On 13/10/20 01:29, Joelle van Dyne wrote:
> From: osy <os...@users.noreply.github.com>
>
> https://developer.apple.com/documentation/apple_silicon/porting_just-in-time_compilers_to_apple_silicon
>
> For < iOS 14, reverse engineered functions from libsystem_pthread.dylib is
> implemented to handle APRR supported SoCs.
>
> The following rules apply for JIT write protect:
> * JIT write-protect is enabled before tcg_qemu_tb_exec()
> * JIT write-protect is disabled after tcg_qemu_tb_exec() returns
> * JIT write-protect is disabled inside do_tb_phys_invalidate() but if it
> is called inside of tcg_qemu_tb_exec() then write-protect will be
> enabled again before returning.
> * JIT write-protect is disabled by cpu_loop_exit() for interrupt handling.
> * JIT write-protect is disabled everywhere else.
>
> Signed-off-by: Joelle van Dyne <j...@getutm.app>
Can this be emulated somehow on other platforms (such as Linux) so that
it does not bitrot?
Paolo
> ---
> accel/tcg/cpu-exec-common.c | 2 +
> accel/tcg/cpu-exec.c | 2 +
> accel/tcg/translate-all.c | 51 ++++++++++++++++++++++
> configure | 20 +++++++++
> include/exec/exec-all.h | 2 +
> include/tcg/tcg-apple-jit.h | 85 +++++++++++++++++++++++++++++++++++++
> include/tcg/tcg.h | 3 ++
> tcg/tcg.c | 4 ++
> 8 files changed, 169 insertions(+)
> create mode 100644 include/tcg/tcg-apple-jit.h
>
> diff --git a/accel/tcg/cpu-exec-common.c b/accel/tcg/cpu-exec-common.c
> index 12c1e3e974..f1eb767b02 100644
> --- a/accel/tcg/cpu-exec-common.c
> +++ b/accel/tcg/cpu-exec-common.c
> @@ -64,6 +64,8 @@ void cpu_reloading_memory_map(void)
>
> void cpu_loop_exit(CPUState *cpu)
> {
> + /* Unlock JIT write protect if applicable. */
> + tb_exec_unlock();
> /* Undo the setting in cpu_tb_exec. */
> cpu->can_do_io = 1;
> siglongjmp(cpu->jmp_env, 1);
> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> index 821aefdea2..d00d17f3c6 100644
> --- a/accel/tcg/cpu-exec.c
> +++ b/accel/tcg/cpu-exec.c
> @@ -175,7 +175,9 @@ static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu,
> TranslationBlock *itb)
> }
> #endif /* DEBUG_DISAS */
>
> + tb_exec_lock();
> ret = tcg_qemu_tb_exec(env, tb_ptr);
> + tb_exec_unlock();
> cpu->can_do_io = 1;
> last_tb = (TranslationBlock *)(ret & ~TB_EXIT_MASK);
> tb_exit = ret & TB_EXIT_MASK;
> diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
> index de9b7d9ab6..98daabbfc0 100644
> --- a/accel/tcg/translate-all.c
> +++ b/accel/tcg/translate-all.c
> @@ -27,6 +27,9 @@
> #include "disas/disas.h"
> #include "exec/exec-all.h"
> #include "tcg/tcg.h"
> +#if defined(CONFIG_DARWIN)
> +#include "tcg/tcg-apple-jit.h"
> +#endif
> #if defined(CONFIG_USER_ONLY)
> #include "qemu.h"
> #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
> @@ -76,6 +79,9 @@ extern kern_return_t mach_vm_remap(vm_map_t target_task,
> );
> #endif
>
> +static bool tb_exec_is_locked(void);
> +static void tb_exec_change(bool locked);
> +
> /* #define DEBUG_TB_INVALIDATE */
> /* #define DEBUG_TB_FLUSH */
> /* make various TB consistency checks */
> @@ -1246,6 +1252,7 @@ void tcg_exec_init(unsigned long tb_size, bool
> mirror_rwx)
> page_init();
> tb_htable_init();
> code_gen_alloc(tb_size, mirror_rwx);
> + tb_exec_unlock();
> #if defined(CONFIG_SOFTMMU)
> /* There's no guest base to take into account, so go ahead and
> initialize the prologue now. */
> @@ -1522,8 +1529,11 @@ static void do_tb_phys_invalidate(TranslationBlock
> *tb, bool rm_from_page_list)
> PageDesc *p;
> uint32_t h;
> tb_page_addr_t phys_pc;
> + bool code_gen_locked;
>
> assert_memory_lock();
> + code_gen_locked = tb_exec_is_locked();
> + tb_exec_unlock();
>
