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Subject[PATCH 26/85] perf augmented_raw_syscalls: Tell which args are filenames and how many bytes to copy
Date
From: Arnaldo Carvalho de Melo <acme@redhat.com>

Since we know what args are strings from reading the syscall
descriptions in tracefs and also already mark such args to be beautified
using the syscall_arg__scnprintf_filename() helper, all we need is to
fill in this info in the 'syscalls' BPF map we were using to state which
syscalls the user is interested in, i.e. the syscall filter.

Right now just set that with PATH_MAX and unroll the syscall arg in the
BPF program, as the verifier isn't liking something clang generates when
unrolling the loop.

This also makes the augmented_raw_syscalls.c program support all arches,
since we removed that set of defines with the hard coded syscall
numbers, all should be automatically set for all arches, with the
syscall id mapping done correcly.

Doing baby steps here, i.e. just the first string arg for a syscall is
printed, syscalls with more than one, say, the various rename* syscalls,
need further work, but lets get first something that the BPF verifier
accepts before increasing the complexity

To test it, something like:

# perf trace -e string -e /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.c

With:

# cat ~/.perfconfig
[llvm]
dump-obj = true
clang-opt = -g
[trace]
#add_events = /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.c
show_zeros = yes
show_duration = no
no_inherit = yes
show_timestamp = no
show_arg_names = no
args_alignment = 40
show_prefix = yes
#

That commented add_events line is needed for developing this
augmented_raw_syscalls.c BPF program, as if we add it via the
'add_events' mechanism so as to shorten the 'perf trace' command lines,
then we end up not setting up the -v option which precludes us having
access to the bpf verifier log :-\

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Link: https://lkml.kernel.org/n/tip-dn863ya0cbsqycxuy0olvbt1@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-trace.c | 31 +++
.../examples/bpf/augmented_raw_syscalls.c | 232 +++++-------------
2 files changed, 95 insertions(+), 168 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 54b2d0fd0d02..19f22127f02e 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -972,8 +972,14 @@ struct syscall {
struct syscall_arg_fmt *arg_fmt;
};

+/*
+ * Must match what is in the BPF program:
+ *
+ * tools/perf/examples/bpf/augmented_raw_syscalls.c
+ */
struct bpf_map_syscall_entry {
bool enabled;
+ u16 string_args_len[6];
};

/*
@@ -2711,6 +2717,25 @@ static int trace__set_ev_qualifier_tp_filter(struct trace *trace)
}

#ifdef HAVE_LIBBPF_SUPPORT
+static void trace__init_bpf_map_syscall_args(struct trace *trace, int id, struct bpf_map_syscall_entry *entry)
+{
+ struct syscall *sc = trace__syscall_info(trace, NULL, id);
+ int arg = 0;
+
+ if (sc == NULL)
+ goto out;
+
+ for (; arg < sc->nr_args; ++arg) {
+ entry->string_args_len[arg] = 0;
+ if (sc->arg_fmt[arg].scnprintf == SCA_FILENAME) {
+ /* Should be set like strace -s strsize */
+ entry->string_args_len[arg] = PATH_MAX;
+ }
+ }
+out:
+ for (; arg < 6; ++arg)
+ entry->string_args_len[arg] = 0;
+}
static int trace__set_ev_qualifier_bpf_filter(struct trace *trace)
{
int fd = bpf_map__fd(trace->syscalls.map);
@@ -2723,6 +2748,9 @@ static int trace__set_ev_qualifier_bpf_filter(struct trace *trace)
for (i = 0; i < trace->ev_qualifier_ids.nr; ++i) {
int key = trace->ev_qualifier_ids.entries[i];

+ if (value.enabled)
+ trace__init_bpf_map_syscall_args(trace, key, &value);
+
err = bpf_map_update_elem(fd, &key, &value, BPF_EXIST);
if (err)
break;
@@ -2740,6 +2768,9 @@ static int __trace__init_syscalls_bpf_map(struct trace *trace, bool enabled)
int err = 0, key;

for (key = 0; key < trace->sctbl->syscalls.nr_entries; ++key) {
+ if (enabled)
+ trace__init_bpf_map_syscall_args(trace, key, &value);
+
err = bpf_map_update_elem(fd, &key, &value, BPF_ANY);
if (err)
break;
diff --git a/tools/perf/examples/bpf/augmented_raw_syscalls.c b/tools/perf/examples/bpf/augmented_raw_syscalls.c
index 68a3d61752ce..c9fd3b4d8e55 100644
--- a/tools/perf/examples/bpf/augmented_raw_syscalls.c
+++ b/tools/perf/examples/bpf/augmented_raw_syscalls.c
@@ -21,8 +21,14 @@
/* bpf-output associated map */
bpf_map(__augmented_syscalls__, PERF_EVENT_ARRAY, int, u32, __NR_CPUS__);

