perf trace: Use a common encoding for augmented arguments, with size + error + payload

We were using a more compact format, without explicitely encoding the
size and possible error in the payload for an argument.

To do it generically, at least as Howard Chu did in his GSoC activities,
it is more convenient to use the same model that was being used for
string arguments, passing { size, error, payload }.

So use that for the non string syscall args we have so far:

  struct timespec
  struct perf_event_attr
  struct sockaddr (this one has even a variable size)

With this in place we have the userspace pretty printers:

  perf_event_attr___scnprintf()
  syscall_arg__scnprintf_augmented_sockaddr()
  syscall_arg__scnprintf_augmented_timespec()

Ready to have the generic BPF collector in tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
sending its generic payload and thus we'll use them instead of a generic
libbpf btf_dump interface that doesn't know about about the sockaddr
mux, perf_event_attr non-trivial fields (sample_type, etc), leaving it
as a (useful) fallback that prints just basic types until we put in
place a more sophisticated pretty printer infrastructure that associates
synthesized enums to struct fields using the header scrapers we have in
tools/perf/trace/beauty/, some of them in this list:

  $ ls tools/perf/trace/beauty/*.sh
  tools/perf/trace/beauty/arch_errno_names.sh
  tools/perf/trace/beauty/kcmp_type.sh
  tools/perf/trace/beauty/perf_ioctl.sh
  tools/perf/trace/beauty/statx_mask.sh
  tools/perf/trace/beauty/clone.sh
  tools/perf/trace/beauty/kvm_ioctl.sh
  tools/perf/trace/beauty/pkey_alloc_access_rights.sh
  tools/perf/trace/beauty/sync_file_range.sh
  tools/perf/trace/beauty/drm_ioctl.sh
  tools/perf/trace/beauty/madvise_behavior.sh
  tools/perf/trace/beauty/prctl_option.sh
  tools/perf/trace/beauty/usbdevfs_ioctl.sh
  tools/perf/trace/beauty/fadvise.sh
  tools/perf/trace/beauty/mmap_flags.sh
  tools/perf/trace/beauty/rename_flags.sh
  tools/perf/trace/beauty/vhost_virtio_ioctl.sh
  tools/perf/trace/beauty/fs_at_flags.sh
  tools/perf/trace/beauty/mmap_prot.sh
  tools/perf/trace/beauty/sndrv_ctl_ioctl.sh
  tools/perf/trace/beauty/x86_arch_prctl.sh
  tools/perf/trace/beauty/fsconfig.sh
  tools/perf/trace/beauty/mount_flags.sh
  tools/perf/trace/beauty/sndrv_pcm_ioctl.sh
  tools/perf/trace/beauty/fsmount.sh
  tools/perf/trace/beauty/move_mount_flags.sh
  tools/perf/trace/beauty/sockaddr.sh
  tools/perf/trace/beauty/fspick.sh
  tools/perf/trace/beauty/mremap_flags.sh
  tools/perf/trace/beauty/socket.sh
  $

Testing it:

  root@number:~# rm -f 987654 ; touch 123456 ; perf trace -e rename* mv 123456 987654
     0.000 ( 0.031 ms): mv/1193096 renameat2(olddfd: CWD, oldname: "123456", newdfd: CWD, newname: "987654", flags: NOREPLACE) = 0
  root@number:~# perf trace -e *nanosleep sleep 1.2345678901
       0.000 (1234.654 ms): sleep/1192697 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 234567891 }, rmtp: 0x7ffe1ea80460) = 0
  root@number:~# perf trace -e perf_event_open* perf stat -e cpu-clock sleep 1
       0.000 ( 0.011 ms): perf/1192701 perf_event_open(attr_uptr: { type: 1 (software), size: 136, config: 0 (PERF_COUNT_SW_CPU_CLOCK), sample_type: IDENTIFIER, read_format: TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING, disabled: 1, inherit: 1, enable_on_exec: 1, exclude_guest: 1 }, pid: 1192702 (perf), cpu: -1, group_fd: -1, flags: FD_CLOEXEC) = 3

   Performance counter stats for 'sleep 1':

