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Commit 5f01c988 authored by Jiri Slaby's avatar Jiri Slaby Committed by Ingo Molnar
Browse files

x86/dumpstack: Fix printk_address for direct addresses 



Consider a kernel crash in a module, simulated the following way:

 static int my_init(void)
 {
         char *map = (void *)0x5;
         *map = 3;
         return 0;
 }
 module_init(my_init);

When we turn off FRAME_POINTERs, the very first instruction in
that function causes a BUG. The problem is that we print IP in
the BUG report using %pB (from printk_address). And %pB
decrements the pointer by one to fix printing addresses of
functions with tail calls.

This was added in commit 71f9e598 ("x86, dumpstack: Use
%pB format specifier for stack trace") to fix the call stack
printouts.

So instead of correct output:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000005
  IP: [<ffffffffa01ac000>] my_init+0x0/0x10 [pb173]

We get:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000005
  IP: [<ffffffffa0152000>] 0xffffffffa0151fff

To fix that, we use %pS only for stack addresses printouts (via
newly added printk_stack_address) and %pB for regs->ip (via
printk_address). I.e. we revert to the old behaviour for all
except call stacks. And since from all those reliable is 1, we
remove that parameter from printk_address.

Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: joe@perches.com
Cc: jirislaby@gmail.com
Link: http://lkml.kernel.org/r/1382706418-8435-1-git-send-email-jslaby@suse.cz


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 9b66bfb2

arch/x86/include/asm/kdebug.h

+1 −1
Original line number Diff line number Diff line
@@ -21,7 +21,7 @@ enum die_val { 
	DIE_NMIUNKNOWN,

};



extern void printk_address(unsigned long address, int reliable);

extern void printk_address(unsigned long address);

extern void die(const char *, struct pt_regs *,long);

extern int __must_check __die(const char *, struct pt_regs *, long);

extern void show_trace(struct task_struct *t, struct pt_regs *regs,

arch/x86/kernel/dumpstack.c

+8 −3
Original line number Diff line number Diff line
@@ -25,12 +25,17 @@ unsigned int code_bytes = 64; 
int kstack_depth_to_print = 3 * STACKSLOTS_PER_LINE;

static int die_counter;



void printk_address(unsigned long address, int reliable)

static void printk_stack_address(unsigned long address, int reliable)

{

	pr_cont(" [<%p>] %s%pB\n",

		(void *)address, reliable ? "" : "? ", (void *)address);

}



void printk_address(unsigned long address)

{

	pr_cont(" [<%p>] %pS\n", (void *)address, (void *)address);

}



#ifdef CONFIG_FUNCTION_GRAPH_TRACER

static void

print_ftrace_graph_addr(unsigned long addr, void *data,
@@ -151,7 +156,7 @@ static void print_trace_address(void *data, unsigned long addr, int reliable) 
{

	touch_nmi_watchdog();

	printk(data);

	printk_address(addr, reliable);

	printk_stack_address(addr, reliable);

}



static const struct stacktrace_ops print_trace_ops = {
@@ -281,7 +286,7 @@ int __kprobes __die(const char *str, struct pt_regs *regs, long err) 
#else

	/* Executive summary in case the oops scrolled away */

	printk(KERN_ALERT "RIP ");

	printk_address(regs->ip, 1);

	printk_address(regs->ip);

	printk(" RSP <%016lx>\n", regs->sp);

#endif

	return 0;

arch/x86/kernel/process_64.c

+1 −1
Original line number Diff line number Diff line
@@ -63,7 +63,7 @@ void __show_regs(struct pt_regs *regs, int all) 
	unsigned int ds, cs, es;



	printk(KERN_DEFAULT "RIP: %04lx:[<%016lx>] ", regs->cs & 0xffff, regs->ip);

	printk_address(regs->ip, 1);

	printk_address(regs->ip);

	printk(KERN_DEFAULT "RSP: %04lx:%016lx  EFLAGS: %08lx\n", regs->ss,

			regs->sp, regs->flags);

	printk(KERN_DEFAULT "RAX: %016lx RBX: %016lx RCX: %016lx\n",

arch/x86/mm/fault.c

+1 −1
Original line number Diff line number Diff line
@@ -596,7 +596,7 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, 


	printk(KERN_CONT " at %p\n", (void *) address);

	printk(KERN_ALERT "IP:");

	printk_address(regs->ip, 1);

	printk_address(regs->ip);



	dump_pagetable(address);

}

arch/x86/platform/uv/uv_nmi.c

+1 −1
Original line number Diff line number Diff line
@@ -399,7 +399,7 @@ static void uv_nmi_dump_cpu_ip(int cpu, struct pt_regs *regs) 
	printk(KERN_DEFAULT "UV: %4d %6d %-32.32s ",

		cpu, current->pid, current->comm);



	printk_address(regs->ip, 1);

	printk_address(regs->ip);

}



/* Dump this cpu's state */