+/*
+ * string_args_len: one per syscall arg, 0 means not a string or don't copy it,
+ * PATH_MAX for copying everything, any other value to limit
+ * it a la 'strace -s strsize'.
+ */
struct syscall {
bool enabled;
+ u16 string_args_len[6];
};

bpf_map(syscalls, ARRAY, int, struct syscall, 512);
@@ -45,81 +51,6 @@ struct augmented_filename {
char value[PATH_MAX];
};

-/* syscalls where the first arg is a string */
-#define SYS_OPEN 2
-#define SYS_STAT 4
-#define SYS_LSTAT 6
-#define SYS_ACCESS 21
-#define SYS_EXECVE 59
-#define SYS_TRUNCATE 76
-#define SYS_CHDIR 80
-#define SYS_RENAME 82
-#define SYS_MKDIR 83
-#define SYS_RMDIR 84
-#define SYS_CREAT 85
-#define SYS_LINK 86
-#define SYS_UNLINK 87
-#define SYS_SYMLINK 88
-#define SYS_READLINK 89
-#define SYS_CHMOD 90
-#define SYS_CHOWN 92
-#define SYS_LCHOWN 94
-#define SYS_MKNOD 133
-#define SYS_STATFS 137
-#define SYS_PIVOT_ROOT 155
-#define SYS_CHROOT 161
-#define SYS_ACCT 163
-#define SYS_SWAPON 167
-#define SYS_SWAPOFF 168
-#define SYS_DELETE_MODULE 176
-#define SYS_SETXATTR 188
-#define SYS_LSETXATTR 189
-#define SYS_GETXATTR 191
-#define SYS_LGETXATTR 192
-#define SYS_LISTXATTR 194
-#define SYS_LLISTXATTR 195
-#define SYS_REMOVEXATTR 197
-#define SYS_LREMOVEXATTR 198
-#define SYS_MQ_OPEN 240
-#define SYS_MQ_UNLINK 241
-#define SYS_ADD_KEY 248
-#define SYS_REQUEST_KEY 249
-#define SYS_SYMLINKAT 266
-#define SYS_MEMFD_CREATE 319
-
-/* syscalls where the second arg is a string */
-
-#define SYS_PWRITE64 18
-#define SYS_EXECVE 59
-#define SYS_RENAME 82
-#define SYS_QUOTACTL 179
-#define SYS_FSETXATTR 190
-#define SYS_FGETXATTR 193
-#define SYS_FREMOVEXATTR 199
-#define SYS_MQ_TIMEDSEND 242
-#define SYS_REQUEST_KEY 249
-#define SYS_INOTIFY_ADD_WATCH 254
-#define SYS_OPENAT 257
-#define SYS_MKDIRAT 258
-#define SYS_MKNODAT 259
-#define SYS_FCHOWNAT 260
-#define SYS_FUTIMESAT 261
-#define SYS_NEWFSTATAT 262
-#define SYS_UNLINKAT 263
-#define SYS_RENAMEAT 264
-#define SYS_LINKAT 265
-#define SYS_READLINKAT 267
-#define SYS_FCHMODAT 268
-#define SYS_FACCESSAT 269
-#define SYS_UTIMENSAT 280
-#define SYS_NAME_TO_HANDLE_AT 303
-#define SYS_FINIT_MODULE 313
-#define SYS_RENAMEAT2 316
-#define SYS_EXECVEAT 322
-#define SYS_STATX 332
-#define SYS_MOVE_MOUNT 429
-#define SYS_FSPICK 433
-
pid_filter(pids_filtered);

