Pages can't be both write and executable at the same time on Apple Silicon. macOS provides public API to switch write protection [1] for JIT applications, like TCG.
1. https://developer.apple.com/documentation/apple_silicon/porting_just-in-time_compilers_to_apple_silicon Signed-off-by: Roman Bolshakov <r.bolsha...@yadro.com> --- v1: https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg00073.html Changes since v1: - Pruned not needed fiddling with W^X and dropped symmetry from write lock/unlock and renamed related functions. Similar approach is used in JavaScriptCore [1]. - Moved jit helper functions to util/osdep As outlined in osdep.h, this matches to (2): * In an ideal world this header would contain only: * (1) things which everybody needs * (2) things without which code would work on most platforms but * fail to compile or misbehave on a minority of host OSes - Fixed a checkpatch error - Limit new behaviour only to macOS 11.0 and above, because of the following declarations: __API_AVAILABLE(macos(11.0)) __API_UNAVAILABLE(ios, tvos, watchos) void pthread_jit_write_protect_np(int enabled); __API_AVAILABLE(macos(11.0)) __API_UNAVAILABLE(ios, tvos, watchos) int pthread_jit_write_protect_supported_np(void); 1. https://bugs.webkit.org/attachment.cgi?id=402515&action=prettypatch accel/tcg/cpu-exec.c | 2 ++ accel/tcg/translate-all.c | 6 ++++++ include/qemu/osdep.h | 3 +++ tcg/tcg.c | 1 + util/osdep.c | 22 ++++++++++++++++++++++ 5 files changed, 34 insertions(+) diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c index 8689c54499..374060eb45 100644 --- a/accel/tcg/cpu-exec.c +++ b/accel/tcg/cpu-exec.c @@ -175,6 +175,7 @@ static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, TranslationBlock *itb) } #endif /* DEBUG_DISAS */ + qemu_thread_jit_execute(); ret = tcg_qemu_tb_exec(env, tb_ptr); cpu->can_do_io = 1; last_tb = (TranslationBlock *)(ret & ~TB_EXIT_MASK); @@ -382,6 +383,7 @@ static inline void tb_add_jump(TranslationBlock *tb, int n, { uintptr_t old; + qemu_thread_jit_write(); assert(n < ARRAY_SIZE(tb->jmp_list_next)); qemu_spin_lock(&tb_next->jmp_lock); diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c index b7d50a73d4..88ae5d35ef 100644 --- a/accel/tcg/translate-all.c +++ b/accel/tcg/translate-all.c @@ -1072,6 +1072,9 @@ static inline void *alloc_code_gen_buffer(void) size_t size = tcg_ctx->code_gen_buffer_size; void *buf; +#if defined(__APPLE__) && defined(MAC_OS_VERSION_11_0) + flags |= MAP_JIT; +#endif buf = mmap(NULL, size, prot, flags, -1, 0); if (buf == MAP_FAILED) { return NULL; @@ -1485,7 +1488,9 @@ static void do_tb_phys_invalidate(TranslationBlock *tb, bool rm_from_page_list) static void tb_phys_invalidate__locked(TranslationBlock *tb) { + qemu_thread_jit_write(); do_tb_phys_invalidate(tb, true); + qemu_thread_jit_execute(); } /* invalidate one TB @@ -1687,6 +1692,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu, #endif assert_memory_lock(); + qemu_thread_jit_write(); phys_pc = get_page_addr_code(env, pc); diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h index f9ec8c84e9..89abebcf5d 100644 --- a/include/qemu/osdep.h +++ b/include/qemu/osdep.h @@ -686,4 +686,7 @@ char *qemu_get_host_name(Error **errp); */ size_t qemu_get_host_physmem(void); +void qemu_thread_jit_write(void); +void qemu_thread_jit_execute(void); + #endif diff --git a/tcg/tcg.c b/tcg/tcg.c index 43c6cf8f52..ab8488f5d5 100644 --- a/tcg/tcg.c +++ b/tcg/tcg.c @@ -1065,6 +1065,7 @@ void tcg_prologue_init(TCGContext *s) s->pool_labels = NULL; #endif + qemu_thread_jit_write(); /* Generate the prologue. */ tcg_target_qemu_prologue(s); diff --git a/util/osdep.c b/util/osdep.c index 66d01b9160..80ec7185da 100644 --- a/util/osdep.c +++ b/util/osdep.c @@ -606,3 +606,25 @@ writev(int fd, const struct iovec *iov, int iov_cnt) return readv_writev(fd, iov, iov_cnt, true); } #endif + +#if defined(__APPLE__) && defined(MAC_OS_VERSION_11_0) +static inline void qemu_thread_jit_write_protect(bool enabled) +{ + if (pthread_jit_write_protect_supported_np()) { + pthread_jit_write_protect_np(enabled); + } +} + +void qemu_thread_jit_execute(void) +{ + qemu_thread_jit_write_protect(true); +} + +void qemu_thread_jit_write(void) +{ + qemu_thread_jit_write_protect(false); +} +#else +void qemu_thread_jit_write(void) {} +void qemu_thread_jit_execute(void) {} +#endif -- 2.29.2