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armv7m: Fix reads of CONTROL register bit 1

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The v7m CONTROL register bit 1 is SPSEL, which indicates
the stack being used. We were storing this information
not in v7m.control but in the separate v7m.other_sp
structure field. Unfortunately, the code handling reads
of the CONTROL register didn't take account of this, and
so if SPSEL was updated by an exception entry or exit then
a subsequent guest read of CONTROL would get the wrong value.

Using a separate structure field doesn't really gain us
anything in efficiency, so drop this unnecessary complexity
in favour of simply storing all the bits in v7m.control.

This is a migration compatibility break for M profile
CPUs only.

Signed-off-by: Michael Davidsaver <mdavidsaver@gmail.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 1484937883-1068-6-git-send-email-peter.maydell@linaro.org
[PMM: rewrote commit message;
 use deposit32(); use FIELD to define constants for
 masking and shifting of CONTROL register fields
]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Michael Davidsaver 2017-01-27 15:20:21 +00:00 • committed by Peter Maydell
parent afb3141c66
commit abc24d86cc
4 changed files with 32 additions and 17 deletions
Download patch file Download diff file Expand all files Collapse all files

35
target/arm/helper.c
View file

@ -5947,14 +5947,19 @@ static uint32_t v7m_pop(CPUARMState *env)
}
/* Switch to V7M main or process stack pointer. */
static void switch_v7m_sp(CPUARMState *env, int process)
static void switch_v7m_sp(CPUARMState *env, bool new_spsel)
{
uint32_t tmp;
if (env->v7m.current_sp != process) {
bool old_spsel = env->v7m.control & R_V7M_CONTROL_SPSEL_MASK;
if (old_spsel != new_spsel) {
tmp = env->v7m.other_sp;
env->v7m.other_sp = env->regs[13];
env->regs[13] = tmp;
env->v7m.current_sp = process;
env->v7m.control = deposit32(env->v7m.control,
R_V7M_CONTROL_SPSEL_SHIFT,
R_V7M_CONTROL_SPSEL_LENGTH, new_spsel);
}
}
@ -6049,8 +6054,9 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
arm_log_exception(cs->exception_index);
lr = 0xfffffff1;
if (env->v7m.current_sp)
if (env->v7m.control & R_V7M_CONTROL_SPSEL_MASK) {
lr |= 4;
}
if (env->v7m.exception == 0)
lr |= 8;
@ -8294,9 +8300,11 @@ uint32_t HELPER(v7m_mrs)(CPUARMState *env, uint32_t reg)
switch (reg) {
case 8: /* MSP */
return env->v7m.current_sp ? env->v7m.other_sp : env->regs[13];
return (env->v7m.control & R_V7M_CONTROL_SPSEL_MASK) ?
env->v7m.other_sp : env->regs[13];
case 9: /* PSP */
return env->v7m.current_sp ? env->regs[13] : env->v7m.other_sp;
return (env->v7m.control & R_V7M_CONTROL_SPSEL_MASK) ?
env->regs[13] : env->v7m.other_sp;
case 16: /* PRIMASK */
return (env->daif & PSTATE_I) != 0;
case 17: /* BASEPRI */
@ -8326,16 +8334,18 @@ void HELPER(v7m_msr)(CPUARMState *env, uint32_t reg, uint32_t val)
}
break;
case 8: /* MSP */
if (env->v7m.current_sp)
if (env->v7m.control & R_V7M_CONTROL_SPSEL_MASK) {
env->v7m.other_sp = val;
else
} else {
env->regs[13] = val;
}
break;
case 9: /* PSP */
if (env->v7m.current_sp)
if (env->v7m.control & R_V7M_CONTROL_SPSEL_MASK) {
env->regs[13] = val;
else
} else {
env->v7m.other_sp = val;
}
break;
case 16: /* PRIMASK */
if (val & 1) {
@ -8360,8 +8370,9 @@ void HELPER(v7m_msr)(CPUARMState *env, uint32_t reg, uint32_t val)
}
break;
case 20: /* CONTROL */
env->v7m.control = val & 3;
switch_v7m_sp(env, (val & 2) != 0);
switch_v7m_sp(env, (val & R_V7M_CONTROL_SPSEL_MASK) != 0);
env->v7m.control = val & (R_V7M_CONTROL_SPSEL_MASK |
R_V7M_CONTROL_NPRIV_MASK);
break;
default:
qemu_log_mask(LOG_GUEST_ERROR, "Attempt to write unknown special"