linux/tools/perf/examples/bpf/augmented_raw_syscalls.c

295 lines
9.0 KiB
C

// 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 <unistd.h>
#include <linux/limits.h>
#include <linux/socket.h>
#include <pid_filter.h>
/* 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_arg {
unsigned int size;
int err;
char value[PATH_MAX];
};
pid_filter(pids_filtered);
struct augmented_args_payload {
struct syscall_enter_args args;
union {
struct {
struct augmented_arg arg, arg2;
};
struct sockaddr_storage saddr;
};
};
// We need more tmp space than the BPF stack can give us
bpf_map(augmented_args_tmp, PERCPU_ARRAY, int, struct augmented_args_payload, 1);
static inline struct augmented_args_payload *augmented_args_payload(void)
{
int key = 0;
return bpf_map_lookup_elem(&augmented_args_tmp, &key);
}
static inline int augmented__output(void *ctx, struct augmented_args_payload *args, int len)
{
/* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */
return perf_event_output(ctx, &__augmented_syscalls__, BPF_F_CURRENT_CPU, args, len);
}
static inline
unsigned int augmented_arg__read_str(struct augmented_arg *augmented_arg, const void *arg, unsigned int arg_len)
{
unsigned int augmented_len = sizeof(*augmented_arg);
int string_len = probe_read_str(&augmented_arg->value, arg_len, arg);
augmented_arg->size = augmented_arg->err = 0;
/*
* probe_read_str may return < 0, e.g. -EFAULT
* So we leave that in the augmented_arg->size that userspace will
*/
if (string_len > 0) {
augmented_len -= sizeof(augmented_arg->value) - string_len;
augmented_len &= sizeof(augmented_arg->value) - 1;
augmented_arg->size = string_len;
} else {
/*
* So that username notice the error while still being able
* to skip this augmented arg record
*/
augmented_arg->err = string_len;
augmented_len = offsetof(struct augmented_arg, value);
}
return augmented_len;
}
SEC("!raw_syscalls:unaugmented")
int syscall_unaugmented(struct syscall_enter_args *args)
{
return 1;
}
/*
* These 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_connect")
int sys_enter_connect(struct syscall_enter_args *args)
{
struct augmented_args_payload *augmented_args = augmented_args_payload();
const void *sockaddr_arg = (const void *)args->args[1];
unsigned int socklen = args->args[2];
unsigned int len = sizeof(augmented_args->args);
if (augmented_args == NULL)
return 1; /* Failure: don't filter */
if (socklen > sizeof(augmented_args->saddr))
socklen = sizeof(augmented_args->saddr);
probe_read(&augmented_args->saddr, socklen, sockaddr_arg);
return augmented__output(args, augmented_args, len + socklen);
}
SEC("!syscalls:sys_enter_sendto")
int sys_enter_sendto(struct syscall_enter_args *args)
{
struct augmented_args_payload *augmented_args = augmented_args_payload();
const void *sockaddr_arg = (const void *)args->args[4];
unsigned int socklen = args->args[5];
unsigned int len = sizeof(augmented_args->args);
if (augmented_args == NULL)
return 1; /* Failure: don't filter */
if (socklen > sizeof(augmented_args->saddr))
socklen = sizeof(augmented_args->saddr);
probe_read(&augmented_args->saddr, socklen, sockaddr_arg);
return augmented__output(args, augmented_args, len + socklen);
}
SEC("!syscalls:sys_enter_open")
int sys_enter_open(struct syscall_enter_args *args)
{
struct augmented_args_payload *augmented_args = augmented_args_payload();
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_arg__read_str(&augmented_args->arg, filename_arg, sizeof(augmented_args->arg.value));
return augmented__output(args, augmented_args, len);
}
SEC("!syscalls:sys_enter_openat")
int sys_enter_openat(struct syscall_enter_args *args)
{
struct augmented_args_payload *augmented_args = augmented_args_payload();
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_arg__read_str(&augmented_args->arg, filename_arg, sizeof(augmented_args->arg.value));
return augmented__output(args, augmented_args, len);
}
SEC("!syscalls:sys_enter_rename")
int sys_enter_rename(struct syscall_enter_args *args)
{
struct augmented_args_payload *augmented_args = augmented_args_payload();
const void *oldpath_arg = (const void *)args->args[0],
*newpath_arg = (const void *)args->args[1];
unsigned int len = sizeof(augmented_args->args), oldpath_len;
if (augmented_args == NULL)
return 1; /* Failure: don't filter */
oldpath_len = augmented_arg__read_str(&augmented_args->arg, oldpath_arg, sizeof(augmented_args->arg.value));
len += oldpath_len + augmented_arg__read_str((void *)(&augmented_args->arg) + oldpath_len, newpath_arg, sizeof(augmented_args->arg.value));
return augmented__output(args, augmented_args, len);
}
SEC("!syscalls:sys_enter_renameat")
int sys_enter_renameat(struct syscall_enter_args *args)
{
struct augmented_args_payload *augmented_args = augmented_args_payload();
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_arg__read_str(&augmented_args->arg, oldpath_arg, sizeof(augmented_args->arg.value));
len += oldpath_len + augmented_arg__read_str((void *)(&augmented_args->arg) + oldpath_len, newpath_arg, sizeof(augmented_args->arg.value));
return augmented__output(args, 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;
if (pid_filter__has(&pids_filtered, getpid()))
return 0;
augmented_args = augmented_args_payload();
if (augmented_args == NULL)
return 1;
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);