From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> Support function or tracepoint parameters by name if BTF support is enabled and the event is for function entry (this feature can be used with kprobe- events, fprobe-events and tracepoint probe events.) Note that the BTF variable syntax does not require a prefix. If it starts with an alphabetic character or an underscore ('_') without a prefix like '$' and '%', it is considered as a BTF variable. If you specify only the BTF variable name, the argument name will also be the same name instead of 'arg*'. # echo 'p vfs_read count pos' >> dynamic_events # echo 'f vfs_write count pos' >> dynamic_events # echo 't sched_overutilized_tp rd overutilized' >> dynamic_events # cat dynamic_events p:kprobes/p_vfs_read_0 vfs_read count=count pos=pos f:fprobes/vfs_write__entry vfs_write count=count pos=pos t:tracepoints/sched_overutilized_tp sched_overutilized_tp rd=rd overutilized=overutilized Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> Reviewed-by: Alan Maguire <alan.maguire@xxxxxxxxxx> Tested-by: Alan Maguire <alan.maguire@xxxxxxxxxx> --- Changes in v8: - Update Kconfig help description. Changes in v7: - Add BTF_KIND_ENUM64 support - Fix to check the ERR_PTR() type return value of bpf_get_btf_vmlinux(). Changes in v6: - update patch description. - use bpf_get_btf_vmlinux() instead of btf_parse_vmlinux(). --- kernel/trace/Kconfig | 12 +++ kernel/trace/trace.c | 4 + kernel/trace/trace_fprobe.c | 49 +++++++---- kernel/trace/trace_kprobe.c | 12 +-- kernel/trace/trace_probe.c | 191 +++++++++++++++++++++++++++++++++++++++++++ kernel/trace/trace_probe.h | 9 ++ 6 files changed, 248 insertions(+), 29 deletions(-) diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 8e10a9453c96..b3f90d602896 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -664,6 +664,18 @@ config FPROBE_EVENTS and the kprobe events on function entry and exit will be transparently converted to this fprobe events. +config PROBE_EVENTS_BTF_ARGS + depends on HAVE_FUNCTION_ARG_ACCESS_API + depends on FPROBE_EVENTS || KPROBE_EVENTS + depends on DEBUG_INFO_BTF && BPF_SYSCALL + bool "Support BTF function arguments for probe events" + default y + help + The user can specify the arguments of the probe event using the names + of the arguments of the probed function, when the probe location is a + kernel function entry or a tracepoint. + This is available only if BTF (BPF Type Format) support is enabled. + config KPROBE_EVENTS depends on KPROBES depends on HAVE_REGS_AND_STACK_ACCESS_API diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index abcc2ca615e8..7bd2741356ef 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5670,7 +5670,11 @@ static const char readme_msg[] = "\t args: <name>=fetcharg[:type]\n" "\t fetcharg: (%<register>|$<efield>), @<address>, @<symbol>[+|-<offset>],\n" #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API +#ifdef CONFIG_PROBE_EVENTS_BTF_ARGS + "\t $stack<index>, $stack, $retval, $comm, $arg<N>, <argname>\n" +#else "\t $stack<index>, $stack, $retval, $comm, $arg<N>,\n" +#endif #else "\t $stack<index>, $stack, $retval, $comm,\n" #endif diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c index 60e1b54fe647..75130a5bdddc 100644 --- a/kernel/trace/trace_fprobe.c +++ b/kernel/trace/trace_fprobe.c @@ -366,6 +366,7 @@ static void free_trace_fprobe(struct trace_fprobe *tf) static struct trace_fprobe *alloc_trace_fprobe(const char *group, const char *event, const char *symbol, + struct tracepoint *tpoint, int maxactive, int nargs, bool is_return) { @@ -385,6 +386,7 @@ static struct trace_fprobe *alloc_trace_fprobe(const