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authorMasami Hiramatsu <mhiramat@kernel.org>2019-06-20 00:08:27 +0900
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2019-08-31 12:19:39 -0400
commit6218bf9f4d2942e88d97b60abc8c2ca0532e41a8 (patch)
treecb0b878e89295891667eefc528e75e69650fc52c /kernel/trace/trace_probe.c
parentab10d69eb714961d1eca4129e4f8cda5e0618f66 (diff)
downloadlinux-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.c18
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 */