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kernel: tracepoints: add support for relative references
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>
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@ -249,6 +249,19 @@ extern void syscall_unregfunc(void);
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return static_key_false(&__tracepoint_##name.key); \
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}
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#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
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#define __TRACEPOINT_ENTRY(name) \
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asm(" .section \"__tracepoints_ptrs\", \"a\" \n" \
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" .balign 4 \n" \
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" .long __tracepoint_" #name " - . \n" \
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" .previous \n")
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#else
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#define __TRACEPOINT_ENTRY(name) \
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static struct tracepoint * const __tracepoint_ptr_##name __used \
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__attribute__((section("__tracepoints_ptrs"))) = \
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&__tracepoint_##name
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#endif
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/*
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* We have no guarantee that gcc and the linker won't up-align the tracepoint
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* structures, so we create an array of pointers that will be used for iteration
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@ -258,11 +271,9 @@ extern void syscall_unregfunc(void);
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static const char __tpstrtab_##name[] \
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__attribute__((section("__tracepoints_strings"))) = #name; \
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struct tracepoint __tracepoint_##name \
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__attribute__((section("__tracepoints"))) = \
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__attribute__((section("__tracepoints"), used)) = \
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{ __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
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static struct tracepoint * const __tracepoint_ptr_##name __used \
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__attribute__((section("__tracepoints_ptrs"))) = \
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&__tracepoint_##name;
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__TRACEPOINT_ENTRY(name);
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#define DEFINE_TRACE(name) \
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DEFINE_TRACE_FN(name, NULL, NULL);
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@ -371,6 +371,27 @@ int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
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}
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EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
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static void for_each_tracepoint_range(struct tracepoint * const *begin,
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struct tracepoint * const *end,
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void (*fct)(struct tracepoint *tp, void *priv),
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void *priv)
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{
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if (!begin)
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return;
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if (IS_ENABLED(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)) {
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const int *iter;
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for (iter = (const int *)begin; iter < (const int *)end; iter++)
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fct(offset_to_ptr(iter), priv);
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} else {
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struct tracepoint * const *iter;
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for (iter = begin; iter < end; iter++)
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fct(*iter, priv);
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}
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}
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#ifdef CONFIG_MODULES
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bool trace_module_has_bad_taint(struct module *mod)
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{
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@ -435,15 +456,9 @@ EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
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* Ensure the tracer unregistered the module's probes before the module
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* teardown is performed. Prevents leaks of probe and data pointers.
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*/
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static void tp_module_going_check_quiescent(struct tracepoint * const *begin,
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struct tracepoint * const *end)
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static void tp_module_going_check_quiescent(struct tracepoint *tp, void *priv)
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{
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struct tracepoint * const *iter;
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if (!begin)
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return;
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for (iter = begin; iter < end; iter++)
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WARN_ON_ONCE((*iter)->funcs);
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WARN_ON_ONCE(tp->funcs);
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}
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static int tracepoint_module_coming(struct module *mod)
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@ -494,8 +509,9 @@ static void tracepoint_module_going(struct module *mod)
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* Called the going notifier before checking for
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* quiescence.
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*/
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tp_module_going_check_quiescent(mod->tracepoints_ptrs,
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mod->tracepoints_ptrs + mod->num_tracepoints);
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for_each_tracepoint_range(mod->tracepoints_ptrs,
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mod->tracepoints_ptrs + mod->num_tracepoints,
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tp_module_going_check_quiescent, NULL);
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break;
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}
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}
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@ -547,19 +563,6 @@ static __init int init_tracepoints(void)
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__initcall(init_tracepoints);
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#endif /* CONFIG_MODULES */
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static void for_each_tracepoint_range(struct tracepoint * const *begin,
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struct tracepoint * const *end,
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void (*fct)(struct tracepoint *tp, void *priv),
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void *priv)
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{
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struct tracepoint * const *iter;
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if (!begin)
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return;
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for (iter = begin; iter < end; iter++)
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fct(*iter, priv);
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}
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/**
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* for_each_kernel_tracepoint - iteration on all kernel tracepoints
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* @fct: callback
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