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kernel: tracepoints: add support for relative references

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To avoid the need for relocating absolute references to tracepoint
structures at boot time when running relocatable kernels (which may
take a disproportionate amount of space), add the option to emit
these tables as relative references instead.

Link: http://lkml.kernel.org/r/20180704083651.24360-7-ard.biesheuvel@linaro.org
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morris <james.morris@microsoft.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Nicolas Pitre <nico@linaro.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ard Biesheuvel 2018-08-21 21:56:22 -07:00 committed by Linus Torvalds
parent c9d8b55fa0
commit 46e0c9be20
2 changed files with 41 additions and 27 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

19
include/linux/tracepoint.h
View file

@ -249,6 +249,19 @@ 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
@ -258,11 +271,9 @@ extern void syscall_unregfunc(void);
static const char __tpstrtab_##name[] \
__attribute__((section("__tracepoints_strings"))) = #name; \
struct tracepoint __tracepoint_##name \
__attribute__((section("__tracepoints"))) = \
__attribute__((section("__tracepoints"), used)) = \
{ __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
static struct tracepoint * const __tracepoint_ptr_##name __used \
__attribute__((section("__tracepoints_ptrs"))) = \
&__tracepoint_##name;
__TRACEPOINT_ENTRY(name);
#define DEFINE_TRACE(name) \
DEFINE_TRACE_FN(name, NULL, NULL);

49
kernel/tracepoint.c
View file

@ -371,6 +371,27 @@ 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,
void (*fct)(struct tracepoint *tp, void *priv),
void *priv)
{
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);
}
}
#ifdef CONFIG_MODULES
bool trace_module_has_bad_taint(struct module *mod)
{
@ -435,15 +456,9 @@ EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
* Ensure the tracer unregistered the module's probes before the module
* teardown is performed. Prevents leaks of probe and data pointers.
*/
static void tp_module_going_check_quiescent(struct tracepoint * const *begin,
struct tracepoint * const *end)
static void tp_module_going_check_quiescent(struct tracepoint *tp, void *priv)
{
struct tracepoint * const *iter;
if (!begin)
return;
for (iter = begin; iter < end; iter++)
WARN_ON_ONCE((*iter)->funcs);
WARN_ON_ONCE(tp->funcs);
}
static int tracepoint_module_coming(struct module *mod)
@ -494,8 +509,9 @@ static void tracepoint_module_going(struct module *mod)
* Called the going notifier before checking for
* quiescence.
*/
tp_module_going_check_quiescent(mod->tracepoints_ptrs,
mod->tracepoints_ptrs + mod->num_tracepoints);
for_each_tracepoint_range(mod->tracepoints_ptrs,
mod->tracepoints_ptrs + mod->num_tracepoints,
tp_module_going_check_quiescent, NULL);
break;
}
}
@ -547,19 +563,6 @@ static __init int init_tracepoints(void)
__initcall(init_tracepoints);
#endif /* CONFIG_MODULES */
static void for_each_tracepoint_range(struct tracepoint * const *begin,
struct tracepoint * const *end,
void (*fct)(struct tracepoint *tp, void *priv),
void *priv)
{
struct tracepoint * const *iter;
if (!begin)
return;
for (iter = begin; iter < end; iter++)
fct(*iter, priv);
}
/**
* for_each_kernel_tracepoint - iteration on all kernel tracepoints
* @fct: callback