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linux-user: Split out mmap_h_gt_g
Signed-off-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org> Acked-by: Helge Deller <deller@gmx.de> Message-Id: <20240102015808.132373-24-richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson
parent
8080b2f804
commit
eb5027ac61
@ -282,7 +282,16 @@ static int do_munmap(void *addr, size_t len)
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return munmap(addr, len);
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}
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/* map an incomplete host page */
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/*
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* Map an incomplete host page.
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*
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* Here be dragons. This case will not work if there is an existing
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* overlapping host page, which is file mapped, and for which the mapping
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* is beyond the end of the file. In that case, we will see SIGBUS when
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* trying to write a portion of this page.
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*
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* FIXME: Work around this with a temporary signal handler and longjmp.
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*/
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static bool mmap_frag(abi_ulong real_start, abi_ulong start, abi_ulong last,
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int prot, int flags, int fd, off_t offset)
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{
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@ -719,19 +728,138 @@ static abi_long mmap_h_lt_g(abi_ulong start, abi_ulong len, int host_prot,
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return mmap_end(start, last, start, pass_last, mmap_flags, page_flags);
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}
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/*
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* Special case host page size > target page size.
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*
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* The two special cases are address and file offsets that are valid
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* for the guest that cannot be directly represented by the host.
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*/
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static abi_long mmap_h_gt_g(abi_ulong start, abi_ulong len,
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int target_prot, int host_prot,
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int flags, int page_flags, int fd,
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off_t offset, int host_page_size)
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{
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void *p, *want_p = g2h_untagged(start);
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off_t host_offset = offset & -host_page_size;
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abi_ulong last, real_start, real_last;
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bool misaligned_offset = false;
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size_t host_len;
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if (!(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
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/*
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* Adjust the offset to something representable on the host.
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*/
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host_len = len + offset - host_offset;
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p = mmap(want_p, host_len, host_prot, flags, fd, host_offset);
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if (p == MAP_FAILED) {
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return -1;
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}
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/* Update start to the file position at offset. */
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p += offset - host_offset;
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start = h2g(p);
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last = start + len - 1;
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return mmap_end(start, last, start, last, flags, page_flags);
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}
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if (!(flags & MAP_ANONYMOUS)) {
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misaligned_offset = (start ^ offset) & (host_page_size - 1);
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/*
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* The fallback for misalignment is a private mapping + read.
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* This carries none of semantics required of MAP_SHARED.
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*/
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if (misaligned_offset && (flags & MAP_TYPE) != MAP_PRIVATE) {
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errno = EINVAL;
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return -1;
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}
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}
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last = start + len - 1;
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real_start = start & -host_page_size;
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real_last = ROUND_UP(last, host_page_size) - 1;
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/*
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* Handle the start and end of the mapping.
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*/
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if (real_start < start) {
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abi_ulong real_page_last = real_start + host_page_size - 1;
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if (last <= real_page_last) {
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/* Entire allocation a subset of one host page. */
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if (!mmap_frag(real_start, start, last, target_prot,
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flags, fd, offset)) {
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return -1;
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}
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return mmap_end(start, last, -1, 0, flags, page_flags);
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}
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if (!mmap_frag(real_start, start, real_page_last, target_prot,
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flags, fd, offset)) {
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return -1;
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}
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real_start = real_page_last + 1;
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}
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if (last < real_last) {
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abi_ulong real_page_start = real_last - host_page_size + 1;
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if (!mmap_frag(real_page_start, real_page_start, last,
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target_prot, flags, fd,
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offset + real_page_start - start)) {
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return -1;
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}
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real_last = real_page_start - 1;
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}
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if (real_start > real_last) {
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return mmap_end(start, last, -1, 0, flags, page_flags);
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}
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/*
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* Handle the middle of the mapping.
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*/
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host_len = real_last - real_start + 1;
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want_p += real_start - start;
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if (flags & MAP_ANONYMOUS) {
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p = mmap(want_p, host_len, host_prot, flags, -1, 0);
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} else if (!misaligned_offset) {
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p = mmap(want_p, host_len, host_prot, flags, fd,
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offset + real_start - start);
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} else {
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p = mmap(want_p, host_len, host_prot | PROT_WRITE,
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flags | MAP_ANONYMOUS, -1, 0);
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}
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if (p != want_p) {
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if (p != MAP_FAILED) {
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do_munmap(p, host_len);
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errno = EEXIST;
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}
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return -1;
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}
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if (misaligned_offset) {
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/* TODO: The read could be short. */
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if (pread(fd, p, host_len, offset + real_start - start) != host_len) {
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do_munmap(p, host_len);
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return -1;
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}
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if (!(host_prot & PROT_WRITE)) {
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mprotect(p, host_len, host_prot);
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}
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}
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return mmap_end(start, last, -1, 0, flags, page_flags);
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}
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static abi_long target_mmap__locked(abi_ulong start, abi_ulong len,
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int target_prot, int flags, int page_flags,
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int fd, off_t offset)
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{
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int host_page_size = qemu_real_host_page_size();
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abi_ulong ret, last, real_start, real_last, retaddr, host_len;
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abi_ulong passthrough_start = -1, passthrough_last = 0;
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off_t host_offset;
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int host_prot;
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real_start = start & -host_page_size;
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host_offset = offset & -host_page_size;
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/*
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* For reserved_va, we are in full control of the allocation.
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* Find a suitable hole and convert to MAP_FIXED.