                0.51 msec cpu-clock                        #    0.001 CPUs utilized

         1.001242090 seconds time elapsed

         0.000000000 seconds user
         0.001010000 seconds sys

  root@number:~# perf trace -e connect* ping -c 1 bsky.app
       0.000 ( 0.130 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: LOCAL, path: /run/systemd/resolve/io.systemd.Resolve }, addrlen: 42) = 0
      23.907 ( 0.006 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: INET, port: 0, addr: 3.20.108.158 }, addrlen: 16) = 0
      23.915 PING bsky.app (3.20.108.158) 56(84) bytes of data.
  ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: UNSPEC }, addrlen: 16)           = 0
      23.917 ( 0.002 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: INET, port: 0, addr: 3.12.170.30 }, addrlen: 16) = 0
      23.921 ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: UNSPEC }, addrlen: 16)           = 0
      23.923 ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: INET, port: 0, addr: 18.217.70.179 }, addrlen: 16) = 0
      23.925 ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: UNSPEC }, addrlen: 16)           = 0
      23.927 ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: INET, port: 0, addr: 3.132.20.46 }, addrlen: 16) = 0
      23.930 ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: UNSPEC }, addrlen: 16)           = 0
      23.931 ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: INET, port: 0, addr: 3.142.89.165 }, addrlen: 16) = 0
      23.934 ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: UNSPEC }, addrlen: 16)           = 0
      23.935 ( 0.002 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: INET, port: 0, addr: 18.119.147.159 }, addrlen: 16) = 0
      23.938 ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: UNSPEC }, addrlen: 16)           = 0
      23.940 ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: INET, port: 0, addr: 3.22.38.164 }, addrlen: 16) = 0
      23.942 ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: UNSPEC }, addrlen: 16)           = 0
      23.944 ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: INET, port: 0, addr: 3.13.14.133 }, addrlen: 16) = 0
      23.956 ( 0.001 ms): ping/1192740 connect(fd: 5, uservaddr: { .family: INET, port: 1025, addr: 3.20.108.158 }, addrlen: 16) = 0
  ^C
  --- bsky.app ping statistics ---
  1 packets transmitted, 0 received, 100% packet loss, time 0ms

  root@number:~#

Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Howard Chu <howardchu95@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/CAP-5=fW4=2GoP6foAN6qbrCiUzy0a_TzHbd8rvDsakTPfdzvfg@mail.gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

4 files changed, 66 insertions, 44 deletions

diff --git a/tools/perf/trace/beauty/perf_event_open.c b/tools/perf/trace/beauty/perf_event_open.c
index 01ee15fe9d0c..632237128640 100644
--- a/tools/perf/trace/beauty/perf_event_open.c
+++ b/tools/perf/trace/beauty/perf_event_open.c
@@ -76,7 +76,7 @@ static size_t perf_event_attr___scnprintf(struct perf_event_attr *attr, char *bf
 
 static size_t syscall_arg__scnprintf_augmented_perf_event_attr(struct syscall_arg *arg, char *bf, size_t size)
 {
-	return perf_event_attr___scnprintf((void *)arg->augmented.args, bf, size, arg->trace->show_zeros);
+	return perf_event_attr___scnprintf((void *)arg->augmented.args->value, bf, size, arg->trace->show_zeros);
 }
 
 static size_t syscall_arg__scnprintf_perf_event_attr(char *bf, size_t size, struct syscall_arg *arg)
diff --git a/tools/perf/trace/beauty/sockaddr.c b/tools/perf/trace/beauty/sockaddr.c
index 2e0e867c0c1b..a17a27ac2a6f 100644
--- a/tools/perf/trace/beauty/sockaddr.c
+++ b/tools/perf/trace/beauty/sockaddr.c
@@ -47,7 +47,7 @@ static size_t (*af_scnprintfs[])(struct sockaddr *sa, char *bf, size_t size) = {
 
 static size_t syscall_arg__scnprintf_augmented_sockaddr(struct syscall_arg *arg, char *bf, size_t size)
 {
-	struct sockaddr *sa = (struct sockaddr *)arg->augmented.args;
+	struct sockaddr *sa = (struct sockaddr *)&arg->augmented.args->value;
 	char family[32];
 	size_t printed;
 
diff --git a/tools/perf/trace/beauty/timespec.c b/tools/perf/trace/beauty/timespec.c
index e1a61f092aad..b14ab72a2738 100644
--- a/tools/perf/trace/beauty/timespec.c
+++ b/tools/perf/trace/beauty/timespec.c
@@ -7,7 +7,7 @@
 
 static size_t syscall_arg__scnprintf_augmented_timespec(struct syscall_arg *arg, char *bf, size_t size)
 {
-	struct timespec *ts = (struct timespec *)arg->augmented.args;
+	struct timespec *ts = (struct timespec *)arg->augmented.args->value;
 
 	return scnprintf(bf, size, "{ .tv_sec: %" PRIu64 ", .tv_nsec: %" PRIu64 " }", ts->tv_sec, ts->tv_nsec);
 }
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 0f9bd2690d4e..9c7d2f855294 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 +10,9 @@
 #include <bpf/bpf_helpers.h>
 #include <linux/limits.h>
 
+#define PERF_ALIGN(x, a)        __PERF_ALIGN_MASK(x, (typeof(x))(a)-1)
+#define __PERF_ALIGN_MASK(x, mask)      (((x)+(mask))&~(mask))
+
 /**
  * is_power_of_2() - check if a value is a power of two
  * @n: the value to check
@@ -66,19 +69,6 @@ struct syscall_exit_args {
 	long		   ret;
 };
 
