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

Jiri Olsa
2014-07-23T12:49:23Z

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/..

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

jirka