x86/dumpstack: yet more stack dump improvements

index 07373be..904fb46 100644
@@ -16,83 +16,46 @@
 
 #include <asm/stacktrace.h>
 
+static char *exception_stack_names[N_EXCEPTION_STACKS] = {
+		[ DOUBLEFAULT_STACK-1	]	= "#DF",
+		[ NMI_STACK-1		]	= "NMI",
+		[ DEBUG_STACK-1		]	= "#DB",
+		[ MCE_STACK-1		]	= "#MC",
+};
 
-#define N_EXCEPTION_STACKS_END \
-		(N_EXCEPTION_STACKS + DEBUG_STKSZ/EXCEPTION_STKSZ - 2)
-
-static char x86_stack_ids[][8] = {
-		[ DEBUG_STACK-1			]	= "#DB",
-		[ NMI_STACK-1			]	= "NMI",
-		[ DOUBLEFAULT_STACK-1		]	= "#DF",
-		[ MCE_STACK-1			]	= "#MC",
-#if DEBUG_STKSZ > EXCEPTION_STKSZ
-		[ N_EXCEPTION_STACKS ...
-		  N_EXCEPTION_STACKS_END	]	= "#DB[?]"
-#endif
+static unsigned long exception_stack_sizes[N_EXCEPTION_STACKS] = {
+	[0 ... N_EXCEPTION_STACKS - 1]		= EXCEPTION_STKSZ,
+	[DEBUG_STACK - 1]			= DEBUG_STKSZ
 };
 
 static unsigned long *in_exception_stack(unsigned long stack, unsigned *usedp,
 					 char **idp)
 {
+	unsigned long begin, end;
 	unsigned k;
 
-	/*
-	 * Iterate over all exception stacks, and figure out whether
-	 * 'stack' is in one of them:
-	 */
+	BUILD_BUG_ON(N_EXCEPTION_STACKS != 4);
+
 	for (k = 0; k < N_EXCEPTION_STACKS; k++) {
-		unsigned long end = raw_cpu_ptr(&orig_ist)->ist[k];
-		/*
-		 * Is 'stack' above this exception frame's end?
-		 * If yes then skip to the next frame.
-		 */
-		if (stack >= end)
+		end   = raw_cpu_ptr(&orig_ist)->ist[k];
+		begin = end - exception_stack_sizes[k];
+
+		if (stack < begin || stack >= end)
 			continue;
+
 		/*
-		 * Is 'stack' above this exception frame's start address?
-		 * If yes then we found the right frame.
-		 */
-		if (stack >= end - EXCEPTION_STKSZ) {
-			/*
-			 * Make sure we only iterate through an exception
-			 * stack once. If it comes up for the second time
-			 * then there's something wrong going on - just
-			 * break out and return NULL:
-			 */
-			if (*usedp & (1U << k))
-				break;
-			*usedp |= 1U << k;
-			*idp = x86_stack_ids[k];
-			return (unsigned long *)end;
-		}
-		/*
-		 * If this is a debug stack, and if it has a larger size than
-		 * the usual exception stacks, then 'stack' might still
-		 * be within the lower portion of the debug stack:
+		 * Make sure we only iterate through an exception stack once.
+		 * If it comes up for the second time then there's something
+		 * wrong going on - just break and return NULL:
 		 */
-#if DEBUG_STKSZ > EXCEPTION_STKSZ
-		if (k == DEBUG_STACK - 1 && stack >= end - DEBUG_STKSZ) {
-			unsigned j = N_EXCEPTION_STACKS - 1;
+		if (*usedp & (1U << k))
+			break;
+		*usedp |= 1U << k;
 
-			/*
-			 * Black magic. A large debug stack is composed of
-			 * multiple exception stack entries, which we
-			 * iterate through now. Dont look:
-			 */
-			do {
-				++j;
-				end -= EXCEPTION_STKSZ;
-				x86_stack_ids[j][4] = '1' +
-						(j - N_EXCEPTION_STACKS);
-			} while (stack < end - EXCEPTION_STKSZ);
-			if (*usedp & (1U << j))
-				break;
-			*usedp |= 1U << j;
-			*idp = x86_stack_ids[j];
-			return (unsigned long *)end;
-		}
-#endif
+		*idp = exception_stack_names[k];
+		return (unsigned long *)end;
 	}
+
 	return NULL;
 }
 

index dcaa887..dd3a1dc 100644
@@ -2271,7 +2271,7 @@ void arch_perf_update_userpage(struct perf_event *event,
  * callchain support
  */
 
