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perf trace: Collect augmented data using BPF

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Include trace_augment.h for TRACE_AUG_MAX_BUF, so that BPF reads
TRACE_AUG_MAX_BUF bytes of buffer maximum.

Determine what type of argument and how many bytes to read from user space, us ing the
value in the beauty_map. This is the relation of parameter type and its corres ponding
value in the beauty map, and how many bytes we read eventually:

string: 1                          -> size of string (till null)
struct: size of struct             -> size of struct
buffer: -1 * (index of paired len) -> value of paired len (maximum: TRACE_AUG_ MAX_BUF)

After reading from user space, we output the augmented data using
bpf_perf_event_output().

If the struct augmenter, augment_sys_enter() failed, we fall back to
using bpf_tail_call().

I have to make the payload 6 times the size of augmented_arg, to pass the
BPF verifier.

Signed-off-by: Howard Chu <howardchu95@gmail.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.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/r/20240815013626.935097-10-howardchu95@gmail.com
Link: https://lore.kernel.org/r/20240824163322.60796-7-howardchu95@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Howard Chu 2024-08-25 00:33:20 +08:00 committed by Arnaldo Carvalho de Melo
parent b257fac12f
commit a68fd6a6cd
1 changed files with 106 additions and 1 deletions
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107
tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c
View File

@ -7,6 +7,8 @@
*/
#include "vmlinux.h"
#include "../trace_augment.h"
#include <bpf/bpf_helpers.h>
#include <linux/limits.h>
@ -131,6 +133,18 @@ struct beauty_map_enter {
__uint(max_entries, 512);
} beauty_map_enter SEC(".maps");
struct beauty_payload_enter {
struct syscall_enter_args args;
struct augmented_arg aug_args[6];
};
struct beauty_payload_enter_map {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__type(key, int);
__type(value, struct beauty_payload_enter);
__uint(max_entries, 1);
} beauty_payload_enter_map SEC(".maps");
static inline struct augmented_args_payload *augmented_args_payload(void)
{
int key = 0;
@ -143,6 +157,11 @@ static inline int augmented__output(void *ctx, struct augmented_args_payload *ar
return bpf_perf_event_output(ctx, &__augmented_syscalls__, BPF_F_CURRENT_CPU, args, len);
}
static inline int augmented__beauty_output(void *ctx, void *data, int len)
{
return bpf_perf_event_output(ctx, &__augmented_syscalls__, BPF_F_CURRENT_CPU, data, len);
}
static inline
unsigned int augmented_arg__read_str(struct augmented_arg *augmented_arg, const void *arg, unsigned int arg_len)
{
@ -401,6 +420,91 @@ static bool pid_filter__has(struct pids_filtered *pids, pid_t pid)
return bpf_map_lookup_elem(pids, &pid) != NULL;
}
static int augment_sys_enter(void *ctx, struct syscall_enter_args *args)
{
bool augmented, do_output = false;
int zero = 0, size, aug_size, index, output = 0,
value_size = sizeof(struct augmented_arg) - offsetof(struct augmented_arg, value);
unsigned int nr, *beauty_map;
struct beauty_payload_enter *payload;
void *arg, *payload_offset;
/* fall back to do predefined tail call */
if (args == NULL)
return 1;
/* use syscall number to get beauty_map entry */
nr = (__u32)args->syscall_nr;
beauty_map = bpf_map_lookup_elem(&beauty_map_enter, &nr);
/* set up payload for output */
payload = bpf_map_lookup_elem(&beauty_payload_enter_map, &zero);
payload_offset = (void *)&payload->aug_args;
if (beauty_map == NULL || payload == NULL)
return 1;
/* copy the sys_enter header, which has the syscall_nr */
__builtin_memcpy(&payload->args, args, sizeof(struct syscall_enter_args));
/*
* Determine what type of argument and how many bytes to read from user space, using the
* value in the beauty_map. This is the relation of parameter type and its corresponding
* value in the beauty map, and how many bytes we read eventually:
*
* string: 1 -> size of string
* struct: size of struct -> size of struct
* buffer: -1 * (index of paired len) -> value of paired len (maximum: TRACE_AUG_MAX_BUF)
*/
for (int i = 0; i < 6; i++) {
arg = (void *)args->args[i];
augmented = false;
size = beauty_map[i];
aug_size = size; /* size of the augmented data read from user space */
if (size == 0 || arg == NULL)
continue;
if (size == 1) { /* string */
aug_size = bpf_probe_read_user_str(((struct augmented_arg *)payload_offset)->value, value_size, arg);
/* minimum of 0 to pass the verifier */
if (aug_size < 0)
aug_size = 0;
augmented = true;
} else if (size > 0 && size <= value_size) { /* struct */
if (!bpf_probe_read_user(((struct augmented_arg *)payload_offset)->value, size, arg))
augmented = true;
} else if (size < 0 && size >= -6) { /* buffer */
index = -(size + 1);
aug_size = args->args[index];
if (aug_size > TRACE_AUG_MAX_BUF)
aug_size = TRACE_AUG_MAX_BUF;
if (aug_size > 0) {
if (!bpf_probe_read_user(((struct augmented_arg *)payload_offset)->value, aug_size, arg))
augmented = true;
}
}
/* write data to payload */
if (augmented) {
int written = offsetof(struct augmented_arg, value) + aug_size;
((struct augmented_arg *)payload_offset)->size = aug_size;
output += written;
payload_offset += written;
do_output = true;
}
}
if (!do_output)
return 1;
return augmented__beauty_output(ctx, payload, sizeof(struct syscall_enter_args) + output);
}
SEC("tp/raw_syscalls/sys_enter")
int sys_enter(struct syscall_enter_args *args)
{
@ -429,7 +533,8 @@ int sys_enter(struct syscall_enter_args *args)
* "!raw_syscalls:unaugmented" that will just return 1 to return the
* unaugmented tracepoint payload.
*/
bpf_tail_call(args, &syscalls_sys_enter, augmented_args->args.syscall_nr);
if (augment_sys_enter(args, &augmented_args->args))
bpf_tail_call(args, &syscalls_sys_enter, augmented_args->args.syscall_nr);
// If not found on the PROG_ARRAY syscalls map, then we're filtering it:
return 0;