Import of the watch repository from Pebble

src/libc/setjmp.c

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+///////////////////////////////////////
+// Implements:
+//   int setjmp(jmp_buf env);
+//   void longjmp(jmp_buf buf, int value);
+///////////////////////////////////////
+// Notes:
+//   This is entirely non-portable. It will need to be rewritten if we stop using ARM.
+//   Unfortunately, there is no portable way to define these.
+//   This means unit tests can't use our setjmp/longjmp either.
+
+#include <include/setjmp.h>
+
+#if __ARM_ARCH_ISA_THUMB >= 2
+// Valid for anything with THUMB2
+
+int __attribute__((__naked__)) setjmp(jmp_buf env) {
+  __asm volatile (
+  // move SP to a register we can store from and don't need to save
+  "mov  %ip, %sp\n"
+  // store all the registers
+  "stmia  %r0!, {%r4-%r9, %sl, %fp, %ip, %lr}\n"
+// using real FPU
+#if defined(__VFP_FP__) && !defined(__SOFTFP__)
+  // store FP registers
+  "vstmia %r0!, {%s16-%s31}\n"
+  // store FPSCR
+  "vmrs %r1, fpscr\n"
+  "str  %r1, [%r0], #4\n"
+#endif
+  // return 0
+  "mov  %r0, #0\n"
+  "bx lr\n"
+  );
+}
+
+void __attribute__((__naked__)) longjmp(jmp_buf buf, int value) {
+  __asm volatile (
+  // load all the registers
+  "ldmia  %r0!, {%r4-%r9, %sl, %fp, %ip, %lr}\n"
+  // load SP from a register we could load to and don't need to restore
+  "mov  %sp, %ip\n"
+// using real FPU
+#if defined(__VFP_FP__) && !defined(__SOFTFP__)
+  // load FP registers
+  "vldmia %r0!, {%s16-%s31}\n"
+  // load FPSCR
+  "ldr  %r2, [%r0], #4\n"
+  "vmsr fpscr, %r2\n"
+#endif
+  // return value
+  "movs %r0, %r1\n"
+  // unless it's 0, in which case, return 1.
+  "it eq\n"
+  "moveq  %r0, #1\n"
+  "bx lr\n"
+  );
+}
+#else
+// Undefined implementations, don't implement!
+// That way we get a link-time error.
+#endif