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Re: [PATCH v2] tcg: Fix execution on Apple Silicon
From: |
Joelle van Dyne |
Subject: |
Re: [PATCH v2] tcg: Fix execution on Apple Silicon |
Date: |
Mon, 4 Jan 2021 18:02:50 -0800 |
Tested-by: Joelle van Dyne <j@getutm.app>
It works for me. But one thing is that if you build it with the macOS
11.x SDK it won't run on < 11.x. This is why apple recommends
something like:
if (__builtin_available(macOS 11, *)) {
pthread_jit_write_protect_np();
}
You still need a compile time check like MAC_OS_VERSION_11_0 to
support linking with older SDKs.
On Sun, Jan 3, 2021 at 6:54 AM Roman Bolshakov <r.bolshakov@yadro.com> wrote:
>
> 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.bolshakov@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
>