295 lines
9.0 KiB
C
295 lines
9.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Augment the raw_syscalls tracepoints with the contents of the pointer arguments.
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*
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* Test it with:
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*
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* perf trace -e tools/perf/examples/bpf/augmented_raw_syscalls.c cat /etc/passwd > /dev/null
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*
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* This exactly matches what is marshalled into the raw_syscall:sys_enter
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* payload expected by the 'perf trace' beautifiers.
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*
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* For now it just uses the existing tracepoint augmentation code in 'perf
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* trace', in the next csets we'll hook up these with the sys_enter/sys_exit
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* code that will combine entry/exit in a strace like way.
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*/
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#include <unistd.h>
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#include <linux/limits.h>
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#include <linux/socket.h>
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#include <pid_filter.h>
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/* bpf-output associated map */
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bpf_map(__augmented_syscalls__, PERF_EVENT_ARRAY, int, u32, __NR_CPUS__);
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/*
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* string_args_len: one per syscall arg, 0 means not a string or don't copy it,
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* PATH_MAX for copying everything, any other value to limit
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* it a la 'strace -s strsize'.
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*/
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struct syscall {
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bool enabled;
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u16 string_args_len[6];
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};
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bpf_map(syscalls, ARRAY, int, struct syscall, 512);
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/*
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* What to augment at entry?
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*
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* Pointer arg payloads (filenames, etc) passed from userspace to the kernel
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*/
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bpf_map(syscalls_sys_enter, PROG_ARRAY, u32, u32, 512);
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/*
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* What to augment at exit?
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*
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* Pointer arg payloads returned from the kernel (struct stat, etc) to userspace.
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*/
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bpf_map(syscalls_sys_exit, PROG_ARRAY, u32, u32, 512);
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struct syscall_enter_args {
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unsigned long long common_tp_fields;
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long syscall_nr;
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unsigned long args[6];
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};
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struct syscall_exit_args {
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unsigned long long common_tp_fields;
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long syscall_nr;
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long ret;
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};
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struct augmented_arg {
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unsigned int size;
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int err;
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char value[PATH_MAX];
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};
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pid_filter(pids_filtered);
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struct augmented_args_payload {
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struct syscall_enter_args args;
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union {
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struct {
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struct augmented_arg arg, arg2;
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};
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struct sockaddr_storage saddr;
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};
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};
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// We need more tmp space than the BPF stack can give us
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bpf_map(augmented_args_tmp, PERCPU_ARRAY, int, struct augmented_args_payload, 1);
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static inline struct augmented_args_payload *augmented_args_payload(void)
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{
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int key = 0;
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return bpf_map_lookup_elem(&augmented_args_tmp, &key);
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}
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static inline int augmented__output(void *ctx, struct augmented_args_payload *args, int len)
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{
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/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */
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return perf_event_output(ctx, &__augmented_syscalls__, BPF_F_CURRENT_CPU, args, len);
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}
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static inline
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unsigned int augmented_arg__read_str(struct augmented_arg *augmented_arg, const void *arg, unsigned int arg_len)
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{
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unsigned int augmented_len = sizeof(*augmented_arg);
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int string_len = probe_read_str(&augmented_arg->value, arg_len, arg);
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augmented_arg->size = augmented_arg->err = 0;
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/*
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* probe_read_str may return < 0, e.g. -EFAULT
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* So we leave that in the augmented_arg->size that userspace will
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*/
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if (string_len > 0) {
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augmented_len -= sizeof(augmented_arg->value) - string_len;
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augmented_len &= sizeof(augmented_arg->value) - 1;
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augmented_arg->size = string_len;
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} else {
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/*
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* So that username notice the error while still being able
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* to skip this augmented arg record
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*/
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augmented_arg->err = string_len;
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augmented_len = offsetof(struct augmented_arg, value);
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}
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return augmented_len;
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}
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SEC("!raw_syscalls:unaugmented")
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int syscall_unaugmented(struct syscall_enter_args *args)
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{
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return 1;
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}
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/*
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* These will be tail_called from SEC("raw_syscalls:sys_enter"), so will find in
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* augmented_args_tmp what was read by that raw_syscalls:sys_enter and go
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* on from there, reading the first syscall arg as a string, i.e. open's
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* filename.
