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authorRichard Henderson <rth@twiddle.net>2015-09-19 12:03:15 -0700
committerRichard Henderson <rth@twiddle.net>2015-10-07 20:36:53 +1100
commitf293709c6af7a65a9bcec09cdba7a60183657a3e (patch)
tree89094383a37819e1498c993098b4e0cb79760ba7
parent8163b74938d8b7d12e70597c4553dd0dc49443d5 (diff)
downloadqemu-arm-f293709c6af7a65a9bcec09cdba7a60183657a3e.tar.gz
tcg: Allocate a guard page after code_gen_buffer
This will catch any overflow of the buffer. Add a native win32 alternative for alloc_code_gen_buffer; remove the malloc alternative. Signed-off-by: Richard Henderson <rth@twiddle.net>
-rw-r--r--translate-all.c210
1 files changed, 119 insertions, 91 deletions
diff --git a/translate-all.c b/translate-all.c
index 0e8d176de0..b43bd03654 100644
--- a/translate-all.c
+++ b/translate-all.c
@@ -312,31 +312,6 @@ bool cpu_restore_state(CPUState *cpu, uintptr_t retaddr)
return false;
}
-#ifdef _WIN32
-static __attribute__((unused)) void map_exec(void *addr, long size)
-{
- DWORD old_protect;
- VirtualProtect(addr, size,
- PAGE_EXECUTE_READWRITE, &old_protect);
-}
-#else
-static __attribute__((unused)) void map_exec(void *addr, long size)
-{
- unsigned long start, end, page_size;
-
- page_size = getpagesize();
- start = (unsigned long)addr;
- start &= ~(page_size - 1);
-
- end = (unsigned long)addr + size;
- end += page_size - 1;
- end &= ~(page_size - 1);
-
- mprotect((void *)start, end - start,
- PROT_READ | PROT_WRITE | PROT_EXEC);
-}
-#endif
-
void page_size_init(void)
{
/* NOTE: we can always suppose that qemu_host_page_size >=
@@ -473,14 +448,6 @@ static inline PageDesc *page_find(tb_page_addr_t index)
#define USE_STATIC_CODE_GEN_BUFFER
#endif
-/* ??? Should configure for this, not list operating systems here. */
-#if (defined(__linux__) \
- || defined(__FreeBSD__) || defined(__FreeBSD_kernel__) \
- || defined(__DragonFly__) || defined(__OpenBSD__) \
- || defined(__NetBSD__))
-# define USE_MMAP
-#endif
-
/* Minimum size of the code gen buffer. This number is randomly chosen,
but not so small that we can't have a fair number of TB's live. */
#define MIN_CODE_GEN_BUFFER_SIZE (1024u * 1024)
@@ -568,22 +535,102 @@ static inline void *split_cross_256mb(void *buf1, size_t size1)
static uint8_t static_code_gen_buffer[DEFAULT_CODE_GEN_BUFFER_SIZE]
__attribute__((aligned(CODE_GEN_ALIGN)));
+# ifdef _WIN32
+static inline void do_protect(void *addr, long size, int prot)
+{
+ DWORD old_protect;
+ VirtualProtect(addr, size, prot, &old_protect);
+}
+
+static inline void map_exec(void *addr, long size)
+{
+ do_protect(addr, size, PAGE_EXECUTE_READWRITE);
+}
+
+static inline void map_none(void *addr, long size)
+{
+ do_protect(addr, size, PAGE_NOACCESS);
+}
+# else
+static inline void do_protect(void *addr, long size, int prot)
+{
+ uintptr_t start, end;
+
+ start = (uintptr_t)addr;
+ start &= qemu_real_host_page_mask;
+
+ end = (uintptr_t)addr + size;
+ end = ROUND_UP(end, qemu_real_host_page_size);
+
+ mprotect((void *)start, end - start, prot);
+}
+
+static inline void map_exec(void *addr, long size)
+{
+ do_protect(addr, size, PROT_READ | PROT_WRITE | PROT_EXEC);
+}
+
+static inline void map_none(void *addr, long size)
+{
+ do_protect(addr, size, PROT_NONE);
+}
+# endif /* WIN32 */
+
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;
+
+ /* 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;
+ }
+ tcg_ctx.code_gen_buffer_size = size;
+
#ifdef __mips__
- if (cross_256mb(buf, tcg_ctx.code_gen_buffer_size)) {
- buf = split_cross_256mb(buf, tcg_ctx.code_gen_buffer_size);
+ if (cross_256mb(buf, size)) {
+ buf = split_cross_256mb(buf, size);
+ size = tcg_ctx.code_gen_buffer_size;
}
#endif
- map_exec(buf, tcg_ctx.code_gen_buffer_size);
+
+ map_exec(buf, size);
+ map_none(buf + size, qemu_real_host_page_size);
+ qemu_madvise(buf, size, QEMU_MADV_HUGEPAGE);
+
return buf;
}
-#elif defined(USE_MMAP)
+#elif defined(_WIN32)
+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);
+ }
+
+ return buf1;
+}
+#else
static inline void *alloc_code_gen_buffer(void)
{
int flags = MAP_PRIVATE | MAP_ANONYMOUS;
uintptr_t start = 0;
+ size_t size = tcg_ctx.code_gen_buffer_size;
void *buf;
/* Constrain the position of the buffer based on the host cpu.
