commit 46e0c9be206f ("kernel: tracepoints: add support for relative
references") changes the layout of the __tracepoint_ptrs section on
architectures supporting relative references. However, it does so
without turning struct tracepoint * const into const int elsewhere in
the tracepoint code, which has the following side-effect:
Setting mod->num_tracepoints is done in by module.c:
mod->tracepoints_ptrs = section_objs(info, "__tracepoints_ptrs",
sizeof(*mod->tracepoints_ptrs),
&mod->num_tracepoints);
Basically, since sizeof(*mod->tracepoints_ptrs) is a pointer size
(rather than sizeof(int)), num_tracepoints is erroneously set to half the
size it should be on 64-bit arch. So a module with an odd number of
tracepoints misses the last tracepoint due to effect of integer
division.
So in the module going notifier:
for_each_tracepoint_range(mod->tracepoints_ptrs,
mod->tracepoints_ptrs + mod->num_tracepoints,
tp_module_going_check_quiescent, NULL);
the expression (mod->tracepoints_ptrs + mod->num_tracepoints) actually
evaluates to something within the bounds of the array, but miss the
last tracepoint if the number of tracepoints is odd on 64-bit arch.
Fix this by introducing a new typedef: tracepoint_ptr_t, which
is either "const int" on architectures that have PREL32 relocations,
or "struct tracepoint * const" on architectures that does not have
this feature.
Also provide a new tracepoint_ptr_defer() static inline to
encapsulate deferencing this type rather than duplicate code and
ugly idefs within the for_each_tracepoint_range() implementation.
This issue appears in 4.19-rc kernels, and should ideally be fixed
before the end of the rc cycle.
Signed-off-by: Mathieu Desnoyers <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Cc: Michael Ellerman <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Steven Rostedt (VMware) <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Bjorn Helgaas <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: James Morris <[email protected]>
Cc: James Morris <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Nicolas Pitre <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Russell King <[email protected]>
Cc: "Serge E. Hallyn" <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Thomas Garnier <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
---
include/linux/module.h | 3 ++-
include/linux/tracepoint-defs.h | 6 ++++++
include/linux/tracepoint.h | 36 +++++++++++++++++++++------------
kernel/tracepoint.c | 24 ++++++++--------------
4 files changed, 39 insertions(+), 30 deletions(-)
diff --git a/include/linux/module.h b/include/linux/module.h
index f807f15bebbe..e19ae08c7fb8 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -20,6 +20,7 @@
#include <linux/export.h>
#include <linux/rbtree_latch.h>
#include <linux/error-injection.h>
+#include <linux/tracepoint-defs.h>
#include <linux/percpu.h>
#include <asm/module.h>
@@ -430,7 +431,7 @@ struct module {
#ifdef CONFIG_TRACEPOINTS
unsigned int num_tracepoints;
- struct tracepoint * const *tracepoints_ptrs;
+ tracepoint_ptr_t *tracepoints_ptrs;
#endif
#ifdef HAVE_JUMP_LABEL
struct jump_entry *jump_entries;
diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index 22c5a46e9693..49ba9cde7e4b 100644
--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -35,6 +35,12 @@ struct tracepoint {
struct tracepoint_func __rcu *funcs;
};
+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
+typedef const int tracepoint_ptr_t;
+#else
+typedef struct tracepoint * const tracepoint_ptr_t;
+#endif
+
struct bpf_raw_event_map {
struct tracepoint *tp;
void *bpf_func;
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 041f7e56a289..538ba1a58f5b 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -99,6 +99,29 @@ extern void syscall_unregfunc(void);
#define TRACE_DEFINE_ENUM(x)
#define TRACE_DEFINE_SIZEOF(x)
+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
