From 47ad7b9bbeaac34e43d9dc8db796f1f68194b9ad Mon Sep 17 00:00:00 2001
From: Chris Metcalf <cmetcalf@ezchip.com>
Date: Fri, 8 May 2015 10:27:35 -0400
Subject: tile: improve stack backtrace
This commit fixes a number of issues with the tile backtrace code.
- Don't try to identify userspace shared object or executable paths
if we are doing a backtrace from an interrupt; it's not legal,
and also unlikely to be interesting. Likewise, don't try to do
it for other address spaces, since d_path() assumes it is being
called in "current" context.
- Move "in_backtrace" from thread_struct to thread_info.
This way we can access it even if our stack thread_info has been
clobbered, which makes backtracing more robust.
- Avoid using "current" directly when testing for is_sigreturn().
Since "current" may be corrupt, we're better off using kbt->task
explicitly to look up the vdso_base for the current task.
Conveniently, this simplifies the internal APIs (we only need
one is_sigreturn() function now).
- Avoid bogus "Odd fault" warning when pc/sp/ex1 are all zero,
as is true for kernel threads above the last frame.
- Hook into Tejun Heo's dump_stack() framework in lib/dump_stack.c.
- Write last entry in save_stack_trace() as ULONG_MAX, not zero,
since ftrace (at least) relies on finding that marker.
- Implement save_stack_trace_regs() and save_strack_trace_user(),
and set CONFIG_USER_STACKTRACE_SUPPORT.
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
---
arch/tile/kernel/stack.c | 125 ++++++++++++++++++++++++++++-------------------
1 file changed, 74 insertions(+), 51 deletions(-)
(limited to 'arch/tile/kernel/stack.c')
diff --git a/arch/tile/kernel/stack.c b/arch/tile/kernel/stack.c
index c42dce50acd8..35d34635e4f1 100644
--- a/arch/tile/kernel/stack.c
+++ b/arch/tile/kernel/stack.c
@@ -23,6 +23,7 @@
#include <linux/mmzone.h>
#include <linux/dcache.h>
#include <linux/fs.h>
+#include <linux/hardirq.h>
#include <linux/string.h>
#include <asm/backtrace.h>
#include <asm/page.h>
@@ -109,7 +110,7 @@ static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
if (kbt->verbose)
pr_err(" <%s while in user mode>\n", fault);
} else {
- if (kbt->verbose)
+ if (kbt->verbose && (p->pc != 0 || p->sp != 0 || p->ex1 != 0))
pr_err(" (odd fault: pc %#lx, sp %#lx, ex1 %#lx?)\n",
p->pc, p->sp, p->ex1);
return NULL;
@@ -119,10 +120,12 @@ static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
return p;
}
-/* Is the pc pointing to a sigreturn trampoline? */
-static int is_sigreturn(unsigned long pc)
+/* Is the iterator pointing to a sigreturn trampoline? */
+static int is_sigreturn(struct KBacktraceIterator *kbt)
{
- return current->mm && (pc == VDSO_SYM(&__vdso_rt_sigreturn));
+ return kbt->task->mm &&
+ (kbt->it.pc == ((ulong)kbt->task->mm->context.vdso_base +
+ (ulong)&__vdso_rt_sigreturn));
}
/* Return a pt_regs pointer for a valid signal handler frame */
@@ -131,7 +134,7 @@ static struct pt_regs *valid_sigframe(struct KBacktraceIterator* kbt,
{
BacktraceIterator *b = &kbt->it;
- if (is_sigreturn(b->pc) && b->sp < PAGE_OFFSET &&
+ if (is_sigreturn(kbt) && b->sp < PAGE_OFFSET &&
b->sp % sizeof(long) == 0) {
int retval;
pagefault_disable();
@@ -151,11 +154,6 @@ static struct pt_regs *valid_sigframe(struct KBacktraceIterator* kbt,
return NULL;
}
-static int KBacktraceIterator_is_sigreturn(struct KBacktraceIterator *kbt)
-{
- return is_sigreturn(kbt->it.pc);
-}
-
static int KBacktraceIterator_restart(struct KBacktraceIterator *kbt)
{
struct pt_regs *p;
@@ -178,7 +176,7 @@ static int KBacktraceIterator_next_item_inclusive(
{
for (;;) {
do {
- if (!KBacktraceIterator_is_sigreturn(kbt))
+ if (!is_sigreturn(kbt))
return KBT_ONGOING;
} while (backtrace_next(&kbt->it));
@@ -357,51 +355,50 @@ static void describe_addr(struct KBacktraceIterator *kbt,
*/
static bool start_backtrace(void)
{
- if (current->thread.in_backtrace) {
+ if (current_thread_info()->in_backtrace) {
pr_err("Backtrace requested while in backtrace!\n");
return false;
}
- current->thread.in_backtrace = true;
+ current_thread_info()->in_backtrace = true;
return true;
}
static void end_backtrace(void)
{
- current->thread.in_backtrace = false;
+ current_thread_info()->in_backtrace = false;
}
/*
* This method wraps the backtracer's more generic support.
