Add location hint to code block mmap call

ruby · Oct 20, 2021 · 304adba · 304adba
1 parent c20066b
commit 304adba
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Showing 2 changed files with 32 additions and 8 deletions.
diff --git a/ujit_asm.c b/ujit_asm.c
@@ -117,7 +117,7 @@ void cb_init(codeblock_t* cb, size_t mem_size)
 {
     // Map the memory as executable
     cb->mem_block = (uint8_t*)mmap(
-        NULL,
+        &cb_init,
         mem_size,
         PROT_READ | PROT_WRITE | PROT_EXEC,
         MAP_PRIVATE | MAP_ANON,
@@ -1083,15 +1083,13 @@ void jmp_rm(codeblock_t* cb, x86opnd_t opnd)
     cb_write_rm(cb, false, false, NO_OPND, opnd, 4, 1, 0xFF);
 }
 
-/*
-/// Opcode for direct jump with relative 8-bit offset
-const ubyte JMP_REL8_OPCODE = 0xEB;
-*/
-
 /*
 /// jmp - Jump with relative 8-bit offset
 void jmp8(CodeBlock cb, int8_t offset)
 {
+    /// Opcode for direct jump with relative 8-bit offset
+    const ubyte JMP_REL8_OPCODE = 0xEB;
+
     cb.writeASM("jmp", ((offset > 0)? "+":"-") ~ to!string(offset));
     cb.writeByte(JMP_REL8_OPCODE);
     cb.writeByte(offset);

diff --git a/ujit_compile.c b/ujit_compile.c
@@ -170,6 +170,7 @@ ujit_compile_insn(rb_iseq_t *iseq, unsigned int insn_idx, unsigned int* next_uji
         st_data_t st_gen_fn;
         if (!rb_st_lookup(gen_fns, opcode, &st_gen_fn))
         {
+            //print_int(cb, imm_opnd(num_instrs));
             //print_str(cb, insn_name(opcode));
             break;
         }
@@ -200,8 +201,6 @@ ujit_compile_insn(rb_iseq_t *iseq, unsigned int insn_idx, unsigned int* next_uji
         return NULL;
     }
 
-    //print_int(cb, imm_opnd(num_instrs));
-
     // Write the adjusted SP back into the CFP
     if (ctx.stack_diff != 0)
     {
@@ -217,6 +216,33 @@ ujit_compile_insn(rb_iseq_t *iseq, unsigned int insn_idx, unsigned int* next_uji
     // Write the post call bytes
     ujit_instr_exit(cb);
 
+    /*
+    // Hack to patch a relative 32-bit jump to the instruction handler
+    int next_opcode = (int)*ctx.pc;
+    const void * const *table = rb_vm_get_insns_address_table();
+    VALUE encoded = (VALUE)table[next_opcode];
+    uint8_t* p_handler = (uint8_t*)encoded;
+
+    uint8_t* p_code = &cb->mem_block[cb->write_pos];
+    int64_t rel64 = ((int64_t)p_handler) - ((int64_t)p_code - 2 + 5);
+
+    //printf("p_handler: %lld\n", (int64_t)p_handler);
+    //printf("rel64: %lld\n", rel64);
+
+    uint8_t byte0 = cb->mem_block[cb->write_pos - 2];
+    uint8_t byte1 = cb->mem_block[cb->write_pos - 1];
+
+    //printf("cb_init: %lld\n", (int64_t)&cb_init);
+    //printf("%lld\n", rel64);
+
+    if (byte0 == 0xFF && byte1 == 0x20 && rel64 >= -2147483648 && rel64 <= 2147483647)
+    {
+        //printf("%02X %02X\n", (int)byte0, (int)byte1);
+        cb->write_pos -= 2;
+        jmp32(cb, (int32_t)rel64);
+    }
+    */
+
     addr2insn_bookkeeping(code_ptr, first_opcode);
 
     return code_ptr;