// SPDX-License-Identifier: GPL-2.0
/*
* Augment the raw_syscalls tracepoints with the contents of the pointer arguments.
*
* This exactly matches what is marshalled into the raw_syscall:sys_enter
* payload expected by the 'perf trace' beautifiers.
*/
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <linux/limits.h>
/**
* is_power_of_2() - check if a value is a power of two
* @n: the value to check
*
* Determine whether some value is a power of two, where zero is *not*
* considered a power of two. Return: true if @n is a power of 2, otherwise
* false.
*/
#define is_power_of_2(n) (n != 0 && ((n & (n - 1)) == 0))
#define MAX_CPUS 4096
/* bpf-output associated map */
struct __augmented_syscalls__ {
__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
__type(key, int);
__type(value, __u32);
__uint(max_entries, MAX_CPUS);
} __augmented_syscalls__ SEC(".maps");
/*
* What to augment at entry?
*
* Pointer arg payloads (filenames, etc) passed from userspace to the kernel
*/
struct syscalls_sys_enter {
__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
__type(key, __u32);
__type(value, __u32);
__uint(max_entries, 512);
} syscalls_sys_enter SEC(".maps");
/*
* What to augment at exit?
*
* Pointer arg payloads returned from the kernel (struct stat, etc) to userspace.
*/
struct syscalls_sys_exit {
__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
__type(key, __u32);
__type(value, __u32);
__uint(max_entries, 512);
} syscalls_sys_exit SEC(".maps");
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];
};
struct pids_filtered {
__uint(type, BPF_MAP_TYPE_HASH);
__type(key, pid_t);
__type(value, bool);
__uint(max_entries, 64);
} pids_filtered SEC(".maps");
/*
* Desired design of maximum size and alignment (see RFC2553)
*/
#define SS_MAXSIZE 128 /* Implementation specific max size */
typedef unsigned short sa_family_t;
/*
* FIXME: Should come from system headers
*
* The definition uses anonymous union and struct in order to control the
* default alignment.
*/
struct sockaddr_storage {
union {
struct {
sa_family_t ss_family; /* address family */
/* Following field(s) are implementation specific */
char __data[SS_MAXSIZE - sizeof(unsigned short)];
/* space to achieve desired size, */
/* _SS_MAXSIZE value minus size of ss_family */
};
void *__align; /* implementation specific desired alignment */
};
};
struct augmented_args_payload {
struct syscall_enter_args args;
union {
struct {
struct augmented_arg arg, arg2;
};
struct sockaddr_storage saddr;
char __data[sizeof(struct augmented_arg)];
};
};
// We need more tmp space than the BPF stack can give us
struct augmented_args_tmp {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__type(key, int);
__type(value, struct augmented_args_payload);
__uint(max_entries, 1);
} augmented_args_tmp SEC(".maps");
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 bpf_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 = bpf_probe_read_user_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;
_Static_assert(is_power_of_2(sizeof(augmented_arg->value)), "sizeof(augmented_arg->value) needs to be a power of two");
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("tp/raw_syscalls/sys_enter")
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("tp/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 */
_Static_assert(is_power_of_2(sizeof(augmented_args->saddr)), "sizeof(augmented_args->saddr) needs to be a power of two");
socklen &= sizeof(augmented_args->saddr) - 1;
bpf_probe_read_user(&augmented_args->saddr, socklen, sockaddr_arg);
return augmented__output(args, augmented_args, len + socklen);
}
SEC("tp/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 */
socklen &= sizeof(augmented_args->saddr) - 1;
bpf_probe_read_user(&augmented_args->saddr, socklen, sockaddr_arg);
return augmented__output(args, augmented_args, len + socklen);
}
SEC("tp/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("tp/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("tp/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("tp/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);
}
#define PERF_ATTR_SIZE_VER0 64 /* sizeof first published struct */
// we need just the start, get the size to then copy it
struct perf_event_attr_size {
__u32 type;
/*
* Size of the attr structure, for fwd/bwd compat.
*/
__u32 size;
};
SEC("tp/syscalls/sys_enter_perf_event_open")
int sys_enter_perf_event_open(struct syscall_enter_args *args)
{
struct augmented_args_payload *augmented_args = augmented_args_payload();
const struct perf_event_attr_size *attr = (const struct perf_event_attr_size *)args->args[0], *attr_read;
unsigned int len = sizeof(augmented_args->args);
if (augmented_args == NULL)
goto failure;
if (bpf_probe_read_user(&augmented_args->__data, sizeof(*attr), attr) < 0)
goto failure;
attr_read = (const struct perf_event_attr_size *)augmented_args->__data;
__u32 size = attr_read->size;
if (!size)
size = PERF_ATTR_SIZE_VER0;
if (size > sizeof(augmented_args->__data))
goto failure;
// Now that we read attr->size and tested it against the size limits, read it completely
if (bpf_probe_read_user(&augmented_args->__data, size, attr) < 0)
goto failure;
return augmented__output(args, augmented_args, len + size);
failure:
return 1; /* Failure: don't filter */
}
SEC("tp/syscalls/sys_enter_clock_nanosleep")
int sys_enter_clock_nanosleep(struct syscall_enter_args *args)
{
struct augmented_args_payload *augmented_args = augmented_args_payload();
const void *rqtp_arg = (const void *)args->args[2];
unsigned int len = sizeof(augmented_args->args);
__u32 size = sizeof(struct timespec64);
if (augmented_args == NULL)
goto failure;
if (size > sizeof(augmented_args->__data))
goto failure;
bpf_probe_read_user(&augmented_args->__data, size, rqtp_arg);
return augmented__output(args, augmented_args, len + size);
failure:
return 1; /* Failure: don't filter */
}
SEC("tp/syscalls/sys_enter_nanosleep")
int sys_enter_nanosleep(struct syscall_enter_args *args)
{
struct augmented_args_payload *augmented_args = augmented_args_payload();
const void *req_arg = (const void *)args->args[0];
unsigned int len = sizeof(augmented_args->args);
__u32 size = sizeof(struct timespec64);
if (augmented_args == NULL)
goto failure;
if (size > sizeof(augmented_args->__data))
goto failure;
bpf_probe_read_user(&augmented_args->__data, size, req_arg);
return augmented__output(args, augmented_args, len + size);
failure:
return 1; /* Failure: don't filter */
}
static pid_t getpid(void)
{
return bpf_get_current_pid_tgid();
}
static bool pid_filter__has(struct pids_filtered *pids, pid_t pid)
{
return bpf_map_lookup_elem(pids, &pid) != NULL;
}
SEC("tp/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.
*/
if (pid_filter__has(&pids_filtered, getpid()))
return 0;
augmented_args = augmented_args_payload();
if (augmented_args == NULL)
return 1;
bpf_probe_read_kernel(&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
* unaugmented 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("tp/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;
bpf_probe_read_kernel(&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
* unaugmented 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;
}
char _license[] SEC("license") = "GPL";
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