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target/arm: Set FPCCR.S when executing M-profile floating point insns

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The M-profile FPCCR.S bit indicates the security status of
the floating point context. In the pseudocode ExecuteFPCheck()
function it is unconditionally set to match the current
security state whenever a floating point instruction is
executed.

Implement this by adding a new TB flag which tracks whether
FPCCR.S is different from the current security state, so
that we only need to emit the code to update it in the
less-common case when it is not already set correctly.

Note that we will add the handling for the other work done
by ExecuteFPCheck() in later commits.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190416125744.27770-19-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2019-04-29 17:36:01 +01:00
parent ea7ac69d12
commit 6d60c67a1a
4 changed files with 28 additions and 0 deletions
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2
target/arm/cpu.h
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@ -3153,6 +3153,8 @@ FIELD(TBFLAG_A32, NS, 6, 1)
FIELD(TBFLAG_A32, VFPEN, 7, 1)
FIELD(TBFLAG_A32, CONDEXEC, 8, 8)
FIELD(TBFLAG_A32, SCTLR_B, 16, 1)
/* For M profile only, set if FPCCR.S does not match current security state */
FIELD(TBFLAG_A32, FPCCR_S_WRONG, 20, 1)
/* For M profile only, Handler (ie not Thread) mode */
FIELD(TBFLAG_A32, HANDLER, 21, 1)
/* For M profile only, whether we should generate stack-limit checks */

5
target/arm/helper.c
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@ -13417,6 +13417,11 @@ void cpu_get_tb_cpu_state(CPUARMState *env, target_ulong *pc,
flags = FIELD_DP32(flags, TBFLAG_A32, STACKCHECK, 1);
}
if (arm_feature(env, ARM_FEATURE_M_SECURITY) &&
FIELD_EX32(env->v7m.fpccr[M_REG_S], V7M_FPCCR, S) != env->v7m.secure) {
flags = FIELD_DP32(flags, TBFLAG_A32, FPCCR_S_WRONG, 1);
}
*pflags = flags;
*cs_base = 0;
}

20
target/arm/translate.c
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@ -3421,6 +3421,25 @@ static int disas_vfp_insn(DisasContext *s, uint32_t insn)
}
}
if (arm_dc_feature(s, ARM_FEATURE_M)) {
/* Handle M-profile lazy FP state mechanics */
/* Update ownership of FP context: set FPCCR.S to match current state */
if (s->v8m_fpccr_s_wrong) {
TCGv_i32 tmp;
tmp = load_cpu_field(v7m.fpccr[M_REG_S]);
if (s->v8m_secure) {
tcg_gen_ori_i32(tmp, tmp, R_V7M_FPCCR_S_MASK);
} else {
tcg_gen_andi_i32(tmp, tmp, ~R_V7M_FPCCR_S_MASK);
}
store_cpu_field(tmp, v7m.fpccr[M_REG_S]);
/* Don't need to do this for any further FP insns in this TB */
s->v8m_fpccr_s_wrong = false;
}
}
if (extract32(insn, 28, 4) == 0xf) {
/*
* Encodings with T=1 (Thumb) or unconditional (ARM):
@ -13341,6 +13360,7 @@ static void arm_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
dc->v8m_secure = arm_feature(env, ARM_FEATURE_M_SECURITY) &&
regime_is_secure(env, dc->mmu_idx);
dc->v8m_stackcheck = FIELD_EX32(tb_flags, TBFLAG_A32, STACKCHECK);
dc->v8m_fpccr_s_wrong = FIELD_EX32(tb_flags, TBFLAG_A32, FPCCR_S_WRONG);
dc->cp_regs = cpu->cp_regs;
dc->features = env->features;

1
target/arm/translate.h
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@ -40,6 +40,7 @@ typedef struct DisasContext {
bool v7m_handler_mode;
bool v8m_secure; /* true if v8M and we're in Secure mode */
bool v8m_stackcheck; /* true if we need to perform v8M stack limit checks */
bool v8m_fpccr_s_wrong; /* true if v8M FPCCR.S != v8m_secure */
/* Immediate value in AArch32 SVC insn; must be set if is_jmp == DISAS_SWI
* so that top level loop can generate correct syndrome information.
*/