[liba] Add setjmp and longjmp

Change-Id: I3a57787199308900de8e7c6ce5961b2a26f6d38e

Makefile

@@ -113,6 +113,10 @@ endif
 	@echo "CC      $@"
 	@$(CC) $(SFLAGS) $(CFLAGS) -c $< -o $@
 
+%.o: %.s
+	@echo "AS      $@"
+	@$(CC) $(SFLAGS) -c $< -o $@
+
 %.o: %.cpp
 	@echo "CXX     $@"
 	@$(CXX) $(SFLAGS) $(CXXFLAGS) -c $< -o $@

liba/Makefile

@@ -3,6 +3,8 @@ SFLAGS += -Iliba/include
 liba/src/external/sqlite/mem5.o: CFLAGS += -w
 
 objs += $(addprefix liba/src/, \
+  armv7m/setjmp.o \
+  armv7m/longjmp.o \
   assert.o \
   bzero.o \
   ctype.o \

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

liba/src/armv7m/longjmp.s

@@ -0,0 +1,24 @@
+.syntax unified
+
+.section .text
+.align 2
+.thumb
+.global longjmp
+longjmp:
+  /* Restore all the regsiters to get back in the original state (whenever the
+     matching setjmp was called. */
+  // General purpose registers
+  ldmia  r0!, { r4-r11, ip, lr }
+  // Floating point registers
+  vldmia r0!, { s16-s31 }
+  // Special case for VFP status register
+  ldr r0, [r0, #4]
+  vmsr fpscr, r0
+  mov  sp, ip
+  /* Put the return value in the integer result register, but return 1 if it is
+     in fact zero. */
+  movs r0, r1
+  it eq
+  moveq r0, #1
+  bx lr
+.type longjmp, function

liba/src/armv7m/setjmp.s

@@ -0,0 +1,20 @@
+.syntax unified
+
+.section .text
+.align 2
+.thumb
+.global setjmp
+setjmp:
+  /* Save all the registers into the jump buffer */
+  mov ip, sp
+  // storing r4-r9, r10=sl, r11=fp, ip=sp, lr
+  stmia r0!, { r4-r11, ip, lr}
+  // storing floating point registers
+  vstmia r0!, {s16-s31}
+  // Special storing: fpscr
+  vmrs r1, fpscr
+  str  r1, [r0, #4]
+  /* And then return 0 */
+  mov  a1, #0
+  bx lr
+.type setjmp, function