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Pre-allocate guest address space

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Allow pre-allocation of the guest virtual address space in usermode emulation.

Signed-off-by: Paul Brook <paul@codesourcery.com>
This commit is contained in:
Paul Brook 2010-05-29 02:27:35 +01:00
parent 0be1d07c0e
commit 68a1c81686
5 changed files with 183 additions and 8 deletions
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120
linux-user/mmap.c
View file

@ -216,6 +216,40 @@ static abi_ulong mmap_next_start = TASK_UNMAPPED_BASE;
unsigned long last_brk;
/* Subroutine of mmap_find_vma, used when we have pre-allocated a chunk
of guest address space. */
static abi_ulong mmap_find_vma_reserved(abi_ulong start, abi_ulong size)
{
abi_ulong addr;
abi_ulong last_addr;
int prot;
int looped = 0;
if (size > reserved_va) {
return (abi_ulong)-1;
}
last_addr = start;
for (addr = start; last_addr + size != addr; addr += qemu_host_page_size) {
if (last_addr + size >= reserved_va
|| (abi_ulong)(last_addr + size) < last_addr) {
if (looped) {
return (abi_ulong)-1;
}
last_addr = qemu_host_page_size;
addr = 0;
looped = 1;
continue;
}
prot = page_get_flags(addr);
if (prot) {
last_addr = addr + qemu_host_page_size;
}
}
mmap_next_start = addr;
return last_addr;
}
/*
* Find and reserve a free memory area of size 'size'. The search
* starts at 'start'.
@ -237,6 +271,10 @@ abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size)
size = HOST_PAGE_ALIGN(size);
if (reserved_va) {
return mmap_find_vma_reserved(start, size);
}
addr = start;
wrapped = repeat = 0;
prev = 0;
@ -525,6 +563,47 @@ fail:
return -1;
}
static void mmap_reserve(abi_ulong start, abi_ulong size)
{
abi_ulong real_start;
abi_ulong real_end;
abi_ulong addr;
abi_ulong end;
int prot;
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 */
prot = 0;
for (addr = real_start; addr < start; addr += TARGET_PAGE_SIZE) {
prot |= page_get_flags(addr);
}
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;
}
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);
}
if (prot != 0)
real_end -= qemu_host_page_size;
}
if (real_start != real_end) {
mmap(g2h(real_start), real_end - real_start, PROT_NONE,
MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE,
-1, 0);
}
}
int target_munmap(abi_ulong start, abi_ulong len)
{
abi_ulong end, real_start, real_end, addr;
@ -572,7 +651,11 @@ int target_munmap(abi_ulong start, abi_ulong len)
ret = 0;
/* unmap what we can */
if (real_start < real_end) {
ret = munmap(g2h(real_start), real_end - real_start);
if (reserved_va) {
mmap_reserve(real_start, real_end - real_start);
} else {
ret = munmap(g2h(real_start), real_end - real_start);
}
}
if (ret == 0)
@ -590,12 +673,18 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
mmap_lock();
if (flags & MREMAP_FIXED)
if (flags & MREMAP_FIXED) {
host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
old_size, new_size,
flags,
new_addr);
else if (flags & MREMAP_MAYMOVE) {
g2h(new_addr));
if (reserved_va && host_addr != MAP_FAILED) {
/* If new and old addresses overlap then the above mremap will
already have failed with EINVAL. */
mmap_reserve(old_addr, old_size);
}
} else if (flags & MREMAP_MAYMOVE) {
abi_ulong mmap_start;
mmap_start = mmap_find_vma(0, new_size);
@ -603,13 +692,32 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
if (mmap_start == -1) {
errno = ENOMEM;
host_addr = MAP_FAILED;
} else
} else {
host_addr = (void *) syscall(__NR_mremap, g2h(old_addr),
old_size, new_size,
flags | MREMAP_FIXED,
g2h(mmap_start));
mmap_reserve(old_addr, old_size);
}
} else {
host_addr = mremap(g2h(old_addr), old_size, new_size, flags);
int prot = 0;
if (reserved_va && old_size < new_size) {
abi_ulong addr;
for (addr = old_addr + old_size;
addr < old_addr + new_size;
addr++) {
prot |= page_get_flags(addr);
}
}
if (prot == 0) {
host_addr = mremap(g2h(old_addr), old_size, new_size, flags);
if (host_addr != MAP_FAILED && reserved_va && old_size > new_size) {
mmap_reserve(old_addr + old_size, new_size - old_size);
}
} else {
errno = ENOMEM;
host_addr = MAP_FAILED;
}
/* Check if address fits target address space */
if ((unsigned long)host_addr + new_size > (abi_ulong)-1) {
/* Revert mremap() changes */