char *group, else tf->fp.entry_handler = fentry_dispatcher; + tf->tpoint = tpoint; tf->fp.nr_maxactive = maxactive; ret = trace_probe_init(&tf->tp, event, group, false); @@ -930,8 +932,12 @@ static int __trace_fprobe_create(int argc, const char *argv[]) int maxactive = 0; char buf[MAX_EVENT_NAME_LEN]; char gbuf[MAX_EVENT_NAME_LEN]; - unsigned int flags = TPARG_FL_KERNEL; + char sbuf[KSYM_NAME_LEN]; bool is_tracepoint = false; + struct tracepoint *tpoint = NULL; + struct traceprobe_parse_context ctx = { + .flags = TPARG_FL_KERNEL | TPARG_FL_FENTRY, + }; if ((argv[0][0] != 'f' && argv[0][0] != 't') || argc < 2) return -ECANCELED; @@ -995,12 +1001,6 @@ static int __trace_fprobe_create(int argc, const char *argv[]) goto parse_error; } - flags |= TPARG_FL_FENTRY; - if (is_return) - flags |= TPARG_FL_RETURN; - if (is_tracepoint) - flags |= TPARG_FL_TPOINT; - trace_probe_log_set_index(0); if (event) { ret = traceprobe_parse_event_name(&event, &group, gbuf, @@ -1012,7 +1012,8 @@ static int __trace_fprobe_create(int argc, const char *argv[]) if (!event) { /* Make a new event name */ if (is_tracepoint) - strscpy(buf, symbol, MAX_EVENT_NAME_LEN); + snprintf(buf, MAX_EVENT_NAME_LEN, "%s%s", + isdigit(*symbol) ? "_" : "", symbol); else snprintf(buf, MAX_EVENT_NAME_LEN, "%s__%s", symbol, is_return ? "exit" : "entry"); @@ -1020,8 +1021,25 @@ static int __trace_fprobe_create(int argc, const char *argv[]) event = buf; } + if (is_return) + ctx.flags |= TPARG_FL_RETURN; + + if (is_tracepoint) { + ctx.flags |= TPARG_FL_TPOINT; + tpoint = find_tracepoint(symbol); + if (!tpoint) { + trace_probe_log_set_index(1); + trace_probe_log_err(0, NO_TRACEPOINT); + goto parse_error; + } + ctx.funcname = kallsyms_lookup( + (unsigned long)tpoint->probestub, + NULL, NULL, NULL, sbuf); + } else + ctx.funcname = symbol; + /* setup a probe */ - tf = alloc_trace_fprobe(group, event, symbol, maxactive, + tf = alloc_trace_fprobe(group, event, symbol, tpoint, maxactive, argc - 2, is_return); if (IS_ERR(tf)) { ret = PTR_ERR(tf); @@ -1030,24 +1048,15 @@ static int __trace_fprobe_create(int argc, const char *argv[]) goto out; /* We know tf is not allocated */ } - if (is_tracepoint) { - tf->tpoint = find_tracepoint(tf->symbol); - if (!tf->tpoint) { - trace_probe_log_set_index(1); - trace_probe_log_err(0, NO_TRACEPOINT); - goto parse_error; - } + if (is_tracepoint) tf->mod = __module_text_address( (unsigned long)tf->tpoint->probestub); - } argc -= 2; argv += 2; - /* parse arguments */ for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) { - struct traceprobe_parse_context ctx = { .flags = flags }; - trace_probe_log_set_index(i + 2); + ctx.offset = 0; ret = traceprobe_parse_probe_arg(&tf->tp, i, argv[i], &ctx); if (ret) goto error; /* This can be -ENOMEM */ diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index fd62de2a2f51..aff6c1a5e161 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -742,7 +742,7 @@ static int __trace_kprobe_create(int argc, const char *argv[]) void *addr = NULL; char buf[MAX_EVENT_NAME_LEN]; char gbuf[MAX_EVENT_NAME_LEN]; - unsigned int flags = TPARG_FL_KERNEL; + struct traceprobe_parse_context ctx = { .flags = TPARG_FL_KERNEL }; switch (argv[0][0]) { case 'r': @@ -823,10 +823,10 @@ static int __trace_kprobe_create(int argc, const char *argv[]) goto parse_error; } if (is_return) - flags |= TPARG_FL_RETURN; + ctx.flags |= TPARG_FL_RETURN; ret = kprobe_on_func_entry(NULL, symbol, offset); if (ret == 0) - flags |= TPARG_FL_FENTRY; + ctx.flags |= TPARG_FL_FENTRY; /* Defer the ENOENT case until register kprobe */ if (ret == -EINVAL && is_return) { trace_probe_log_err(0, BAD_RETPROBE); @@ -856,7 +856,7 @@ static int __trace_kprobe_create(int argc, const char *argv[]) /* setup a probe */ tk = alloc_trace_kprobe(group, event, addr, symbol, offset, maxactive, - argc - 2, is_return); + argc - 2, is_return); if (IS_ERR(tk)) { ret = PTR_ERR(tk); /* This must return -ENOMEM, else there is a bug */ @@ -866,10 +866,10 @@ static int __trace_kprobe_create(int argc, const char *argv[]) argc -= 2; argv += 2; /* parse arguments */ + ctx.funcname = symbol; for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) { - struct traceprobe_parse_context ctx = { .flags = flags }; - trace_probe_log_set_index(i + 2); + ctx.offset = 0; ret = traceprobe_parse_probe_arg(&tk->tp, i, argv[i], &ctx); if (ret) goto error; /* This can be -ENOMEM */ diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 30eeac5e9b61..525341c42851 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -11,6 +11,8 @@ */ #define pr_fmt(fmt) "trace_probe: " fmt +#include <linux/bpf.h> + #include "trace_probe.h" #undef C @@ -300,6 +302,171 @@ static int parse_trace_event_arg(char *arg, struct fetch_insn *code, return -ENOENT; } +#ifdef CONFIG_PROBE_EVENTS_BTF_ARGS + +static struct btf *traceprobe_get_btf(void) +{ + struct btf *btf = bpf_get_btf_vmlinux(); + + if (IS_ERR_OR_NULL(btf)) + return NULL; + + return btf; +} + +static u32 btf_type_int(const struct btf_type *t) +{ + return *(u32 *)(t + 1); +} + +static const char *type_from_btf_id(struct btf *btf, s32 id) +{ + const struct btf_type *t; + u32 intdata; + s32 tid; + + /* TODO: const char * could be converted as a string */ + t = btf_type_skip_modifiers(btf, id, &tid); + + switch (BTF_INFO_KIND(t->info)) { + case BTF_KIND_ENUM: + /* enum is "int", so convert to "s32" */ + return "s32"; + case BTF_KIND_ENUM64: + return "s64"; + case BTF_KIND_PTR: + /* pointer will be converted to "x??" */ + if (IS_ENABLED(CONFIG_64BIT)) + return "x64"; + else + return "x32"; + case BTF_KIND_INT: + intdata = btf_type_int(t); + if (BTF_INT_ENCODING(intdata) & BTF_INT_SIGNED) { + switch (BTF_INT_BITS(intdata)) { + case 8: + return "s8"; + case 16: + return "s16"; + case 32: + return "s32"; + case 64: + return "s64"; + } + } else { /* unsigned */ + switch (BTF_INT_BITS(intdata)) { + case 8: + return "u8"; + case 16: + return "u16"; + case 32: + return "u32"; + case 64: + return "u64"; + } + } + } + /* TODO: support other types */ + + return NULL; +} + +static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr) +{ + struct btf *btf = traceprobe_get_btf(); + const struct btf_type *t; + s32 id; + + if (!btf || !funcname || !nr) + return ERR_PTR(-EINVAL); + + id = btf_find_by_name_kind(btf, funcname, BTF_KIND_FUNC); + if (id <= 0) + return ERR_PTR(-ENOENT); + + /* Get BTF_KIND_FUNC type */ + t = btf_type_by_id(btf, id); + if (!btf_type_is_func(t)) + return ERR_PTR(-ENOENT); + + /* The type of BTF_KIND_FUNC is BTF_KIND_FUNC_PROTO */ + t = btf_type_by_id(btf, t->type); + if (!btf_type_is_func_proto(t)) + return ERR_PTR(-ENOENT); + + *nr = btf_type_vlen(t); + + if (*nr) + return (const struct btf_param *)(t + 1); + else + return NULL; +} + +static int parse_btf_arg(const char *varname, struct fetch_insn *code, + struct traceprobe_parse_context *ctx) +{ + struct btf *btf = traceprobe_get_btf(); + const struct btf_param *params; + int i; + + if (!btf) { + trace_probe_log_err(ctx->offset, NOSUP_BTFARG); + return -EOPNOTSUPP; + } + + if (WARN_ON_ONCE(!ctx->funcname)) + return -EINVAL; + + if (!ctx->params) { + params = find_btf_func_param(ctx->funcname, &ctx->nr_params); + if (IS_ERR(params)) { + trace_probe_log_err(ctx->offset, NO_BTF_ENTRY); + return