Parse segment register on x64

`mov %fs:0,%rax`
tyfkda · Mar 28, 2024 · e7e5cee · e7e5cee
1 parent c99f3df
commit e7e5cee
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diff --git a/src/as/asm_x86.c b/src/as/asm_x86.c
@@ -269,6 +269,24 @@ static unsigned char *asm_mov_rd(Inst *inst, Code *code) {
   return p;
 }
 
+static unsigned char *asm_mov_sr(Inst *inst, Code *code) {
+  if (inst->src.segment.reg == FS && inst->dst.reg.size == REG64) {
+    Expr *offset = inst->src.segment.offset;
+    if (offset == NULL || offset->kind == EX_FIXNUM) {
+      uint64_t value = offset == NULL ? 0 : offset->fixnum;
+      short buf[] = {
+        0x64, 0x48, 0x8b, 0x04, 0x25,
+      };
+      unsigned char *p = code->buf;
+      p = put_code_filtered(p, buf, ARRAY_SIZE(buf));
+      PUT_CODE(p, IM32(value));
+      p += 4;
+      return p;
+    }
+  }
+  return NULL;
+}
+
 static unsigned char *asm_movbwlq_imi(Inst *inst, Code *code) {
   long offset = inst->dst.indirect.offset->fixnum;
   unsigned char sno = 0;
@@ -1506,6 +1524,7 @@ static const AsmInstTable *table[] = {
     {asm_mov_iir, INDIRECT_WITH_INDEX, REG},
     {asm_mov_dr, DIRECT, REG},
     {asm_mov_rd, REG, DIRECT},
+    {asm_mov_sr, SEGMENT_OFFSET, REG},
     {NULL} },
   [MOVB] = table_movbwlq,  [MOVW] = table_movbwlq,  [MOVL] = table_movbwlq,  [MOVQ] = table_movbwlq,
   [MOVSX] = table_movszx,  [MOVZX] = table_movszx,

diff --git a/src/as/inst.h b/src/as/inst.h
@@ -205,6 +205,14 @@ enum RegType {
   R15,
 
   RIP,
+
+  // Segment register
+  CS,
+  DS,
+  ES,
+  FS,
+  GS,
+  SS,
 };
 
 enum RegXmmType {
@@ -237,6 +245,7 @@ enum OperandType {
   DEREF_INDIRECT,  // *ofs(%rax)
   DEREF_INDIRECT_WITH_INDEX,  // *(%rax, %rcx, 4)
   REG_XMM,
+  SEGMENT_OFFSET,
 };
 
 enum ExprKind {
@@ -292,6 +301,10 @@ typedef struct {
       Reg index_reg;
     } indirect_with_index;
     enum RegXmmType regxmm;
+    struct {
+      enum RegType reg;
+      Expr *offset;
+    } segment;
   };
 } Operand;
 

diff --git a/src/as/parse_asm.c b/src/as/parse_asm.c
@@ -205,6 +205,13 @@ static const struct {
   {"r15", R15},
 
   {"rip", RIP},
+
+  {"cs", CS},
+  {"ds", DS},
+  {"es", ES},
+  {"fs", FS},
+  {"gs", GS},
+  {"ss", SS},
 };
 
 static const char kXmmRegisters[][6] = {
@@ -258,6 +265,10 @@ inline bool is_reg64(enum RegType reg) {
   return reg >= RAX && reg <= R15;
 }
 
+inline bool is_segment(enum RegType reg) {
+  return reg >= CS && reg <= SS;
+}
+
 static int find_match_index(const char **pp, const char **table, size_t count) {
   const char *p = *pp;
   const char *start = p;
@@ -454,6 +465,18 @@ static enum RegType parse_direct_register(ParseInfo *info, Operand *operand) {
   }
 
   enum RegType reg = find_register(&info->p);
+  if (is_segment(reg)) {
+    Expr *offset = NULL;
+    if (*info->p == ':') {
+      ++info->p;
+      offset = parse_expr(info);
+    }
+    operand->type = SEGMENT_OFFSET;
+    operand->segment.reg = reg;
+    operand->segment.offset = offset;
+    return true;
+  }
+
   enum RegSize size;
   int no;
   if (is_reg8(reg)) {