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arm: Remove workarounds for old M-profile exception return implementation 

Now that we've rewritten M-profile exception return so that the magic
PC values are not visible to other parts of QEMU, we can delete the
special casing of them elsewhere.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Message-id: 1491844419-12485-10-git-send-email-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2017-04-20 17:32:31 +01:00
parent 3bb8a96f53
commit f4e8e4edda
2 changed files with 2 additions and 49 deletions
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43
target/arm/cpu.c
View File

@ -304,33 +304,6 @@ bool arm_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
}
#if !defined(CONFIG_USER_ONLY) || !defined(TARGET_AARCH64)
static void arm_v7m_unassigned_access(CPUState *cpu, hwaddr addr,
bool is_write, bool is_exec, int opaque,
unsigned size)
{
ARMCPU *arm = ARM_CPU(cpu);
CPUARMState *env = &arm->env;
/* ARMv7-M interrupt return works by loading a magic value into the PC.
* On real hardware the load causes the return to occur. The qemu
* implementation performs the jump normally, then does the exception
* return by throwing a special exception when when the CPU tries to
* execute code at the magic address.
*/
if (env->v7m.exception != 0 && addr >= 0xfffffff0 && is_exec) {
cpu->exception_index = EXCP_EXCEPTION_EXIT;
cpu_loop_exit(cpu);
}
/* In real hardware an attempt to access parts of the address space
* with nothing there will usually cause an external abort.
* However our QEMU board models are often missing device models where
* the guest can boot anyway with the default read-as-zero/writes-ignored
* behaviour that you get without a QEMU unassigned_access hook.
* So just return here to retain that default behaviour.
*/
}
static bool arm_v7m_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
{
CPUClass *cc = CPU_GET_CLASS(cs);
@ -338,17 +311,7 @@ static bool arm_v7m_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
CPUARMState *env = &cpu->env;
bool ret = false;
/* ARMv7-M interrupt return works by loading a magic value
* into the PC. On real hardware the load causes the
* return to occur. The qemu implementation performs the
* jump normally, then does the exception return when the
* CPU tries to execute code at the magic address.
* This will cause the magic PC value to be pushed to
* the stack if an interrupt occurred at the wrong time.
* We avoid this by disabling interrupts when
* pc contains a magic address.
*
* ARMv7-M interrupt masking works differently than -A or -R.
/* ARMv7-M interrupt masking works differently than -A or -R.
* There is no FIQ/IRQ distinction. Instead of I and F bits
* masking FIQ and IRQ interrupts, an exception is taken only
* if it is higher priority than the current execution priority
@ -356,8 +319,7 @@ static bool arm_v7m_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
* currently active exception).
*/
if (interrupt_request & CPU_INTERRUPT_HARD
&& (armv7m_nvic_can_take_pending_exception(env->nvic))
&& (env->regs[15] < 0xfffffff0)) {
&& (armv7m_nvic_can_take_pending_exception(env->nvic))) {
cs->exception_index = EXCP_IRQ;
cc->do_interrupt(cs);
ret = true;
@ -1091,7 +1053,6 @@ static void arm_v7m_class_init(ObjectClass *oc, void *data)
cc->do_interrupt = arm_v7m_cpu_do_interrupt;
#endif
cc->do_unassigned_access = arm_v7m_unassigned_access;
cc->cpu_exec_interrupt = arm_v7m_cpu_exec_interrupt;
}

8
target/arm/translate.c
View File

@ -11927,14 +11927,6 @@ void gen_intermediate_code(CPUARMState *env, TranslationBlock *tb)
dc->is_jmp = DISAS_EXC;
break;
}
#else
if (arm_dc_feature(dc, ARM_FEATURE_M)) {
/* Branches to the magic exception-return addresses should
* already have been caught via the arm_v7m_unassigned_access hook,
* and never get here.
*/
assert(dc->pc < 0xfffffff0);
}
#endif
if (unlikely(!QTAILQ_EMPTY(&cs->breakpoints))) {