On Fri, 5 Aug 2016 20:53:21 +0900
Naohiro Aota <naohiro.a...@hgst.com> wrote:
> Perf-probe detects a variable's type and use the detected type to add new
> probe. Then, kprobes prints its variable in hexadecimal format if the
> variable is unsigned and prints in decimal if it is signed.
>
> We sometimes want to see unsigned variable in decimal format (i.e.
> sector_t or size_t). In that case, we need to investigate variable's
> size manually to specify just signedness.
>
> This patch add signedness casting support. By specifying "s" or "u" as a
> type, perf-probe will investigate variable size as usual and use
> the specified signedness.
>
> E.g. without this:
>
> $ perf probe -a 'submit_bio bio->bi_iter.bi_sector'
> Added new event:
> probe:submit_bio (on submit_bio with bi_sector=bio->bi_iter.bi_sector)
> You can now use it in all perf tools, such as:
> perf record -e probe:submit_bio -aR sleep 1
> $ cat trace_pipe|head
> dbench-9692 [003] d..1 971.096633: submit_bio:
> (submit_bio+0x0/0x140) bi_sector=0x3a3d00
> dbench-9692 [003] d..1 971.096685: submit_bio:
> (submit_bio+0x0/0x140) bi_sector=0x1a3d80
> dbench-9692 [003] d..1 971.096687: submit_bio:
> (submit_bio+0x0/0x140) bi_sector=0x3a3d80
> ...
> // need to investigate the variable size
> $ perf probe -a 'submit_bio bio->bi_iter.bi_sector:s64'
> Added new event:
> probe:submit_bio (on submit_bio with
> bi_sector=bio->bi_iter.bi_sector:s64)
> You can now use it in all perf tools, such as:
> perf record -e probe:submit_bio -aR sleep 1
>
> With this:
>
> // just use "s" to cast its signedness
> $ perf probe -v -a 'submit_bio bio->bi_iter.bi_sector:s'
> Added new event:
> probe:submit_bio (on submit_bio with bi_sector=bio->bi_iter.bi_sector:s)
> You can now use it in all perf tools, such as:
> perf record -e probe:submit_bio -aR sleep 1
> $ cat trace_pipe|head
> dbench-9689 [001] d..1 1212.391237: submit_bio:
> (submit_bio+0x0/0x140) bi_sector=128
> dbench-9689 [001] d..1 1212.391252: submit_bio:
> (submit_bio+0x0/0x140) bi_sector=131072
> dbench-9697 [006] d..1 1212.398611: submit_bio:
> (submit_bio+0x0/0x140) bi_sector=30208
>
> This commit also update perf-probe.txt to describe "types". Most parts
> are based on existing documentation: Documentation/trace/kprobetrace.txt
>
> Signed-off-by: Naohiro Aota <naohiro.a...@hgst.com>
> ---
> tools/perf/Documentation/perf-probe.txt | 10 +++++++++-
> tools/perf/util/probe-finder.c | 15 ++++++++++++---
> 2 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-probe.txt
> b/tools/perf/Documentation/perf-probe.txt
> index 736da44..a23b124 100644
> --- a/tools/perf/Documentation/perf-probe.txt
> +++ b/tools/perf/Documentation/perf-probe.txt
> @@ -176,10 +176,18 @@ 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. 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.
> +'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), "string" and bitfield are supported. (see
> TYPES for detail)
Hmm, have you added the 's' and 'u' here too ??
>
> 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) are integer types. Prefix 's'
> and 'u' means those types are signed and unsigned respectively. 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.
So, not only the details, but also the brief information about the TYPE, there
should be 's' and 'u'.
Other are good to me.
Thanks,
> +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;
> +
> + b<bit-width>@<bit-offset>/<container-size>
> +
> LINE SYNTAX
> -----------
> Line range is described by following syntax.
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index f2d9ff0..5c290c6 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -297,10 +297,13 @@ static int convert_variable_type(Dwarf_Die *vr_die,
> char sbuf[STRERR_BUFSIZE];
> int bsize, boffs, total;
> int ret;
> + char sign;
>
> /* TODO: check all types */
> - if (cast && strcmp(cast, "string") != 0) {
> + if (cast && strcmp(cast, "string") != 0 &&
> + strcmp(cast, "s") != 0 && strcmp(cast, "u") != 0) {
> /* Non string type is OK */
> + /* and respect signedness cast */
> tvar->type = strdup(cast);
> return (tvar->type == NULL) ? -ENOMEM : 0;
> }
> @@ -361,6 +364,13 @@ static int convert_variable_type(Dwarf_Die *vr_die,
> return (tvar->type == NULL) ? -ENOMEM : 0;
> }
>
> + if (cast && (strcmp(cast, "u") == 0))
> + sign = 'u';
> + else if (cast && (strcmp(cast, "s") == 0))
> + sign = 's';
> + else
> + sign = die_is_signed_type(&type) ? 's' : 'u';
> +
> ret = dwarf_bytesize(&type);
> if (ret <= 0)
> /* No size ... try to use default type */
> @@ -373,8 +383,7 @@ 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",
> - die_is_signed_type(&type) ? 's' : 'u', ret);
> + ret = snprintf(buf, 16, "%c%d", sign, ret);
>
> formatted:
> if (ret < 0 || ret >= 16) {
--
Masami Hiramatsu <mhira...@kernel.org>
