From f31b200b58e994b7505707931d4278e3f61cc2d6 Mon Sep 17 00:00:00 2001
From: Camil Staps
Date: Mon, 24 Dec 2018 14:15:16 +0100
Subject: Iterative development

---
 sjit_c.c | 35 +++++++++++++++++++++++------------
 1 file changed, 23 insertions(+), 12 deletions(-)

(limited to 'sjit_c.c')

diff --git a/sjit_c.c b/sjit_c.c
index 50e8f57..879ec18 100644
--- a/sjit_c.c
+++ b/sjit_c.c
@@ -106,7 +106,7 @@ static inline void gen_instr(char *full_code, char **code_p, uint64_t **pgm_p, u
 		case Call:
 			arg=pgm[1];
 #ifdef DEBUG_JIT_INSTRUCTIONS
-			fprintf(stderr,"Call %lu -> %d\n",arg,mapping[arg]-(&code[5]-full_code));
+			fprintf(stderr,"Call %lu -> %d\n",arg,mapping[arg]-(uint32_t)(&code[5]-full_code));
 #endif
 			code[0]='\xe8'; /* callq ARG */
 			*(uint32_t*)&code[1]=mapping[arg]-(&code[5]-full_code);
@@ -181,15 +181,20 @@ static inline void gen_instr(char *full_code, char **code_p, uint64_t **pgm_p, u
 	*pgm_p=pgm;
 }
 
-unsigned int jit(uint64_t *pgm) {
+void init_jit(uint64_t max_instrs, uint64_t max_code_len,
+		char **code_block, uint32_t **mapping) {
+	*code_block=mmap (NULL,max_code_len,PROT_READ | PROT_EXEC,MAP_ANONYMOUS | MAP_PRIVATE,0,0);
+	*mapping=malloc (max_instrs*sizeof(uint32_t));
+}
+
+char *jit_append(char *code_block, uint32_t code_len, char *code_ptr,
+		uint32_t *mapping, uint32_t n_instr, uint64_t *pgm, int is_main) {
 	uint32_t len=*pgm++;
 	uint32_t i;
-
-	uint32_t *mapping=malloc(len*sizeof(uint32_t));
-	uint32_t code_i=0;
+	uint32_t code_i=code_ptr-code_block;
 
 	uint64_t *pgm_p=pgm;
-	for (i=0; i<len; i++) {
+	for (i=n_instr; i<n_instr+len; i++) {
 		enum instr instr=(enum instr)*pgm_p;
 
 		mapping[i]=code_i;
@@ -209,14 +214,20 @@ unsigned int jit(uint64_t *pgm) {
 		}
 	}
 
-	char *code=mmap(NULL, code_i, PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
-	char *code_wr=code;
+	mprotect (code_block,code_len,PROT_WRITE);
+
+	if (is_main)
+		*(uint32_t*)&code_block[9]=code_ptr-code_block-13;
+
 	pgm_p=pgm;
 	for (i=0; i<len; i++)
-		gen_instr(code, &code_wr, &pgm_p, mapping);
+		gen_instr (code_block,&code_ptr,&pgm_p,mapping);
+
+	mprotect (code_block,code_len,PROT_READ | PROT_EXEC);
 
-	mprotect(code, code_i, PROT_READ | PROT_EXEC);
-	int (*fun)(void) = (int(*)(void)) code;
+	return code_ptr;
+}
 
-	return fun();
+uint64_t jit_exec(char *code_block) {
+	return ((uint64_t(*)(void))code_block)();
 }
-- 
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