[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[PULL 1/6] bsd-user/freebsd/os-syscall.c: lock_iovec
From: |
Warner Losh |
Subject: |
[PULL 1/6] bsd-user/freebsd/os-syscall.c: lock_iovec |
Date: |
Sat, 11 Jun 2022 07:55:09 -0600 |
lock_iovec will lock an I/O vec and the memory to which it refers and
create a iovec in the host space that refers to it, with full error
unwinding. Add helper_iovec_unlock to unlock the partially locked iovec
in case there's an error. The code will be used in iovec_unlock when
that is committed.
Note: memory handling likely could be rewritten to use q_autofree. That
will be explored in the future since what we have now works well enough.
Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
bsd-user/freebsd/os-syscall.c | 102 ++++++++++++++++++++++++++++++++++
1 file changed, 102 insertions(+)
diff --git a/bsd-user/freebsd/os-syscall.c b/bsd-user/freebsd/os-syscall.c
index d272478e7b0..67851937a8f 100644
--- a/bsd-user/freebsd/os-syscall.c
+++ b/bsd-user/freebsd/os-syscall.c
@@ -73,6 +73,108 @@ bool is_error(abi_long ret)
return (abi_ulong)ret >= (abi_ulong)(-4096);
}
+/*
+ * Unlocks a iovec. Unlike unlock_iovec, it assumes the tvec array itself is
+ * already locked from target_addr. It will be unlocked as well as all the
iovec
+ * elements.
+ */
+static void helper_unlock_iovec(struct target_iovec *target_vec,
+ abi_ulong target_addr, struct iovec *vec,
+ int count, int copy)
+{
+ for (int i = 0; i < count; i++) {
+ abi_ulong base = tswapal(target_vec[i].iov_base);
+
+ if (vec[i].iov_base) {
+ unlock_user(vec[i].iov_base, base, copy ? vec[i].iov_len : 0);
+ }
+ }
+ unlock_user(target_vec, target_addr, 0);
+}
+
+struct iovec *lock_iovec(int type, abi_ulong target_addr,
+ int count, int copy)
+{
+ struct target_iovec *target_vec;
+ struct iovec *vec;
+ abi_ulong total_len, max_len;
+ int i;
+ int err = 0;
+
+ if (count == 0) {
+ errno = 0;
+ return NULL;
+ }
+ if (count < 0 || count > IOV_MAX) {
+ errno = EINVAL;
+ return NULL;
+ }
+
+ vec = g_try_new0(struct iovec, count);
+ if (vec == NULL) {
+ errno = ENOMEM;
+ return NULL;
+ }
+
+ target_vec = lock_user(VERIFY_READ, target_addr,
+ count * sizeof(struct target_iovec), 1);
+ if (target_vec == NULL) {
+ err = EFAULT;
+ goto fail2;
+ }
+
+ max_len = 0x7fffffff & MIN(TARGET_PAGE_MASK, PAGE_MASK);
+ total_len = 0;
+
+ for (i = 0; i < count; i++) {
+ abi_ulong base = tswapal(target_vec[i].iov_base);
+ abi_long len = tswapal(target_vec[i].iov_len);
+
+ if (len < 0) {
+ err = EINVAL;
+ goto fail;
+ } else if (len == 0) {
+ /* Zero length pointer is ignored. */
+ vec[i].iov_base = 0;
+ } else {
+ vec[i].iov_base = lock_user(type, base, len, copy);
+ /*
+ * If the first buffer pointer is bad, this is a fault. But
+ * subsequent bad buffers will result in a partial write; this is
+ * realized by filling the vector with null pointers and zero
+ * lengths.
+ */
+ if (!vec[i].iov_base) {
+ if (i == 0) {
+ err = EFAULT;
+ goto fail;
+ } else {
+ /*
+ * Fail all the subsequent addresses, they are already
+ * zero'd.
+ */
+ goto out;
+ }
+ }
+ if (len > max_len - total_len) {
+ len = max_len - total_len;
+ }
+ }
+ vec[i].iov_len = len;
+ total_len += len;
+ }
+out:
+ unlock_user(target_vec, target_addr, 0);
+ return vec;
+
+fail:
+ helper_unlock_iovec(target_vec, target_addr, vec, i, copy);
+fail2:
+ g_free(vec);
+ errno = err;
+ return NULL;
+}
+
/*
* do_syscall() should always have a single exit point at the end so that
* actions, such as logging of syscall results, can be performed. All errnos
--
2.33.1
- [PULL 0/6] Bsd user preen 2022q2 patches, Warner Losh, 2022/06/11
- [PULL 1/6] bsd-user/freebsd/os-syscall.c: lock_iovec,
Warner Losh <=
- [PULL 2/6] bsd-user/freebsd/os-syscall.c: unlock_iovec, Warner Losh, 2022/06/11
- [PULL 5/6] bsd-user/bsd-file.h: Meat of the write system calls, Warner Losh, 2022/06/11
- [PULL 6/6] bsd-user/freebsd/os-syscall.c: Implement exit, Warner Losh, 2022/06/11
- [PULL 4/6] bsd-user/bsd-file.h: Add implementations for read, pread, readv and preadv, Warner Losh, 2022/06/11
- [PULL 3/6] bsd-user/freebsd/os-syscall.c: Tracing and error boilerplate, Warner Losh, 2022/06/11
- Re: [PULL 0/6] Bsd user preen 2022q2 patches, Richard Henderson, 2022/06/12