On Tue, 12 May 2020 15:19:10 +0300 Adrian Hunter <[email protected]> wrote:
> Symbols are needed for tools to describe instruction addresses. Pages > allocated for kprobe's purposes need symbols to be created for them. > Add such symbols to be visible via /proc/kallsyms. > > Note: kprobe insn pages are not used if ftrace is configured. To see the > effect of this patch, the kernel must be configured with: Note, if you put a probe inside the function body, kprobe_insn_pages is used even if ftrace is configured. (Ftrace is used only for the function entry) > > # CONFIG_FUNCTION_TRACER is not set > CONFIG_KPROBES=y > > and for optimised kprobes: > > CONFIG_OPTPROBES=y > > Example on x86: > > # perf probe __schedule > Added new event: > probe:__schedule (on __schedule) > # cat /proc/kallsyms | grep '\[__builtin__kprobes\]' > ffffffffc00d4000 t kprobe_insn_page [__builtin__kprobes] > ffffffffc00d6000 t kprobe_optinsn_page [__builtin__kprobes] > > Note: This patch adds "__builtin__kprobes" as a module name in > /proc/kallsyms for symbols for pages allocated for kprobes' purposes, even > though "__builtin__kprobes" is not a module. Anyway, except for the Peter's sparc64 issue, the code is good to me. Acked-by: Masami Hiramatsu <[email protected]> Thank you, > > Signed-off-by: Adrian Hunter <[email protected]> > Acked-by: Peter Zijlstra (Intel) <[email protected]> > --- > include/linux/kprobes.h | 15 ++++++++++++++ > kernel/kallsyms.c | 37 +++++++++++++++++++++++++++++---- > kernel/kprobes.c | 45 +++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 93 insertions(+), 4 deletions(-) > > diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h > index 04bdaf01112c..62d682f47b5e 100644 > --- a/include/linux/kprobes.h > +++ b/include/linux/kprobes.h > @@ -242,6 +242,7 @@ struct kprobe_insn_cache { > struct mutex mutex; > void *(*alloc)(void); /* allocate insn page */ > void (*free)(void *); /* free insn page */ > + const char *sym; /* symbol for insn pages */ > struct list_head pages; /* list of kprobe_insn_page */ > size_t insn_size; /* size of instruction slot */ > int nr_garbage; > @@ -272,6 +273,8 @@ static inline bool is_kprobe_##__name##_slot(unsigned > long addr) \ > { \ > return __is_insn_slot_addr(&kprobe_##__name##_slots, addr); \ > } > +#define KPROBE_INSN_PAGE_SYM "kprobe_insn_page" > +#define KPROBE_OPTINSN_PAGE_SYM "kprobe_optinsn_page" > #else /* __ARCH_WANT_KPROBES_INSN_SLOT */ > #define DEFINE_INSN_CACHE_OPS(__name) > \ > static inline bool is_kprobe_##__name##_slot(unsigned long addr) \ > @@ -373,6 +376,13 @@ void dump_kprobe(struct kprobe *kp); > void *alloc_insn_page(void); > void free_insn_page(void *page); > > +int kprobe_get_kallsym(unsigned int symnum, unsigned long *value, char *type, > + char *sym); > +int kprobe_cache_get_kallsym(struct kprobe_insn_cache *c, unsigned int > *symnum, > + unsigned long *value, char *type, char *sym); > + > +int arch_kprobe_get_kallsym(unsigned int *symnum, unsigned long *value, > + char *type, char *sym); > #else /* !CONFIG_KPROBES: */ > > static inline int kprobes_built_in(void) > @@ -435,6 +445,11 @@ static inline bool within_kprobe_blacklist(unsigned long > addr) > { > return true; > } > +static inline int kprobe_get_kallsym(unsigned int symnum, unsigned long > *value, > + char *type, char *sym) > +{ > + return -ERANGE; > +} > #endif /* CONFIG_KPROBES */ > static inline int disable_kretprobe(struct kretprobe *rp) > { > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c > index 16c8c605f4b0..c6cc293c0e67 100644 > --- a/kernel/kallsyms.c > +++ b/kernel/kallsyms.c > @@ -24,6 +24,7 @@ > #include <linux/slab.h> > #include <linux/filter.h> > #include <linux/ftrace.h> > +#include <linux/kprobes.h> > #include <linux/compiler.h> > > /* > @@ -437,6 +438,7 @@ struct kallsym_iter { > loff_t pos_arch_end; > loff_t pos_mod_end; > loff_t pos_ftrace_mod_end; > + loff_t pos_bpf_end; > unsigned long value; > unsigned int nameoff; /* If iterating in core kernel symbols. */ > char type; > @@ -496,11 +498,33 @@ static int get_ksymbol_ftrace_mod(struct kallsym_iter > *iter) > > static int get_ksymbol_bpf(struct kallsym_iter *iter) > { > + int ret; > + > strlcpy(iter->module_name, "bpf", MODULE_NAME_LEN); > iter->exported = 0; > - return bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end, > - &iter->value, &iter->type, > - iter->name) < 0 ? 