// SPDX-License-Identifier: GPL-2.0 /* * Augment the raw_syscalls tracepoints with the contents of the pointer arguments. * * Test it with: * * perf trace -e tools/perf/examples/bpf/augmented_raw_syscalls.c cat /etc/passwd > /dev/null * * This exactly matches what is marshalled into the raw_syscall:sys_enter * payload expected by the 'perf trace' beautifiers. * * For now it just uses the existing tracepoint augmentation code in 'perf * trace', in the next csets we'll hook up these with the sys_enter/sys_exit * code that will combine entry/exit in a strace like way. */ #include #include #include /* 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); /* * What to augment at entry? * * Pointer arg payloads (filenames, etc) passed from userspace to the kernel */ bpf_map(syscalls_sys_enter, PROG_ARRAY, u32, u32, 512); /* * What to augment at exit? * * Pointer arg payloads returned from the kernel (struct stat, etc) to userspace. */ bpf_map(syscalls_sys_exit, PROG_ARRAY, u32, u32, 512); struct syscall_enter_args { unsigned long long common_tp_fields; long syscall_nr; unsigned long args[6]; }; struct syscall_exit_args { unsigned long long common_tp_fields; long syscall_nr; long ret; }; struct augmented_filename { unsigned int size; int err; char value[PATH_MAX]; }; pid_filter(pids_filtered); struct augmented_args_payload { struct syscall_enter_args args; struct { struct augmented_filename filename; struct augmented_filename filename2; }; }; bpf_map(augmented_args_tmp, PERCPU_ARRAY, int, struct augmented_args_payload, 1); static inline unsigned int augmented_filename__read(struct augmented_filename *augmented_filename, const void *filename_arg, unsigned int filename_len) { unsigned int len = sizeof(*augmented_filename); int size = probe_read_str(&augmented_filename->value, filename_len, filename_arg); augmented_filename->size = augmented_filename->err = 0; /* * probe_read_str may return < 0, e.g. -EFAULT * So we leave that in the augmented_filename->size that userspace will */ if (size > 0) { len -= sizeof(augmented_filename->value) - size; len &= sizeof(augmented_filename->value) - 1; augmented_filename->size = size; } else { /* * So that username notice the error while still being able * to skip this augmented arg record */ augmented_filename->err = size; len = offsetof(struct augmented_filename, value); } return len; } SEC("!raw_syscalls:unaugmented") int syscall_unaugmented(struct syscall_enter_args *args) { return 1; } /* * This will be tail_called from SEC("raw_syscalls:sys_enter"), so will find in * augmented_args_tmp what was read by that raw_syscalls:sys_enter and go * on from there, reading the first syscall arg as a string, i.e. open's * filename. */ SEC("!syscalls:sys_enter_open") int sys_enter_open(struct syscall_enter_args *args) { int key = 0; struct augmented_args_payload *augmented_args = bpf_map_lookup_elem(&augmented_args_tmp, &key); const void *filename_arg = (const void *)args->args[0]; unsigned int len = sizeof(augmented_args->args); if (augmented_args == NULL) return 1; /* Failure: don't filter */ len += augmented_filename__read(&augmented_args->filename, filename_arg, sizeof(augmented_args->filename.value)); /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */ return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, augmented_args, len); } SEC("!syscalls:sys_enter_openat") int sys_enter_openat(struct syscall_enter_args *args) { int key = 0; struct augmented_args_payload *augmented_args = bpf_map_lookup_elem(&augmented_args_tmp, &key); const void *filename_arg = (const void *)args->args[1]; unsigned int len = sizeof(augmented_args->args); if (augmented_args == NULL) return 1; /* Failure: don't filter */ len += augmented_filename__read(&augmented_args->filename, filename_arg, sizeof(augmented_args->filename.value)); /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */ return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, augmented_args, len); } SEC("!syscalls:sys_enter_renameat") int sys_enter_renameat(struct syscall_enter_args *args) { int key = 0; struct augmented_args_payload *augmented_args = bpf_map_lookup_elem(&augmented_args_tmp, &key); 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; if (augmented_args == NULL) return 1; /* Failure: don't filter */ oldpath_len = augmented_filename__read(&augmented_args->filename, oldpath_arg, sizeof(augmented_args->filename.value)); len += oldpath_len + augmented_filename__read((void *)(&augmented_args->filename) + oldpath_len, newpath_arg, sizeof(augmented_args->filename.value)); /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */ return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, augmented_args, len); } SEC("raw_syscalls:sys_enter") int sys_enter(struct syscall_enter_args *args) { struct augmented_args_payload *augmented_args; /* * We start len, the amount of data that will be in the perf ring * buffer, if this is not filtered out by one of pid_filter__has(), * syscall->enabled, etc, with the non-augmented raw syscall payload, * i.e. sizeof(augmented_args->args). * * We'll add to this as we add augmented syscalls right after that * initial, non-augmented raw_syscalls:sys_enter payload. */ unsigned int len = sizeof(augmented_args->args); struct syscall *syscall; int key = 0; augmented_args = bpf_map_lookup_elem(&augmented_args_tmp, &key); if (augmented_args == NULL) return 1; if (pid_filter__has(&pids_filtered, getpid())) return 0; probe_read(&augmented_args->args, sizeof(augmented_args->args), args); /* * Jump to syscall specific augmenter, even if the default one, * "!raw_syscalls:unaugmented" that will just return 1 to return the * unagmented tracepoint payload. */ 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; } SEC("raw_syscalls:sys_exit") int sys_exit(struct syscall_exit_args *args) { struct syscall_exit_args exit_args; if (pid_filter__has(&pids_filtered, getpid())) return 0; probe_read(&exit_args, sizeof(exit_args), args); /* * Jump to syscall specific return augmenter, even if the default one, * "!raw_syscalls:unaugmented" that will just return 1 to return the * unagmented tracepoint payload. */ bpf_tail_call(args, &syscalls_sys_exit, exit_args.syscall_nr); /* * If not found on the PROG_ARRAY syscalls map, then we're filtering it: */ return 0; } license(GPL);