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target/arm: Add v8M stack checks on exception entry

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Add checks for breaches of the v8M stack limit when the
stack pointer is decremented to push the exception frame
for exception entry.

Note that the exception-entry case is unique in that the
stack pointer is updated to be the limit value if the limit
is hit (per rule R_ZLZG).

Backports commit c32da7aa6205a5ff62ae8d5062f7cad0eae4c1fd from qemu
This commit is contained in:
Peter Maydell 2018-10-08 14:09:10 -04:00 committed by Lioncash
parent 0fc6e2c183
commit ed3c951fb6
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GPG key ID: 4E3C3CC1031BA9C7
1 changed files with 46 additions and 8 deletions
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54
qemu/target/arm/helper.c
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@ -6055,6 +6055,8 @@ static bool v7m_push_callee_stack(ARMCPU *cpu, uint32_t lr, bool dotailchain,
uint32_t frameptr;
ARMMMUIdx mmu_idx;
bool stacked_ok;
uint32_t limit;
bool want_psp;
if (dotailchain) {
bool mode = lr & R_V7M_EXCRET_MODE_MASK;
@ -6064,12 +6066,34 @@ static bool v7m_push_callee_stack(ARMCPU *cpu, uint32_t lr, bool dotailchain,
mmu_idx = arm_v7m_mmu_idx_for_secstate_and_priv(env, M_REG_S, priv);
frame_sp_p = get_v7m_sp_ptr(env, M_REG_S, mode,
lr & R_V7M_EXCRET_SPSEL_MASK);
want_psp = mode && (lr & R_V7M_EXCRET_SPSEL_MASK);
if (want_psp) {
limit = env->v7m.psplim[M_REG_S];
} else {
limit = env->v7m.msplim[M_REG_S];
}
} else {
mmu_idx = core_to_arm_mmu_idx(env, cpu_mmu_index(env, false));
frame_sp_p = &env->regs[13];
limit = v7m_sp_limit(env);
}
frameptr = *frame_sp_p - 0x28;
if (frameptr < limit) {
/*
* Stack limit failure: set SP to the limit value, and generate
* STKOF UsageFault. Stack pushes below the limit must not be
* performed. It is IMPDEF whether pushes above the limit are
* performed; we choose not to.
*/
qemu_log_mask(CPU_LOG_INT,
"...STKOF during callee-saves register stacking\n");
env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_STKOF_MASK;
//armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE,
// env->v7m.secure);
*frame_sp_p = limit;
return true;
}
/* Write as much of the stack frame as we can. A write failure may
* cause us to pend a derived exception.
@ -6093,10 +6117,7 @@ static bool v7m_push_callee_stack(ARMCPU *cpu, uint32_t lr, bool dotailchain,
v7m_stack_write(cpu, frameptr + 0x24, env->regs[11], mmu_idx,
ignore_faults);
/* Update SP regardless of whether any of the stack accesses failed.
* When we implement v8M stack limit checking then this attempt to
* update SP might also fail and result in a derived exception.
*/
/* Update SP regardless of whether any of the stack accesses failed. */
*frame_sp_p = frameptr;
return !stacked_ok;
@ -6241,6 +6262,26 @@ static bool v7m_push_stack(ARMCPU *cpu)
frameptr -= 0x20;
if (arm_feature(env, ARM_FEATURE_V8)) {
uint32_t limit = v7m_sp_limit(env);
if (frameptr < limit) {
/*
* Stack limit failure: set SP to the limit value, and generate
* STKOF UsageFault. Stack pushes below the limit must not be
* performed. It is IMPDEF whether pushes above the limit are
* performed; we choose not to.
*/
qemu_log_mask(CPU_LOG_INT,
"...STKOF during stacking\n");
env->v7m.cfsr[env->v7m.secure] |= R_V7M_CFSR_STKOF_MASK;
//armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE,
// env->v7m.secure);
env->regs[13] = limit;
return true;
}
}
/* Write as much of the stack frame as we can. If we fail a stack
* write this will result in a derived exception being pended
* (which may be taken in preference to the one we started with
@ -6256,10 +6297,7 @@ static bool v7m_push_stack(ARMCPU *cpu)
v7m_stack_write(cpu, frameptr + 24, env->regs[15], mmu_idx, false) &&
v7m_stack_write(cpu, frameptr + 28, xpsr, mmu_idx, false);
/* Update SP regardless of whether any of the stack accesses failed.
* When we implement v8M stack limit checking then this attempt to
* update SP might also fail and result in a derived exception.
*/
/* Update SP regardless of whether any of the stack accesses failed. */
env->regs[13] = frameptr;
return !stacked_ok;