* It is only invoked from the architecture-specific code; show_stack()
- * and dump_stack() (in entry.S) are architecture-independent entry points.
+ * and dump_stack() are architecture-independent entry points.
*/
-void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
+void tile_show_stack(struct KBacktraceIterator *kbt)
{
int i;
int have_mmap_sem = 0;
if (!start_backtrace())
return;
- if (headers) {
- /*
- * Add a blank line since if we are called from panic(),
- * then bust_spinlocks() spit out a space in front of us
- * and it will mess up our KERN_ERR.
- */
- pr_err("Starting stack dump of tid %d, pid %d (%s) on cpu %d at cycle %lld\n",
- kbt->task->pid, kbt->task->tgid, kbt->task->comm,
- raw_smp_processor_id(), get_cycles());
- }
kbt->verbose = 1;
i = 0;
for (; !KBacktraceIterator_end(kbt); KBacktraceIterator_next(kbt)) {
char namebuf[KSYM_NAME_LEN+100];
unsigned long address = kbt->it.pc;
- /* Try to acquire the mmap_sem as we pass into userspace. */
- if (address < PAGE_OFFSET && !have_mmap_sem && kbt->task->mm)
+ /*
+ * Try to acquire the mmap_sem as we pass into userspace.
+ * If we're in an interrupt context, don't even try, since
+ * it's not safe to call e.g. d_path() from an interrupt,
+ * since it uses spin locks without disabling interrupts.
+ * Note we test "kbt->task == current", not "kbt->is_current",
+ * since we're checking that "current" will work in d_path().
+ */
+ if (kbt->task == current && address < PAGE_OFFSET &&
+ !have_mmap_sem && kbt->task->mm && !in_interrupt()) {
have_mmap_sem =
down_read_trylock(&kbt->task->mm->mmap_sem);
+ }
describe_addr(kbt, address, have_mmap_sem,
namebuf, sizeof(namebuf));
@@ -416,24 +413,12 @@ void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
}
if (kbt->end == KBT_LOOP)
pr_err("Stack dump stopped; next frame identical to this one\n");
- if (headers)
- pr_err("Stack dump complete\n");
if (have_mmap_sem)
up_read(&kbt->task->mm->mmap_sem);
end_backtrace();
}
EXPORT_SYMBOL(tile_show_stack);
-
-/* This is called from show_regs() and _dump_stack() */
-void dump_stack_regs(struct pt_regs *regs)
-{
- struct KBacktraceIterator kbt;
- KBacktraceIterator_init(&kbt, NULL, regs);
- tile_show_stack(&kbt, 1);
-}
-EXPORT_SYMBOL(dump_stack_regs);
-
static struct pt_regs *regs_to_pt_regs(struct pt_regs *regs,
ulong pc, ulong lr, ulong sp, ulong r52)
{
@@ -445,11 +430,15 @@ static struct pt_regs *regs_to_pt_regs(struct pt_regs *regs,
return regs;
}
-/* This is called from dump_stack() and just converts to pt_regs */
+/* Deprecated function currently only used by kernel_double_fault(). */
void _dump_stack(int dummy, ulong pc, ulong lr, ulong sp, ulong r52)
{
+ struct KBacktraceIterator kbt;
struct pt_regs regs;
- dump_stack_regs(regs_to_pt_regs(®s, pc, lr, sp, r52));
+
+ regs_to_pt_regs(®s, pc, lr, sp, r52);
+ KBacktraceIterator_init(&kbt, NULL, ®s);
+ tile_show_stack(&kbt);
}
/* This is called from KBacktraceIterator_init_current() */
@@ -461,22 +450,30 @@ void _KBacktraceIterator_init_current(struct KBacktraceIterator *kbt, ulong pc,
regs_to_pt_regs(®s, pc, lr, sp, r52));
}
-/* This is called only from kernel/sched/core.c, with esp == NULL */
+/*
+ * Called from sched_show_task() with task != NULL, or dump_stack()
+ * with task == NULL. The esp argument is always NULL.
