From f208bd8df08d0659ecd9e09e992c79aab26cddfa Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Fri, 20 Mar 2015 17:46:53 -0300 Subject: [PATCH] perf trace: Handle legacy syscalls tracepoints Currently the code skips the first field with the expectation that it is 'nr'. But older kernels do not have the 'nr' field: field:int nr; offset:8; size:4; signed:1; Change perf-trace to drop the field if it exists after parsing the format file. This fixes the off-by-one problem with older kernels (e.g., RHEL6). e.g, perf-trace shows this for write: 1.515 ( 0.006 ms): dd/4245 write(buf: 2, count: 140733837536224 ) = 26 where 2 is really the fd, the huge number is really the buf address, etc. With this patch you get the more appropriate: 1.813 ( 0.003 ms): dd/6330 write(fd: 2, buf: 0x7fff22fc81f0, count: 25) = 25 Based-on-a-patch-by: David Ahern Acked-by: David Ahern Cc: Adrian Hunter Cc: Borislav Petkov Cc: Don Zickus Cc: Frederic Weisbecker Cc: Jiri Olsa Cc: Namhyung Kim Cc: Stephane Eranian Link: http://lkml.kernel.org/n/tip-gvpdave4u2yq2jnzbcdznpvf@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-trace.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c index 6af6bcec930e..001c6ae9a1b1 100644 --- a/tools/perf/builtin-trace.c +++ b/tools/perf/builtin-trace.c @@ -1135,6 +1135,8 @@ static struct syscall_fmt *syscall_fmt__find(const char *name) struct syscall { struct event_format *tp_format; + int nr_args; + struct format_field *args; const char *name; bool filtered; bool is_exit; @@ -1442,14 +1444,14 @@ static int syscall__set_arg_fmts(struct syscall *sc) struct format_field *field; int idx = 0; - sc->arg_scnprintf = calloc(sc->tp_format->format.nr_fields - 1, sizeof(void *)); + sc->arg_scnprintf = calloc(sc->nr_args, sizeof(void *)); if (sc->arg_scnprintf == NULL) return -1; if (sc->fmt) sc->arg_parm = sc->fmt->arg_parm; - for (field = sc->tp_format->format.fields->next; field; field = field->next) { + for (field = sc->args; field; field = field->next) { if (sc->fmt && sc->fmt->arg_scnprintf[idx]) sc->arg_scnprintf[idx] = sc->fmt->arg_scnprintf[idx]; else if (field->flags & FIELD_IS_POINTER) @@ -1515,6 +1517,14 @@ static int trace__read_syscall_info(struct trace *trace, int id) if (sc->tp_format == NULL) return -1; + sc->args = sc->tp_format->format.fields; + sc->nr_args = sc->tp_format->format.nr_fields; + /* drop nr field - not relevant here; does not exist on older kernels */ + if (sc->args && strcmp(sc->args->name, "nr") == 0) { + sc->args = sc->args->next; + --sc->nr_args; + } + sc->is_exit = !strcmp(name, "exit_group") || !strcmp(name, "exit"); return syscall__set_arg_fmts(sc); @@ -1537,7 +1547,7 @@ static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size, unsigned char *p; unsigned long val; - if (sc->tp_format != NULL) { + if (sc->args != NULL) { struct format_field *field; u8 bit = 1; struct syscall_arg arg = { @@ -1547,7 +1557,7 @@ static size_t syscall__scnprintf_args(struct syscall *sc, char *bf, size_t size, .thread = thread, }; - for (field = sc->tp_format->format.fields->next; field; + for (field = sc->args; field; field = field->next, ++arg.idx, bit <<= 1) { if (arg.mask & bit) continue; -- 2.20.1