From: "Steven Rostedt (VMware)" Allow referencing any address during the function based event. The syntax is to use = For example: # echo 'do_IRQ(long total_forks=0xffffffffa2a4b4c0)' > function_events # echo 1 > events/function/enable # cat trace sshd-832 [000] d... 221639.210845: ret_from_intr->do_IRQ(total_forks=855) sshd-832 [000] d... 221639.211114: ret_from_intr->do_IRQ(total_forks=855) -0 [000] d... 221639.211198: ret_from_intr->do_IRQ(total_forks=855) Signed-off-by: Steven Rostedt (VMware) --- Documentation/trace/function-based-events.rst | 40 +++++++- kernel/trace/trace_event_ftrace.c | 129 +++++++++++++++++++++----- 2 files changed, 143 insertions(+), 26 deletions(-) diff --git a/Documentation/trace/function-based-events.rst b/Documentation/trace/function-based-events.rst index f18c8f3ef330..b0e6725f3032 100644 --- a/Documentation/trace/function-based-events.rst +++ b/Documentation/trace/function-based-events.rst @@ -91,7 +91,7 @@ as follows: ARGS := ARG | ARG ',' ARGS | '' - ARG := TYPE FIELD | ARG '|' ARG + ARG := TYPE FIELD | TYPE '=' ADDR | TYPE ADDR | ARG '|' ARG TYPE := ATOM | 'unsigned' ATOM @@ -107,6 +107,8 @@ as follows: OFFSET := '+' + ADDR := A hexidecimal address starting with '0x' + Where is a unique string starting with an alphabetic character and consists only of letters and numbers and underscores. @@ -267,3 +269,39 @@ Again, using gdb to find the offset of the "func" field of struct work_struct -0 [000] dNs3 6241.172004: delayed_work_timer_fn->__queue_work(cpu=128, wq=ffff88011a010800, func=vmstat_shepherd+0x0/0xb0) worker/0:2-1689 [000] d..2 6241.172026: __queue_delayed_work->__queue_work(cpu=7, wq=ffff88011a11da00, func=vmstat_update+0x0/0x70) -0 [005] d.s3 6241.347996: queue_work_on->__queue_work(cpu=128, wq=ffff88011a011200, func=fb_flashcursor+0x0/0x110 [fb]) + + +Direct memory access +==================== + +Function arguments are not the only thing that can be recorded from a function +based event. Memory addresses can also be examined. If there's a global variable +that you want to monitor via an interrupt, you can put in the address directly. + + # grep total_forks /proc/kallsyms +ffffffff82354c18 B total_forks + + # echo 'do_IRQ(int total_forks=0xffffffff82354c18)' > function_events + + # echo 1 events/functions/do_IRQ/enable + # cat trace + -0 [003] d..3 337.076709: ret_from_intr->do_IRQ(total_forks=1419) + -0 [003] d..3 337.077046: ret_from_intr->do_IRQ(total_forks=1419) + -0 [003] d..3 337.077076: ret_from_intr->do_IRQ(total_forks=1420) + +Note, address notations do not affect the argument count. For instance, with + +__visible unsigned int __irq_entry do_IRQ(struct pt_regs *regs) + + # echo 'do_IRQ(int total_forks=0xffffffff82354c18, symbol regs[16])' > function_events + +Is the same as + + # echo 'do_IRQ(int total_forks=0xffffffff82354c18 | symbol regs[16])' > function_events + + # cat trace + -0 [003] d..3 653.839546: ret_from_intr->do_IRQ(total_forks=1504, regs=cpuidle_enter_state+0xb1/0x330) + -0 [003] d..3 653.906011: ret_from_intr->do_IRQ(total_forks=1504, regs=cpuidle_enter_state+0xb1/0x330) + -0 [003] d..3 655.823498: ret_from_intr->do_IRQ(total_forks=1504, regs=tick_nohz_idle_enter+0x4c/0x50) + -0 [003] d..3 655.954096: ret_from_intr->do_IRQ(total_forks=1504, regs=cpuidle_enter_state+0xb1/0x330) + diff --git a/kernel/trace/trace_event_ftrace.c b/kernel/trace/trace_event_ftrace.c index 1359f714a1b1..97748edc8bcb 100644 --- a/kernel/trace/trace_event_ftrace.c +++ b/kernel/trace/trace_event_ftrace.c @@ -63,6 +63,8 @@ enum func_states { FUNC_STATE_BRACKET_END, FUNC_STATE_INDIRECT, FUNC_STATE_UNSIGNED, + FUNC_STATE_ADDR, + FUNC_STATE_EQUAL, FUNC_STATE_PIPE, FUNC_STATE_PLUS, FUNC_STATE_TYPE, @@ -201,6 +203,7 @@ static char *next_token(char **ptr, char *last) *str == ',' || *str == '|' || *str == '+' || + *str == '=' || *str == ')') break; } @@ -245,12 +248,39 @@ static int add_arg(struct func_event *fevent, int ftype, int unsign) arg->sign = func_type->sign; arg->offset = ALIGN(fevent->arg_offset, arg->size); arg->func_type = ftype; - arg->arg = fevent->arg_cnt; fevent->arg_offset = arg->offset + arg->size; list_add_tail(&arg->list, &fevent->args); fevent->last_arg = arg; - fevent->arg_cnt++; + + return 0; +} + +static int update_arg_name(struct func_event *fevent, const char *name) +{ + struct func_arg *arg = fevent->last_arg; + + if (WARN_ON(!arg)) + return -EINVAL; + + arg->name = kstrdup(name, GFP_KERNEL); + if (!arg->name) + return -ENOMEM; + return 0; +} + +static int update_arg_arg(struct func_event *fevent) +{ + struct func_arg *arg = fevent->last_arg; + + if (WARN_ON(!arg)) + return -EINVAL; + + /* Make sure the arch can support this many args */ + if (fevent->arg_cnt >= max_args) + return -EINVAL; + + arg->arg = fevent->arg_cnt; return 0; } @@ -258,14 +288,16 @@ static int add_arg(struct func_event *fevent, int ftype, int unsign) static enum func_states process_event(struct func_event *fevent, const char *token, enum func_states state) { + static bool update_arg; static int unsign; - long val; + unsigned long val; int ret; int i; switch (state) { case FUNC_STATE_INIT: unsign = 0; + update_arg = false; if (!isalpha(token[0]) && token[0] != '_') break; /* Do not allow wild cards */ @@ -281,15 +313,15 @@ process_event(struct func_event *fevent, const char *token, enum func_states sta break; return FUNC_STATE_PARAM; - case FUNC_STATE_PIPE: - fevent->arg_cnt--; - goto comma; case FUNC_STATE_PARAM: if (token[0] == ')') return FUNC_STATE_END; /* Fall through */ case FUNC_STATE_COMMA: - comma: + if (update_arg) + fevent->arg_cnt++; + update_arg = false; + case FUNC_STATE_PIPE: if (strcmp(token, "unsigned") == 0) { unsign = 2; return FUNC_STATE_UNSIGNED; @@ -309,18 +341,20 @@ process_event(struct func_event *fevent, const char *token, enum func_states sta return FUNC_STATE_TYPE; case FUNC_STATE_TYPE: - if (!isalpha(token[0]) || token[0] == '_') - break; if (WARN_ON(!fevent->last_arg)) break; - fevent->last_arg->name = kstrdup(token, GFP_KERNEL); - if (!fevent->last_arg->name) + if (update_arg_name(fevent, token) < 0) + break; + if (strncmp(token, "0x", 2) == 0) + goto equal; + if (!isalpha(token[0]) && token[0] != '_') break; + update_arg = true; return FUNC_STATE_VAR; case FUNC_STATE_BRACKET: WARN_ON(!fevent->last_arg); - ret = kstrtol(token, 0, &val); + ret = kstrtoul(token, 