[PATCH 4/6] perf probe: Support hexadecimal casting

Masami Hiramatsu
2016-08-18T09:01:00Z

Support hexadecimal unsigned integer casting by 'x'.
This allows user to explicitly specify the output
format of the probe arguments as hexadecimal.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
tools/perf/Documentation/perf-probe.txt | 4 ++--
tools/perf/util/probe-finder.c | 17 ++++++++++-------
2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt
index aa33325..d217617 100644
--- a/tools/perf/Documentation/perf-probe.txt
+++ b/tools/perf/Documentation/perf-probe.txt
@@ -176,13 +176,13 @@ Each probe argument follows below syntax.

'NAME' specifies the name of this argument (optional). You can use the name of local variable, local data structure member (e.g. var->field, var.field2), local array with fixed index (e.g. array[1], var->array[0], var->pointer[2]), or kprobe-tracer argument format (e.g. $retval, %ax, etc). Note that the name of this argument will be set as the last member name if you specify a local data structure member (e.g. field2 for 'var->field1.field2'.)
'$vars' and '$params' special arguments are also available for NAME, '$vars' is expanded to the local variables (including function parameters) which can access at given probe point. '$params' is expanded to only the function parameters.
-'TYPE' casts the type of this argument (optional). If omitted, perf probe automatically set the type based on debuginfo. Currently, basic types (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal integers (x8/x16/x32/x64), signedness casting (u/s), "string" and bitfield are supported. (see TYPES for detail)
+'TYPE' casts the type of this argument (optional). If omitted, perf probe automatically set the type based on debuginfo. Currently, basic types (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal integers (x/x8/x16/x32/x64), signedness casting (u/s), "string" and bitfield are supported. (see TYPES for detail)

On x86 systems %REG is always the short form of the register: for example %AX. %RAX or %EAX is not valid.

TYPES
-----
-Basic types (u8/u16/u32/u64/s8/s16/s32/s64) and hexadecimal integers (x8/x16/x32/x64) are integer types. Prefix 's' and 'u' means those types are signed and unsigned respectively, and 'x' means that is shown in hexadecimal format. Traced arguments are shown in decimal (signed) or hex (unsigned). You can also use 's' or 'u' to specify only signedness and leave its size auto-detected by perf probe.
+Basic types (u8/u16/u32/u64/s8/s16/s32/s64) and hexadecimal integers (x8/x16/x32/x64) are integer types. Prefix 's' and 'u' means those types are signed and unsigned respectively, and 'x' means that is shown in hexadecimal format. Traced arguments are shown in decimal (signed) or hex (unsigned). You can also use 's' or 'u' to specify only signedness and leave its size auto-detected by perf probe. Moreover, you can use 'x' to explicitly specify to be shown in hexadecimal (the size is also auto-detected).
String type is a special type, which fetches a "null-terminated" string from kernel space. This means it will fail and store NULL if the string container has been paged out. You can specify 'string' type only for the local variable or structure member which is an array of or a pointer to 'char' or 'unsigned char' type.
Bitfield is another special type, which takes 3 parameters, bit-width, bit-offset, and container-size (usually 32). The syntax is;

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 24dbe23..f18cd6b 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -298,13 +298,13 @@ static int convert_variable_type(Dwarf_Die *vr_die,
char sbuf[STRERR_BUFSIZE];
int bsize, boffs, total;
int ret;
- char sign;
+ char prefix;

/* TODO: check all types */
- if (cast && strcmp(cast, "string") != 0 &&
+ if (cast && strcmp(cast, "string") != 0 && strcmp(cast, "x") != 0 &&
strcmp(cast, "s") != 0 && strcmp(cast, "u") != 0) {
/* Non string type is OK */
- /* and respect signedness cast */
+ /* and respect signedness/hexadecimal cast */
tvar->type = strdup(cast);
return (tvar->type == NULL) ? -ENOMEM : 0;
}
@@ -366,11 +366,14 @@ static int convert_variable_type(Dwarf_Die *vr_die,
}

if (cast && (strcmp(cast, "u") == 0))
- sign = 'u';
+ prefix = 'u';
else if (cast && (strcmp(cast, "s") == 0))
- sign = 's';
+ prefix = 's';
+ else if (cast && (strcmp(cast, "x") == 0) &&
+ probe_type_is_available(PROBE_TYPE_X))
+ prefix = 'x';
else
- sign = die_is_signed_type(&type) ? 's' : 'u';
+ prefix = die_is_signed_type(&type) ? 's' : 'u';

ret = dwarf_bytesize(&type);
if (ret <= 0)
@@ -384,7 +387,7 @@ static int convert_variable_type(Dwarf_Die *vr_die,
dwarf_diename(&type), MAX_BASIC_TYPE_BITS);
ret = MAX_BASIC_TYPE_BITS;
}
- ret = snprintf(buf, 16, "%c%d", sign, ret);
+ ret = snprintf(buf, 16, "%c%d", prefix, ret);

formatted:
if (ret < 0 || ret >= 16) {