@@ -222,73 +222,76 @@ int target_mprotect(abi_ulong start, abi_ulong len, int target_prot)
}
/* map an incomplete host page */
-static int mmap_frag(abi_ulong real_start,
- abi_ulong start, abi_ulong end,
- int prot, int flags, int fd, off_t offset)
+static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last,
+ int prot, int flags, int fd, off_t offset)
{
- abi_ulong real_end, addr;
+ abi_ulong real_last;
void *host_start;
- int prot1, prot_new;
+ int prot_old, prot_new;
+ int host_prot_old, host_prot_new;
- real_end = real_start + qemu_host_page_size;
- host_start = g2h_untagged(real_start);
-
- /* get the protection of the target pages outside the mapping */
- prot1 = 0;
- for (addr = real_start; addr < real_end; addr++) {
- if (addr < start || addr >= end) {
- prot1 |= page_get_flags(addr);
- }
+ if (!(flags & MAP_ANONYMOUS)
+ && (flags & MAP_TYPE) == MAP_SHARED
+ && (prot & PROT_WRITE)) {
+ /*
+ * msync() won't work with the partial page, so we return an
+ * error if write is possible while it is a shared mapping.
+ */
+ errno = EINVAL;
+ return false;
}
- if (prot1 == 0) {
- /* no page was there, so we allocate one */
+ real_last = real_start + qemu_host_page_size - 1;
+ host_start = g2h_untagged(real_start);
+
+ /* Get the protection of the target pages outside the mapping. */
+ prot_old = 0;
+ for (abi_ulong a = real_start; a < start; a += TARGET_PAGE_SIZE) {
+ prot_old |= page_get_flags(a);
+ }
+ for (abi_ulong a = real_last; a > last; a -= TARGET_PAGE_SIZE) {
+ prot_old |= page_get_flags(a);
+ }
+
+ if (prot_old == 0) {
+ /*
+ * Since !(prot_old & PAGE_VALID), there were no guest pages
+ * outside of the fragment we need to map. Allocate a new host
+ * page to cover, discarding whatever else may have been present.
+ */
void *p = mmap(host_start, qemu_host_page_size,
target_to_host_prot(prot),
flags | MAP_ANONYMOUS, -1, 0);
if (p == MAP_FAILED) {
- return -1;
+ return false;
}
- prot1 = prot;
+ prot_old = prot;
}
- prot1 &= PAGE_BITS;
+ prot_new = prot | prot_old;
- prot_new = prot | prot1;
- if (!(flags & MAP_ANONYMOUS)) {
- /*
- * msync() won't work here, so we return an error if write is
- * possible while it is a shared mapping.
- */
- if ((flags & MAP_TYPE) == MAP_SHARED && (prot & PROT_WRITE)) {
- return -1;
- }
+ host_prot_old = target_to_host_prot(prot_old);
+ host_prot_new = target_to_host_prot(prot_new);
- /* adjust protection to be able to read */
- if (!(prot1 & PROT_WRITE)) {
- mprotect(host_start, qemu_host_page_size,
- target_to_host_prot(prot1) | PROT_WRITE);
- }
+ /* Adjust protection to be able to write. */
+ if (!(host_prot_old & PROT_WRITE)) {
+ host_prot_old |= PROT_WRITE;
+ mprotect(host_start, qemu_host_page_size, host_prot_old);
+ }
- /* read the corresponding file data */
- if (pread(fd, g2h_untagged(start), end - start, offset) == -1) {
- return -1;
- }
-
- /* put final protection */
- if (prot_new != (prot1 | PROT_WRITE)) {
- mprotect(host_start, qemu_host_page_size,
- target_to_host_prot(prot_new));
- }
+ /* Read or zero the new guest pages. */
+ if (flags & MAP_ANONYMOUS) {
+ memset(g2h_untagged(start), 0, last - start + 1);
} else {
- if (prot_new != prot1) {
- mprotect(host_start, qemu_host_page_size,
- target_to_host_prot(prot_new));
- }
- if (prot_new & PROT_WRITE) {
- memset(g2h_untagged(start), 0, end - start);
+ if (pread(fd, g2h_untagged(start), last - start + 1, offset) == -1) {
+ return false;
}
}
- return 0;
+
+ /* Put final protection */
+ if (host_prot_new != host_prot_old) {
+ mprotect(host_start, qemu_host_page_size, host_prot_new);
+ }
+ return true;
}
#if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64
@@ -681,27 +684,25 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
if (start > real_start) {
if (real_end == real_start + qemu_host_page_size) {
/* one single host page */
- ret = mmap_frag(real_start, start, end,
- target_prot, flags, fd, offset);
- if (ret == -1) {
+ if (!mmap_frag(real_start, start, end - 1,
+ target_prot, flags, fd, offset)) {
goto fail;
}
goto the_end1;
}
- ret = mmap_frag(real_start, start, real_start + qemu_host_page_size,
- target_prot, flags, fd, offset);
- if (ret == -1) {
+ if (!mmap_frag(real_start, start,
+ real_start + qemu_host_page_size - 1,
+ target_prot, flags, fd, offset)) {
goto fail;
}
real_start += qemu_host_page_size;
}
/* handle the end of the mapping */
if (end < real_end) {
- ret = mmap_frag(real_end - qemu_host_page_size,
- real_end - qemu_host_page_size, end,
- target_prot, flags, fd,
- offset + real_end - qemu_host_page_size - start);
- if (ret == -1) {
+ if (!mmap_frag(real_end - qemu_host_page_size,
+ real_end - qemu_host_page_size, end - 1,
+ target_prot, flags, fd,
+ offset + real_end - qemu_host_page_size - start)) {
goto fail;
}
real_end -= qemu_host_page_size;
Use 'last' variables instead of 'end' variables. Always zero MAP_ANONYMOUS fragments, which we previously failed to do if they were not writable; early exit in case we allocate a new page from the kernel, known zeros. Signed-off-by: Richard Henderson <richard.henderson@linaro.org> Message-Id: <20230707204054.8792-16-richard.henderson@linaro.org> --- linux-user/mmap.c | 123 +++++++++++++++++++++++----------------------- 1 file changed, 62 insertions(+), 61 deletions(-)