+static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
+{
+ return offset_to_ptr(p);
+}
+
+#define __TRACEPOINT_ENTRY(name) \
+ asm(" .section \"__tracepoints_ptrs\", \"a\" \n" \
+ " .balign 4 \n" \
+ " .long __tracepoint_" #name " - . \n" \
+ " .previous \n")
+#else
+static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
+{
+ return *p;
+}
+
+#define __TRACEPOINT_ENTRY(name) \
+ static tracepoint_ptr_t __tracepoint_ptr_##name __used \
+ __attribute__((section("__tracepoints_ptrs"))) = \
+ &__tracepoint_##name
+#endif
+
#endif /* _LINUX_TRACEPOINT_H */
/*
@@ -253,19 +276,6 @@ extern void syscall_unregfunc(void);
return static_key_false(&__tracepoint_##name.key); \
}
-#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
-#define __TRACEPOINT_ENTRY(name) \
- asm(" .section \"__tracepoints_ptrs\", \"a\" \n" \
- " .balign 4 \n" \
- " .long __tracepoint_" #name " - . \n" \
- " .previous \n")
-#else
-#define __TRACEPOINT_ENTRY(name) \
- static struct tracepoint * const __tracepoint_ptr_##name __used \
- __attribute__((section("__tracepoints_ptrs"))) = \
- &__tracepoint_##name
-#endif
-
/*
* We have no guarantee that gcc and the linker won't up-align the tracepoint
* structures, so we create an array of pointers that will be used for iteration
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index bf2c06ef9afc..a3be42304485 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -28,8 +28,8 @@
#include <linux/sched/task.h>
#include <linux/static_key.h>
-extern struct tracepoint * const __start___tracepoints_ptrs[];
-extern struct tracepoint * const __stop___tracepoints_ptrs[];
+extern tracepoint_ptr_t __start___tracepoints_ptrs[];
+extern tracepoint_ptr_t __stop___tracepoints_ptrs[];
DEFINE_SRCU(tracepoint_srcu);
EXPORT_SYMBOL_GPL(tracepoint_srcu);
@@ -371,25 +371,17 @@ int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
}
EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
-static void for_each_tracepoint_range(struct tracepoint * const *begin,
- struct tracepoint * const *end,
+static void for_each_tracepoint_range(
+ tracepoint_ptr_t *begin, tracepoint_ptr_t *end,
void (*fct)(struct tracepoint *tp, void *priv),
void *priv)
{
+ tracepoint_ptr_t *iter;
+
if (!begin)
return;
-
- if (IS_ENABLED(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)) {
- const int *iter;
-
- for (iter = (const int *)begin; iter < (const int *)end; iter++)
- fct(offset_to_ptr(iter), priv);
- } else {
- struct tracepoint * const *iter;
-
- for (iter = begin; iter < end; iter++)
- fct(*iter, priv);
- }
+ for (iter = begin; iter < end; iter++)
+ fct(tracepoint_ptr_deref(iter), priv);
}
#ifdef CONFIG_MODULES
--
2.17.1
+++ Mathieu Desnoyers [13/10/18 15:10 -0400]:
>commit 46e0c9be206f ("kernel: tracepoints: add support for relative
>references") changes the layout of the __tracepoint_ptrs section on
>architectures supporting relative references. However, it does so
>without turning struct tracepoint * const into const int elsewhere in
>the tracepoint code, which has the following side-effect:
>
>Setting mod->num_tracepoints is done in by module.c:
>
> mod->tracepoints_ptrs = section_objs(info, "__tracepoints_ptrs",
> sizeof(*mod->tracepoints_ptrs),
> &mod->num_tracepoints);
>
>Basically, since sizeof(*mod->tracepoints_ptrs) is a pointer size
>(rather than sizeof(int)), num_tracepoints is erroneously set to half the
>size it should be on 64-bit arch. So a module with an odd number of
>tracepoints misses the last tracepoint due to effect of integer
>division.
>
>So in the module going notifier:
>
> for_each_tracepoint_range(mod->tracepoints_ptrs,
> mod->tracepoints_ptrs + mod->num_tracepoints,
> tp_module_going_check_quiescent, NULL);
>
>the expression (mod->tracepoints_ptrs + mod->num_tracepoints) actually
>evaluates to something within the bounds of the array, but miss the
>last tracepoint if the number of tracepoints is odd on 64-bit arch.