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@ -745,6 +873,8 @@ static abi_long target_mmap__locked(abi_ulong start, abi_ulong len,
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}
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flags = (flags & ~MAP_FIXED_NOREPLACE) | MAP_FIXED;
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} else if (!(flags & MAP_FIXED)) {
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abi_ulong real_start = start & -host_page_size;
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off_t host_offset = offset & -host_page_size;
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size_t real_len = len + offset - host_offset;
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abi_ulong align = MAX(host_page_size, TARGET_PAGE_SIZE);
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@ -766,150 +896,10 @@ static abi_long target_mmap__locked(abi_ulong start, abi_ulong len,
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} else if (host_page_size < TARGET_PAGE_SIZE) {
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return mmap_h_lt_g(start, len, host_prot, flags,
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page_flags, fd, offset, host_page_size);
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}
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if (!(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
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uintptr_t host_start;
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void *p;
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host_len = len + offset - host_offset;
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host_len = ROUND_UP(host_len, host_page_size);
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/* Note: we prefer to control the mapping address. */
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p = mmap(g2h_untagged(start), host_len, host_prot,
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flags | MAP_FIXED | MAP_ANONYMOUS, -1, 0);
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if (p == MAP_FAILED) {
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return -1;
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}
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/* update start so that it points to the file position at 'offset' */
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host_start = (uintptr_t)p;
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if (!(flags & MAP_ANONYMOUS)) {
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p = mmap(g2h_untagged(start), len, host_prot,
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flags | MAP_FIXED, fd, host_offset);
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if (p == MAP_FAILED) {
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do_munmap(g2h_untagged(start), host_len);
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return -1;
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}
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host_start += offset - host_offset;
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}
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start = h2g(host_start);
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last = start + len - 1;
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passthrough_start = start;
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passthrough_last = last;
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} else {
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last = start + len - 1;
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real_last = ROUND_UP(last, host_page_size) - 1;
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if (flags & MAP_FIXED_NOREPLACE) {
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/* Validate that the chosen range is empty. */
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if (!page_check_range_empty(start, last)) {
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errno = EEXIST;
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return -1;
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}
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/*
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* With reserved_va, the entire address space is mmaped in the
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* host to ensure it isn't accidentally used for something else.
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* We have just checked that the guest address is not mapped
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* within the guest, but need to replace the host reservation.
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*
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* Without reserved_va, despite the guest address check above,
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* keep MAP_FIXED_NOREPLACE so that the guest does not overwrite
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* any host address mappings.
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*/
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if (reserved_va) {
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flags = (flags & ~MAP_FIXED_NOREPLACE) | MAP_FIXED;
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}
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}
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/*
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* worst case: we cannot map the file because the offset is not
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* aligned, so we read it
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*/
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if (!(flags & MAP_ANONYMOUS) &&
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(offset & (host_page_size - 1)) != (start & (host_page_size - 1))) {
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/*
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* msync() won't work here, so we return an error if write is
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* possible while it is a shared mapping
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*/
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if ((flags & MAP_TYPE) == MAP_SHARED
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&& (target_prot & PROT_WRITE)) {
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errno = EINVAL;
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return -1;
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}
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retaddr = target_mmap(start, len, target_prot | PROT_WRITE,
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(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))
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| MAP_PRIVATE | MAP_ANONYMOUS,
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-1, 0);
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if (retaddr == -1) {
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return -1;
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}
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if (pread(fd, g2h_untagged(start), len, offset) == -1) {
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return -1;
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}
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if (!(target_prot & PROT_WRITE)) {
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ret = target_mprotect(start, len, target_prot);
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assert(ret == 0);
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}
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return mmap_end(start, last, -1, 0, flags, page_flags);
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}
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/* handle the start of the mapping */
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if (start > real_start) {
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if (real_last == real_start + host_page_size - 1) {
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/* one single host page */
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if (!mmap_frag(real_start, start, last,
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target_prot, flags, fd, offset)) {
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return -1;
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}
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return mmap_end(start, last, -1, 0, flags, page_flags);
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}
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if (!mmap_frag(real_start, start,
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real_start + host_page_size - 1,
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target_prot, flags, fd, offset)) {
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return -1;
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}
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real_start += host_page_size;
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}
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/* handle the end of the mapping */
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if (last < real_last) {
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abi_ulong real_page = real_last - host_page_size + 1;
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if (!mmap_frag(real_page, real_page, last,
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target_prot, flags, fd,
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offset + real_page - start)) {
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return -1;
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}
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real_last -= host_page_size;
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}
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/* map the middle (easier) */
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if (real_start < real_last) {
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void *p, *want_p;
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off_t offset1;
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size_t len1;
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if (flags & MAP_ANONYMOUS) {
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offset1 = 0;
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} else {
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offset1 = offset + real_start - start;
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}
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len1 = real_last - real_start + 1;
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want_p = g2h_untagged(real_start);
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p = mmap(want_p, len1, host_prot, flags, fd, offset1);
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if (p != want_p) {
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if (p != MAP_FAILED) {
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do_munmap(p, len1);
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errno = EEXIST;
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}
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return -1;
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}
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passthrough_start = real_start;
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passthrough_last = real_last;
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}
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return mmap_h_gt_g(start, len, target_prot, host_prot, flags,
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page_flags, fd, offset, host_page_size);
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}
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return mmap_end(start, last, passthrough_start, passthrough_last,
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flags, page_flags);
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}
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/* NOTE: all the constants are the HOST ones */
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