Re: [PATCH 49/52] perf tools: Build programs to copy 32-bit compatibility VDSOs

Arnaldo Carvalho de Melo
2014-07-23T20:44:18Z

Em Wed, Jul 23, 2014 at 04:55:03PM +0300, Adrian Hunter escreveu:
> On 07/23/2014 03:48 PM, Jiri Olsa wrote:
> > On Tue, Jul 22, 2014 at 04:17:58PM +0300, Adrian Hunter wrote:
> >
> > SNIP
> >
> >> index 1f67aa0..45ab040 100644
> >> --- a/tools/perf/config/Makefile
> >> +++ b/tools/perf/config/Makefile
> >> @@ -604,6 +604,27 @@ ifdef HAVE_KVM_STAT_SUPPORT
> >> CFLAGS += -DHAVE_KVM_STAT_SUPPORT
> >> endif
> >>
> >> +ifeq (${IS_64_BIT}, 1)
> >> + ifndef NO_PERF_READ_VDSO32
> >> + CAN_DO := $(shell echo "main() {}" | ${CC} -m32 -x c - >/dev/null 2>/dev/null && echo 1 || echo 0)
> >> + ifneq (${CAN_DO}, 1)
> >> + NO_PERF_READ_VDSO32 := 1
> >> + endif
> >> + endif
> >> + ifneq (${IS_X86_64}, 1)
> >> + NO_PERF_READ_VDSOX32 := 1
> >> + endif
> >> + ifndef NO_PERF_READ_VDSOX32
> >> + CAN_DO := $(shell echo 'main() {}' | ${CC} -mx32 -x c - >/dev/null 2>/dev/null && echo 1 || echo 0)
> >> + ifneq (${CAN_DO}, 1)
> >> + NO_PERF_READ_VDSOX32 := 1
> >> + endif
> >> + endif

> > please move those check into feature config code under config/features/..

> I will look at doing that.

Ok, probably this can be done in a follow up patch, Jiri?

> > SNIP
> >> +++ b/tools/perf/perf-read-vdso.c
> >> @@ -0,0 +1,59 @@
> >> +#include <stdio.h>
> >> +#include <string.h>
> >> +
> >> +#define VDSO__MAP_NAME "[vdso]"
> >> +
> >> +static int find_vdso_map(void **start, void **end)
> >> +{
> >> + FILE *maps;
> >> + char line[128];
> >> + int found = 0;
> >> +
> >> + maps = fopen("/proc/self/maps", "r");
> >> + if (!maps) {
> >> + fprintf(stderr, "vdso: cannot open maps\n");
> >> + return -1;
> >> + }
> >> +
> >> + while (!found && fgets(line, sizeof(line), maps)) {
> >> + int m = -1;
> >> +
> >> + /* We care only about private r-x mappings. */
> >> + if (2 != sscanf(line, "%p-%p r-xp %*x %*x:%*x %*u %n",
> >> + start, end, &m))
> >> + continue;
> >> + if (m < 0)
> >> + continue;
> >> +
> >> + if (!strncmp(&line[m], VDSO__MAP_NAME,
> >> + sizeof(VDSO__MAP_NAME) - 1))
> >> + found = 1;
> >> + }
> >> +
> >> + fclose(maps);
> >> + return !found;
> >> +}
> >
> > hum, any easy way to use/share find_vdso_map from vdso.c?
> > I guess this way is more straighforward and clear.. it's
> > probably not worthy for function this simple
>
> Would have to create another source file and include it.
> I am not sure it is worth it. Maybe Arnaldo can decide?

I think it is, either do direct sourcing with #include or add it to a
linking list for the binaries that use it.

- Arnaldo