+ */
void show_stack(struct task_struct *task, unsigned long *esp)
{
struct KBacktraceIterator kbt;
- if (task == NULL || task == current)
+ if (task == NULL || task == current) {
KBacktraceIterator_init_current(&kbt);
- else
+ KBacktraceIterator_next(&kbt); /* don't show first frame */
+ } else {
KBacktraceIterator_init(&kbt, task, NULL);
- tile_show_stack(&kbt, 0);
+ }
+ tile_show_stack(&kbt);
}
#ifdef CONFIG_STACKTRACE
/* Support generic Linux stack API too */
-void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
+static void save_stack_trace_common(struct task_struct *task,
+ struct pt_regs *regs,
+ bool user,
+ struct stack_trace *trace)
{
struct KBacktraceIterator kbt;
int skip = trace->skip;
@@ -484,31 +481,57 @@ void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
if (!start_backtrace())
goto done;
- if (task == NULL || task == current)
+ if (regs != NULL) {
+ KBacktraceIterator_init(&kbt, NULL, regs);
+ } else if (task == NULL || task == current) {
KBacktraceIterator_init_current(&kbt);
- else
+ skip++; /* don't show KBacktraceIterator_init_current */
+ } else {
KBacktraceIterator_init(&kbt, task, NULL);
+ }
for (; !KBacktraceIterator_end(&kbt); KBacktraceIterator_next(&kbt)) {
if (skip) {
--skip;
continue;
}
- if (i >= trace->max_entries || kbt.it.pc < PAGE_OFFSET)
+ if (i >= trace->max_entries ||
+ (!user && kbt.it.pc < PAGE_OFFSET))
break;
trace->entries[i++] = kbt.it.pc;
}
end_backtrace();
done:
+ if (i < trace->max_entries)
+ trace->entries[i++] = ULONG_MAX;
trace->nr_entries = i;
}
+
+void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
+{
+ save_stack_trace_common(task, NULL, false, trace);
+}
EXPORT_SYMBOL(save_stack_trace_tsk);
void save_stack_trace(struct stack_trace *trace)
{
- save_stack_trace_tsk(NULL, trace);
+ save_stack_trace_common(NULL, NULL, false, trace);
}
EXPORT_SYMBOL_GPL(save_stack_trace);
+void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
+{
+ save_stack_trace_common(NULL, regs, false, trace);
+}
+
+void save_stack_trace_user(struct stack_trace *trace)
+{
+ /* Trace user stack if we are not a kernel thread. */
+ if (current->mm)
+ save_stack_trace_common(NULL, task_pt_regs(current),
+ true, trace);
+ else if (trace->nr_entries < trace->max_entries)
+ trace->entries[trace->nr_entries++] = ULONG_MAX;
+}
#endif
/* In entry.S */
--
cgit