TCG regions already have a guard page.
Signed-off-by: Emilio G. Cota <c...@braap.org>
---
accel/tcg/translate-all.c | 47 ++++++++++++-----------------------------------
1 file changed, 12 insertions(+), 35 deletions(-)
diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index c30d400..98aa63e 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -608,19 +608,11 @@ static uint8_t
static_code_gen_buffer[DEFAULT_CODE_GEN_BUFFER_SIZE]
static inline void *alloc_code_gen_buffer(void)
{
void *buf = static_code_gen_buffer;
- size_t full_size, size;
-
- /* The size of the buffer, rounded down to end on a page boundary. */
- full_size = (((uintptr_t)buf + sizeof(static_code_gen_buffer))
- & qemu_real_host_page_mask) - (uintptr_t)buf;
-
- /* Reserve a guard page. */
- size = full_size - qemu_real_host_page_size;
+ size_t size = sizeof(static_code_gen_buffer);
/* Honor a command-line option limiting the size of the buffer. */
if (size > tcg_ctx->code_gen_buffer_size) {
- size = (((uintptr_t)buf + tcg_ctx->code_gen_buffer_size)
- & qemu_real_host_page_mask) - (uintptr_t)buf;
+ size = tcg_ctx->code_gen_buffer_size;
}
tcg_ctx->code_gen_buffer_size = size;
@@ -634,9 +626,6 @@ static inline void *alloc_code_gen_buffer(void)
if (qemu_mprotect_rwx(buf, size)) {
abort();
}
- if (qemu_mprotect_none(buf + size, qemu_real_host_page_size)) {
- abort();
- }
qemu_madvise(buf, size, QEMU_MADV_HUGEPAGE);
return buf;
@@ -645,22 +634,16 @@ static inline void *alloc_code_gen_buffer(void)
static inline void *alloc_code_gen_buffer(void)
{
size_t size = tcg_ctx->code_gen_buffer_size;
- void *buf1, *buf2;
-
- /* Perform the allocation in two steps, so that the guard page
- is reserved but uncommitted. */
- buf1 = VirtualAlloc(NULL, size + qemu_real_host_page_size,
- MEM_RESERVE, PAGE_NOACCESS);
- if (buf1 != NULL) {
- buf2 = VirtualAlloc(buf1, size, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
- assert(buf1 == buf2);
- }
+ void *buf;
- return buf1;
+ buf = VirtualAlloc(NULL, size, MEM_RESERVE | MEM_COMMIT,
+ PAGE_EXECUTE_READWRITE);
+ return buf;
}
#else
static inline void *alloc_code_gen_buffer(void)
{
+ int prot = PROT_WRITE | PROT_READ | PROT_EXEC;
int flags = MAP_PRIVATE | MAP_ANONYMOUS;
uintptr_t start = 0;
size_t size = tcg_ctx->code_gen_buffer_size;
@@ -694,8 +677,7 @@ static inline void *alloc_code_gen_buffer(void)
# endif
# endif
- buf = mmap((void *)start, size + qemu_real_host_page_size,
- PROT_NONE, flags, -1, 0);
+ buf = mmap((void *)start, size, prot, flags, -1, 0);
if (buf == MAP_FAILED) {
return NULL;
}
@@ -705,24 +687,23 @@ static inline void *alloc_code_gen_buffer(void)
/* Try again, with the original still mapped, to avoid re-acquiring
that 256mb crossing. This time don't specify an address. */
size_t size2;
- void *buf2 = mmap(NULL, size + qemu_real_host_page_size,
- PROT_NONE, flags, -1, 0);
+ void *buf2 = mmap(NULL, size, prot, flags, -1, 0);
switch ((int)(buf2 != MAP_FAILED)) {
case 1:
if (!cross_256mb(buf2, size)) {
/* Success! Use the new buffer. */
- munmap(buf, size + qemu_real_host_page_size);
+ munmap(buf, size);
break;
}
/* Failure. Work with what we had. */
- munmap(buf2, size + qemu_real_host_page_size);
+ munmap(buf2, size);
/* fallthru */
default:
/* Split the original buffer. Free the smaller half. */
buf2 = split_cross_256mb(buf, size);
size2 = tcg_ctx->code_gen_buffer_size;
if (buf == buf2) {
- munmap(buf + size2 + qemu_real_host_page_size, size - size2);
+ munmap(buf + size2, size - size2);
} else {
munmap(buf, size - size2);
}
@@ -733,10 +714,6 @@ static inline void *alloc_code_gen_buffer(void)
}
#endif
- /* Make the final buffer accessible. The guard page at the end
- will remain inaccessible with PROT_NONE. */
- mprotect(buf, size, PROT_WRITE | PROT_READ | PROT_EXEC);
-
/* Request large pages for the buffer. */
qemu_madvise(buf, size, QEMU_MADV_HUGEPAGE);
--
2.7.4