-struct augmented_arg {
-	unsigned int	size;
-	int		err;
-	char		value[PATH_MAX];
-};
-
-struct pids_filtered {
-	__uint(type, BPF_MAP_TYPE_HASH);
-	__type(key, pid_t);
-	__type(value, bool);
-	__uint(max_entries, 64);
-} pids_filtered SEC(".maps");
-
 /*
  * Desired design of maximum size and alignment (see RFC2553)
  */
@@ -105,17 +95,27 @@ struct sockaddr_storage {
 	};
 };
 
-struct augmented_args_payload {
-       struct syscall_enter_args args;
-       union {
-		struct {
-			struct augmented_arg arg, arg2;
-		};
+struct augmented_arg {
+	unsigned int	size;
+	int		err;
+	union {
+		char   value[PATH_MAX];
 		struct sockaddr_storage saddr;
-		char   __data[sizeof(struct augmented_arg)];
 	};
 };
 
+struct pids_filtered {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__type(key, pid_t);
+	__type(value, bool);
+	__uint(max_entries, 64);
+} pids_filtered SEC(".maps");
+
+struct augmented_args_payload {
+	struct syscall_enter_args args;
+	struct augmented_arg arg, arg2; // We have to reserve space for two arguments (rename, etc)
+};
+
 // We need more tmp space than the BPF stack can give us
 struct augmented_args_tmp {
 	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
@@ -182,15 +182,17 @@ int sys_enter_connect(struct syscall_enter_args *args)
 	struct augmented_args_payload *augmented_args = augmented_args_payload();
 	const void *sockaddr_arg = (const void *)args->args[1];
 	unsigned int socklen = args->args[2];
-	unsigned int len = sizeof(augmented_args->args);
+	unsigned int len = sizeof(u64) + sizeof(augmented_args->args); // the size + err in all 'augmented_arg' structs
 
         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;
+	_Static_assert(is_power_of_2(sizeof(augmented_args->arg.saddr)), "sizeof(augmented_args->arg.saddr) needs to be a power of two");
+	socklen &= sizeof(augmented_args->arg.saddr) - 1;
 
-	bpf_probe_read_user(&augmented_args->saddr, socklen, sockaddr_arg);
+	bpf_probe_read_user(&augmented_args->arg.saddr, socklen, sockaddr_arg);
+	augmented_args->arg.size = socklen;
+	augmented_args->arg.err = 0;
 
 	return augmented__output(args, augmented_args, len + socklen);
 }
@@ -201,14 +203,14 @@ int sys_enter_sendto(struct syscall_enter_args *args)
 	struct augmented_args_payload *augmented_args = augmented_args_payload();
 	const void *sockaddr_arg = (const void *)args->args[4];
 	unsigned int socklen = args->args[5];
-	unsigned int len = sizeof(augmented_args->args);
+	unsigned int len = sizeof(u64) + sizeof(augmented_args->args); // the size + err in all 'augmented_arg' structs
 
         if (augmented_args == NULL)
                 return 1; /* Failure: don't filter */
 
-	socklen &= sizeof(augmented_args->saddr) - 1;
+	socklen &= sizeof(augmented_args->arg.saddr) - 1;
 
-	bpf_probe_read_user(&augmented_args->saddr, socklen, sockaddr_arg);
+	bpf_probe_read_user(&augmented_args->arg.saddr, socklen, sockaddr_arg);
 
 	return augmented__output(args, augmented_args, len + socklen);
 }
@@ -249,13 +251,23 @@ int sys_enter_rename(struct syscall_enter_args *args)
 	struct augmented_args_payload *augmented_args = augmented_args_payload();
 	const void *oldpath_arg = (const void *)args->args[0],
 		   *newpath_arg = (const void *)args->args[1];
-	unsigned int len = sizeof(augmented_args->args), oldpath_len;
+	unsigned int len = sizeof(augmented_args->args), oldpath_len, newpath_len;
 
         if (augmented_args == NULL)
                 return 1; /* Failure: don't filter */
 
