From 9c0be3f6b5d776dfe3ed249862c244a4486414dc Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sat, 13 Oct 2018 15:10:50 -0400 Subject: [PATCH] tracepoint: Fix tracepoint array element size mismatch 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. Acked-by: Ard Biesheuvel Acked-by: Jessica Yu Link: http://lkml.kernel.org/r/20181013191050.22389-1-mathieu.desnoyers@efficios.com Link: http://lkml.kernel.org/r/20180704083651.24360-7-ard.biesheuvel@linaro.org Cc: Michael Ellerman Cc: Ingo Molnar Cc: Ard Biesheuvel Cc: Arnd Bergmann Cc: Benjamin Herrenschmidt Cc: Bjorn Helgaas Cc: Catalin Marinas Cc: James Morris Cc: James Morris Cc: Josh Poimboeuf Cc: Kees Cook Cc: Nicolas Pitre Cc: Paul Mackerras Cc: Petr Mladek Cc: Russell King Cc: "Serge E. Hallyn" Cc: Sergey Senozhatsky Cc: Thomas Garnier Cc: Thomas Gleixner Cc: Will Deacon Cc: Andrew Morton Cc: Linus Torvalds Cc: Greg Kroah-Hartman Signed-off-by: Mathieu Desnoyers Signed-off-by: Steven Rostedt (VMware) --- 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 #include #include +#include #include #include @@ -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 #include -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