Implement setjmp / longjmp in jerry-libc.

JerryScript-DCO-1.0-Signed-off-by: Ruben Ayrapetyan r.ayrapetyan@samsung.com

jerry-libc/arch/x86-32.h

@@ -92,6 +92,17 @@
   pop %edi;               \
   ret;
 
+/*
+ * push argv (%esp + 4)
+ * push argc ([%esp + 0x4])
+ *
+ * call main
+ *
+ * push main_ret (%eax)
+ * call exit
+ *
+ * infinite loop
+ */
 #define _START             \
    mov %esp, %eax;         \
    add $4, %eax;           \
@@ -103,7 +114,100 @@
                            \
    push %eax;              \
    call exit;              \
+                           \
    1:                      \
    jmp 1b
 
+/*
+ * setjmp
+ *
+ * According to x86_32 System V ABI, the following registers are
+ * callee-saved, and so need to be stored in context:
+ *   - %ebx
+ *   - %esp
+ *   - %ebp
+ *   - %esi
+ *   - %edi
+ *   - x87 control word
+ *
+ * Also, we should store:
+ *   - return address (to jump to upon longjmp)
+ *
+ * mov return_address ([%esp]) -> %eax
+ *
+ * mov env ([%esp + 0x4]) -> %edx
+ *
+ * mov %ebx -> jmp_buf_0  ([%edx + 0x0])
+ * mov %esp -> jmp_buf_4  ([%edx + 0x4])
+ * mov %ebp -> jmp_buf_8  ([%edx + 0x8])
+ * mov %esi -> jmp_buf_12 ([%edx + 0xc])
+ * mov %edi -> jmp_buf_16 ([%edx + 0x10])
+ * mov %eax -> jmp_buf_20 ([%edx + 0x14])
+ * fnstcw   -> jmp_buf_24 ([%edx + 0x18])
+ *
+ * ret
+ */
+#define _SETJMP \
+  mov (%esp), %eax;       \
+  mov 0x4 (%esp), %edx;   \
+                          \
+  mov %ebx, 0x00 (%edx);  \
+  mov %esp, 0x04 (%edx);  \
+  mov %ebp, 0x08 (%edx);  \
+  mov %esi, 0x0c (%edx);  \
+  mov %edi, 0x10 (%edx);  \
+  mov %eax, 0x14 (%edx);  \
+  fnstcw 0x18 (%edx);     \
+                          \
+  xor %eax, %eax;         \
+                          \
+  ret
+
+/*
+ * longjmp
+ *
+ * See also:
+ *          _SETJMP
+ *
+ * mov env ([%esp + 0x4]) -> %edx
+ * mov val ([%esp + 0x8]) -> %eax
+ *
+ * mov jmp_buf_0    ([%edx + 0x0])  -> %ebx
+ * mov jmp_buf_4    ([%edx + 0x8])  -> %esp
+ * mov jmp_buf_8    ([%edx + 0x10]) -> %ebp
+ * mov jmp_buf_12   ([%edx + 0x18]) -> %esi
+ * mov jmp_buf_16   ([%edx + 0x20]) -> %edi
+ * mov jmp_buf_20   ([%edx + 0x28]) -> %ecx
+ * fldcw jmp_buf_24 ([%edx + 0x30])
+ *
+ * mov return_address (%ecx) -> ([%esp])
+ *
+ * cmp (%eax), 0x0
+ * jnz 1f
+ * xor %eax, %eax
+ * 1:
+ *
+ * ret
+ */
+#define _LONGJMP \
+  mov 0x4 (%esp), %edx;   \
+  mov 0x8 (%esp), %eax;   \
+                          \
+  mov 0x0 (%edx), %ebx;   \
+  mov 0x4 (%edx), %esp;   \
+  mov 0x8 (%edx), %ebp;   \
+  mov 0xc (%edx), %esi;   \
+  mov 0x10 (%edx), %edi;  \
+  mov 0x14 (%edx), %ecx;  \
+  fldcw 0x18 (%edx);      \
+                          \
+  mov %ecx, (%esp);       \
+                          \
+  test %eax, %eax;        \
+  jnz 1f;                 \
+  xor %eax, %eax;         \
+ 1:                       \
+                          \
+  ret
+
 #endif /* !ASM_X86_H */