>
>Fix this by introducing a new typedef: tracepoint_ptr_t, which
>is either "const int" on architectures that have PREL32 relocations,
>or "struct tracepoint * const" on architectures that does not have
>this feature.
>
>Also provide a new tracepoint_ptr_defer() static inline to
>encapsulate deferencing this type rather than duplicate code and
>ugly idefs within the for_each_tracepoint_range() implementation.
>
>This issue appears in 4.19-rc kernels, and should ideally be fixed
>before the end of the rc cycle.
>
>Signed-off-by: Mathieu Desnoyers <[email protected]>
>Acked-by: Ard Biesheuvel <[email protected]>
>Link: http://lkml.kernel.org/r/[email protected]
>Cc: Michael Ellerman <[email protected]>
>Cc: Ingo Molnar <[email protected]>
>Cc: Steven Rostedt (VMware) <[email protected]>
>Cc: Ard Biesheuvel <[email protected]>
>Cc: Arnd Bergmann <[email protected]>
>Cc: Benjamin Herrenschmidt <[email protected]>
>Cc: Bjorn Helgaas <[email protected]>
>Cc: Catalin Marinas <[email protected]>
>Cc: James Morris <[email protected]>
>Cc: James Morris <[email protected]>
>Cc: Jessica Yu <[email protected]>
>Cc: Josh Poimboeuf <[email protected]>
>Cc: Kees Cook <[email protected]>
>Cc: Nicolas Pitre <[email protected]>
>Cc: Paul Mackerras <[email protected]>
>Cc: Petr Mladek <[email protected]>
>Cc: Russell King <[email protected]>
>Cc: "Serge E. Hallyn" <[email protected]>
>Cc: Sergey Senozhatsky <[email protected]>
>Cc: Thomas Garnier <[email protected]>
>Cc: Thomas Gleixner <[email protected]>
>Cc: Will Deacon <[email protected]>
>Cc: Andrew Morton <[email protected]>
>Cc: Linus Torvalds <[email protected]>
>Cc: Greg Kroah-Hartman <[email protected]>
Whoops, acked the first version of the patch instead of this one.
In any case, for module parts:
Acked-by: Jessica Yu <[email protected]>
>---
> include/linux/module.h | 3 ++-
> include/linux/tracepoint-defs.h | 6 ++++++
> include/linux/tracepoint.h | 36 +++++++++++++++++++++------------
> kernel/tracepoint.c | 24 ++++++++--------------
> 4 files changed, 39 insertions(+), 30 deletions(-)
>
>diff --git a/include/linux/module.h b/include/linux/module.h
>index f807f15bebbe..e19ae08c7fb8 100644
>--- a/include/linux/module.h
>+++ b/include/linux/module.h
>@@ -20,6 +20,7 @@
> #include <linux/export.h>
> #include <linux/rbtree_latch.h>
> #include <linux/error-injection.h>
>+#include <linux/tracepoint-defs.h>
>
> #include <linux/percpu.h>
> #include <asm/module.h>
>@@ -430,7 +431,7 @@ struct module {
>
> #ifdef CONFIG_TRACEPOINTS
> unsigned int num_tracepoints;
>- struct tracepoint * const *tracepoints_ptrs;
>+ tracepoint_ptr_t *tracepoints_ptrs;
> #endif
> #ifdef HAVE_JUMP_LABEL
> struct jump_entry *jump_entries;
>diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
>index 22c5a46e9693..49ba9cde7e4b 100644
>--- a/include/linux/tracepoint-defs.h
>+++ b/include/linux/tracepoint-defs.h
>@@ -35,6 +35,12 @@ struct tracepoint {
> struct tracepoint_func __rcu *funcs;
> };
>
>+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
>+typedef const int tracepoint_ptr_t;
>+#else
>+typedef struct tracepoint * const tracepoint_ptr_t;
>+#endif
>+
> struct bpf_raw_event_map {
> struct tracepoint *tp;
> void *bpf_func;
>diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
>index 041f7e56a289..538ba1a58f5b 100644
