From a68fd6a6cdd309bb51c72df4a39f49aa408728d0 Mon Sep 17 00:00:00 2001 From: Howard Chu Date: Sun, 25 Aug 2024 00:33:20 +0800 Subject: [PATCH] perf trace: Collect augmented data using BPF 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 Tested-by: Arnaldo Carvalho de Melo Cc: Adrian Hunter Cc: Ian Rogers Cc: Jiri Olsa Cc: Kan Liang Cc: Namhyung Kim 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 --- .../bpf_skel/augmented_raw_syscalls.bpf.c | 107 +++++++++++++++++- 1 file changed, 106 insertions(+), 1 deletion(-) 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 4ebce6763743..b2f17cca014b 100644 --- a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c +++ b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c @@ -7,6 +7,8 @@ */ #include "vmlinux.h" +#include "../trace_augment.h" + #include #include @@ -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; -- 2.50.1