> /* make sure no further incoming jumps will be chained to this TB */
> qemu_spin_lock(&tb->jmp_lock);
> @@ -1536,6 +1546,7 @@ static void do_tb_phys_invalidate(TranslationBlock *tb,
> bool rm_from_page_list)
> tb->trace_vcpu_dstate);
> if (!(tb->cflags & CF_NOCACHE) &&
> !qht_remove(&tb_ctx.htable, tb, h)) {
> + tb_exec_change(code_gen_locked);
> return;
> }
>
> @@ -1568,6 +1579,8 @@ static void do_tb_phys_invalidate(TranslationBlock *tb,
> bool rm_from_page_list)
>
> qatomic_set(&tcg_ctx->tb_phys_invalidate_count,
> tcg_ctx->tb_phys_invalidate_count + 1);
> +
> + tb_exec_change(code_gen_locked);
> }
>
> static void tb_phys_invalidate__locked(TranslationBlock *tb)
> @@ -2808,3 +2821,41 @@ void tcg_flush_softmmu_tlb(CPUState *cs)
> tlb_flush(cs);
> #endif
> }
> +
> +#if defined(CONFIG_DARWIN) && !defined(CONFIG_TCG_INTERPRETER)
> +static bool tb_exec_is_locked(void)
> +{
> + return tcg_ctx->code_gen_locked;
> +}
> +
> +static void tb_exec_change(bool locked)
> +{
> +#if defined(HAVE_PTHREAD_JIT_PROTECT)
> + if (__builtin_available(macOS 11, iOS 14, watchOS 7, tvOS 14, *)) {
> + pthread_jit_write_protect_np(locked);
> + } else
> +#endif
> + if (jit_write_protect_supported()) {
> + jit_write_protect(locked);
> + }
> + tcg_ctx->code_gen_locked = locked;
> +}
> +#else /* not needed on non-Darwin platforms */
> +static bool tb_exec_is_locked(void)
> +{
> + return false;
> +}
> +
> +static void tb_exec_change(bool locked) {}
> +#endif
> +
> +void tb_exec_lock(void)
> +{
> + /* assumes sys_icache_invalidate already called */
> + tb_exec_change(true);
> +}
> +
> +void tb_exec_unlock(void)
> +{
> + tb_exec_change(false);
> +}
> diff --git a/configure b/configure
> index c5a6584683..4c8cb63670 100755
> --- a/configure
> +++ b/configure
> @@ -5874,6 +5874,22 @@ but not implemented on your system"
> fi
> fi
>
> +##########################################
> +# check for Apple Silicon JIT function
> +
> +if [ "$darwin" = "yes" ] ; then
> + cat > $TMPC << EOF
> +#include <pthread.h>
> +int main() { pthread_jit_write_protect_np(0); return 0; }
> +EOF
> + if ! compile_prog ""; then
> + have_pthread_jit_protect='no'
> + else
> + have_pthread_jit_protect='yes'
> + fi
> +fi
> +
> +
> ##########################################
> # End of CC checks
> # After here, no more $cc or $ld runs
> @@ -6994,6 +7010,10 @@ if test "$secret_keyring" = "yes" ; then
> echo "CONFIG_SECRET_KEYRING=y" >> $config_host_mak
> fi
>
> +if test "$have_pthread_jit_protect" = "yes" ; then
> + echo "HAVE_PTHREAD_JIT_PROTECT=y" >> $config_host_mak
> +fi
> +
> if test "$tcg_interpreter" = "yes"; then
> QEMU_INCLUDES="-iquote ${source_path}/tcg/tci $QEMU_INCLUDES"
> elif test "$ARCH" = "sparc64" ; then
> diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
> index 2db155a772..253af30a2e 100644
> --- a/include/exec/exec-all.h
> +++ b/include/exec/exec-all.h
> @@ -521,6 +521,8 @@ TranslationBlock *tb_htable_lookup(CPUState *cpu,
> target_ulong pc,
> target_ulong cs_base, uint32_t flags,
> uint32_t cf_mask);
> void tb_set_jmp_target(TranslationBlock *tb, int n, uintptr_t addr);
> +void tb_exec_lock(void);
> +void tb_exec_unlock(void);
>
> /* GETPC is the true target of the return instruction that we'll execute. */
> #if defined(CONFIG_TCG_INTERPRETER)
> diff --git a/include/tcg/tcg-apple-jit.h b/include/tcg/tcg-apple-jit.h
> new file mode 100644
> index 0000000000..1e70bf3afe
> --- /dev/null
> +++ b/include/tcg/tcg-apple-jit.h
> @@ -0,0 +1,85 @@
> +/*
> + * Apple Silicon APRR functions for JIT handling
> + *
> + * Copyright (c) 2020 osy
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, see
> <http://www.gnu.org/licenses/>.