struct augmented_args_filename {
@@ -133,7 +64,7 @@ SEC("raw_syscalls:sys_enter")
int sys_enter(struct syscall_enter_args *args)
{
struct augmented_args_filename *augmented_args;
- unsigned int len = sizeof(*augmented_args);
+ unsigned int len = sizeof(*augmented_args), filename_len;
const void *filename_arg = NULL;
struct syscall *syscall;
int key = 0;
@@ -191,104 +122,69 @@ int sys_enter(struct syscall_enter_args *args)
* after the ctx memory access to prevent their down stream merging.
*/
/*
- * This table of what args are strings will be provided by userspace,
- * in the syscalls map, i.e. we will already have to do the lookup to
- * see if this specific syscall is filtered, so we can as well get more
- * info about what syscall args are strings or pointers, and how many
- * bytes to copy, per arg, etc.
+ * For now copy just the first string arg, we need to improve the protocol
+ * and have more than one.
*
- * For now hard code it, till we have all the basic mechanisms in place
- * to automate everything and make the kernel part be completely driven
- * by information obtained in userspace for each kernel version and
- * processor architecture, making the kernel part the same no matter what
- * kernel version or processor architecture it runs on.
- */
- switch (augmented_args->args.syscall_nr) {
- case SYS_ACCT:
- case SYS_ADD_KEY:
- case SYS_CHDIR:
- case SYS_CHMOD:
- case SYS_CHOWN:
- case SYS_CHROOT:
- case SYS_CREAT:
- case SYS_DELETE_MODULE:
- case SYS_EXECVE:
- case SYS_GETXATTR:
- case SYS_LCHOWN:
- case SYS_LGETXATTR:
- case SYS_LINK:
- case SYS_LISTXATTR:
- case SYS_LLISTXATTR:
- case SYS_LREMOVEXATTR:
- case SYS_LSETXATTR:
- case SYS_LSTAT:
- case SYS_MEMFD_CREATE:
- case SYS_MKDIR:
- case SYS_MKNOD:
- case SYS_MQ_OPEN:
- case SYS_MQ_UNLINK:
- case SYS_PIVOT_ROOT:
- case SYS_READLINK:
- case SYS_REMOVEXATTR:
- case SYS_RENAME:
- case SYS_REQUEST_KEY:
- case SYS_RMDIR:
- case SYS_SETXATTR:
- case SYS_STAT:
- case SYS_STATFS:
- case SYS_SWAPOFF:
- case SYS_SWAPON:
- case SYS_SYMLINK:
- case SYS_SYMLINKAT:
- case SYS_TRUNCATE:
- case SYS_UNLINK:
- case SYS_ACCESS:
- case SYS_OPEN: filename_arg = (const void *)args->args[0];
+ * Using the unrolled loop is not working, only when we do it manually,
+ * check this out later...
+
+ u8 arg;
+#pragma clang loop unroll(full)
+ for (arg = 0; arg < 6; ++arg) {
+ if (syscall->string_args_len[arg] != 0) {
+ filename_len = syscall->string_args_len[arg];
+ filename_arg = (const void *)args->args[arg];
__asm__ __volatile__("": : :"memory");
- break;
- case SYS_EXECVEAT:
- case SYS_FACCESSAT:
- case SYS_FCHMODAT:
- case SYS_FCHOWNAT:
- case SYS_FGETXATTR:
- case SYS_FINIT_MODULE:
- case SYS_FREMOVEXATTR:
- case SYS_FSETXATTR:
- case SYS_FSPICK:
- case SYS_FUTIMESAT:
- case SYS_INOTIFY_ADD_WATCH:
- case SYS_LINKAT:
- case SYS_MKDIRAT:
- case SYS_MKNODAT:
- // case SYS_MOVE_MOUNT:
- // For now don't copy move_mount first string arg, as it has two and
- // 'perf trace's syscall_arg__scnprintf_filename() will use the one
- // copied here, the first, for both args, duplicating the first and
- // ignoring the second.
- //
- // We need to copy both here and make syscall_arg__scnprintf_filename
- // skip the first when reading the second, using the size of the first, etc.
- // Shouldn't be difficult, but now its perf/urgent time, lets wait for
- // the next devel window.
- case SYS_MQ_TIMEDSEND:
- case SYS_NAME_TO_HANDLE_AT:
- case SYS_NEWFSTATAT:
- case SYS_PWRITE64:
- case SYS_QUOTACTL:
- case SYS_READLINKAT:
- case SYS_RENAMEAT:
- case SYS_RENAMEAT2:
- case SYS_STATX:
- case SYS_UNLINKAT:
- case SYS_UTIMENSAT:
- case SYS_OPENAT: filename_arg = (const void *)args->args[1];
- break;
+ break;
+ }
}

