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Date: Mon, 21 Aug 2023 10:40:02 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] perf bpf_skel augmented_raw_syscalls: Cap the
socklen parameter using &= sizeof(saddr)
Em Wed, Aug 16, 2023 at 03:10:00PM -0700, Ian Rogers escreveu:
> On Wed, Aug 16, 2023 at 2:48 PM Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> > R2 min value is negative, either use unsigned or 'var &= const'
> > processed 22 insns (limit 1000000) max_states_per_insn 0 total_states 1 peak_states 1 mark_read 1
> > -- END PROG LOAD LOG --
> > libbpf: prog 'sys_enter_sendto': failed to load: -13
> > libbpf: failed to load object 'augmented_raw_syscalls_bpf'
> > libbpf: failed to load BPF skeleton 'augmented_raw_syscalls_bpf': -13
> >
> > So use the suggested &= variant since sizeof(saddr) == 128 bytes.
>
> Could this be an assert?
you mean (removing the change to saddr to make it trigger):
diff --git a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
index 9c1d0b271b20f693..521ce2d7357d983c 100644
--- a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
+++ b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
@@ -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
@@ -112,7 +122,10 @@ struct augmented_args_payload {
struct {
struct augmented_arg arg, arg2;
};
- struct sockaddr_storage saddr;
+ struct {
+ struct sockaddr_storage real_saddr;
+ char padding;
+ } saddr;
char __data[sizeof(struct augmented_arg)];
};
};
@@ -187,6 +200,7 @@ 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);
--------------------------------
CLANG /tmp/build/perf-tools-next/util/bpf_skel/.tmp/augmented_raw_syscalls.bpf.o
util/bpf_skel/augmented_raw_syscalls.bpf.c:203:2: error: static_assert failed due to requirement 'sizeof (augmented_args->saddr) != 0 && ((sizeof (augmented_args->saddr) & (sizeof (augmented_args->saddr) - 1)) == 0)' "sizeof(augmented_args->saddr) needs to be a power of two"
_Static_assert(is_power_of_2(sizeof(augmented_args->saddr)), "sizeof(augmented_args->saddr) needs to be a power of two");
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
make[2]: *** [Makefile.perf:1104: /tmp/build/perf-tools-next/util/bpf_skel/.tmp/augmented_raw_syscalls.bpf.o] Error 1
make[1]: *** [Makefile.perf:238: sub-make] Error 2
make: *** [Makefile:113: install-bin] Error 2
make: Leaving directory '/var/home/acme/git/perf-tools-next/tools/perf'
And here the assert being satisfied:
⬢[acme@...lbox perf-tools-next]$ git diff
diff --git a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
index 9c1d0b271b20f693..43549b63b433d81e 100644
--- a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
+++ b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
@@ -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);
⬢[acme@...lbox perf-tools-next]$ m
make: Entering directory '/var/home/acme/git/perf-tools-next/tools/perf'
BUILD: Doing 'make -j32' parallel build
INSTALL libsubcmd_headers
INSTALL libperf_headers
INSTALL libapi_headers
INSTALL libbpf_headers
CLANG /tmp/build/perf-tools-next/util/bpf_skel/.tmp/augmented_raw_syscalls.bpf.o
GENSKEL /tmp/build/perf-tools-next/util/bpf_skel/augmented_raw_syscalls.skel.h
INSTALL libsymbol_headers
CC /tmp/build/perf-tools-next/builtin-trace.o
LD /tmp/build/perf-tools-next/perf-in.o
LINK /tmp/build/perf-tools-next/perf
INSTALL binaries
INSTALL tests
INSTALL libperf-jvmti.so
INSTALL libexec
INSTALL perf-archive
INSTALL perf-iostat
INSTALL strace/groups
INSTALL perl-scripts
INSTALL python-scripts
INSTALL dlfilters
INSTALL perf_completion-script
INSTALL perf-tip
make: Leaving directory '/var/home/acme/git/perf-tools-next/tools/perf'
⬢[acme@...lbox perf-tools-next]$
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