lind_syscall.c

#include <errno.h>
#include <stdint.h> // For uint64_t definition
#include "addr_translation.h"
#include "lind_syscall_num.h"
#include "lind_constants.h"

// Entry point for wasmtime, lind_syscall is an imported function from wasmtime
int __lind_make_syscall_trampoline(unsigned int callnumber, 
    uint64_t callname, 
    uint64_t self_cageid, uint64_t target_cageid,
    uint64_t arg1, uint64_t arg1cageid,
    uint64_t arg2, uint64_t arg2cageid,
    uint64_t arg3, uint64_t arg3cageid,
    uint64_t arg4, uint64_t arg4cageid,
    uint64_t arg5, uint64_t arg5cageid,
    uint64_t arg6, uint64_t arg6cageid
) __attribute__((
    __import_module__("lind"),
    __import_name__("make-syscall")
));

/*
 * make_threei_call:
 *
 * Unified function used to invoke threei style syscalls.  This is the
 * core entry point for all syscall transitions into the lind runtime,
 * including inter-cage calls and grates.  Unlike MAKE_LEGACY_SYSCALL, this function
 * explicitly specifies both `self_cageid` and `target_cageid`, allowing
 * fine-grained routing of syscalls across cage boundaries.
 *
 * Each logical argument is passed in a (value, cageid) pair, enabling
 * three-i's interposition layer to perform selective rewriting, mediation,
 * or redirection.  The final argument, `translate_errno`, determines whether
 * lind_syscall should apply standard POSIX errno translation or return
 * the raw trampoline result directly.
 *
 * make_threei_call is designed to be the **canonical** macro for all new
 * inter-cage or grate-level syscall invocations.  Grates and higher-level
 * components should call make_threei_call directly rather than relying on
 * MAKE_LEGACY_SYSCALL.
 *
 * This function acts as the middle layer between:
 *   (1) the MAKE_LEGACY_SYSCALL macros in glibc, and
 *   (2) the actual Wasmtime entry function (__lind_make_syscall_trampoline).
 *
 * It forwards all syscall parameters—including the inter-cage metadata
 * (self_cageid, target_cageid, argX_cageid pairs) to the underlying
 * trampoline, but also optionally performs post-processing on the return
 * value depending on `translate_errno`.
 *
 * The `translate_errno` controls whether this wrapper should apply the standard
 * errno handling:
 *
 *   translate_errno == 1 (TRANSLATE_ERRNO_ON):
 *       The return value is treated as a complete syscall result.
 *       Negative values in the range [-255, -1] are interpreted as
 *       `-errno`, errno is set accordingly, and the wrapper returns -1.
 *       All other values are returned directly.
 *
 *   translate_errno == 0 (TRANSLATE_ERRNO_OFF):
 *       The wrapper does *not* apply any errno translation.
 *       The raw return value from the trampoline is returned as-is.
 *
 * This distinction is required because some syscalls—especially futex-related
 * operations (e.g., lll_futex_wake, lll_futex_requeue, etc.) expect the
 * trampoline to return raw -errno value and must not receive additional errno 
 * post-processing at this layer. Other syscalls, however, rely on the standard 
 * POSIX errno translation implemented here.
 */
int make_threei_call (unsigned int callnumber, 
    uint64_t callname, 
    uint64_t self_cageid, uint64_t target_cageid,
    uint64_t arg1, uint64_t arg1cageid,
    uint64_t arg2, uint64_t arg2cageid,
    uint64_t arg3, uint64_t arg3cageid,
    uint64_t arg4, uint64_t arg4cageid,
    uint64_t arg5, uint64_t arg5cageid,
    uint64_t arg6, uint64_t arg6cageid,
    int translate_errno)
{
    int ret = __lind_make_syscall_trampoline(callnumber, 
        callname, 
        self_cageid, target_cageid,
        TRANSLATE_ARG_TO_HOST(arg1, arg1cageid),
        TRANSLATE_ARG_TO_HOST(arg2, arg2cageid),
        TRANSLATE_ARG_TO_HOST(arg3, arg3cageid),
        TRANSLATE_ARG_TO_HOST(arg4, arg4cageid),
        TRANSLATE_ARG_TO_HOST(arg5, arg5cageid),
        TRANSLATE_ARG_TO_HOST(arg6, arg6cageid));

