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).
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <phi...@redhat.com>
Reviewed-by: Richard Henderson <richard.hender...@linaro.org>
Message-id: 20181002163556.10279-7-peter.mayd...@linaro.org
---
target/arm/helper.c | 54 ++++++++++++++++++++++++++++++++++++++-------
1 file changed, 46 insertions(+), 8 deletions(-)
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 7ffd1840447..4cc43692550 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6867,6 +6867,8 @@ 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;
@@ -6876,12 +6878,34 @@ 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.
@@ -6905,10 +6929,7 @@ 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;
@@ -7056,6 +7077,26 @@ 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
@@ -7071,10 +7112,7 @@ 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;
--
2.19.0