@@ -599,86 +646,70 @@ static inline void *alloc_code_gen_buffer(void)
Leave the choice of exact location with the kernel. */
flags |= MAP_32BIT;
/* Cannot expect to map more than 800MB in low memory. */
- if (tcg_ctx.code_gen_buffer_size > 800u * 1024 * 1024) {
- tcg_ctx.code_gen_buffer_size = 800u * 1024 * 1024;
+ if (size > 800u * 1024 * 1024) {
+ tcg_ctx.code_gen_buffer_size = size = 800u * 1024 * 1024;
}
# elif defined(__sparc__)
start = 0x40000000ul;
# elif defined(__s390x__)
start = 0x90000000ul;
# elif defined(__mips__)
- /* ??? We ought to more explicitly manage layout for softmmu too. */
-# ifdef CONFIG_USER_ONLY
- start = 0x68000000ul;
-# elif _MIPS_SIM == _ABI64
+# if _MIPS_SIM == _ABI64
start = 0x128000000ul;
# else
start = 0x08000000ul;
# endif
# endif
- buf = mmap((void *)start, tcg_ctx.code_gen_buffer_size,
- PROT_WRITE | PROT_READ | PROT_EXEC, flags, -1, 0);
+ buf = mmap((void *)start, size + qemu_real_host_page_size,
+ PROT_NONE, flags, -1, 0);
if (buf == MAP_FAILED) {
return NULL;
}
#ifdef __mips__
- if (cross_256mb(buf, tcg_ctx.code_gen_buffer_size)) {
+ if (cross_256mb(buf, size)) {
/* Try again, with the original still mapped, to avoid re-acquiring
that 256mb crossing. This time don't specify an address. */
- size_t size2, size1 = tcg_ctx.code_gen_buffer_size;
- void *buf2 = mmap(NULL, size1, PROT_WRITE | PROT_READ | PROT_EXEC,
- flags, -1, 0);
- if (buf2 != MAP_FAILED) {
- if (!cross_256mb(buf2, size1)) {
+ size_t size2;
+ void *buf2 = mmap(NULL, size + qemu_real_host_page_size,
+ PROT_NONE, flags, -1, 0);
+ switch (buf2 != MAP_FAILED) {
+ case 1:
+ if (!cross_256mb(buf2, size)) {
/* Success! Use the new buffer. */
- munmap(buf, size1);
- return buf2;
+ munmap(buf, size);
+ break;
}
/* Failure. Work with what we had. */
- munmap(buf2, size1);
+ 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);
+ } else {
+ munmap(buf, size - size2);
+ }
+ size = size2;
+ break;
}
-
- /* Split the original buffer. Free the smaller half. */
- buf2 = split_cross_256mb(buf, size1);
- size2 = tcg_ctx.code_gen_buffer_size;
- munmap(buf + (buf == buf2 ? size2 : 0), size1 - size2);
- return buf2;
+ buf = buf2;
}
#endif
- return buf;
-}
-#else
-static inline void *alloc_code_gen_buffer(void)
-{
- void *buf = g_try_malloc(tcg_ctx.code_gen_buffer_size);
+ /* 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);
- if (buf == NULL) {
- return NULL;
- }
+ /* Request large pages for the buffer. */
+ qemu_madvise(buf, size, QEMU_MADV_HUGEPAGE);
-#ifdef __mips__
- if (cross_256mb(buf, tcg_ctx.code_gen_buffer_size)) {
- void *buf2 = g_malloc(tcg_ctx.code_gen_buffer_size);
- if (buf2 != NULL && !cross_256mb(buf2, size1)) {
- /* Success! Use the new buffer. */
- free(buf);
- buf = buf2;
- } else {
- /* Failure. Work with what we had. Since this is malloc
- and not mmap, we can't free the other half. */
- free(buf2);
- buf = split_cross_256mb(buf, tcg_ctx.code_gen_buffer_size);
- }
- }
-#endif
-
- map_exec(buf, tcg_ctx.code_gen_buffer_size);
return buf;
}
-#endif /* USE_STATIC_CODE_GEN_BUFFER, USE_MMAP */
+#endif /* USE_STATIC_CODE_GEN_BUFFER, WIN32, POSIX */
static inline void code_gen_alloc(size_t tb_size)
{
@@ -689,9 +720,6 @@ static inline void code_gen_alloc(size_t tb_size)
exit(1);
}
- qemu_madvise(tcg_ctx.code_gen_buffer, tcg_ctx.code_gen_buffer_size,
- QEMU_MADV_HUGEPAGE);
-
/* Estimate a good size for the number of TBs we can support. We
still haven't deducted the prologue from the buffer size here,
but that's minimal and won't affect the estimate much. */
@@ -708,8 +736,8 @@ static inline void code_gen_alloc(size_t tb_size)
void tcg_exec_init(unsigned long tb_size)
{
cpu_gen_init();
- code_gen_alloc(tb_size);
page_init();
+ code_gen_alloc(tb_size);
#if defined(CONFIG_SOFTMMU)
/* There's no guest base to take into account, so go ahead and
initialize the prologue now. */