This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.
===============
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 71f9e59800e5ad4 ("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: Jiri Slaby <jslaby@xxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: joe@xxxxxxxxxxx
Cc: jirislaby@xxxxxxxxx
Link: http://lkml.kernel.org/r/1382706418-8435-1-git-send-email-jslaby@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
arch/x86/include/asm/kdebug.h | 2 +-
arch/x86/kernel/dumpstack.c | 11 ++++++++---
arch/x86/kernel/process_64.c | 2 +-
arch/x86/mm/fault.c | 2 +-
4 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/kdebug.h b/arch/x86/include/asm/kdebug.h
index 2c37aadcbc35..32ce71375b21 100644
--- a/arch/x86/include/asm/kdebug.h
+++ b/arch/x86/include/asm/kdebug.h
@@ -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,
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index deb6421c9e69..d9c12d3022a7 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -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;
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index bb1dc51bab05..8e9fe8dfd37b 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -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",
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index d8b1ff68dbb9..5b90bbcad9f6 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -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);
}
--
1.9.0
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