fixup! c18n: Rework implementation to be interrupt-safe

libexec/rtld-elf/aarch64/rtld_c18n_asm.S

@@ -437,7 +437,7 @@ TRAMP(tramp_pop_frame)
 	 * Load the address of the previous trusted frame, the compartment ID of
 	 * the caller, and the number of return value registers.
 	 */
-	ldp	c16, c10, [TRUSTED_STACK_C, #(CAP_WIDTH * 14)]
+	ldp	c17, c10, [TRUSTED_STACK_C, #(CAP_WIDTH * 14)]
 
 	/*
 	 * Load the caller's current stack top and old stack top.
@@ -454,15 +454,6 @@ TRAMP(tramp_pop_frame)
 	ldp	c19, c20, [TRUSTED_STACK_C, #(CAP_WIDTH * 2)]
 	ldp	c29, c30, [TRUSTED_STACK_C]
 
-	/*
-	 * Get the stack lookup table.
-	 */
-	mrs	STACK_TABLE_C, STACK_TABLE
-	/*
-	 * Store the caller's old stack top in the stack lookup table.
-	 */
-	str	c12, [STACK_TABLE_C, w10, uxtw #0]
-
 	/*
 	 * Install the caller's stack.
 	 *
@@ -474,7 +465,16 @@ TRAMP(tramp_pop_frame)
 	/*
 	 * Bump the trusted stack pointer.
 	 */
-	msr	TRUSTED_STACK, c16
+	msr	TRUSTED_STACK, c17
+
+	/*
+	 * Get the stack lookup table.
+	 */
+	mrs	STACK_TABLE_C, STACK_TABLE
+	/*
+	 * Store the caller's old stack top in the stack lookup table.
+	 */
+	str	c12, [STACK_TABLE_C, w10, uxtw #0]
 
 	/*
 	 * Extrace the number of return value registers.

libexec/rtld-elf/rtld_c18n.c

@@ -1744,7 +1744,8 @@ _rtld_sighandler_impl(int sig, siginfo_t *info, ucontext_t *ucp, void *nsp
 	 */
 	intr_idx = tf->callee;
 	intr = index_to_cid(intr_idx);
-	if (table->sizes->capacity >= intr || table->sizes->data[intr] == 0) {
+	if (table->sizes->capacity >= intr ||
+	    table->sizes->data[intr].size == 0) {
 		/*
 		 * If the interrupt occurred at a point in the trampoline where
 		 * stack resolution is taking place, nsp would remain the