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| author | Masami Hiramatsu <mhiramat@kernel.org> | 2019-06-20 00:08:27 +0900 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-08-31 12:19:39 -0400 |
| commit | 6218bf9f4d2942e88d97b60abc8c2ca0532e41a8 (patch) | |
| tree | cb0b878e89295891667eefc528e75e69650fc52c /kernel/trace/trace_probe.c | |
| parent | ab10d69eb714961d1eca4129e4f8cda5e0618f66 (diff) | |
| download | linux-6218bf9f4d2942e88d97b60abc8c2ca0532e41a8.tar.bz2 | |
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.
Link: http://lkml.kernel.org/r/156095690733.28024.13258186548822649469.stgit@devnote2
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace_probe.c')
| -rw-r--r-- | kernel/trace/trace_probe.c | 18 |
1 files changed, 18 insertions, 0 deletions
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 @@ inval_var: 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 */ |