[liba] Add setjmp and longjmp

Change-Id: I3a57787199308900de8e7c6ce5961b2a26f6d38e

liba/include/setjmp.h

@@ -1,4 +1,17 @@
 #ifndef LIBA_SETJMP_H
 #define LIBA_SETJMP_H
 
+/* We are preseving registers:
+ * - sp & lr -> 2x4 bytes
+ * - General purpose registers: r4-r9, r10 = sl, r11 = fp -> 8x4 bytes
+ * - Floating point registers: s16-s31 -> 8x8 bytes
+ * - VFP status register: fpscr ->1x4 bytes
+ * The buffer size has to include room for setjmp implementation: 4x4 bytes.
+ * (See C Library ABI for the ARM architecture documentation)
+ * The minimum buffer size is then (2+8+16+1+4)xsizeof(int64_t). */
+
+typedef int jmp_buf[31];
+void longjmp(jmp_buf env, int val);
+int setjmp(jmp_buf env);
+
 #endif