0 : 1; > + ret = bpf_get_kallsym(iter->pos - iter->pos_ftrace_mod_end, > + &iter->value, &iter->type, > + iter->name); > + if (ret < 0) { > + iter->pos_bpf_end = iter->pos; > + return 0; > + } > + > + return 1; > +} > + > +/* > + * This uses "__builtin__kprobes" as a module name for symbols for pages > + * allocated for kprobes' purposes, even though "__builtin__kprobes" is not a > + * module. > + */ > +static int get_ksymbol_kprobe(struct kallsym_iter *iter) > +{ > + strlcpy(iter->module_name, "__builtin__kprobes", MODULE_NAME_LEN); > + iter->exported = 0; > + return kprobe_get_kallsym(iter->pos - iter->pos_bpf_end, > + &iter->value, &iter->type, > + iter->name) < 0 ? 0 : 1; > } > > /* Returns space to next name. */ > @@ -527,6 +551,7 @@ static void reset_iter(struct kallsym_iter *iter, loff_t > new_pos) > iter->pos_arch_end = 0; > iter->pos_mod_end = 0; > iter->pos_ftrace_mod_end = 0; > + iter->pos_bpf_end = 0; > } > } > > @@ -551,7 +576,11 @@ static int update_iter_mod(struct kallsym_iter *iter, > loff_t pos) > get_ksymbol_ftrace_mod(iter)) > return 1; > > - return get_ksymbol_bpf(iter); > + if ((!iter->pos_bpf_end || iter->pos_bpf_end > pos) && > + get_ksymbol_bpf(iter)) > + return 1; > + > + return get_ksymbol_kprobe(iter); > } > > /* Returns false if pos at or past end of file. */ > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 2625c241ac00..229d1b596690 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -118,6 +118,7 @@ struct kprobe_insn_cache kprobe_insn_slots = { > .mutex = __MUTEX_INITIALIZER(kprobe_insn_slots.mutex), > .alloc = alloc_insn_page, > .free = free_insn_page, > + .sym = KPROBE_INSN_PAGE_SYM, > .pages = LIST_HEAD_INIT(kprobe_insn_slots.pages), > .insn_size = MAX_INSN_SIZE, > .nr_garbage = 0, > @@ -296,6 +297,7 @@ struct kprobe_insn_cache kprobe_optinsn_slots = { > .mutex = __MUTEX_INITIALIZER(kprobe_optinsn_slots.mutex), > .alloc = alloc_insn_page, > .free = free_insn_page, > + .sym = KPROBE_OPTINSN_PAGE_SYM, > .pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages), > /* .insn_size is initialized later */ > .nr_garbage = 0, > @@ -2179,6 +2181,49 @@ int kprobe_add_area_blacklist(unsigned long start, > unsigned long end) > return 0; > } > > +int kprobe_cache_get_kallsym(struct kprobe_insn_cache *c, unsigned int > *symnum, > + unsigned long *value, char *type, char *sym) > +{ > + struct kprobe_insn_page *kip; > + int ret = -ERANGE; > + > + rcu_read_lock(); > + list_for_each_entry_rcu(kip, &c->pages, list) { > + if ((*symnum)--) > + continue; > + strlcpy(sym, c->sym, KSYM_NAME_LEN); > + *type = 't'; > + *value = (unsigned long)kip->insns; > + ret = 0; > + break; > + } > + rcu_read_unlock(); > + > + return ret; > +} > + > +int __weak arch_kprobe_get_kallsym(unsigned int *symnum, unsigned long > *value, > + char *type, char *sym) > +{ > + return -ERANGE; > +} > + > +int kprobe_get_kallsym(unsigned int symnum, unsigned long *value, char *type, > + char *sym) > +{ > +#ifdef __ARCH_WANT_KPROBES_INSN_SLOT > + if (!kprobe_cache_get_kallsym(&kprobe_insn_slots, &symnum, value, type, > sym)) > + return 0; > +#ifdef CONFIG_OPTPROBES > + if (!kprobe_cache_get_kallsym(&kprobe_optinsn_slots, &symnum, value, > type, sym)) > + return 0; > +#endif > +#endif > + if (!arch_kprobe_get_kallsym(&symnum, value, type, sym)) > + return 0; > + return -ERANGE; > +} > + > int __init __weak arch_populate_kprobe_blacklist(void) > { > return 0; > -- > 2.17.1 > -- Masami Hiramatsu <[email protected]>