    // if translate_errno is not enabled, we do not do any further process to errno handling and directly return the result
    if(translate_errno == TRANSLATE_ERRNO_OFF) return ret;
    // handle the errno
    // in rawposix, we use -errno as the return value to indicate the error
    // but this may cause some issues for mmap syscall, because mmap syscall
    // is returning an 32-bit address, which may overflow the int type (i32)
    // luckily we can handle this easily because the return value of mmap is always
    // multiple of pages (typically 4096) even when overflow, therefore we can distinguish
    // the errno and mmap result by simply checking if the return value is
    // within the valid errno range
    if(ret < 0 && ret > -MAX_ERRNO)
    {
        errno = -ret;
        return -1;
    }
    else
    {
        errno = 0;
    }
    return ret;
}

// ---------------------------------------------------------------------------------------------------------------------

// 3i function call to register or deregister a syscall handler in a target cage
// targetcage: the cage id where the syscall will be registered
// targetcallnum: the syscall number to be registered in the target cage
// this_grate_id: the grate id of the syscall jump ends
// register_flag: deregister(0) or register(non-0)
// in_grate_fn_ptr_u64: the function pointer (cast to uint64_t) of the syscall handler in the grate, only used when register_flag is non-0
int register_handler (int64_t targetcage, 
    uint64_t targetcallnum, 
    uint64_t this_grate_id,
    uint64_t in_grate_fn_ptr_u64)
{
    return make_threei_call(
        REGISTER_HANDLER_SYSCALL, 
        NOTUSED, // callname is not used in the trampoline
        targetcage, // pass targetcage as self_cageid
        targetcage, // pass targetcage as target_cageid. Self_cageid and target_cageid are the same to adapt with regular make_syscall lookup logic in 3i
        targetcage, 
        targetcallnum, 
        NOTUSED, // runtime_id currently not used
        this_grate_id, // handlefunccage is the grate id of the handler function, which is the same as this_grate_id
        in_grate_fn_ptr_u64,
        NOTUSED, NOTUSED, NOTUSED, NOTUSED, NOTUSED, NOTUSED, NOTUSED,
        TRANSLATE_ERRNO_OFF /* do not translate errno: return the raw result */
    );
}

// ---------------------------------------------------------------------------------------------------------------------

// 3i function call to copy data between cages
// thiscage: the cage id of the caller cage
// targetcage: the cage id of the target cage
// srcaddr: the source address to copy from
// srccage: the cage id of the source address
// destaddr: the destination address to copy to
// destcage: the cage id of the destination address
// len: the length of data to copy
// copytype: the type of copy, 0 for normal copy, 1 for string copy
int copy_data_between_cages(uint64_t thiscage, uint64_t targetcage, uint64_t srcaddr, uint64_t srccage, uint64_t destaddr, uint64_t destcage, uint64_t len, uint64_t copytype)
{
    return make_threei_call(
        COPY_DATA_BETWEEN_CAGES_SYSCALL, 
        NOTUSED, // callname is not used in the trampoline
        thiscage, // self_cageid
        thiscage, // target_cageid. Self_cageid and target_cageid are the same to adapt with regular make_syscall lookup logic in 3i
        TRANSLATE_UADDR_TO_HOST(srcaddr, srccage),
        TRANSLATE_UADDR_TO_HOST(destaddr, destcage),
        len, NOTUSED,
        copytype, NOTUSED,
        NOTUSED, NOTUSED, NOTUSED, NOTUSED,
        TRANSLATE_ERRNO_OFF /* do not translate errno: return the raw result */
    );
}

// 3i function call to copy handler table to a target cage
// typically used when a new cage is created and we need to copy the syscall handler 
// table from another cage (has the handlers different than default rawposix registration) 
// to the new cage
// thiscage: the cage id of the caller cage
// targetcage: the cage id of the target cage
int copy_handler_table_to_cage(uint64_t thiscage, uint64_t targetcage)
{
    return make_threei_call(
        COPY_HANDLER_TABLE_TO_CAGE_SYSCALL, 
        NOTUSED, // callname is not used in the trampoline
        thiscage, // self_cageid
        thiscage, // target_cageid. Self_cageid and target_cageid are the same to adapt with regular make_syscall lookup logic in 3i
        thiscage, 
        targetcage,
        NOTUSED, NOTUSED,
        NOTUSED, NOTUSED,
        NOTUSED, NOTUSED,
        NOTUSED, NOTUSED,
        NOTUSED, NOTUSED,
        TRANSLATE_ERRNO_OFF /* do not translate errno: return the raw result */
    );
}