PTR_ERR(params); + } + ctx->params = params; + } else + params = ctx->params; + + for (i = 0; i < ctx->nr_params; i++) { + const char *name = btf_name_by_offset(btf, params[i].name_off); + + if (name && !strcmp(name, varname)) { + code->op = FETCH_OP_ARG; + code->param = i; + return 0; + } + } + trace_probe_log_err(ctx->offset, NO_BTFARG); + return -ENOENT; +} + +static const struct fetch_type *parse_btf_arg_type(int arg_idx, + struct traceprobe_parse_context *ctx) +{ + struct btf *btf = traceprobe_get_btf(); + const char *typestr = NULL; + + if (btf && ctx->params) + typestr = type_from_btf_id(btf, ctx->params[arg_idx].type); + + return find_fetch_type(typestr, ctx->flags); +} +#else +static struct btf *traceprobe_get_btf(void) +{ + return NULL; +} + +static int parse_btf_arg(const char *varname, struct fetch_insn *code, + struct traceprobe_parse_context *ctx) +{ + trace_probe_log_err(ctx->offset, NOSUP_BTFARG); + return -EOPNOTSUPP; +} +#define parse_btf_arg_type(idx, ctx) \ + find_fetch_type(NULL, ctx->flags) +#endif + #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long)) static int parse_probe_vars(char *arg, const struct fetch_type *t, @@ -570,6 +737,15 @@ parse_probe_arg(char *arg, const struct fetch_type *type, code->op = FETCH_OP_IMM; } break; + default: + if (isalpha(arg[0]) || arg[0] == '_') { /* BTF variable */ + if (!tparg_is_function_entry(ctx->flags)) { + trace_probe_log_err(ctx->offset, NOSUP_BTFARG); + return -EINVAL; + } + ret = parse_btf_arg(arg, code, ctx); + break; + } } if (!ret && code->op == FETCH_OP_NOP) { /* Parsed, but do not find fetch method */ @@ -718,6 +894,11 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size, if (ret) goto fail; + /* Update storing type if BTF is available */ + if (IS_ENABLED(CONFIG_PROBE_EVENTS_BTF_ARGS) && + !t && code->op == FETCH_OP_ARG) + parg->type = parse_btf_arg_type(code->param, ctx); + ret = -EINVAL; /* Store operation */ if (parg->type->is_string) { @@ -871,8 +1052,14 @@ int traceprobe_parse_probe_arg(struct trace_probe *tp, int i, const char *arg, parg->name = kmemdup_nul(arg, body - arg, GFP_KERNEL); body++; } else { - /* If argument name is omitted, set "argN" */ - parg->name = kasprintf(GFP_KERNEL, "arg%d", i + 1); + /* + * If argument name is omitted, try arg as a name (BTF variable) + * or "argN". + */ + if (is_good_name(arg)) + parg->name = kstrdup(arg, GFP_KERNEL); + else + parg->name = kasprintf(GFP_KERNEL, "arg%d", i + 1); body = arg; } if (!parg->name) diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 2dc1e5c4c9e8..9ea5c7e8753f 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -23,6 +23,7 @@ #include <linux/limits.h> #include <linux/uaccess.h> #include <linux/bitops.h> +#include <linux/btf.h> #include <asm/bitsperlong.h> #include "trace.h" @@ -376,6 +377,9 @@ static inline bool tparg_is_function_entry(unsigned int flags) struct traceprobe_parse_context { struct trace_event_call *event; + const struct btf_param *params; + s32 nr_params; + const char *funcname; unsigned int flags; int offset; }; @@ -474,7 +478,10 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, C(NO_EVENT_INFO, "This requires both group and event name to attach"),\ C(BAD_ATTACH_EVENT, "Attached event does not exist"),\ C(BAD_ATTACH_ARG, "Attached event does not have this field"),\ - C(NO_EP_FILTER, "No filter rule after 'if'"), + C(NO_EP_FILTER, "No filter rule after 'if'"), \ + C(NOSUP_BTFARG, "BTF is not available or not supported"), \ + C(NO_BTFARG, "This variable is not found at this probe point"),\ + C(NO_BTF_ENTRY, "No BTF entry for this probe point"), #undef C #define C(a, b) TP_ERR_##a