-static int backtrace_stack(void *data, char *name)
+static int backtrace_stack(void *data, const char *name)
 {
 	return 0;
 }

70 lines not on this page · raw message

index c6c6c39..aa208e5 100644
@@ -25,6 +25,23 @@ unsigned int code_bytes = 64;
 int kstack_depth_to_print = 3 * STACKSLOTS_PER_LINE;
 static int die_counter;
 
+bool in_task_stack(unsigned long *stack, struct task_struct *task,
+		   struct stack_info *info)
+{
+	unsigned long *begin = task_stack_page(task);
+	unsigned long *end   = task_stack_page(task) + THREAD_SIZE;
+
+	if (stack < begin || stack >= end)
+		return false;
+
+	info->type	= STACK_TYPE_TASK;
+	info->begin	= begin;
+	info->end	= end;
+	info->next_sp	= NULL;
+
+	return true;
+}
+
 static void printk_stack_address(unsigned long address, int reliable,
 				 char *log_lvl)
 {

@@ -46,24 +63,11 @@ void printk_address(unsigned long address)
  * severe exception (double fault, nmi, stack fault, debug, mce) hardware stack
  */
 
-static inline int valid_stack_ptr(struct task_struct *task,
-			void *p, unsigned int size, void *end)
-{
-	void *t = task_stack_page(task);
-	if (end) {
-		if (p < end && p >= (end-THREAD_SIZE))
-			return 1;
-		else
-			return 0;
-	}
-	return p >= t && p < t + THREAD_SIZE - size;
-}
-
 unsigned long
 print_context_stack(struct task_struct *task,
 		unsigned long *stack, unsigned long bp,
 		const struct stacktrace_ops *ops, void *data,
-		unsigned long *end, int *graph)
+		struct stack_info *info, int *graph)
 {
 	struct stack_frame *frame = (struct stack_frame *)bp;
 

@@ -75,7 +79,7 @@ print_context_stack(struct task_struct *task,
 	    PAGE_SIZE)
 		stack = (unsigned long *)task_stack_page(task);
 
-	while (valid_stack_ptr(task, stack, sizeof(*stack), end)) {
+	while (on_stack(info, stack, sizeof(*stack))) {
 		unsigned long addr = *stack;
 
 		if (__kernel_text_address(addr)) {

@@ -114,12 +118,12 @@ unsigned long
 print_context_stack_bp(struct task_struct *task,
 		       unsigned long *stack, unsigned long bp,
 		       const struct stacktrace_ops *ops, void *data,
-		       unsigned long *end, int *graph)
+		       struct stack_info *info, int *graph)
 {
 	struct stack_frame *frame = (struct stack_frame *)bp;
 	unsigned long *retp = &frame->return_address;
 
-	while (valid_stack_ptr(task, retp, sizeof(*retp), end)) {
+	while (on_stack(info, stack, sizeof(*stack) * 2)) {
 		unsigned long addr = *retp;
 		unsigned long real_addr;
 

@@ -138,7 +142,7 @@ print_context_stack_bp(struct task_struct *task,
 }
 EXPORT_SYMBOL_GPL(print_context_stack_bp);
 
-static int print_trace_stack(void *data, char *name)
+static int print_trace_stack(void *data, const char *name)
 {
 	printk("%s <%s> ", (char *)data, name);
 	return 0;

142 lines not on this page · raw message

239 lines not on this page · raw message

index 4738f5e..785aef1 100644
@@ -9,7 +9,7 @@
 #include <linux/uaccess.h>
 #include <asm/stacktrace.h>
 
-static int save_stack_stack(void *data, char *name)
+static int save_stack_stack(void *data, const char *name)
 {
 	return 0;
 }

index d950f9e..7539148 100644
@@ -17,7 +17,7 @@
 #include <asm/ptrace.h>
 #include <asm/stacktrace.h>
 
-static int backtrace_stack(void *data, char *name)
+static int backtrace_stack(void *data, const char *name)
 {
 	/* Yes, we want all stacks */
 	return 0;

index c92da5a..50076d4 100644
@@ -35,7 +35,11 @@ static bool in_hardirq_stack(unsigned long *stack, struct stack_info *info)
 	unsigned long *begin = (unsigned long *)this_cpu_read(hardirq_stack);
 	unsigned long *end   = begin + (THREAD_SIZE / sizeof(long));
 
