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


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