#!/bin/bash -e

bt=/usr/bin/bpftrace

default_allow_filter=$(cat << EOF
{
    	scmp_filter_ctx ctx;
    
    	ctx = seccomp_init(SCMP_ACT_ALLOW);
    	seccomp_load(ctx);
    	seccomp_release(ctx);
}
EOF
)

default_block_filter=$(cat << EOF
{
    	scmp_filter_ctx ctx;
    
    	ctx = seccomp_init(SCMP_ACT_KILL);
    	for (int i = 0; i < num_syscalls; i++) {
    		seccomp_rule_add(ctx, SCMP_ACT_ALLOW,
    				 seccomp_syscall_resolve_name(syscalls[i]), 0);
    	}
    	seccomp_load(ctx);
    	seccomp_release(ctx);
}
EOF
)

allow_uretprobe_filter=$(cat << EOF
{
    	scmp_filter_ctx ctx;
    
    	ctx = seccomp_init(SCMP_ACT_KILL);
    	for (int i = 0; i < num_syscalls; i++) {
    		seccomp_rule_add(ctx, SCMP_ACT_ALLOW,
    				 seccomp_syscall_resolve_name(syscalls[i]), 0);
    	}
    	seccomp_rule_add(ctx, SCMP_ACT_ALLOW, 335, 0);
    	seccomp_load(ctx);
    	seccomp_release(ctx);
}
EOF
)

block_uretprobe_filter=$(cat << EOF
{
    	scmp_filter_ctx ctx;
    
    	ctx = seccomp_init(SCMP_ACT_ALLOW);
    	seccomp_rule_add(ctx, SCMP_ACT_KILL, 335, 0);
    	seccomp_load(ctx);
    	seccomp_release(ctx);
}
EOF
)

t()
{
    with_uretprobe=$1;
    filter_name=$2;
    filter=${!filter_name};

    echo "Test: uretprobe $with_uretprobe, filter $filter_name"

    cat > /tmp/x.c << EOF
    #include <stdio.h>
    #include <seccomp.h>
    
    char *syscalls[] = {
    	"exit_group",
    };
    
    __attribute__((noinline)) int probed(void)
    {
    	return 1;
    }
    
    void apply_seccomp_filter(char **syscalls, int num_syscalls)
	$filter
    
    int main(int argc, char *argv[])
    {
    	int num_syscalls = sizeof(syscalls) / sizeof(syscalls[0]);
    
    	apply_seccomp_filter(syscalls, num_syscalls);
    
    	probed();
    
    	return 0;
    }
EOF
    
    cat > /tmp/trace.bt << EOF
    uretprobe:/tmp/x:probed
    {
        printf("ret=%d\n", retval);
    }
EOF
    
    gcc -o /tmp/x /tmp/x.c -lseccomp
    
    $with_uretprobe && {
	$bt /tmp/trace.bt &
	btpid=$!
        sleep 5 # wait for uretprobe attach
    }
    
    /tmp/x
    
    $with_uretprobe && kill $btpid
    
    rm /tmp/x /tmp/x.c /tmp/trace.bt
}

t false "default_allow_filter"
t true "default_allow_filter"
t false "default_block_filter"
t true "default_block_filter"
t false "allow_uretprobe_filter"
t true "allow_uretprobe_filter"
t false "block_uretprobe_filter"
t true "block_uretprobe_filter"