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> --- v2: https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg00146.html Changes since v2: - Wrapped pthread_jit_write_protect_np() with __builtin_available() [1] to allow build with modern SDK while targeting older macOS (Joelle) - Dropped redundant calls to pthread_jit_write_protect_supported_np() (Alex) 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 [2]. - 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://developer.apple.com/videos/play/wwdc2017/411/ 2. https://bugs.webkit.org/attachment.cgi?id=402515&action=prettypatch accel/tcg/cpu-exec.c | 2 ++ accel/tcg/translate-all.c | 9 +++++++++ include/qemu/osdep.h | 7 +++++++ tcg/tcg.c | 1 + util/osdep.c | 20 ++++++++++++++++++++ 5 files changed, 39 insertions(+) diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c index e0df9b6a1d..014810bf0a 100644 --- a/accel/tcg/cpu-exec.c +++ b/accel/tcg/cpu-exec.c @@ -185,6 +185,7 @@ cpu_tb_exec(CPUState *cpu, TranslationBlock *itb, int *tb_exit) } #endif /* DEBUG_DISAS */ + qemu_thread_jit_execute(); ret = tcg_qemu_tb_exec(env, tb_ptr); cpu->can_do_io = 1; /* @@ -405,6 +406,7 @@ 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 e9de6ff9dd..f5f4c7cc17 100644 --- a/accel/tcg/translate-all.c +++ b/accel/tcg/translate-all.c @@ -1083,6 +1083,12 @@ static bool alloc_code_gen_buffer_anon(size_t size, int prot, { void *buf; +#if defined(MAC_OS_VERSION_11_0) && \ + MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_VERSION_11_0 + if (__builtin_available(macOS 11.0, *)) { + flags |= MAP_JIT; + } +#endif buf = mmap(NULL, size, prot, flags, -1, 0); if (buf == MAP_FAILED) { error_setg_errno(errp, errno, @@ -1669,7 +1675,9 @@ 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 @@ -1871,6 +1879,7 @@ 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..929e970b0e 100644 --- a/include/qemu/osdep.h +++ b/include/qemu/osdep.h @@ -123,6 +123,10 @@ extern int daemon(int, int); #include "sysemu/os-posix.h" #endif +#ifdef __APPLE__ +#include <AvailabilityMacros.h> +#endif + #include "glib-compat.h" #include "qemu/typedefs.h" @@ -686,4 +690,7 @@ 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 472bf1755b..16b044eae7 100644 --- a/tcg/tcg.c +++ b/tcg/tcg.c @@ -1112,6 +1112,7 @@ 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..e211939a0c 100644 --- a/util/osdep.c +++ b/util/osdep.c @@ -606,3 +606,23 @@ writev(int fd, const struct iovec *iov, int iov_cnt) return readv_writev(fd, iov, iov_cnt, true); } #endif + +#if defined(MAC_OS_VERSION_11_0) && \ + MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_VERSION_11_0 +void qemu_thread_jit_execute(void) +{ + if (__builtin_available(macOS 11.0, *)) { + pthread_jit_write_protect_np(true); + } +} + +void qemu_thread_jit_write(void) +{ + if (__builtin_available(macOS 11.0, *)) { + pthread_jit_write_protect_np(false); + } +} +#else +void qemu_thread_jit_write(void) {} +void qemu_thread_jit_execute(void) {} +#endif -- 2.30.0
