
+
+	die("stack guard page", regs, 0);
 
 	/* Be absolutely certain we don't return. */
-	panic("%s", message);
+	panic("%s stack guard hit", name);
 }
 #endif
 
@@ -353,6 +355,7 @@ DEFINE_IDTENTRY_DF(exc_double_fault)
 
 #ifdef CONFIG_VMAP_STACK
 	unsigned long address = read_cr2();
+	struct stack_info info;
 #endif
 
 #ifdef CONFIG_X86_ESPFIX64
@@ -455,10 +458,8 @@ DEFINE_IDTENTRY_DF(exc_double_fault)
 	 * stack even if the actual trigger for the double fault was
 	 * something else.
 	 */
-	if ((unsigned long)task_stack_page(tsk) - 1 - address < PAGE_SIZE) {
-		handle_stack_overflow("kernel stack overflow (double-fault)",
-				      regs, address);
-	}
+	if (get_stack_guard_info((void *)address, &info))
+		handle_stack_overflow(regs, address, &info);
 #endif
 
 	pr_emerg("PANIC: double fault, error_code: 0x%lx\n", error_code);
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index b2eefdefc108..edb5152f0866 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -32,6 +32,7 @@
 #include <asm/pgtable_areas.h>		/* VMALLOC_START, ...		*/
 #include <asm/kvm_para.h>		/* kvm_handle_async_pf		*/
 #include <asm/vdso.h>			/* fixup_vdso_exception()	*/
+#include <asm/irq_stack.h>
 
 #define CREATE_TRACE_POINTS
 #include <asm/trace/exceptions.h>
@@ -631,6 +632,9 @@ static noinline void
 page_fault_oops(struct pt_regs *regs, unsigned long error_code,
 		unsigned long address)
 {
+#ifdef CONFIG_VMAP_STACK
+	struct stack_info info;
+#endif
 	unsigned long flags;
 	int sig;
 
@@ -649,9 +653,7 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code,
 	 * that we're in vmalloc space to avoid this.
 	 */
 	if (is_vmalloc_addr((void *)address) &&
-	    (((unsigned long)current->stack - 1 - address < PAGE_SIZE) ||
-	     address - ((unsigned long)current->stack + THREAD_SIZE) < PAGE_SIZE)) {
-		unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *);
+	    get_stack_guard_info((void *)address, &info)) {
 		/*
 		 * We're likely to be running with very little stack space
 		 * left.  It's plausible that we'd hit this condition but
@@ -662,13 +664,11 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code,
 		 * and then double-fault, though, because we're likely to
 		 * break the console driver and lose most of the stack dump.
 		 */
-		asm volatile ("movq %[stack], %%rsp\n\t"
-			      "call handle_stack_overflow\n\t"
-			      "1: jmp 1b"
-			      : ASM_CALL_CONSTRAINT
-			      : "D" ("kernel stack overflow (page fault)"),
-				"S" (regs), "d" (address),
-				[stack] "rm" (stack));
+		call_on_stack(__this_cpu_ist_top_va(DF) - sizeof(void*),
+			      handle_stack_overflow,
+			      ASM_CALL_ARG3,
+			      , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info));
+
 		unreachable();
 	}
 #endif
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