From: Peter Maydell Date: Fri, 25 Jul 2025 17:55:10 +0000 (+0100) Subject: linux-user/aarch64: Support ZT_MAGIC signal frame record X-Git-Tag: v10.1.0-rc1~6^2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e35215db401113867e20634622a370c0e8931797;p=thirdparty%2Fqemu.git linux-user/aarch64: Support ZT_MAGIC signal frame record FEAT_SME2 adds the ZT0 register, whose contents may need to be preserved and restored on signal handler entry and exit. This is done with a new ZT_MAGIC record. We forgot to implement support for this in our linux-user code before enabling the SME2p1 emulation, which meant that a signal handler using SME would corrupt the ZT0 register value, and code that attempted to unwind an exception from inside a signal handler would not work. Add the missing record handling. Fixes: 7b1613a1020d2942 ("target/arm: Enable FEAT_SME2p1 on -cpu max") Signed-off-by: Peter Maydell Reviewed-by: Pierrick Bouvier Reviewed-by: Richard Henderson Signed-off-by: Richard Henderson Message-ID: <20250725175510.3864231-4-peter.maydell@linaro.org> --- diff --git a/linux-user/aarch64/signal.c b/linux-user/aarch64/signal.c index f28ba80754..668353bbda 100644 --- a/linux-user/aarch64/signal.c +++ b/linux-user/aarch64/signal.c @@ -128,6 +128,23 @@ struct target_tpidr2_context { uint64_t tpidr2; }; +#define TARGET_ZT_MAGIC 0x5a544e01 + +struct target_zt_context { + struct target_aarch64_ctx head; + uint16_t nregs; + uint16_t reserved[3]; + /* ZTn register data immediately follows */ +}; + +#define TARGET_ZT_SIG_REG_BYTES (512 / 8) +#define TARGET_ZT_SIG_REGS_SIZE(n) (TARGET_ZT_SIG_REG_BYTES * (n)) +#define TARGET_ZT_SIG_CONTEXT_SIZE(n) (sizeof(struct target_zt_context) + \ + TARGET_ZT_SIG_REGS_SIZE(n)) +#define TARGET_ZT_SIG_REGS_OFFSET sizeof(struct target_zt_context) +QEMU_BUILD_BUG_ON(TARGET_ZT_SIG_REG_BYTES != \ + sizeof_field(CPUARMState, za_state.zt0)); + struct target_rt_sigframe { struct target_siginfo info; struct target_ucontext uc; @@ -268,6 +285,28 @@ static void target_setup_tpidr2_record(struct target_tpidr2_context *tpidr2, __put_user(env->cp15.tpidr2_el0, &tpidr2->tpidr2); } +static void target_setup_zt_record(struct target_zt_context *zt, + CPUARMState *env, int size) +{ + uint64_t *z; + + memset(zt, 0, sizeof(*zt)); + __put_user(TARGET_ZT_MAGIC, &zt->head.magic); + __put_user(size, &zt->head.size); + /* + * The record format allows for multiple ZT regs, but + * currently there is only one, ZT0. + */ + __put_user(1, &zt->nregs); + assert(size == TARGET_ZT_SIG_CONTEXT_SIZE(1)); + + /* ZT0 is the same byte-stream format as SVE regs and ZA */ + z = (void *)zt + TARGET_ZT_SIG_REGS_OFFSET; + for (int i = 0; i < ARRAY_SIZE(env->za_state.zt0); i++) { + __put_user_e(env->za_state.zt0[i], z + i, le); + } +} + static void target_restore_general_frame(CPUARMState *env, struct target_rt_sigframe *sf) { @@ -424,6 +463,30 @@ static void target_restore_tpidr2_record(CPUARMState *env, __get_user(env->cp15.tpidr2_el0, &tpidr2->tpidr2); } +static bool target_restore_zt_record(CPUARMState *env, + struct target_zt_context *zt, int size, + int svcr) +{ + uint16_t nregs; + uint64_t *z; + + if (!(FIELD_EX64(svcr, SVCR, ZA))) { + return false; + } + + __get_user(nregs, &zt->nregs); + + if (nregs != 1) { + return false; + } + + z = (void *)zt + TARGET_ZT_SIG_REGS_OFFSET; + for (int i = 0; i < ARRAY_SIZE(env->za_state.zt0); i++) { + __get_user_e(env->za_state.zt0[i], z + i, le); + } + return true; +} + static int target_restore_sigframe(CPUARMState *env, struct target_rt_sigframe *sf) { @@ -432,10 +495,12 @@ static int target_restore_sigframe(CPUARMState *env, struct target_sve_context *sve = NULL; struct target_za_context *za = NULL; struct target_tpidr2_context *tpidr2 = NULL; + struct target_zt_context *zt = NULL; uint64_t extra_datap = 0; bool used_extra = false; int sve_size = 0; int za_size = 0; + int zt_size = 0; int svcr = 0; target_restore_general_frame(env, sf); @@ -490,6 +555,15 @@ static int target_restore_sigframe(CPUARMState *env, tpidr2 = (struct target_tpidr2_context *)ctx; break; + case TARGET_ZT_MAGIC: + if (zt || size != TARGET_ZT_SIG_CONTEXT_SIZE(1) || + !cpu_isar_feature(aa64_sme2, env_archcpu(env))) { + goto err; + } + zt = (struct target_zt_context *)ctx; + zt_size = size; + break; + case TARGET_EXTRA_MAGIC: if (extra || size != sizeof(struct target_extra_context)) { goto err; @@ -530,6 +604,13 @@ static int target_restore_sigframe(CPUARMState *env, if (tpidr2) { target_restore_tpidr2_record(env, tpidr2); } + /* + * NB that we must restore ZT after ZA so the check that there's + * no ZT record if SVCR.ZA is 0 gets the right value of SVCR. + */ + if (zt && !target_restore_zt_record(env, zt, zt_size, svcr)) { + goto err; + } if (env->svcr != svcr) { env->svcr = svcr; arm_rebuild_hflags(env); @@ -602,7 +683,8 @@ static void target_setup_frame(int usig, struct target_sigaction *ka, uc.tuc_mcontext.__reserved), }; int fpsimd_ofs, fr_ofs, sve_ofs = 0, za_ofs = 0, tpidr2_ofs = 0; - int sve_size = 0, za_size = 0, tpidr2_size = 0; + int zt_ofs = 0; + int sve_size = 0, za_size = 0, tpidr2_size = 0, zt_size = 0; struct target_rt_sigframe *frame; struct target_rt_frame_record *fr; abi_ulong frame_addr, return_addr; @@ -628,6 +710,12 @@ static void target_setup_frame(int usig, struct target_sigaction *ka, } za_ofs = alloc_sigframe_space(za_size, &layout); } + if (cpu_isar_feature(aa64_sme2, env_archcpu(env)) && + FIELD_EX64(env->svcr, SVCR, ZA)) { + /* If SME ZA storage is enabled, we must also save SME2 ZT0 */ + zt_size = TARGET_ZT_SIG_CONTEXT_SIZE(1); + zt_ofs = alloc_sigframe_space(zt_size, &layout); + } if (layout.extra_ofs) { /* Reserve space for the extra end marker. The standard end marker @@ -682,6 +770,9 @@ static void target_setup_frame(int usig, struct target_sigaction *ka, if (tpidr2_ofs) { target_setup_tpidr2_record((void *)frame + tpidr2_ofs, env); } + if (zt_ofs) { + target_setup_zt_record((void *)frame + zt_ofs, env, zt_size); + } /* Set up the stack frame for unwinding. */ fr = (void *)frame + fr_ofs;