// 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
         * 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("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
         * 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;
}

license(GPL);