+
+/*
+ * Bits which are always architecturally RES0 per ARM DDI 0487A.h
+ * Userspace cannot use these until they have an architectural meaning.
+ * We also reserve IL for the kernel; SS is handled dynamically.
+ */
+#define SPSR_EL1_AARCH64_RES0_BITS \
+ (GENMASK_ULL(63,32) | GENMASK_ULL(27, 22) | GENMASK_ULL(20, 10) | \
+ GENMASK_ULL(5, 5))
+#define SPSR_EL1_AARCH32_RES0_BITS \
+ (GENMASK_ULL(63,32) | GENMASK_ULL(24, 22) | GENMASK_ULL(20,20))
+
+static int valid_compat_regs(struct user_pt_regs *regs)
+{
+ regs->pstate &= ~SPSR_EL1_AARCH32_RES0_BITS;
+
+ if (!system_supports_mixed_endian_el0()) {
+ if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
+ regs->pstate |= COMPAT_PSR_E_BIT;
+ else
+ regs->pstate &= ~COMPAT_PSR_E_BIT;
+ }
+
+ if (user_mode(regs) && (regs->pstate & PSR_MODE32_BIT) &&
+ (regs->pstate & COMPAT_PSR_A_BIT) == 0 &&
+ (regs->pstate & COMPAT_PSR_I_BIT) == 0 &&
+ (regs->pstate & COMPAT_PSR_F_BIT) == 0) {
+ return 1;
+ }
+
+ /*
+ * Force PSR to a valid 32-bit EL0t, preserving the same bits as
+ * arch/arm.
+ */
+ regs->pstate &= COMPAT_PSR_N_BIT | COMPAT_PSR_Z_BIT |
+ COMPAT_PSR_C_BIT | COMPAT_PSR_V_BIT |
+ COMPAT_PSR_Q_BIT | COMPAT_PSR_IT_MASK |
+ COMPAT_PSR_GE_MASK | COMPAT_PSR_E_BIT |
+ COMPAT_PSR_T_BIT;
+ regs->pstate |= PSR_MODE32_BIT;
+
+ return 0;
+}
+
+static int valid_native_regs(struct user_pt_regs *regs)
+{
+ regs->pstate &= ~SPSR_EL1_AARCH64_RES0_BITS;
+
+ if (user_mode(regs) && !(regs->pstate & PSR_MODE32_BIT) &&
+ (regs->pstate & PSR_D_BIT) == 0 &&
+ (regs->pstate & PSR_A_BIT) == 0 &&
+ (regs->pstate & PSR_I_BIT) == 0 &&
+ (regs->pstate & PSR_F_BIT) == 0) {
+ return 1;
+ }
+
+ /* Force PSR to a valid 64-bit EL0t */
+ regs->pstate &= PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT;
+
+ return 0;
+}
+
+/*
+ * Are the current registers suitable for user mode? (used to maintain
+ * security in signal handlers)
+ */
+int valid_user_regs(struct user_pt_regs *regs, struct task_struct *task)
+{
+ if (!test_tsk_thread_flag(task, TIF_SINGLESTEP))
+ regs->pstate &= ~DBG_SPSR_SS;
+
+ if (is_compat_thread(task_thread_info(task)))
+ return valid_compat_regs(regs);
+ else
+ return valid_native_regs(regs);
+}