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target-arm: Handle exception return from AArch64 to non-EL0 AArch32

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Remove the assumptions that the AArch64 exception return code was
making about a return to AArch32 always being a return to EL0.
This includes pulling out the illegal-SPSR checks so we can apply
them for return to 32 bit as well as return to 64-bit.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
This commit is contained in:
Peter Maydell 2016-01-21 14:15:09 +00:00
parent 3d6f761713
commit 3809951bf6
1 changed files with 59 additions and 21 deletions
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80
target-arm/op_helper.c
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@ -641,12 +641,51 @@ void HELPER(pre_smc)(CPUARMState *env, uint32_t syndrome)
}
}
static int el_from_spsr(uint32_t spsr)
{
/* Return the exception level that this SPSR is requesting a return to,
* or -1 if it is invalid (an illegal return)
*/
if (spsr & PSTATE_nRW) {
switch (spsr & CPSR_M) {
case ARM_CPU_MODE_USR:
return 0;
case ARM_CPU_MODE_HYP:
return 2;
case ARM_CPU_MODE_FIQ:
case ARM_CPU_MODE_IRQ:
case ARM_CPU_MODE_SVC:
case ARM_CPU_MODE_ABT:
case ARM_CPU_MODE_UND:
case ARM_CPU_MODE_SYS:
return 1;
case ARM_CPU_MODE_MON:
/* Returning to Mon from AArch64 is never possible,
* so this is an illegal return.
*/
default:
return -1;
}
} else {
if (extract32(spsr, 1, 1)) {
/* Return with reserved M[1] bit set */
return -1;
}
if (extract32(spsr, 0, 4) == 1) {
/* return to EL0 with M[0] bit set */
return -1;
}
return extract32(spsr, 2, 2);
}
}
void HELPER(exception_return)(CPUARMState *env)
{
int cur_el = arm_current_el(env);
unsigned int spsr_idx = aarch64_banked_spsr_index(cur_el);
uint32_t spsr = env->banked_spsr[spsr_idx];
int new_el;
bool return_to_aa64 = (spsr & PSTATE_nRW) == 0;
aarch64_save_sp(env, cur_el);
@ -663,35 +702,34 @@ void HELPER(exception_return)(CPUARMState *env)
spsr &= ~PSTATE_SS;
}
if (spsr & PSTATE_nRW) {
/* TODO: We currently assume EL1/2/3 are running in AArch64. */
new_el = el_from_spsr(spsr);
if (new_el == -1) {
goto illegal_return;
}
if (new_el > cur_el
|| (new_el == 2 && !arm_feature(env, ARM_FEATURE_EL2))) {
/* Disallow return to an EL which is unimplemented or higher
* than the current one.
*/
goto illegal_return;
}
if (new_el != 0 && arm_el_is_aa64(env, new_el) != return_to_aa64) {
/* Return to an EL which is configured for a different register width */
goto illegal_return;
}
if (!return_to_aa64) {
env->aarch64 = 0;
new_el = 0;
env->uncached_cpsr = 0x10;
env->uncached_cpsr = spsr & CPSR_M;
cpsr_write(env, spsr, ~0);
if (!arm_singlestep_active(env)) {
env->uncached_cpsr &= ~PSTATE_SS;
}
aarch64_sync_64_to_32(env);
env->regs[15] = env->elr_el[1] & ~0x1;
env->regs[15] = env->elr_el[cur_el] & ~0x1;
} else {
new_el = extract32(spsr, 2, 2);
if (new_el > cur_el
|| (new_el == 2 && !arm_feature(env, ARM_FEATURE_EL2))) {
/* Disallow return to an EL which is unimplemented or higher
* than the current one.
*/
goto illegal_return;
}
if (extract32(spsr, 1, 1)) {
/* Return with reserved M[1] bit set */
goto illegal_return;
}
if (new_el == 0 && (spsr & PSTATE_SP)) {
/* Return to EL0 with M[0] bit set */
goto illegal_return;
}
env->aarch64 = 1;
pstate_write(env, spsr);
if (!arm_singlestep_active(env)) {