This patch fixes the undefined instruction oops due to execution
of thumb-2 code in ARM mode. The zero bit in the symbol address
returned by kallsyms_lookup_name is not set, leading to switching
to ARM mode that generates oops while executing thumb-2 code. For
detailed discussion, see [1].
[1] http://lists.casi.polymtl.ca/pipermail/ltt-dev/2011-September/005176.html
v1:
- include wrapper function kallsyms_lookup_funcptr as suggested
by Dave Martin
Signed-off-by: Avik Sil <[email protected]>
---
lttng-context-prio.c | 3 ++-
wrapper/ftrace.h | 5 +++--
wrapper/kallsyms.h | 28 ++++++++++++++++++++++++++++
wrapper/splice.c | 3 ++-
wrapper/vmalloc.h | 3 ++-
5 files changed, 37 insertions(+), 5 deletions(-)
create mode 100644 wrapper/kallsyms.h
diff --git a/lttng-context-prio.c b/lttng-context-prio.c
index ad1c42f..1ee3a54 100644
--- a/lttng-context-prio.c
+++ b/lttng-context-prio.c
@@ -13,6 +13,7 @@
#include "ltt-events.h"
#include "wrapper/ringbuffer/frontend_types.h"
#include "wrapper/vmalloc.h"
+#include "wrapper/kallsyms.h"
#include "ltt-tracer.h"
static
@@ -20,7 +21,7 @@ int (*wrapper_task_prio_sym)(struct task_struct *t);
int wrapper_task_prio_init(void)
{
- wrapper_task_prio_sym = (void *) kallsyms_lookup_name("task_prio");
+ wrapper_task_prio_sym = (void *) kallsyms_lookup_funcptr("task_prio");
if (!wrapper_task_prio_sym) {
printk(KERN_WARNING "LTTng: task_prio symbol lookup failed.\n");
return -EINVAL;
diff --git a/wrapper/ftrace.h b/wrapper/ftrace.h
index 9c18cc5..ace33c5 100644
--- a/wrapper/ftrace.h
+++ b/wrapper/ftrace.h
@@ -16,6 +16,7 @@
#ifdef CONFIG_KALLSYMS
#include <linux/kallsyms.h>
+#include "kallsyms.h"
static inline
int wrapper_register_ftrace_function_probe(char *glob,
@@ -24,7 +25,7 @@ int wrapper_register_ftrace_function_probe(char *glob,
int (*register_ftrace_function_probe_sym)(char *glob,
struct ftrace_probe_ops *ops, void *data);
- register_ftrace_function_probe_sym = (void *)
kallsyms_lookup_name("register_ftrace_function_probe");
+ register_ftrace_function_probe_sym = (void *)
kallsyms_lookup_funcptr("register_ftrace_function_probe");
if (register_ftrace_function_probe_sym) {
return register_ftrace_function_probe_sym(glob, ops, data);
} else {
@@ -40,7 +41,7 @@ void wrapper_unregister_ftrace_function_probe(char *glob,
void (*unregister_ftrace_function_probe_sym)(char *glob,
struct ftrace_probe_ops *ops, void *data);
- unregister_ftrace_function_probe_sym = (void *)
kallsyms_lookup_name("unregister_ftrace_function_probe");
+ unregister_ftrace_function_probe_sym = (void *)
kallsyms_lookup_funcptr("unregister_ftrace_function_probe");
if (unregister_ftrace_function_probe_sym) {
unregister_ftrace_function_probe_sym(glob, ops, data);
} else {
diff --git a/wrapper/kallsyms.h b/wrapper/kallsyms.h
new file mode 100644
index 0000000..bb45f38
--- /dev/null
+++ b/wrapper/kallsyms.h
@@ -0,0 +1,28 @@
+#ifndef _LTT_WRAPPER_KALLSYMS_H
+#define _LTT_WRAPPER_KALLSYMS_H
+
+/*
+ * Copyright (C) 2011 Avik Sil ([email protected])
+ *
+ * wrapper around kallsyms_lookup_name. Implements arch-dependent code for
+ * arches where the address of the start of the function body is different
+ * from the pointer which can be used to call the function, e.g. ARM THUMB2.
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ */
+
+static inline
+unsigned long kallsyms_lookup_funcptr(const char *name)
+{
+ unsigned long addr;
+
+ addr = kallsyms_lookup_name(name);
+#ifdef CONFIG_ARM
+#ifdef CONFIG_THUMB2_KERNEL
+ if (addr)
+ addr |= 1; /* set bit 0 in address for thumb mode */
+#endif
+#endif
+ return addr;
+}
+#endif /* _LTT_WRAPPER_KALLSYMS_H */
diff --git a/wrapper/splice.c b/wrapper/splice.c
index edc499c..ba224ee 100644
--- a/wrapper/splice.c
+++ b/wrapper/splice.c
@@ -13,6 +13,7 @@
#include <linux/kallsyms.h>
#include <linux/fs.h>
#include <linux/splice.h>
+#include "kallsyms.h"
static
ssize_t (*splice_to_pipe_sym)(struct pipe_inode_info *pipe,
@@ -22,7 +23,7 @@ ssize_t wrapper_splice_to_pipe(struct pipe_inode_info *pipe,
struct splice_pipe_desc *spd)
{
if (!splice_to_pipe_sym)
- splice_to_pipe_sym = (void *)
kallsyms_lookup_name("splice_to_pipe");
+ splice_to_pipe_sym = (void *)
kallsyms_lookup_funcptr("splice_to_pipe");
if (splice_to_pipe_sym) {
return splice_to_pipe_sym(pipe, spd);
} else {
diff --git a/wrapper/vmalloc.h b/wrapper/vmalloc.h
index 7d87855..765f2ad 100644
--- a/wrapper/vmalloc.h
+++ b/wrapper/vmalloc.h
@@ -14,13 +14,14 @@
#ifdef CONFIG_KALLSYMS
#include <linux/kallsyms.h>
+#include "kallsyms.h"
static inline
void wrapper_vmalloc_sync_all(void)
{
void (*vmalloc_sync_all_sym)(void);
- vmalloc_sync_all_sym = (void *)
kallsyms_lookup_name("vmalloc_sync_all");
+ vmalloc_sync_all_sym = (void *)
kallsyms_lookup_funcptr("vmalloc_sync_all");
if (vmalloc_sync_all_sym) {
vmalloc_sync_all_sym();
} else {
--
1.7.0.4
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