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Subject[PATCH RESEND v5 -tip] x86, dumpstack: Correct stack dump info when frame pointer is available
Date
Current stack dump code scans entire stack and check each entry
contains a pointer to kernel code. If CONFIG_FRAME_POINTER=y it
could mark whether the pointer is valid or not based on value of
the frame pointer. Invalid entries could be preceded by '?' sign.

However this was not going to happen because scan start point was
always higher than the frame pointer so that they could not meet.

Commit 9c0729dc8062 ("x86: Eliminate bp argument from the stack
tracing routines") delayed bp acquisition point, so the bp was
read in lower frame, thus all of the entries were marked invalid.

This patch fixes this by reverting above commit while retaining
stack_frame() helper as suggested by Frederic Weisbecker.
End result looks like below:

before:
[ 3.508329] Call Trace:
[ 3.508551] [<ffffffff814f35c9>] ? panic+0x91/0x199
[ 3.508662] [<ffffffff814f3739>] ? printk+0x68/0x6a
[ 3.508770] [<ffffffff81a981b2>] ? mount_block_root+0x257/0x26e
[ 3.508876] [<ffffffff81a9821f>] ? mount_root+0x56/0x5a
[ 3.508975] [<ffffffff81a98393>] ? prepare_namespace+0x170/0x1a9
[ 3.509216] [<ffffffff81a9772b>] ? kernel_init+0x1d2/0x1e2
[ 3.509335] [<ffffffff81003894>] ? kernel_thread_helper+0x4/0x10
[ 3.509442] [<ffffffff814f6880>] ? restore_args+0x0/0x30
[ 3.509542] [<ffffffff81a97559>] ? kernel_init+0x0/0x1e2
[ 3.509641] [<ffffffff81003890>] ? kernel_thread_helper+0x0/0x10

after:
[ 3.522991] Call Trace:
[ 3.523351] [<ffffffff814f35b9>] panic+0x91/0x199
[ 3.523468] [<ffffffff814f3729>] ? printk+0x68/0x6a
[ 3.523576] [<ffffffff81a981b2>] mount_block_root+0x257/0x26e
[ 3.523681] [<ffffffff81a9821f>] mount_root+0x56/0x5a
[ 3.523780] [<ffffffff81a98393>] prepare_namespace+0x170/0x1a9
[ 3.523885] [<ffffffff81a9772b>] kernel_init+0x1d2/0x1e2
[ 3.523987] [<ffffffff81003894>] kernel_thread_helper+0x4/0x10
[ 3.524228] [<ffffffff814f6880>] ? restore_args+0x0/0x30
[ 3.524345] [<ffffffff81a97559>] ? kernel_init+0x0/0x1e2
[ 3.524445] [<ffffffff81003890>] ? kernel_thread_helper+0x0/0x10

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Soren Sandmann <ssp@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Robert Richter <robert.richter@amd.com>
---
v5:
* fix build breakage with oprofile

v4:
* use 0 instead of regs->bp
* separate out printk changes

v3:
* apply comment from Frederic
* add a couple of printk fixes

arch/x86/include/asm/kdebug.h | 2 +-
arch/x86/include/asm/stacktrace.h | 6 +++---
arch/x86/kernel/cpu/perf_event.c | 2 +-
arch/x86/kernel/dumpstack.c | 14 ++++++++------
arch/x86/kernel/dumpstack_32.c | 15 ++++++++-------
arch/x86/kernel/dumpstack_64.c | 14 +++++++-------
arch/x86/kernel/process.c | 2 +-
arch/x86/kernel/stacktrace.c | 6 +++---
arch/x86/oprofile/backtrace.c | 2 +-
9 files changed, 33 insertions(+), 30 deletions(-)

diff --git a/arch/x86/include/asm/kdebug.h b/arch/x86/include/asm/kdebug.h
index 518bbbb9ee59..fe2cc6e105fa 100644
--- a/arch/x86/include/asm/kdebug.h
+++ b/arch/x86/include/asm/kdebug.h
@@ -26,7 +26,7 @@ extern void die(const char *, struct pt_regs *,long);
extern int __must_check __die(const char *, struct pt_regs *, long);
extern void show_registers(struct pt_regs *regs);
extern void show_trace(struct task_struct *t, struct pt_regs *regs,
- unsigned long *sp);
+ unsigned long *sp, unsigned long bp);
extern void __show_regs(struct pt_regs *regs, int all);
extern void show_regs(struct pt_regs *regs);
extern unsigned long oops_begin(void);
diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index 52b5c7ed3608..d7e89c83645d 100644
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -47,7 +47,7 @@ struct stacktrace_ops {
};