-	if (stack < begin || stack >= end)
+	/*
+	 * This is a software stack, so 'end' can be a valid stack pointer.
+	 * It just means the stack is empty.
+	 */
+	if (stack < begin || stack > end)
 		return false;
 
 	info->type	= STACK_TYPE_IRQ;

@@ -56,7 +60,11 @@ static bool in_softirq_stack(unsigned long *stack, struct stack_info *info)
 	unsigned long *begin = (unsigned long *)this_cpu_read(softirq_stack);
 	unsigned long *end   = begin + (THREAD_SIZE / sizeof(long));
 
-	if (stack < begin || stack >= end)
+	/*
+	 * This is a software stack, so 'end' can be a valid stack pointer.
+	 * It just means the stack is empty.
+	 */
+	if (stack < begin || stack > end)
 		return false;
 
 	info->type	= STACK_TYPE_SOFTIRQ;

index 41813ab..2e708af 100644
@@ -90,7 +90,11 @@ static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
 	unsigned long *end   = (unsigned long *)this_cpu_read(irq_stack_ptr);
 	unsigned long *begin = end - (IRQ_STACK_SIZE / sizeof(long));
 
-	if (stack < begin || stack >= end)
+	/*
+	 * This is a software stack, so 'end' can be a valid stack pointer.
+	 * It just means the stack is empty.
+	 */
+	if (stack < begin || stack > end)
 		return false;
 
 	info->type	= STACK_TYPE_IRQ;

index 50076d4..2d65cfa 100644
@@ -89,16 +89,32 @@ int get_stack_info(unsigned long *stack, struct task_struct *task,
 	task = task ? : current;
 
 	if (in_task_stack(stack, task, info))
-		return 0;
+		goto recursion_check;
 
 	if (task != current)
 		goto unknown;
 
 	if (in_hardirq_stack(stack, info))
-		return 0;
+		goto recursion_check;
 
 	if (in_softirq_stack(stack, info))
-		return 0;
+		goto recursion_check;
+
+	goto unknown;
+
+recursion_check:
+	/*
+	 * Make sure we don't iterate through any given stack more than once.
+	 * If it comes up a second time then there's something wrong going on:
+	 * just break out and report an unknown stack type.
+	 */
+	if (visit_mask) {
+		if (*visit_mask & (1UL << info->type))
+			goto unknown;
+		*visit_mask |= 1UL << info->type;
+	}
+
+	return 0;
 
 unknown:
 	info->type = STACK_TYPE_UNKNOWN;

index 2e708af..8cb6004 100644
@@ -47,8 +47,7 @@ void stack_type_str(enum stack_type type, const char **begin, const char **end)
 	}
 }
 
-static bool in_exception_stack(unsigned long *stack, struct stack_info *info,
-			       unsigned long *visit_mask)
+static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
 {
 	unsigned long *begin, *end;
 	struct pt_regs *regs;

@@ -64,16 +63,6 @@ static bool in_exception_stack(unsigned long *stack, struct stack_info *info,
 		if (stack < begin || stack >= end)
 			continue;
 
-		/*
-		 * Make sure we don't iterate through an exception stack more
-		 * than once.  If it comes up a second time then there's
-		 * something wrong going on - just break out and report an
-		 * unknown stack type.
-		 */
-		if (*visit_mask & (1U << k))
-			break;
-		*visit_mask |= 1U << k;
-
 		info->type	= STACK_TYPE_EXCEPTION + k;
 		info->begin	= begin;
 		info->end	= end;

@@ -119,16 +108,30 @@ int get_stack_info(unsigned long *stack, struct task_struct *task,
 	task = task ? : current;
 
 	if (in_task_stack(stack, task, info))
-		return 0;
+		goto recursion_check;
 
 	if (task != current)
 		goto unknown;
 
-	if (in_exception_stack(stack, info, visit_mask))
-		return 0;
+	if (in_exception_stack(stack, info))
+		goto recursion_check;
 
 	if (in_irq_stack(stack, info))
-		return 0;
+		goto recursion_check;
+
+	goto unknown;
+
+recursion_check:
+	/*
+	 * Make sure we don't iterate through any given stack more than once.
+	 * If it comes up a second time then there's something wrong going on:
+	 * just break out and report an unknown stack type.
+	 */
+	if (visit_mask) {
+		if (*visit_mask & (1UL << info->type))
+			goto unknown;
+		*visit_mask |= 1UL << info->type;
+	}
 
 	return 0;