> + */
> +
> +/*
> + * Credits to: https://siguza.github.io/APRR/
> + * Reversed from /usr/lib/system/libsystem_pthread.dylib
> + */
> +
> +#ifndef TCG_APPLE_JIT_H
> +#define TCG_APPLE_JIT_H
> +
> +#if defined(__aarch64__) && defined(CONFIG_DARWIN)
> +
> +#define _COMM_PAGE_START_ADDRESS (0x0000000FFFFFC000ULL) /* In TTBR0
> */
> +#define _COMM_PAGE_APRR_SUPPORT (_COMM_PAGE_START_ADDRESS + 0x10C)
> +#define _COMM_PAGE_APPR_WRITE_ENABLE (_COMM_PAGE_START_ADDRESS + 0x110)
> +#define _COMM_PAGE_APRR_WRITE_DISABLE (_COMM_PAGE_START_ADDRESS + 0x118)
> +
> +static __attribute__((__always_inline__)) bool
> jit_write_protect_supported(void)
> +{
> + /* Access shared kernel page at fixed memory location. */
> + uint8_t aprr_support = *(volatile uint8_t *)_COMM_PAGE_APRR_SUPPORT;
> + return aprr_support > 0;
> +}
> +
> +/* write protect enable = write disable */
> +static __attribute__((__always_inline__)) void jit_write_protect(int enabled)
> +{
> + /* Access shared kernel page at fixed memory location. */
> + uint8_t aprr_support = *(volatile uint8_t *)_COMM_PAGE_APRR_SUPPORT;
> + if (aprr_support == 0 || aprr_support > 3) {
> + return;
> + } else if (aprr_support == 1) {
> + __asm__ __volatile__ (
> + "mov x0, %0\n"
> + "ldr x0, [x0]\n"
> + "msr S3_4_c15_c2_7, x0\n"
> + "isb sy\n"
> + :: "r" (enabled ? _COMM_PAGE_APRR_WRITE_DISABLE
> + : _COMM_PAGE_APPR_WRITE_ENABLE)
> + : "memory", "x0"
> + );
> + } else {
> + __asm__ __volatile__ (
> + "mov x0, %0\n"
> + "ldr x0, [x0]\n"
> + "msr S3_6_c15_c1_5, x0\n"
> + "isb sy\n"
> + :: "r" (enabled ? _COMM_PAGE_APRR_WRITE_DISABLE
> + : _COMM_PAGE_APPR_WRITE_ENABLE)
> + : "memory", "x0"
> + );
> + }
> +}
> +
> +#else /* defined(__aarch64__) && defined(CONFIG_DARWIN) */
> +
> +static __attribute__((__always_inline__)) bool
> jit_write_protect_supported(void)
> +{
> + return false;
> +}
> +
> +static __attribute__((__always_inline__)) void jit_write_protect(int enabled)
> +{
> +}
> +
> +#endif
> +
> +#endif /* define TCG_APPLE_JIT_H */
> diff --git a/include/tcg/tcg.h b/include/tcg/tcg.h
> index 40d1a7a85e..fbe00af4e1 100644
> --- a/include/tcg/tcg.h
> +++ b/include/tcg/tcg.h
> @@ -630,6 +630,9 @@ struct TCGContext {
> #if defined(CONFIG_IOS_JIT)
> ptrdiff_t code_rw_mirror_diff;
> #endif
> +#if defined(CONFIG_DARWIN) && !defined(CONFIG_TCG_INTERPRETER)
> + bool code_gen_locked; /* on Darwin each thread tracks W^X flags */
> +#endif
>
> /* Threshold to flush the translated code buffer. */
> void *code_gen_highwater;
> diff --git a/tcg/tcg.c b/tcg/tcg.c
> index ef203a34a6..244a0a43bf 100644
> --- a/tcg/tcg.c
> +++ b/tcg/tcg.c
> @@ -781,6 +781,8 @@ static void alloc_tcg_plugin_context(TCGContext *s)
> void tcg_register_thread(void)
> {
> tcg_ctx = &tcg_init_ctx;
> +
> + tb_exec_unlock();
> }
> #else
> void tcg_register_thread(void)
> @@ -815,6 +817,8 @@ void tcg_register_thread(void)
> err = tcg_region_initial_alloc__locked(tcg_ctx);
> g_assert(!err);
> qemu_mutex_unlock(®ion.lock);
> +
> + tb_exec_unlock();
> }
> #endif /* !CONFIG_USER_ONLY */
>
>