>--- a/include/linux/tracepoint.h
>+++ b/include/linux/tracepoint.h
>@@ -99,6 +99,29 @@ extern void syscall_unregfunc(void);
> #define TRACE_DEFINE_ENUM(x)
> #define TRACE_DEFINE_SIZEOF(x)
>
>+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
>+static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
>+{
>+ return offset_to_ptr(p);
>+}
>+
>+#define __TRACEPOINT_ENTRY(name) \
>+ asm(" .section \"__tracepoints_ptrs\", \"a\" \n" \
>+ " .balign 4 \n" \
>+ " .long __tracepoint_" #name " - . \n" \
>+ " .previous \n")
>+#else
>+static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
>+{
>+ return *p;
>+}
>+
>+#define __TRACEPOINT_ENTRY(name) \
>+ static tracepoint_ptr_t __tracepoint_ptr_##name __used \
>+ __attribute__((section("__tracepoints_ptrs"))) = \
>+ &__tracepoint_##name
>+#endif
>+
> #endif /* _LINUX_TRACEPOINT_H */
>
> /*
>@@ -253,19 +276,6 @@ extern void syscall_unregfunc(void);
> return static_key_false(&__tracepoint_##name.key); \
> }
>
>-#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
>-#define __TRACEPOINT_ENTRY(name) \
>- asm(" .section \"__tracepoints_ptrs\", \"a\" \n" \
>- " .balign 4 \n" \
>- " .long __tracepoint_" #name " - . \n" \
>- " .previous \n")
>-#else
>-#define __TRACEPOINT_ENTRY(name) \
>- static struct tracepoint * const __tracepoint_ptr_##name __used \
>- __attribute__((section("__tracepoints_ptrs"))) = \
>- &__tracepoint_##name
>-#endif
>-
> /*
> * We have no guarantee that gcc and the linker won't up-align the tracepoint
> * structures, so we create an array of pointers that will be used for iteration
>diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
>index bf2c06ef9afc..a3be42304485 100644
>--- a/kernel/tracepoint.c
>+++ b/kernel/tracepoint.c
>@@ -28,8 +28,8 @@
> #include <linux/sched/task.h>
> #include <linux/static_key.h>
>
>-extern struct tracepoint * const __start___tracepoints_ptrs[];
>-extern struct tracepoint * const __stop___tracepoints_ptrs[];
>+extern tracepoint_ptr_t __start___tracepoints_ptrs[];
>+extern tracepoint_ptr_t __stop___tracepoints_ptrs[];
>
> DEFINE_SRCU(tracepoint_srcu);
> EXPORT_SYMBOL_GPL(tracepoint_srcu);
>@@ -371,25 +371,17 @@ int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
> }
> EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
>
>-static void for_each_tracepoint_range(struct tracepoint * const *begin,
>- struct tracepoint * const *end,
>+static void for_each_tracepoint_range(
>+ tracepoint_ptr_t *begin, tracepoint_ptr_t *end,
> void (*fct)(struct tracepoint *tp, void *priv),
> void *priv)
> {
>+ tracepoint_ptr_t *iter;
>+
> if (!begin)
> return;
>-
>- if (IS_ENABLED(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)) {
>- const int *iter;
>-
>- for (iter = (const int *)begin; iter < (const int *)end; iter++)
>- fct(offset_to_ptr(iter), priv);
>- } else {
>- struct tracepoint * const *iter;
>-
>- for (iter = begin; iter < end; iter++)
>- fct(*iter, priv);
>- }
>+ for (iter = begin; iter < end; iter++)
>+ fct(tracepoint_ptr_deref(iter), priv);
> }
>
> #ifdef CONFIG_MODULES
>--
>2.17.1
>
On Mon, 15 Oct 2018 14:23:23 +0200
Jessica Yu <[email protected]> wrote:
> Whoops, acked the first version of the patch instead of this one.
> In any case, for module parts:
>
> Acked-by: Jessica Yu <[email protected]>
Yep, I meant I was going to pull this patch in ;-)
-- Steve