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*/
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SEC("!syscalls:sys_enter_connect")
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int sys_enter_connect(struct syscall_enter_args *args)
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{
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struct augmented_args_payload *augmented_args = augmented_args_payload();
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const void *sockaddr_arg = (const void *)args->args[1];
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unsigned int socklen = args->args[2];
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unsigned int len = sizeof(augmented_args->args);
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if (augmented_args == NULL)
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return 1; /* Failure: don't filter */
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if (socklen > sizeof(augmented_args->saddr))
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socklen = sizeof(augmented_args->saddr);
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probe_read(&augmented_args->saddr, socklen, sockaddr_arg);
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return augmented__output(args, augmented_args, len + socklen);
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}
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SEC("!syscalls:sys_enter_sendto")
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int sys_enter_sendto(struct syscall_enter_args *args)
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{
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struct augmented_args_payload *augmented_args = augmented_args_payload();
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const void *sockaddr_arg = (const void *)args->args[4];
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unsigned int socklen = args->args[5];
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unsigned int len = sizeof(augmented_args->args);
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if (augmented_args == NULL)
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return 1; /* Failure: don't filter */
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if (socklen > sizeof(augmented_args->saddr))
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socklen = sizeof(augmented_args->saddr);
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probe_read(&augmented_args->saddr, socklen, sockaddr_arg);
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return augmented__output(args, augmented_args, len + socklen);
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}
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SEC("!syscalls:sys_enter_open")
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int sys_enter_open(struct syscall_enter_args *args)
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{
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struct augmented_args_payload *augmented_args = augmented_args_payload();
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const void *filename_arg = (const void *)args->args[0];
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unsigned int len = sizeof(augmented_args->args);
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if (augmented_args == NULL)
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return 1; /* Failure: don't filter */
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len += augmented_arg__read_str(&augmented_args->arg, filename_arg, sizeof(augmented_args->arg.value));
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return augmented__output(args, augmented_args, len);
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}
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SEC("!syscalls:sys_enter_openat")
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int sys_enter_openat(struct syscall_enter_args *args)
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{
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struct augmented_args_payload *augmented_args = augmented_args_payload();
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const void *filename_arg = (const void *)args->args[1];
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unsigned int len = sizeof(augmented_args->args);
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if (augmented_args == NULL)
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return 1; /* Failure: don't filter */
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len += augmented_arg__read_str(&augmented_args->arg, filename_arg, sizeof(augmented_args->arg.value));
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return augmented__output(args, augmented_args, len);
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}
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SEC("!syscalls:sys_enter_rename")
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int sys_enter_rename(struct syscall_enter_args *args)
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{
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struct augmented_args_payload *augmented_args = augmented_args_payload();
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const void *oldpath_arg = (const void *)args->args[0],
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*newpath_arg = (const void *)args->args[1];
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unsigned int len = sizeof(augmented_args->args), oldpath_len;
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if (augmented_args == NULL)
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return 1; /* Failure: don't filter */
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oldpath_len = augmented_arg__read_str(&augmented_args->arg, oldpath_arg, sizeof(augmented_args->arg.value));
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len += oldpath_len + augmented_arg__read_str((void *)(&augmented_args->arg) + oldpath_len, newpath_arg, sizeof(augmented_args->arg.value));
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return augmented__output(args, augmented_args, len);
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}
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SEC("!syscalls:sys_enter_renameat")
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int sys_enter_renameat(struct syscall_enter_args *args)
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{
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struct augmented_args_payload *augmented_args = augmented_args_payload();
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const void *oldpath_arg = (const void *)args->args[1],
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*newpath_arg = (const void *)args->args[3];
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unsigned int len = sizeof(augmented_args->args), oldpath_len;
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if (augmented_args == NULL)
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return 1; /* Failure: don't filter */
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oldpath_len = augmented_arg__read_str(&augmented_args->arg, oldpath_arg, sizeof(augmented_args->arg.value));
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len += oldpath_len + augmented_arg__read_str((void *)(&augmented_args->arg) + oldpath_len, newpath_arg, sizeof(augmented_args->arg.value));
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return augmented__output(args, augmented_args, len);
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}
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SEC("raw_syscalls:sys_enter")
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int sys_enter(struct syscall_enter_args *args)
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{
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struct augmented_args_payload *augmented_args;
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/*
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* We start len, the amount of data that will be in the perf ring
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* buffer, if this is not filtered out by one of pid_filter__has(),
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* syscall->enabled, etc, with the non-augmented raw syscall payload,
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* i.e. sizeof(augmented_args->args).
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*
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* We'll add to this as we add augmented syscalls right after that
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* initial, non-augmented raw_syscalls:sys_enter payload.
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*/
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unsigned int len = sizeof(augmented_args->args);
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struct syscall *syscall;
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if (pid_filter__has(&pids_filtered, getpid()))
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return 0;
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augmented_args = augmented_args_payload();
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if (augmented_args == NULL)
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return 1;
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probe_read(&augmented_args->args, sizeof(augmented_args->args), args);
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/*
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* Jump to syscall specific augmenter, even if the default one,
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* "!raw_syscalls:unaugmented" that will just return 1 to return the
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* unaugmented tracepoint payload.
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*/
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bpf_tail_call(args, &syscalls_sys_enter, augmented_args->args.syscall_nr);
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// If not found on the PROG_ARRAY syscalls map, then we're filtering it:
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return 0;
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}
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SEC("raw_syscalls:sys_exit")
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int sys_exit(struct syscall_exit_args *args)
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{
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struct syscall_exit_args exit_args;
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if (pid_filter__has(&pids_filtered, getpid()))
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return 0;
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probe_read(&exit_args, sizeof(exit_args), args);
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/*
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* Jump to syscall specific return augmenter, even if the default one,
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* "!raw_syscalls:unaugmented" that will just return 1 to return the
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* unaugmented tracepoint payload.
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*/
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bpf_tail_call(args, &syscalls_sys_exit, exit_args.syscall_nr);
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/*
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* If not found on the PROG_ARRAY syscalls map, then we're filtering it:
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*/
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return 0;
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}
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license(GPL);
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