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Mon, 26 Oct 2020 10:25:41 -0700 (PDT) From: Joelle van Dyne To: qemu-devel@nongnu.org Subject: [PATCH 2/4] tcg: implement mirror mapped JIT for Linux Date: Mon, 26 Oct 2020 10:25:33 -0700 Message-Id: <20201026172535.10419-3-j@getutm.app> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201026172535.10419-1-j@getutm.app> References: <20201026172535.10419-1-j@getutm.app> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=209.85.214.196; envelope-from=osy86github@gmail.com; helo=mail-pl1-f196.google.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/26 13:25:42 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -13 X-Spam_score: -1.4 X-Spam_bar: - X-Spam_report: (-1.4 / 5.0 requ) BAYES_00=-1.9, FREEMAIL_FORGED_FROMDOMAIN=0.25, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.249, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , Joelle van Dyne , Richard Henderson Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Type: text/plain; charset="utf-8" When configured with --enable-debug-tcg on Linux, we enable JIT mirror map which separates the JIT allocation into a RX-only address and a RW-only address. The backing is a memfd_create() object. This allows us to catch bugs where we unintentionally write to the JIT region. However, the main use case will be for other platforms that require strict W^X separation to run. Signed-off-by: Joelle van Dyne --- configure | 13 ++++++++ meson.build | 1 + include/exec/exec-all.h | 8 +++++ include/tcg/tcg.h | 18 ++++++++++ accel/tcg/cpu-exec.c | 7 +++- accel/tcg/translate-all.c | 69 +++++++++++++++++++++++++++++++++++---- 6 files changed, 108 insertions(+), 8 deletions(-) diff --git a/configure b/configure index e6754c1e87..9a632821c4 100755 --- a/configure +++ b/configure @@ -448,6 +448,7 @@ meson=3D"" ninja=3D"" skip_meson=3Dno gettext=3D"" +mirror_jit=3D"no" =20 bogus_os=3D"no" malloc_trim=3D"auto" @@ -5725,6 +5726,14 @@ if test "$mingw32" =3D "yes" ; then done fi =20 +# Enable mirror mapping if debug_tcg on supported platform + +if test "$debug_tcg" =3D "yes"; then + if test "$linux" =3D "yes"; then + mirror_jit=3Dyes + fi +fi + qemu_confdir=3D"$sysconfdir/$qemu_suffix" qemu_moddir=3D"$libdir/$qemu_suffix" qemu_datadir=3D"$datadir/$qemu_suffix" @@ -6843,6 +6852,10 @@ if test "$safe_stack" =3D "yes"; then echo "CONFIG_SAFESTACK=3Dy" >> $config_host_mak fi =20 +if test "$mirror_jit" =3D "yes"; then + echo "CONFIG_MIRROR_JIT=3Dy" >> $config_host_mak +fi + # If we're using a separate build tree, set it up now. # DIRS are directories which we simply mkdir in the build tree; # LINKS are things to symlink back into the source tree diff --git a/meson.build b/meson.build index 7627a0ae46..9630edff9f 100644 --- a/meson.build +++ b/meson.build @@ -2114,6 +2114,7 @@ endif summary_info +=3D {'thread sanitizer': config_host.has_key('CONFIG_TSAN')} summary_info +=3D {'rng-none': config_host.has_key('CONFIG_RNG_NO= NE')} summary_info +=3D {'Linux keyring': config_host.has_key('CONFIG_SECRET= _KEYRING')} +summary_info +=3D {'mirror JIT': config_host.has_key('CONFIG_MIRROR= _JIT')} summary(summary_info, bool_yn: true) =20 if not supported_cpus.contains(cpu) diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h index 4707ac140c..921767a51b 100644 --- a/include/exec/exec-all.h +++ b/include/exec/exec-all.h @@ -519,6 +519,14 @@ struct TranslationBlock { uintptr_t jmp_list_head; uintptr_t jmp_list_next[2]; uintptr_t jmp_dest[2]; + +#if defined(CONFIG_MIRROR_JIT) + /* + * Store difference to writable mirror + * We need this when patching the jump instructions + */ + ptrdiff_t code_rw_mirror_diff; +#endif }; =20 extern bool parallel_cpus; diff --git a/include/tcg/tcg.h b/include/tcg/tcg.h index 79c5ff8dab..a76c259d1b 100644 --- a/include/tcg/tcg.h +++ b/include/tcg/tcg.h @@ -627,6 +627,10 @@ struct TCGContext { size_t code_gen_buffer_size; void *code_gen_ptr; void *data_gen_ptr; +#if defined(CONFIG_MIRROR_JIT) + int code_gen_buffer_fd; + ptrdiff_t code_rw_mirror_diff; +#endif =20 /* Threshold to flush the translated code buffer. */ void *code_gen_highwater; @@ -677,6 +681,20 @@ struct TCGContext { target_ulong gen_insn_data[TCG_MAX_INSNS][TARGET_INSN_START_WORDS]; }; =20 +static inline void *tcg_mirror_ptr_rw(TCGContext *s, const void *rx) +{ +#if defined(CONFIG_MIRROR_JIT) + return (void *)rx + s->code_rw_mirror_diff; +#else + return (void *)rx; +#endif +} + +static inline tcg_insn_unit *tcg_code_ptr_rw(TCGContext *s, const void *rx) +{ + return (tcg_insn_unit *)tcg_mirror_ptr_rw(s, rx); +} + extern TCGContext tcg_init_ctx; extern __thread TCGContext *tcg_ctx; extern TCGv_env cpu_env; diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c index 58aea605d8..f7eb6fcd77 100644 --- a/accel/tcg/cpu-exec.c +++ b/accel/tcg/cpu-exec.c @@ -354,7 +354,12 @@ void tb_set_jmp_target(TranslationBlock *tb, int n, ui= ntptr_t addr) if (TCG_TARGET_HAS_direct_jump) { uintptr_t offset =3D tb->jmp_target_arg[n]; uintptr_t tc_ptr =3D (uintptr_t)tb->tc.ptr; - tb_target_set_jmp_target(tc_ptr, tc_ptr + offset, addr); +#if defined(CONFIG_MIRROR_JIT) + uintptr_t wr_addr =3D tc_ptr + offset + tb->code_rw_mirror_diff; +#else + uintptr_t wr_addr =3D tc_ptr + offset; +#endif + tb_target_set_jmp_target(tc_ptr, tc_ptr + offset, addr, wr_addr); } else { tb->jmp_target_arg[n] =3D addr; } diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c index d76097296d..bfb856ac1a 100644 --- a/accel/tcg/translate-all.c +++ b/accel/tcg/translate-all.c @@ -59,6 +59,7 @@ #include "sysemu/cpus.h" #include "sysemu/cpu-timers.h" #include "sysemu/tcg.h" +#include "qemu/memfd.h" =20 /* #define DEBUG_TB_INVALIDATE */ /* #define DEBUG_TB_FLUSH */ @@ -302,10 +303,12 @@ static target_long decode_sleb128(uint8_t **pp) =20 static int encode_search(TranslationBlock *tb, uint8_t *block) { - uint8_t *highwater =3D tcg_ctx->code_gen_highwater; - uint8_t *p =3D block; + const uint8_t *highwater, *start; + uint8_t *p; int i, j, n; =20 + highwater =3D tcg_mirror_ptr_rw(tcg_ctx, tcg_ctx->code_gen_highwater); + start =3D p =3D tcg_mirror_ptr_rw(tcg_ctx, block); for (i =3D 0, n =3D tb->icount; i < n; ++i) { target_ulong prev; =20 @@ -329,7 +332,7 @@ static int encode_search(TranslationBlock *tb, uint8_t = *block) } } =20 - return p - block; + return p - start; } =20 /* The cpu state corresponding to 'searched_pc' is restored. @@ -1067,12 +1070,29 @@ static inline void *alloc_code_gen_buffer(void) #else static inline void *alloc_code_gen_buffer(void) { - int prot =3D PROT_WRITE | PROT_READ | PROT_EXEC; - int flags =3D MAP_PRIVATE | MAP_ANONYMOUS; + int prot =3D PROT_READ | PROT_EXEC; + int flags =3D 0; size_t size =3D tcg_ctx->code_gen_buffer_size; + int fd =3D -1; void *buf; =20 - buf =3D mmap(NULL, size, prot, flags, -1, 0); +#if defined(CONFIG_MIRROR_JIT) +#if defined(CONFIG_LINUX) + fd =3D qemu_memfd_create("tcg-jit", size, false, 0, 0, NULL); + if (fd < 0) { + return NULL; + } + tcg_ctx->code_gen_buffer_fd =3D fd; + flags |=3D MAP_SHARED; +#else /* defined(CONFIG_LINUX) */ +#error "Mirror JIT unimplemented for this platform." +#endif /* defined(CONFIG_LINUX) */ +#else /* defined(CONFIG_MIRROR_JIT) */ + prot |=3D PROT_WRITE; + flags |=3D MAP_ANONYMOUS | MAP_PRIVATE; +#endif /* defined(CONFIG_MIRROR_JIT) */ + + buf =3D mmap(NULL, size, prot, flags, fd, 0); if (buf =3D=3D MAP_FAILED) { return NULL; } @@ -1118,7 +1138,28 @@ static inline void *alloc_code_gen_buffer(void) } #endif /* USE_STATIC_CODE_GEN_BUFFER, WIN32, POSIX */ =20 -static inline void code_gen_alloc(size_t tb_size) +#if defined(CONFIG_MIRROR_JIT) +#if defined(CONFIG_LINUX) +static inline void *alloc_jit_rw_mirror(void) +{ + int fd =3D tcg_ctx->code_gen_buffer_fd; + size_t size =3D tcg_ctx->code_gen_buffer_size; + void *buf; + + assert(fd >=3D 0); + buf =3D mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); + if (buf =3D=3D MAP_FAILED) { + return NULL; + } + + return buf; +} +#else +#error "Mirror JIT unimplemented for this platform." +#endif /* CONFIG_IOS */ +#endif /* CONFIG_MIRROR_JIT */ + +static inline void code_gen_alloc(size_t tb_size, bool mirror_jit) { tcg_ctx->code_gen_buffer_size =3D size_code_gen_buffer(tb_size); tcg_ctx->code_gen_buffer =3D alloc_code_gen_buffer(); @@ -1126,6 +1167,17 @@ static inline void code_gen_alloc(size_t tb_size) fprintf(stderr, "Could not allocate dynamic translator buffer\n"); exit(1); } +#if defined(CONFIG_MIRROR_JIT) + void *mirror; + + /* For platforms that need a mirror mapping for code execution */ + mirror =3D alloc_jit_rw_mirror(); + if (mirror =3D=3D NULL) { + fprintf(stderr, "Could not remap code buffer mirror\n"); + exit(1); + } + tcg_ctx->code_rw_mirror_diff =3D mirror - tcg_ctx->code_gen_buffer; +#endif /* CONFIG_MIRROR_JIT */ } =20 static bool tb_cmp(const void *ap, const void *bp) @@ -1721,6 +1773,9 @@ TranslationBlock *tb_gen_code(CPUState *cpu, cpu_loop_exit(cpu); } =20 +#if defined(CONFIG_MIRROR_JIT) + tb->code_rw_mirror_diff =3D tcg_ctx->code_rw_mirror_diff; +#endif gen_code_buf =3D tcg_ctx->code_gen_ptr; tb->tc.ptr =3D gen_code_buf; tb->pc =3D pc; --=20 2.28.0