362222f877
From the syscall_fmts->arg entries for formatting strace-like syscalls.
This is when resolving the string "whence" on a filter expression for
the syscalls:sys_enter_lseek:
Breakpoint 3, perf_evsel__syscall_arg_fmt (evsel=0xc91ed0, arg=0x7fffffff7cd0 "whence") at builtin-trace.c:3626
3626 {
(gdb) n
3628 struct syscall_arg_fmt *fmt = __evsel__syscall_arg_fmt(evsel);
(gdb) n
3630 if (evsel->tp_format == NULL || fmt == NULL)
(gdb) n
3633 for (field = evsel->tp_format->format.fields; field; field = field->next, ++fmt)
(gdb) n
3634 if (strcmp(field->name, arg) == 0)
(gdb) p field->name
$3 = 0xc945e0 "__syscall_nr"
(gdb) n
3633 for (field = evsel->tp_format->format.fields; field; field = field->next, ++fmt)
(gdb) p *fmt
$4 = {scnprintf = 0x0, strtoul = 0x0, mask_val = 0x0, parm = 0x0, name = 0x0, nr_entries = 0, show_zero = false}
(gdb) n
3634 if (strcmp(field->name, arg) == 0)
(gdb) p field->name
$5 = 0xc94690 "fd"
(gdb) n
3633 for (field = evsel->tp_format->format.fields; field; field = field->next, ++fmt)
(gdb) n
3634 if (strcmp(field->name, arg) == 0)
(gdb) n
3633 for (field = evsel->tp_format->format.fields; field; field = field->next, ++fmt)
(gdb) n
3634 if (strcmp(field->name, arg) == 0)
(gdb) p *fmt
$9 = {scnprintf = 0x489be2 <syscall_arg__scnprintf_strarray>, strtoul = 0x0, mask_val = 0x0, parm = 0xa2da80 <strarray.whences>, name = 0x0,
nr_entries = 0, show_zero = false}
(gdb) p field->name
$10 = 0xc947b0 "whence"
(gdb) p fmt->parm
$11 = (void *) 0xa2da80 <strarray.whences>
(gdb) p *(struct strarray *)fmt->parm
$12 = {offset = 0, nr_entries = 5, prefix = 0x724d37 "SEEK_", entries = 0xa2da40 <whences>}
(gdb) p (struct strarray *)fmt->parm)->entries
Junk after end of expression.
(gdb) p ((struct strarray *)fmt->parm)->entries
$13 = (const char **) 0xa2da40 <whences>
(gdb) p ((struct strarray *)fmt->parm)->entries[0]
$14 = 0x724d21 "SET"
(gdb) p ((struct strarray *)fmt->parm)->entries[1]
$15 = 0x724d25 "CUR"
(gdb) p ((struct strarray *)fmt->parm)->entries[2]
$16 = 0x724d29 "END"
(gdb) p ((struct strarray *)fmt->parm)->entries[2]
$17 = 0x724d29 "END"
(gdb) p ((struct strarray *)fmt->parm)->entries[3]
$18 = 0x724d2d "DATA"
(gdb) p ((struct strarray *)fmt->parm)->entries[4]
$19 = 0x724d32 "HOLE"
(gdb)
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-lc8h9jgvbnboe0g7ic8tra1y@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.