- if (filename_arg != NULL) {
+ verifier log:
+
+; if (syscall->string_args_len[arg] != 0) {
+37: (69) r3 = *(u16 *)(r0 +2)
+ R0=map_value(id=0,off=0,ks=4,vs=14,imm=0) R1_w=inv0 R2_w=map_value(id=0,off=2,ks=4,vs=14,imm=0) R6=ctx(id=0,off=0,imm=0) R7=map_value(id=0,off=0,ks=4,vs=4168,imm=0) R10=fp0,call_-1 fp-8=mmmmmmmm
+; if (syscall->string_args_len[arg] != 0) {
+38: (55) if r3 != 0x0 goto pc+5
+ R0=map_value(id=0,off=0,ks=4,vs=14,imm=0) R1=inv0 R2=map_value(id=0,off=2,ks=4,vs=14,imm=0) R3=inv0 R6=ctx(id=0,off=0,imm=0) R7=map_value(id=0,off=0,ks=4,vs=4168,imm=0) R10=fp0,call_-1 fp-8=mmmmmmmm
+39: (b7) r1 = 1
+; if (syscall->string_args_len[arg] != 0) {
+40: (bf) r2 = r0
+41: (07) r2 += 4
+42: (69) r3 = *(u16 *)(r0 +4)
+ R0=map_value(id=0,off=0,ks=4,vs=14,imm=0) R1_w=inv1 R2_w=map_value(id=0,off=4,ks=4,vs=14,imm=0) R3_w=inv0 R6=ctx(id=0,off=0,imm=0) R7=map_value(id=0,off=0,ks=4,vs=4168,imm=0) R10=fp0,call_-1 fp-8=mmmmmmmm
+; if (syscall->string_args_len[arg] != 0) {
+43: (15) if r3 == 0x0 goto pc+32
+ R0=map_value(id=0,off=0,ks=4,vs=14,imm=0) R1=inv1 R2=map_value(id=0,off=4,ks=4,vs=14,imm=0) R3=inv(id=0,umax_value=65535,var_off=(0x0; 0xffff)) R6=ctx(id=0,off=0,imm=0) R7=map_value(id=0,off=0,ks=4,vs=4168,imm=0) R10=fp0,call_-1 fp-8=mmmmmmmm
+; filename_arg = (const void *)args->args[arg];
+44: (67) r1 <<= 3
+45: (bf) r3 = r6
+46: (0f) r3 += r1
+47: (b7) r5 = 64
+48: (79) r3 = *(u64 *)(r3 +16)
+dereference of modified ctx ptr R3 off=8 disallowed
+processed 46 insns (limit 1000000) max_states_per_insn 0 total_states 12 peak_states 12 mark_read 7
+ */
+
+#define __loop_iter(arg) \
+ if (syscall->string_args_len[arg] != 0) { \
+ filename_len = syscall->string_args_len[arg]; \
+ filename_arg = (const void *)args->args[arg];
+#define loop_iter_first() __loop_iter(0); }
+#define loop_iter(arg) else __loop_iter(arg); }
+#define loop_iter_last(arg) else __loop_iter(arg); __asm__ __volatile__("": : :"memory"); }
+
+ loop_iter_first()
+ loop_iter(1)
+ loop_iter(2)
+ loop_iter(3)
+ loop_iter(4)
+ loop_iter_last(5)
+
+ if (filename_arg != NULL && filename_len <= sizeof(augmented_args->filename.value)) {
augmented_args->filename.reserved = 0;
augmented_args->filename.size = probe_read_str(&augmented_args->filename.value,
- sizeof(augmented_args->filename.value),
+ filename_len,
filename_arg);
if (augmented_args->filename.size < sizeof(augmented_args->filename.value)) {
len -= sizeof(augmented_args->filename.value) - augmented_args->filename.size;
--
2.20.1
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