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linux-user: Rewrite mmap_reserve

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Use 'last' variables instead of 'end' variables; be careful
about avoiding overflow.  Assert that the mmap succeeded.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230707204054.8792-21-richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2023-07-07 21:40:48 +01:00
parent f9cd8f5eca
commit 260561d873
1 changed files with 42 additions and 26 deletions
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68
linux-user/mmap.c
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@ -722,47 +722,63 @@ fail:
return -1;
}
static void mmap_reserve(abi_ulong start, abi_ulong size)
static void mmap_reserve(abi_ulong start, abi_ulong len)
{
abi_ulong real_start;
abi_ulong real_end;
abi_ulong addr;
abi_ulong end;
abi_ulong real_last;
abi_ulong real_len;
abi_ulong last;
abi_ulong a;
void *host_start, *ptr;
int prot;
last = start + len - 1;
real_start = start & qemu_host_page_mask;
real_end = HOST_PAGE_ALIGN(start + size);
end = start + size;
if (start > real_start) {
/* handle host page containing start */
real_last = HOST_PAGE_ALIGN(last) - 1;
/*
* If guest pages remain on the first or last host pages,
* adjust the deallocation to retain those guest pages.
* The single page special case is required for the last page,
* lest real_start overflow to zero.
*/
if (real_last - real_start < qemu_host_page_size) {
prot = 0;
for (addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
prot |= page_get_flags(addr);
for (a = real_start; a < start; a += TARGET_PAGE_SIZE) {
prot |= page_get_flags(a);
}
if (real_end == real_start + qemu_host_page_size) {
for (addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
prot |= page_get_flags(addr);
}
end = real_end;
for (a = last; a < real_last; a += TARGET_PAGE_SIZE) {
prot |= page_get_flags(a + 1);
}
if (prot != 0) {
return;
}
} else {
for (prot = 0, a = real_start; a < start; a += TARGET_PAGE_SIZE) {
prot |= page_get_flags(a);
}
if (prot != 0) {
real_start += qemu_host_page_size;
}
}
if (end < real_end) {
prot = 0;
for (addr = end; addr < real_end; addr += TARGET_PAGE_SIZE) {
prot |= page_get_flags(addr);
for (prot = 0, a = last; a < real_last; a += TARGET_PAGE_SIZE) {
prot |= page_get_flags(a + 1);
}
if (prot != 0) {
real_end -= qemu_host_page_size;
real_last -= qemu_host_page_size;
}
if (real_last < real_start) {
return;
}
}
if (real_start != real_end) {
mmap(g2h_untagged(real_start), real_end - real_start, PROT_NONE,
MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE,
-1, 0);
}
real_len = real_last - real_start + 1;
host_start = g2h_untagged(real_start);
ptr = mmap(host_start, real_len, PROT_NONE,
MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE, -1, 0);
assert(ptr == host_start);
}
int target_munmap(abi_ulong start, abi_ulong len)