+	len += 2 * sizeof(u64); // The overhead of size and err, just before the payload...
+
 	oldpath_len = augmented_arg__read_str(&augmented_args->arg, oldpath_arg, sizeof(augmented_args->arg.value));
-	len += oldpath_len + augmented_arg__read_str((void *)(&augmented_args->arg) + oldpath_len, newpath_arg, sizeof(augmented_args->arg.value));
+	augmented_args->arg.size = PERF_ALIGN(oldpath_len + 1, sizeof(u64));
+	len += augmented_args->arg.size;
+
+	struct augmented_arg *arg2 = (void *)&augmented_args->arg.value + augmented_args->arg.size;
+
+	newpath_len = augmented_arg__read_str(arg2, newpath_arg, sizeof(augmented_args->arg.value));
+	arg2->size = newpath_len;
+
+	len += newpath_len;
 
 	return augmented__output(args, augmented_args, len);
 }
@@ -266,13 +278,23 @@ int sys_enter_renameat2(struct syscall_enter_args *args)
 	struct augmented_args_payload *augmented_args = augmented_args_payload();
 	const void *oldpath_arg = (const void *)args->args[1],
 		   *newpath_arg = (const void *)args->args[3];
-	unsigned int len = sizeof(augmented_args->args), oldpath_len;
+	unsigned int len = sizeof(augmented_args->args), oldpath_len, newpath_len;
 
         if (augmented_args == NULL)
                 return 1; /* Failure: don't filter */
 
+	len += 2 * sizeof(u64); // The overhead of size and err, just before the payload...
+
 	oldpath_len = augmented_arg__read_str(&augmented_args->arg, oldpath_arg, sizeof(augmented_args->arg.value));
-	len += oldpath_len + augmented_arg__read_str((void *)(&augmented_args->arg) + oldpath_len, newpath_arg, sizeof(augmented_args->arg.value));
+	augmented_args->arg.size = PERF_ALIGN(oldpath_len + 1, sizeof(u64));
+	len += augmented_args->arg.size;
+
+	struct augmented_arg *arg2 = (void *)&augmented_args->arg.value + augmented_args->arg.size;
+
+	newpath_len = augmented_arg__read_str(arg2, newpath_arg, sizeof(augmented_args->arg.value));
+	arg2->size = newpath_len;
+
+	len += newpath_len;
 
 	return augmented__output(args, augmented_args, len);
 }
@@ -293,26 +315,26 @@ int sys_enter_perf_event_open(struct syscall_enter_args *args)
 {
 	struct augmented_args_payload *augmented_args = augmented_args_payload();
 	const struct perf_event_attr_size *attr = (const struct perf_event_attr_size *)args->args[0], *attr_read;
-	unsigned int len = sizeof(augmented_args->args);
+	unsigned int len = sizeof(u64) + sizeof(augmented_args->args); // the size + err in all 'augmented_arg' structs
 
         if (augmented_args == NULL)
 		goto failure;
 
-	if (bpf_probe_read_user(&augmented_args->__data, sizeof(*attr), attr) < 0)
+	if (bpf_probe_read_user(&augmented_args->arg.value, sizeof(*attr), attr) < 0)
 		goto failure;
 
-	attr_read = (const struct perf_event_attr_size *)augmented_args->__data;
+	attr_read = (const struct perf_event_attr_size *)augmented_args->arg.value;
 
 	__u32 size = attr_read->size;
 
 	if (!size)
 		size = PERF_ATTR_SIZE_VER0;
 
-	if (size > sizeof(augmented_args->__data))
+	if (size > sizeof(augmented_args->arg.value))
                 goto failure;
 
 	// Now that we read attr->size and tested it against the size limits, read it completely
-	if (bpf_probe_read_user(&augmented_args->__data, size, attr) < 0)
+	if (bpf_probe_read_user(&augmented_args->arg.value, size, attr) < 0)
 		goto failure;
 
 	return augmented__output(args, augmented_args, len + size);
@@ -325,16 +347,16 @@ int sys_enter_clock_nanosleep(struct syscall_enter_args *args)
 {
 	struct augmented_args_payload *augmented_args = augmented_args_payload();
 	const void *rqtp_arg = (const void *)args->args[2];
-	unsigned int len = sizeof(augmented_args->args);
+	unsigned int len = sizeof(u64) + sizeof(augmented_args->args); // the size + err in all 'augmented_arg' structs
 	__u32 size = sizeof(struct timespec64);
 
         if (augmented_args == NULL)
 		goto failure;
 
-	if (size > sizeof(augmented_args->__data))
+	if (size > sizeof(augmented_args->arg.value))
                 goto failure;
 
-	bpf_probe_read_user(&augmented_args->__data, size, rqtp_arg);
+	bpf_probe_read_user(&augmented_args->arg.value, size, rqtp_arg);
 
 	return augmented__output(args, augmented_args, len + size);
 failure:
@@ -352,10 +374,10 @@ int sys_enter_nanosleep(struct syscall_enter_args *args)
         if (augmented_args == NULL)
 		goto failure;
 
-	if (size > sizeof(augmented_args->__data))
+	if (size > sizeof(augmented_args->arg.value))
                 goto failure;
 
-	bpf_probe_read_user(&augmented_args->__data, size, req_arg);
+	bpf_probe_read_user(&augmented_args->arg.value, size, req_arg);
 
 	return augmented__output(args, augmented_args, len + size);
 failure: