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linux-user: Rewrite target_mprotect 

Use 'last' variables instead of 'end' variables.
When host page size > guest page size, detect when
adjacent host pages have the same protection and
merge that expanded host range into fewer syscalls.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230707204054.8792-15-richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2023-07-07 21:40:42 +01:00
parent 55baec0f4c
commit 7bdc1acc24
1 changed files with 67 additions and 39 deletions
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106
linux-user/mmap.c
View File

@ -120,8 +120,11 @@ static int target_to_host_prot(int prot)
/* NOTE: all the constants are the HOST ones, but addresses are target. */
int target_mprotect(abi_ulong start, abi_ulong len, int target_prot)
{
abi_ulong end, host_start, host_end, addr;
int prot1, ret, page_flags;
abi_ulong starts[3];
abi_ulong lens[3];
int prots[3];
abi_ulong host_start, host_last, last;
int prot1, ret, page_flags, nranges;
trace_target_mprotect(start, len, target_prot);
@ -132,63 +135,88 @@ int target_mprotect(abi_ulong start, abi_ulong len, int target_prot)
if (!page_flags) {
return -TARGET_EINVAL;
}
len = TARGET_PAGE_ALIGN(len);
end = start + len;
if (!guest_range_valid_untagged(start, len)) {
return -TARGET_ENOMEM;
}
if (len == 0) {
return 0;
}
len = TARGET_PAGE_ALIGN(len);
if (!guest_range_valid_untagged(start, len)) {
return -TARGET_ENOMEM;
}
last = start + len - 1;
host_start = start & qemu_host_page_mask;
host_last = HOST_PAGE_ALIGN(last) - 1;
nranges = 0;
mmap_lock();
host_start = start & qemu_host_page_mask;
host_end = HOST_PAGE_ALIGN(end);
if (start > host_start) {
/* handle host page containing start */
if (host_last - host_start < qemu_host_page_size) {
/* Single host page contains all guest pages: sum the prot. */
prot1 = target_prot;
for (addr = host_start; addr < start; addr += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(addr);
for (abi_ulong a = host_start; a < start; a += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(a);
}
if (host_end == host_start + qemu_host_page_size) {
for (addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(addr);
for (abi_ulong a = last; a < host_last; a += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(a + 1);
}
starts[nranges] = host_start;
lens[nranges] = qemu_host_page_size;
prots[nranges] = prot1;
nranges++;
} else {
if (host_start < start) {
/* Host page contains more than one guest page: sum the prot. */
prot1 = target_prot;
for (abi_ulong a = host_start; a < start; a += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(a);
}
/* If the resulting sum differs, create a new range. */
if (prot1 != target_prot) {
starts[nranges] = host_start;
lens[nranges] = qemu_host_page_size;
prots[nranges] = prot1;
nranges++;
host_start += qemu_host_page_size;
}
end = host_end;
}
ret = mprotect(g2h_untagged(host_start), qemu_host_page_size,
target_to_host_prot(prot1));
if (ret != 0) {
goto error;
if (last < host_last) {
/* Host page contains more than one guest page: sum the prot. */
prot1 = target_prot;
for (abi_ulong a = last; a < host_last; a += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(a + 1);
}
/* If the resulting sum differs, create a new range. */
if (prot1 != target_prot) {
host_last -= qemu_host_page_size;
starts[nranges] = host_last + 1;
lens[nranges] = qemu_host_page_size;
prots[nranges] = prot1;
nranges++;
}
}
host_start += qemu_host_page_size;
}
if (end < host_end) {
prot1 = target_prot;
for (addr = end; addr < host_end; addr += TARGET_PAGE_SIZE) {
prot1 |= page_get_flags(addr);
/* Create a range for the middle, if any remains. */
if (host_start < host_last) {
starts[nranges] = host_start;
lens[nranges] = host_last - host_start + 1;
prots[nranges] = target_prot;
nranges++;
}
ret = mprotect(g2h_untagged(host_end - qemu_host_page_size),
qemu_host_page_size, target_to_host_prot(prot1));
if (ret != 0) {
goto error;
}
host_end -= qemu_host_page_size;
}
/* handle the pages in the middle */
if (host_start < host_end) {
ret = mprotect(g2h_untagged(host_start), host_end - host_start,
target_to_host_prot(target_prot));
for (int i = 0; i < nranges; ++i) {
ret = mprotect(g2h_untagged(starts[i]), lens[i],
target_to_host_prot(prots[i]));
if (ret != 0) {
goto error;
}
}
page_set_flags(start, start + len - 1, page_flags);
page_set_flags(start, last, page_flags);
ret = 0;
error:
error:
mmap_unlock();
return ret;
}