Commit 262b54b6 authored by Arnaldo Carvalho de Melo's avatar Arnaldo Carvalho de Melo
Browse files

perf bpf augmented_raw_syscalls: Add an assert to make sure sizeof(saddr) is a power of two. 



We're using the BPF verifier suggestion:

    22: (85) call bpf_probe_read#4
    R2 min value is negative, either use unsigned or 'var &= const'

That works only when const is a (power of two - 1) so add an assert to
make sure that that is the case.

Suggested-by: default avatarIan Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/ZONrFmJBNlQpSpZj@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent a50b8db3

tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c

+11 −0
Original line number Diff line number Diff line
@@ -10,6 +10,16 @@ 
#include <bpf/bpf_helpers.h>

#include <linux/limits.h>



/**

 * is_power_of_2() - check if a value is a power of two

 * @n: the value to check

 *

 * Determine whether some value is a power of two, where zero is *not*

 * considered a power of two.  Return: true if @n is a power of 2, otherwise

 * false.

 */

#define is_power_of_2(n) (n != 0 && ((n & (n - 1)) == 0))



#define MAX_CPUS  4096



// FIXME: These should come from system headers
@@ -187,6 +197,7 @@ int sys_enter_connect(struct syscall_enter_args *args) 
        if (augmented_args == NULL)

                return 1; /* Failure: don't filter */



	_Static_assert(is_power_of_2(sizeof(augmented_args->saddr)), "sizeof(augmented_args->saddr) needs to be a power of two");

	socklen &= sizeof(augmented_args->saddr) - 1;



	bpf_probe_read(&augmented_args->saddr, socklen, sockaddr_arg);