x86: add the capability to print fuzzy backtraces

For enhancing the 32 bit EBP based backtracer, I need the capability
for the backtracer to tell it's customer that an entry is either
reliable or unreliable, and the backtrace printing code then needs to
print the unreliable ones slightly different.

This patch adds the basic capability, the next patch will add a user
of this capability.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 23 insertions, 16 deletions

diff --git a/arch/x86/kernel/traps_64.c b/arch/x86/kernel/traps_64.c
index 37b07d08704..62c4d8f46ee 100644
--- a/arch/x86/kernel/traps_64.c
+++ b/arch/x86/kernel/traps_64.c
@@ -99,13 +99,14 @@ static inline void preempt_conditional_cli(struct pt_regs *regs)
 int kstack_depth_to_print = 12;
 
 #ifdef CONFIG_KALLSYMS
-void printk_address(unsigned long address)
+void printk_address(unsigned long address, int reliable)
 {
         unsigned long offset = 0, symsize;
         const char *symname;
         char *modname;
         char *delim = ":";
         char namebuf[128];
+        char reliab[4] = "";;
 
         symname = kallsyms_lookup(address, &symsize, &offset,
                                         &modname, namebuf);
@@ -113,13 +114,16 @@ void printk_address(unsigned long address)
                 printk(" [<%016lx>]\n", address);
                 return;
         }
+        if (!reliable)
+                strcpy(reliab, "? ");
+
         if (!modname)
                 modname = delim = "";           
-        printk(" [<%016lx>] %s%s%s%s+0x%lx/0x%lx\n",
-                address, delim, modname, delim, symname, offset, symsize);
+        printk(" [<%016lx>] %s%s%s%s%s+0x%lx/0x%lx\n",
+                address, reliab, delim, modname, delim, symname, offset, symsize);
 }
 #else
-void printk_address(unsigned long address)
+void printk_address(unsigned long address, int reliable)
 {
         printk(" [<%016lx>]\n", address);
 }
@@ -215,7 +219,7 @@ static inline int valid_stack_ptr(struct thread_info *tinfo, void *p)
 }
 
 void dump_trace(struct task_struct *tsk, struct pt_regs *regs,
-                unsigned long *stack,
+                unsigned long *stack, unsigned long bp,
                 const struct stacktrace_ops *ops, void *data)
 {
         const unsigned cpu = get_cpu();
@@ -252,7 +256,7 @@ void dump_trace(struct task_struct *tsk, struct pt_regs *regs,
                          * down the cause of the crash will be able to figure \
                          * out the call path that was taken. \
                          */ \
-                        ops->address(data, addr);   \
+                        ops->address(data, addr, 1);   \
                 } \
         } while (0)
 
@@ -331,10 +335,10 @@ static int print_trace_stack(void *data, char *name)
         return 0;
 }
 
-static void print_trace_address(void *data, unsigned long addr)
+static void print_trace_address(void *data, unsigned long addr, int reliable)
 {
         touch_nmi_watchdog();
-        printk_address(addr);
+        printk_address(addr, reliable);
 }
 
 static const struct stacktrace_ops print_trace_ops = {
@@ -345,15 +349,17 @@ static const struct stacktrace_ops print_trace_ops = {
 };
 
 void
-show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long *stack)
+show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long *stack,
+                unsigned long bp)
 {
         printk("\nCall Trace:\n");
-        dump_trace(tsk, regs, stack, &print_trace_ops, NULL);
+        dump_trace(tsk, regs, stack, bp, &print_trace_ops, NULL);
         printk("\n");
 }
 
 static void
-_show_stack(struct task_struct *tsk, struct pt_regs *regs, unsigned long *sp)
+_show_stack(struct task_struct *tsk, struct pt_regs *regs, unsigned long *sp,
+                                                        unsigned long bp)
 {
         unsigned long *stack;
         int i;
@@ -387,12 +393,12 @@ _show_stack(struct task_struct *tsk, struct pt_regs *regs, unsigned long *sp)
                 printk(" %016lx", *stack++);
                 touch_nmi_watchdog();
         }
-        show_trace(tsk, regs, sp);
+        show_trace(tsk, regs, sp, bp);
 }
 
 void show_stack(struct task_struct *tsk, unsigned long * sp)
 {
-        _show_stack(tsk, NULL, sp);
+        _show_stack(tsk, NULL, sp, 0);
 }
 
 /*
@@ -401,13 +407,14 @@ void show_stack(struct task_struct *tsk, unsigned long * sp)
 void dump_stack(void)
 {
         unsigned long dummy;
+        unsigned long bp = 0;
 
         printk("Pid: %d, comm: %.20s %s %s %.*s\n",
                 current->pid, current->comm, print_tainted(),
                 init_utsname()->release,
                 (int)strcspn(init_utsname()->version, " "),
                 init_utsname()->version);
-        show_trace(NULL, NULL, &dummy);
+        show_trace(NULL, NULL, &dummy, bp);
 }
 
 EXPORT_SYMBOL(dump_stack);
@@ -432,7 +439,7 @@ void show_registers(struct pt_regs *regs)
          */
         if (in_kernel) {
                 printk("Stack: ");
-                _show_stack(NULL, regs, (unsigned long*)sp);
+                _show_stack(NULL, regs, (unsigned long *)sp, regs->bp);
 
                 printk("\nCode: ");
                 if (regs->ip < PAGE_OFFSET)
@@ -527,7 +534,7 @@ int __kprobes __die(const char * str, struct pt_regs * regs, long err)
         add_taint(TAINT_DIE);
         /* Executive summary in case the oops scrolled away */
         printk(KERN_ALERT "RIP ");
-        printk_address(regs->ip);
+        printk_address(regs->ip, regs->bp);
         printk(" RSP <%016lx>\n", regs->sp);
         if (kexec_should_crash(current))
                 crash_kexec(regs);