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Date: Thu, 20 Jun 2019 00:08:27 +0900 From: Masami Hiramatsu <mhiramat@...nel.org> To: Steven Rostedt <rostedt@...dmis.org> Cc: Masami Hiramatsu <mhiramat@...nel.org>, Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org, Tom Zanussi <tom.zanussi@...ux.intel.com>, Ravi Bangoria <ravi.bangoria@...ux.ibm.com>, Namhyung Kim <namhyung@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org> Subject: [PATCH v2 08/12] tracing/probe: Add immediate parameter support Add immediate value parameter (\1234) support to probe events. This allows you to specify an immediate (or dummy) parameter instead of fetching from memory or register. This feature looks odd, but imagine when you put a probe on a code to trace some data. If the code is compiled into 2 instructions and 1 instruction has a value but other has nothing since it is optimized out. In that case, you can not fold those into one event, even if ftrace supported multiple probes on one event. With this feature, you can set a dummy value like foo=\deadbeef instead of something like foo=%di. Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org> --- Documentation/trace/kprobetrace.rst | 1 + Documentation/trace/uprobetracer.rst | 1 + kernel/trace/trace.c | 2 +- kernel/trace/trace_probe.c | 18 ++++++++++++++++++ kernel/trace/trace_probe.h | 1 + 5 files changed, 22 insertions(+), 1 deletion(-) diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst index af776989caca..772467f65a36 100644 --- a/Documentation/trace/kprobetrace.rst +++ b/Documentation/trace/kprobetrace.rst @@ -52,6 +52,7 @@ Synopsis of kprobe_events $retval : Fetch return value.(\*2) $comm : Fetch current task comm. +|-[u]OFFS(FETCHARG) : Fetch memory at FETCHARG +|- OFFS address.(\*3)(\*4) + \IMM : Store an immediate value to the argument. NAME=FETCHARG : Set NAME as the argument name of FETCHARG. FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types diff --git a/Documentation/trace/uprobetracer.rst b/Documentation/trace/uprobetracer.rst index ab13319c66ac..2b4697c0bed7 100644 --- a/Documentation/trace/uprobetracer.rst +++ b/Documentation/trace/uprobetracer.rst @@ -45,6 +45,7 @@ Synopsis of uprobe_tracer $retval : Fetch return value.(\*1) $comm : Fetch current task comm. +|-[u]OFFS(FETCHARG) : Fetch memory at FETCHARG +|- OFFS address.(\*2)(\*3) + \IMM : Store an immediate value to the argument. NAME=FETCHARG : Set NAME as the argument name of FETCHARG. FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 73fbe3b0dd08..3608535f1935 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4846,7 +4846,7 @@ static const char readme_msg[] = #else "\t $stack<index>, $stack, $retval, $comm,\n" #endif - "\t +|-[u]<offset>(<fetcharg>)\n" + "\t +|-[u]<offset>(<fetcharg>), \\imm-value\n" "\t type: s8/16/32/64, u8/16/32/64, x8/16/32/64, string, symbol,\n" "\t b<bit-width>@<bit-offset>/<container-size>, ustring,\n" "\t <type>\\[<array-size>\\]\n" diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index f8c3c65c035d..fb90baec3cd8 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -316,6 +316,17 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t, return -EINVAL; } +static int str_to_immediate(char *str, unsigned long *imm) +{ + if (isdigit(str[0])) + return kstrtoul(str, 0, imm); + else if (str[0] == '-') + return kstrtol(str, 0, (long *)imm); + else if (str[0] == '+') + return kstrtol(str + 1, 0, (long *)imm); + return -EINVAL; +} + /* Recursive argument parser */ static int parse_probe_arg(char *arg, const struct fetch_type *type, @@ -444,6 +455,13 @@ parse_probe_arg(char *arg, const struct fetch_type *type, code->offset = offset; } break; + case '\\': /* Immediate value */ + ret = str_to_immediate(arg + 1, &code->immediate); + if (ret) + trace_probe_log_err(offs + 1, BAD_IMM); + else + code->op = FETCH_OP_IMM; + break; } if (!ret && code->op == FETCH_OP_NOP) { /* Parsed, but do not find fetch method */ diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 2dcc4e317787..cc113b82a4ce 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -408,6 +408,7 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, C(BAD_VAR, "Invalid $-valiable specified"), \ C(BAD_REG_NAME, "Invalid register name"), \ C(BAD_MEM_ADDR, "Invalid memory address"), \ + C(BAD_IMM, "Invalid immediate value"), \ C(FILE_ON_KPROBE, "File offset is not available with kprobe"), \ C(BAD_FILE_OFFS, "Invalid file offset value"), \ C(SYM_ON_UPROBE, "Symbol is not available with uprobe"), \
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