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);

#ifdef CONFIG_X86_32
@@ -86,11 +86,11 @@ stack_frame(struct task_struct *task, struct pt_regs *regs)

extern void
show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
- unsigned long *stack, char *log_lvl);
+ unsigned long *stack, unsigned long bp, char *log_lvl);

extern void
show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
- unsigned long *sp, char *log_lvl);
+ unsigned long *sp, unsigned long bp, char *log_lvl);

extern unsigned int code_bytes;

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 26604188aa49..1c81bf72d85a 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1790,7 +1790,7 @@ perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)

perf_callchain_store(entry, regs->ip);

- dump_trace(NULL, regs, NULL, &backtrace_ops, entry);
+ dump_trace(NULL, regs, NULL, 0, &backtrace_ops, entry);
}

#ifdef CONFIG_COMPAT
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 220a1c11cfde..999e2793590b 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -175,21 +175,21 @@ static const struct stacktrace_ops print_trace_ops = {

void
show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
- unsigned long *stack, char *log_lvl)
+ unsigned long *stack, unsigned long bp, char *log_lvl)
{
printk("%sCall Trace:\n", log_lvl);
- dump_trace(task, regs, stack, &print_trace_ops, log_lvl);
+ dump_trace(task, regs, stack, bp, &print_trace_ops, log_lvl);
}

void show_trace(struct task_struct *task, struct pt_regs *regs,
- unsigned long *stack)
+ unsigned long *stack, unsigned long bp)
{
- show_trace_log_lvl(task, regs, stack, "");
+ show_trace_log_lvl(task, regs, stack, bp, "");
}

void show_stack(struct task_struct *task, unsigned long *sp)
{
- show_stack_log_lvl(task, NULL, sp, "");
+ show_stack_log_lvl(task, NULL, sp, 0, "");
}

/*
@@ -197,14 +197,16 @@ void show_stack(struct task_struct *task, unsigned long *sp)
*/
void dump_stack(void)
{
+ unsigned long bp;
unsigned long stack;

+ bp = stack_frame(current, NULL);
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, &stack);
+ show_trace(NULL, NULL, &stack, bp);
}
EXPORT_SYMBOL(dump_stack);

diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index 74cc1eda384b..3b97a80ce329 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -17,12 +17,11 @@
#include <asm/stacktrace.h>


-void dump_trace(struct task_struct *task,
- struct pt_regs *regs, unsigned long *stack,
+void dump_trace(struct task_struct *task, struct pt_regs *regs,
+ unsigned long *stack, unsigned long bp,
const struct stacktrace_ops *ops, void *data)
{
int graph = 0;
- unsigned long bp;

if (!task)
task = current;
@@ -35,7 +34,9 @@ void dump_trace(struct task_struct *task,
stack = (unsigned long *)task->thread.sp;
}

- bp = stack_frame(task, regs);
+ if (!bp)
+ bp = stack_frame(task, regs);
+
for (;;) {
struct thread_info *context;

@@ -55,7 +56,7 @@ EXPORT_SYMBOL(dump_trace);

void
show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
- unsigned long *sp, char *log_lvl)
+ unsigned long *sp, unsigned long bp, char *log_lvl)
{
unsigned long *stack;
int i;
@@ -77,7 +78,7 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
touch_nmi_watchdog();
}
printk(KERN_CONT "\n");
- show_trace_log_lvl(task, regs, sp, log_lvl);
+ show_trace_log_lvl(task, regs, sp, bp, log_lvl);
}


@@ -102,7 +103,7 @@ void show_registers(struct pt_regs *regs)
u8 *ip;

printk(KERN_EMERG "Stack:\n");
- show_stack_log_lvl(NULL, regs, &regs->sp, KERN_EMERG);
+ show_stack_log_lvl(NULL, regs, &regs->sp, 0, KERN_EMERG);

printk(KERN_EMERG "Code: ");

diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index a6b6fcf7f0ae..e71c98d3c0d2 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -139,8 +139,8 @@ fixup_bp_irq_link(unsigned long bp, unsigned long *stack,
* severe exception (double fault, nmi, stack fault, debug, mce) hardware stack
*/

