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Pull the pread/pwrite emulation code out into separate functions.
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@kmeisthax
kmeisthax committed Oct 25, 2021
1 parent 86956a9 commit d1ebd3b
Showing 1 changed file with 110 additions and 90 deletions.
200 changes: 110 additions & 90 deletions kernel/aio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -182,6 +182,114 @@ dword_t sys_io_cancel(dword_t ctx_id, addr_t iocb, addr_t result) {
return _ENOSYS;
}

/**
* Do a single PREAD operation, falling back to seek-and-read if necessary.
*
* The return code corresponds to the 'sync error' concept of fallback_submit,
* while async errors should be flagged by writing to *err.
*/
static signed int __aio_fallback_pread(
struct fd *fd,
addr_t guest_buf,
uint64_t nbytes,
int64_t offset,
signed int *err) {

if (nbytes > 0xFFFFFFFE) return _ENOMEM;

// Don't ask me why, but the sync I/O code null-terminates it's
// buffers, so I'm doing it here too.
char *buf = malloc(nbytes + 1);
if (buf == NULL) return _ENOMEM;

if (fd->ops->pread) {
*err = fd->ops->pread(fd, buf, nbytes, offset);
} else if (fd->ops->read && fd->ops->lseek) {
off_t_ saved_off = fd->ops->lseek(fd, 0, LSEEK_CUR);
if ((*err = fd->ops->lseek(fd, offset, LSEEK_SET))) goto fail_async;

ssize_t read_bytes = fd->ops->read(fd, buf, nbytes);

off_t_ seek_result = fd->ops->lseek(fd, saved_off, LSEEK_SET);
if (seek_result < 0) {
*err = seek_result;
goto fail_async;
}

*err = read_bytes;
} else {
goto fail_einval;
}

if (*err < 0) goto fail_async;

buf[*err] = '\0';
if (user_write(guest_buf, buf, *err)) goto fail_efault;

fail_async:
free(buf);
return 0;

fail_einval:
free(buf);
return _EINVAL;

fail_efault:
free(buf);
return _EFAULT;
}

/**
* Do a single PWRITE operation, falling back to seek-and-write if necessary.
*
* The return code corresponds to the 'sync error' concept of fallback_submit,
* while async errors should be flagged by writing to *err.
*/
static signed int __aio_fallback_pwrite(
struct fd *fd,
addr_t guest_buf,
uint64_t nbytes,
int64_t offset,
signed int *err) {

if (nbytes > 0xFFFFFFFE) return _ENOMEM;

char *buf = malloc(nbytes);
if (buf == NULL) return _ENOMEM;

if (user_read(guest_buf, buf, nbytes)) {
free(buf);
return _EFAULT;
}

ssize_t written_bytes;
if (fd->ops->pwrite) {
written_bytes = fd->ops->pwrite(fd, buf, nbytes, offset);
} else if (fd->ops->write && fd->ops->lseek) {
off_t_ saved_off = fd->ops->lseek(fd, 0, LSEEK_CUR);
if ((*err = fd->ops->lseek(fd, offset, LSEEK_SET))) {
goto fail_async;
}

written_bytes = fd->ops->write(fd, buf, nbytes);

off_t_ seek_result = fd->ops->lseek(fd, saved_off, LSEEK_SET);
if (seek_result < 0) {
*err = seek_result;
goto fail_async;
}
} else {
free(buf);
return _EINVAL;
}

*err = (signed int)written_bytes;

fail_async:
free(buf);
return 0;
}

int aio_fallback_submit(struct fd *fd, struct aioctx *ctx, unsigned int event_id) {
aioctx_lock(ctx);

Expand Down Expand Up @@ -211,98 +319,10 @@ int aio_fallback_submit(struct fd *fd, struct aioctx *ctx, unsigned int event_id
char *buf = NULL;
switch (evt->op) {
case AIOCTX_PREAD:
if (evt->nbytes > 0xFFFFFFFE) {
sync_err = _ENOMEM;
break;
}

// Don't ask me why, but the sync I/O code null-terminates it's
// buffers, so I'm doing it here too.
buf = malloc(evt->nbytes + 1);
if (buf == NULL) {
sync_err = _ENOMEM;
break;
}

if (fd->ops->pread) {
async_result0 = fd->ops->pread(fd, buf, evt->nbytes, evt->offset);
} else if (fd->ops->read && fd->ops->lseek) {
off_t_ saved_off = fd->ops->lseek(fd, 0, LSEEK_CUR);
if ((async_result0 = fd->ops->lseek(fd, evt->offset, LSEEK_SET))) {
free(buf);
break;
}

ssize_t read_bytes = fd->ops->read(fd, buf, evt->nbytes);

off_t_ seek_result = fd->ops->lseek(fd, saved_off, LSEEK_SET);
if (seek_result < 0) {
async_result0 = seek_result;
free(buf);
break;
}

async_result0 = read_bytes;
} else {
free(buf);
sync_err = _EINVAL;
break;
}

if (async_result0 < 0) {
free(buf);
break;
}

buf[async_result0] = '\0';
if (user_write((addr_t)evt->buf, buf, async_result0)) sync_err = _EFAULT;

free(buf);
sync_err = __aio_fallback_pread(fd, (addr_t)evt->buf, evt->nbytes, evt->offset, &async_result0);
break;
case AIOCTX_PWRITE:
if (evt->nbytes > 0xFFFFFFFE) {
sync_err = _ENOMEM;
break;
}

buf = malloc(evt->nbytes);
if (buf == NULL) {
sync_err = _ENOMEM;
break;
}

if (user_read((addr_t)evt->buf, buf, evt->nbytes)) {
free(buf);
sync_err = _EFAULT;
break;
}

ssize_t written_bytes;
if (fd->ops->pwrite) {
written_bytes = fd->ops->pwrite(fd, buf, evt->nbytes, evt->offset);
} else if (fd->ops->write && fd->ops->lseek) {
off_t_ saved_off = fd->ops->lseek(fd, 0, LSEEK_CUR);
if ((async_result0 = fd->ops->lseek(fd, evt->offset, LSEEK_SET))) {
free(buf);
break;
}

written_bytes = fd->ops->write(fd, buf, evt->nbytes);

off_t_ seek_result = fd->ops->lseek(fd, saved_off, LSEEK_SET);
if (seek_result < 0) {
async_result0 = seek_result;
free(buf);
break;
}
} else {
free(buf);
sync_err = _EINVAL;
break;
}

async_result0 = (signed int)written_bytes;
free(buf);
sync_err = __aio_fallback_pwrite(fd, (addr_t)evt->buf, evt->nbytes, evt->offset, &async_result0);
break;
case AIOCTX_FSYNC:
case AIOCTX_FDSYNC:
Expand Down

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