libc: Implement setjmp() and longjmp()

apps/src/init.c

@@ -1,4 +1,5 @@
 #include <luna.h>
+#include <setjmp.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -167,11 +168,16 @@ int main()
         perror("execv");
         return 1;
     }
+    else { printf("Success!! Got PID %ld\n", child); }
+
+    jmp_buf env;
+    int val = setjmp(env);
+    if (val == 0) { printf("Returning from setjmp!\n"); }
     else
     {
-        printf("Success!! Got PID %ld\n", child);
+        printf("Returning from longjmp! val=%d\n", val);
         return 0;
     }
 
-    return 0;
+    longjmp(env, 3);
 }

libs/libc/include/setjmp.h

@@ -2,19 +2,28 @@
 #define _SETJMP_H
 
 #include <bits/macros.h>
+#include <stdint.h>
 
-typedef int jmp_buf[1];
-typedef int sigjmp_buf[1];
+typedef uintptr_t jmp_buf[8];
+typedef uintptr_t sigjmp_buf[8];
 
 #ifdef __cplusplus
 extern "C"
 {
 #endif
 
-    int setjmp(jmp_buf env);                                // Not implemented.
-    int sigsetjmp(sigjmp_buf env, int savesigs);            // Not implemented.
-    __lc_noreturn void longjmp(jmp_buf env, int val);       // Not implemented.
-    __lc_noreturn void siglongjmp(sigjmp_buf env, int val); // Not implemented.
+    /* Saves the current execution state in env. Returns 0 when called from the first time, or nonzero when returning
+     * from longjmp.  */
+    int setjmp(jmp_buf env);
+
+    /* Right now, does the exact same as setjmp() (savesigs is ignored), since signals are not implemented. */
+    int sigsetjmp(sigjmp_buf env, int savesigs);
+
+    /* Restores the execution state saved in env by a setjmp() call. */
+    __lc_noreturn void longjmp(jmp_buf env, int val);
+
+    /* Right now, does the exact same as longjmp(), since signals are not implemented. */
+    __lc_noreturn void siglongjmp(sigjmp_buf env, int val);
 
 #ifdef __cplusplus
 }

libs/libc/src/setjmp.asm

@@ -0,0 +1,36 @@
+global _setjmp
+global setjmp
+_setjmp:
+setjmp:
+    mov rsi, 0
+    mov [rdi], rbx
+    mov [rdi+8], r12
+    mov [rdi+16], r13
+    mov [rdi+24], r14
+    mov [rdi+32], r15
+    mov [rdi+40], rbp 
+    mov [rdi+48], rsp
+    mov rax, [rsp]
+    mov [rdi+56], rax
+    xor rax, rax
+    ret
+
+global _longjmp
+global longjmp
+_longjmp:
+longjmp:
+    mov rax, rsi
+    cmp rax, 0
+    jne .nonzero
+    mov rax, 1
+.nonzero:
+    mov rbx, [rdi]
+    mov r12, [rdi+8]
+    mov r13, [rdi+16]
+    mov r14, [rdi+24]
+    mov r15, [rdi+32]
+    mov rbp, [rdi+40]
+    mov rsp, [rdi+48]
+    mov rcx, [rdi+56]
+    mov [rsp], rcx
+    ret

libs/libc/src/setjmp.cpp

@@ -3,23 +3,13 @@
 
 extern "C"
 {
-    int setjmp(jmp_buf)
+    int sigsetjmp(sigjmp_buf env, int)
     {
-        NOT_IMPLEMENTED("setjmp");
+        return setjmp(env);
     }
 
-    int sigsetjmp(sigjmp_buf, int)
+    __lc_noreturn void siglongjmp(sigjmp_buf env, int val)
     {
-        NOT_IMPLEMENTED("sigsetjmp");
-    }
-
-    __lc_noreturn void longjmp(jmp_buf, int)
-    {
-        NOT_IMPLEMENTED("longjmp");
-    }
-
-    __lc_noreturn void siglongjmp(sigjmp_buf, int)
-    {
-        NOT_IMPLEMENTED("siglongjmp");
+        longjmp(env, val);
     }
 }