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SubjectRe: [PATCH v3 4/4] perf: Use CAP_SYS_ADMIN instead of euid==0 with ftrace
Em Mon, Aug 12, 2019 at 05:22:51PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Wed, Aug 07, 2019 at 10:44:17AM -0400, Igor Lubashev escreveu:
> > Kernel requires CAP_SYS_ADMIN instead of euid==0 to mount debugfs for ftrace.
> > Make perf do the same.
> >
> > Signed-off-by: Igor Lubashev <ilubashe@akamai.com>
> > ---
> > tools/perf/builtin-ftrace.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> > index ae1466aa3b26..d09eac8a6d57 100644
> > --- a/tools/perf/builtin-ftrace.c
> > +++ b/tools/perf/builtin-ftrace.c
> > @@ -13,6 +13,7 @@
> > #include <signal.h>
> > #include <fcntl.h>
> > #include <poll.h>
> > +#include <linux/capability.h>
> >
> > #include "debug.h"
> > #include <subcmd/parse-options.h>
> > @@ -21,6 +22,7 @@
> > #include "target.h"
> > #include "cpumap.h"
> > #include "thread_map.h"
> > +#include "util/cap.h"
> > #include "util/config.h"
> >
> >
> > @@ -281,7 +283,7 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
> > .events = POLLIN,
> > };
> >
> > - if (geteuid() != 0) {
> > + if (!perf_cap__capable(CAP_SYS_ADMIN)) {
> > pr_err("ftrace only works for root!\n");
>
> I guess we should update the error message too?
>

I.e. I applied this as a follow up patch:

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 01a5bb58eb04..ba8b65c2f9dc 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -284,7 +284,12 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
};

if (!perf_cap__capable(CAP_SYS_ADMIN)) {
- pr_err("ftrace only works for root!\n");
+ pr_err("ftrace only works for %s!\n",
+#ifdef HAVE_LIBCAP_SUPPORT
+ "users with the SYS_ADMIN capability"
+#else
+ "root"
+#endif
return -1;
}

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