x86/dumpstack: Add get_stack_info() interface

valid_stack_ptr() is buggy: it assumes that all stacks are of size
THREAD_SIZE, which is not true for exception stacks.  So the
walk_stack() callbacks will need to know the location of the beginning
of the stack as well as the end.

Another issue is that in general the various features of a stack (type,
size, next stack pointer, description string) are scattered around in
various places throughout the stack dump code.

Encapsulate all that information in a single place with a new stack_info
struct and a get_stack_info() interface.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/8164dd0db96b7e6a279fa17ae5e6dc375eecb4a9.1473905218.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 22 insertions, 18 deletions

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index c6c6c39c367f..aa208e565b03 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -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;