-void dump_trace(struct task_struct *task,
- struct pt_regs *regs, unsigned long *stack,
+void dump_trace(struct task_struct *task, struct pt_regs *regs,
+ unsigned long *stack, unsigned long bp,
const struct stacktrace_ops *ops, void *data)
{
const unsigned cpu = get_cpu();
@@ -150,7 +150,6 @@ void dump_trace(struct task_struct *task,
struct thread_info *tinfo;
int graph = 0;
unsigned long dummy;
- unsigned long bp;

if (!task)
task = current;
@@ -161,7 +160,8 @@ void dump_trace(struct task_struct *task,
stack = (unsigned long *)task->thread.sp;
}

- bp = stack_frame(task, regs);
+ if (!bp)
+ bp = stack_frame(task, regs);
/*
* Print function call entries in all stacks, starting at the
* current stack address. If the stacks consist of nested
@@ -225,7 +225,7 @@ EXPORT_SYMBOL(dump_trace);

void
show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
- unsigned long *sp, char *log_lvl)
+ unsigned long *sp, unsigned long bp, char *log_lvl)
{
unsigned long *irq_stack_end;
unsigned long *irq_stack;
@@ -269,7 +269,7 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
preempt_enable();

printk(KERN_CONT "\n");
- show_trace_log_lvl(task, regs, sp, log_lvl);
+ show_trace_log_lvl(task, regs, sp, bp, log_lvl);
}

void show_registers(struct pt_regs *regs)
@@ -298,7 +298,7 @@ void show_registers(struct pt_regs *regs)

printk(KERN_EMERG "Stack:\n");
show_stack_log_lvl(NULL, regs, (unsigned long *)sp,
- KERN_EMERG);
+ 0, KERN_EMERG);

printk(KERN_EMERG "Code: ");

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 99fa3adf0141..d46cbe46b7ab 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -86,7 +86,7 @@ void exit_thread(void)
void show_regs(struct pt_regs *regs)
{
show_registers(regs);
- show_trace(NULL, regs, (unsigned long *)kernel_stack_pointer(regs));
+ show_trace(NULL, regs, (unsigned long *)kernel_stack_pointer(regs), 0);
}

void show_regs_common(void)
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index 938c8e10a19a..6515733a289d 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -73,7 +73,7 @@ static const struct stacktrace_ops save_stack_ops_nosched = {
*/
void save_stack_trace(struct stack_trace *trace)
{
- dump_trace(current, NULL, NULL, &save_stack_ops, trace);
+ dump_trace(current, NULL, NULL, 0, &save_stack_ops, trace);
if (trace->nr_entries < trace->max_entries)
trace->entries[trace->nr_entries++] = ULONG_MAX;
}
@@ -81,14 +81,14 @@ EXPORT_SYMBOL_GPL(save_stack_trace);

void save_stack_trace_regs(struct stack_trace *trace, struct pt_regs *regs)
{
- dump_trace(current, regs, NULL, &save_stack_ops, trace);
+ dump_trace(current, regs, NULL, 0, &save_stack_ops, trace);
if (trace->nr_entries < trace->max_entries)
trace->entries[trace->nr_entries++] = ULONG_MAX;
}

void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
- dump_trace(tsk, NULL, NULL, &save_stack_ops_nosched, trace);
+ dump_trace(tsk, NULL, NULL, 0, &save_stack_ops_nosched, trace);
if (trace->nr_entries < trace->max_entries)
trace->entries[trace->nr_entries++] = ULONG_MAX;
}
diff --git a/arch/x86/oprofile/backtrace.c b/arch/x86/oprofile/backtrace.c
index 72cbec14d783..2d49d4e19a36 100644
--- a/arch/x86/oprofile/backtrace.c
+++ b/arch/x86/oprofile/backtrace.c
@@ -126,7 +126,7 @@ x86_backtrace(struct pt_regs * const regs, unsigned int depth)
if (!user_mode_vm(regs)) {
unsigned long stack = kernel_stack_pointer(regs);
if (depth)
- dump_trace(NULL, regs, (unsigned long *)stack,
+ dump_trace(NULL, regs, (unsigned long *)stack, 0,
&backtrace_ops, &depth);
return;
}
--
1.7.4


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