0, &val); if (ret) break; val *= fevent->last_arg->size; @@ -335,7 +369,7 @@ process_event(struct func_event *fevent, const char *token, enum func_states sta case FUNC_STATE_BRACKET_END: switch (token[0]) { case ')': - return FUNC_STATE_END; + goto end; case ',': return FUNC_STATE_COMMA; case '|': @@ -346,16 +380,33 @@ process_event(struct func_event *fevent, const char *token, enum func_states sta case FUNC_STATE_PLUS: if (WARN_ON(!fevent->last_arg)) break; - ret = kstrtol(token, 0, &val); + ret = kstrtoul(token, 0, &val); if (ret) break; fevent->last_arg->index += val; return FUNC_STATE_VAR; + case FUNC_STATE_ADDR: + switch (token[0]) { + case ')': + goto end; + case ',': + return FUNC_STATE_COMMA; + case '|': + return FUNC_STATE_PIPE; + } + break; + case FUNC_STATE_VAR: + if (token[0] == '=') + return FUNC_STATE_EQUAL; + if (WARN_ON(!fevent->last_arg)) + break; + update_arg_arg(fevent); + update_arg = true; switch (token[0]) { case ')': - return FUNC_STATE_END; + goto end; case ',': return FUNC_STATE_COMMA; case '|': @@ -367,10 +418,29 @@ process_event(struct func_event *fevent, const char *token, enum func_states sta } break; + case FUNC_STATE_EQUAL: + if (strncmp(token, "0x", 2) != 0) + break; + equal: + if (WARN_ON(!fevent->last_arg)) + break; + ret = kstrtoul(token, 0, &val); + if (ret < 0) + break; + update_arg = false; + fevent->last_arg->index = val; + fevent->last_arg->arg = -1; + fevent->last_arg->indirect = INDIRECT_FLAG; + return FUNC_STATE_ADDR; + default: break; } return FUNC_STATE_ERROR; + end: + if (update_arg) + fevent->arg_cnt++; + return FUNC_STATE_END; } static long long get_arg(struct func_arg *arg, unsigned long val) @@ -419,7 +489,7 @@ static void func_event_trace(struct trace_event_file *trace_file, long args[func_event->arg_cnt]; long long val = 1; unsigned long irq_flags; - int nr_args; + int nr_args = 0; int size; int pc; @@ -440,12 +510,17 @@ static void func_event_trace(struct trace_event_file *trace_file, entry = ring_buffer_event_data(event); entry->ip = ip; entry->parent_ip = parent_ip; - nr_args = arch_get_func_args(pt_regs, 0, func_event->arg_cnt, args); + if (func_event->arg_cnt) + nr_args = arch_get_func_args(pt_regs, 0, func_event->arg_cnt, args); list_for_each_entry(arg, &func_event->args, list) { - if (arg->arg < nr_args) - val = get_arg(arg, args[arg->arg]); - else + if (arg->arg < nr_args) { + /* Is arg an address and not a parameter? */ + if (arg->arg < 0) + val = get_arg(arg, 0); + else + val = get_arg(arg, args[arg->arg]); + } else val = 0; memcpy(&entry->data[arg->offset], &val, arg->size); } @@ -817,11 +892,15 @@ static int func_event_seq_show(struct seq_file *m, void *v) last_arg = arg->arg; comma = true; seq_printf(m, "%s %s", arg->type, arg->name); - if (arg->index) - seq_printf(m, "+%ld", arg->index); - if (arg->indirect && arg->size) - seq_printf(m, "[%ld]", - (arg->indirect ^ INDIRECT_FLAG) / arg->size); + if (arg->arg < 0) { + seq_printf(m, "=0x%lx", arg->index); + } else { + if (arg->index) + seq_printf(m, "+%ld", arg->index); + if (arg->indirect && arg->size) + seq_printf(m, "[%ld]", + (arg->indirect ^ INDIRECT_FLAG) / arg->size); + } } seq_puts(m, ")\n"); -- 2.15.1