| Message ID | 20230127175507.2895013-7-peter.maydell@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | target/arm: Implement FEAT_FGT fine-grained traps | expand |
On 1/27/23 07:54, Peter Maydell wrote: > +void HELPER(hstr_trap_check)(CPUARMState *env, uint32_t mask, uint32_t syndrome) > +{ > + if (env->cp15.hstr_el2 & mask) { > + raise_exception(env, EXCP_UDEF, syndrome, 2); > + } This is so simple... > @@ -4760,6 +4761,28 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64, > break; > } > > + if (s->hstr_active && cpnum == 15 && s->current_el == 1) { > + /* > + * At EL1, check for a HSTR_EL2 trap, which must take precedence > + * over the UNDEF for "no such register" or the UNDEF for "access > + * permissions forbid this EL1 access". HSTR_EL2 traps from EL0 > + * only happen if the cpreg doesn't UNDEF at EL0, so we do those in > + * access_check_cp_reg(), after the checks for whether the access > + * configurably trapped to EL1. > + */ > + uint32_t maskbit = is64 ? crm : crn; > + > + if (maskbit != 4 && maskbit != 14) { > + /* T4 and T14 are RES0 so never cause traps */ > + gen_set_condexec(s); > + gen_update_pc(s, 0); > + emitted_update_pc = true; > + gen_helper_hstr_trap_check(cpu_env, > + tcg_constant_i32(1 << maskbit), > + tcg_constant_i32(syndrome)); > + } How about if (maskbit...) { TCGv_i32 t = load_cpu_offset(offsetoflow32(CPUARMState, hstr_el2)); DisasLabel *over = gen_disas_label(s); tcg_gen_andi_i32(t, t, 1u << maskbit); tcg_gen_brcondi_i32(TCG_COND_EQ, t, 0, over.label); tcg_temp_free_i32(t); gen_exception_insn(s, 0, EXCP_UDEF, syndrome); set_disas_label(s, over); } which also eliminates the need for emitted_update_pc. r~
On Sat, 28 Jan 2023 at 01:47, Richard Henderson <richard.henderson@linaro.org> wrote: > > On 1/27/23 07:54, Peter Maydell wrote: > > +void HELPER(hstr_trap_check)(CPUARMState *env, uint32_t mask, uint32_t syndrome) > > +{ > > + if (env->cp15.hstr_el2 & mask) { > > + raise_exception(env, EXCP_UDEF, syndrome, 2); > > + } > > This is so simple... > > > > @@ -4760,6 +4761,28 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64, > > break; > > } > > > > + if (s->hstr_active && cpnum == 15 && s->current_el == 1) { > > + /* > > + * At EL1, check for a HSTR_EL2 trap, which must take precedence > > + * over the UNDEF for "no such register" or the UNDEF for "access > > + * permissions forbid this EL1 access". HSTR_EL2 traps from EL0 > > + * only happen if the cpreg doesn't UNDEF at EL0, so we do those in > > + * access_check_cp_reg(), after the checks for whether the access > > + * configurably trapped to EL1. > > + */ > > + uint32_t maskbit = is64 ? crm : crn; > > + > > + if (maskbit != 4 && maskbit != 14) { > > + /* T4 and T14 are RES0 so never cause traps */ > > + gen_set_condexec(s); > > + gen_update_pc(s, 0); > > + emitted_update_pc = true; > > + gen_helper_hstr_trap_check(cpu_env, > > + tcg_constant_i32(1 << maskbit), > > + tcg_constant_i32(syndrome)); > > + } > > How about > > if (maskbit...) { > TCGv_i32 t = load_cpu_offset(offsetoflow32(CPUARMState, hstr_el2)); > DisasLabel *over = gen_disas_label(s); > > tcg_gen_andi_i32(t, t, 1u << maskbit); > tcg_gen_brcondi_i32(TCG_COND_EQ, t, 0, over.label); > tcg_temp_free_i32(t); > > gen_exception_insn(s, 0, EXCP_UDEF, syndrome); > set_disas_label(s, over); > } > > which also eliminates the need for emitted_update_pc. I really dislike use of brcond in generated TCG, because of the massive beartrap it sets up where all your temporaries get nuked but there's no compile-time checking that you didn't try to keep using one after the brcond. So I generally prefer an approach that avoids brcond over one that uses it, if it's available. thanks -- PMM
diff --git a/target/arm/helper.h b/target/arm/helper.h index 018b00ea75b..17634b3e7b6 100644 --- a/target/arm/helper.h +++ b/target/arm/helper.h @@ -81,6 +81,7 @@ DEF_HELPER_FLAGS_2(check_bxj_trap, TCG_CALL_NO_WG, void, env, i32) DEF_HELPER_4(access_check_cp_reg, cptr, env, i32, i32, i32) DEF_HELPER_FLAGS_2(lookup_cp_reg, TCG_CALL_NO_RWG_SE, cptr, env, i32) +DEF_HELPER_3(hstr_trap_check, void, env, i32, i32) DEF_HELPER_3(set_cp_reg, void, env, cptr, i32) DEF_HELPER_2(get_cp_reg, i32, env, cptr) DEF_HELPER_3(set_cp_reg64, void, env, cptr, i64) diff --git a/target/arm/op_helper.c b/target/arm/op_helper.c index 660dae696dd..8ac176e0742 100644 --- a/target/arm/op_helper.c +++ b/target/arm/op_helper.c @@ -624,6 +624,13 @@ uint32_t HELPER(mrs_banked)(CPUARMState *env, uint32_t tgtmode, uint32_t regno) } } +void HELPER(hstr_trap_check)(CPUARMState *env, uint32_t mask, uint32_t syndrome) +{ + if (env->cp15.hstr_el2 & mask) { + raise_exception(env, EXCP_UDEF, syndrome, 2); + } +} + const void *HELPER(access_check_cp_reg)(CPUARMState *env, uint32_t key, uint32_t syndrome, uint32_t isread) { @@ -658,7 +665,11 @@ const void *HELPER(access_check_cp_reg)(CPUARMState *env, uint32_t key, goto fail; } - if (!is_a64(env) && arm_current_el(env) < 2 && ri->cp == 15 && + /* + * HSTR_EL2 traps from EL1 are checked earlier, via hstr_trap_check; + * we only need to check here for traps from EL0. + */ + if (!is_a64(env) && arm_current_el(env) == 0 && ri->cp == 15 && (arm_hcr_el2_eff(env) & (HCR_E2H | HCR_TGE)) != (HCR_E2H | HCR_TGE)) { uint32_t mask = 1 << ri->crn; diff --git a/target/arm/translate.c b/target/arm/translate.c index 9252a464a12..ec1f2288ff8 100644 --- a/target/arm/translate.c +++ b/target/arm/translate.c @@ -4719,6 +4719,7 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64, TCGv_ptr tcg_ri = NULL; bool need_exit_tb; uint32_t syndrome; + bool emitted_update_pc = false; /* * Note that since we are an implementation which takes an @@ -4760,6 +4761,28 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64, break; } + if (s->hstr_active && cpnum == 15 && s->current_el == 1) { + /* + * At EL1, check for a HSTR_EL2 trap, which must take precedence + * over the UNDEF for "no such register" or the UNDEF for "access + * permissions forbid this EL1 access". HSTR_EL2 traps from EL0 + * only happen if the cpreg doesn't UNDEF at EL0, so we do those in + * access_check_cp_reg(), after the checks for whether the access + * configurably trapped to EL1. + */ + uint32_t maskbit = is64 ? crm : crn; + + if (maskbit != 4 && maskbit != 14) { + /* T4 and T14 are RES0 so never cause traps */ + gen_set_condexec(s); + gen_update_pc(s, 0); + emitted_update_pc = true; + gen_helper_hstr_trap_check(cpu_env, + tcg_constant_i32(1 << maskbit), + tcg_constant_i32(syndrome)); + } + } + if (!ri) { /* * Unknown register; this might be a guest error or a QEMU @@ -4788,7 +4811,7 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64, return; } - if (s->hstr_active || ri->accessfn || + if ((s->hstr_active && s->current_el == 0) || ri->accessfn || (arm_dc_feature(s, ARM_FEATURE_XSCALE) && cpnum < 14)) { /* * Emit code to perform further access permissions checks at @@ -4796,8 +4819,10 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64, * Note that on XScale all cp0..c13 registers do an access check * call in order to handle c15_cpar. */ - gen_set_condexec(s); - gen_update_pc(s, 0); + if (!emitted_update_pc) { + gen_set_condexec(s); + gen_update_pc(s, 0); + } tcg_ri = tcg_temp_new_ptr(); gen_helper_access_check_cp_reg(tcg_ri, cpu_env, tcg_constant_i32(key), @@ -4808,8 +4833,10 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64, * The readfn or writefn might raise an exception; * synchronize the CPU state in case it does. */ - gen_set_condexec(s); - gen_update_pc(s, 0); + if (!emitted_update_pc) { + gen_set_condexec(s); + gen_update_pc(s, 0); + } } /* Handle special cases first */
The semantics of HSTR_EL2 require that it traps cpreg accesses to EL2 for: * EL1 accesses * EL0 accesses, if the access is not UNDEFINED when the trap bit is 0 (You can see this in the I_ZFGJP priority ordering, where HSTR_EL2 traps from EL1 to EL2 are priority 12, UNDEFs are priority 13, and HSTR_EL2 traps from EL0 are priority 15.) However, we don't get this right for EL1 accesses which UNDEF because the register doesn't exist at all or because its ri->access bits non-configurably forbid the access. At EL1, check for the HSTR_EL2 trap early, before either of these UNDEF reasons. We have to retain the HSTR_EL2 check in access_check_cp_reg(), because at EL0 any kind of UNDEF-to-EL1 (including "no such register", "bad ri->access" and "ri->accessfn returns 'trap to EL1'") takes precedence over the trap to EL2. But we only need to do that check for EL0 now. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- target/arm/helper.h | 1 + target/arm/op_helper.c | 13 ++++++++++++- target/arm/translate.c | 37 ++++++++++++++++++++++++++++++++----- 3 files changed, 45 insertions(+), 6 deletions(-)