Handle stos and movs

zyedidia · Jun 5, 2024 · 49bc004 · 49bc004
1 parent c88450e
commit 49bc004
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diff --git a/lfi-leg/lfi-amd64.leg b/lfi-leg/lfi-amd64.leg
@@ -105,6 +105,8 @@ Insn = INDENT Label? (
       FnDirective
     | Directive
     | Lea
+    | Stos
+    | Movs
     | Lock
     | ModSP
     | Triple1
@@ -141,6 +143,32 @@ REMAINDER = < (!(EOL | ';') .)* > { $$ = (Transform) { .val = strndup(yytext, yy
 
 # --- loads and stores ---
 
+Stos = s:STOS r:REG COMMA '%es:(%rdi)' - {
+    mkdirective(".p2align 4\n");
+    mkinsn("movl %%edi, %%edi\n");
+    mkinsn("orq %%r14, %%rdi\n");
+    mkinsn("%s %s, %%es:(%%rdi)\n", s.val, r.val);
+    tfree(r);
+}
+
+STOS = < ('rep' -)? 'stos' - > {
+    $$ = (Transform) { .val = strndup(yytext, yyleng) }
+}
+
+Movs = m:MOVS '%ds:(%rsi)' - COMMA '%es:(%rdi)' - {
+    mkdirective(".p2align 4\n");
+    mkinsn("movl %%esi, %%esi\n");
+    mkinsn("movl %%edi, %%edi\n");
+    mkinsn("orq %%r14, %%rsi\n");
+    mkinsn("orq %%r14, %%rdi\n");
+    mkinsn("%s %%ds:(%%rsi), %%es:(%%rdi)\n", m.val);
+    tfree(m);
+}
+
+MOVS = < ('rep' -)? 'movs' [qlb] - > {
+    $$ = (Transform) { .val = strndup(yytext, yyleng) }
+}
+
 Lea = l:LEA a:AddrNoMod COMMA r:REG {
     mkinsn("%s %s, %s\n", l.val, a.val, r.val);
     tfree(l); tfree(a); tfree(r);

diff --git a/lfi-leg/test/amd64/test.s b/lfi-leg/test/amd64/test.s
@@ -26,3 +26,7 @@ add $0xc0, %rsp
 lock ; cmpxchg
 
 call *32+output(%rip)
+
+rep stos %eax, %es:(%rdi)
+
+rep movsq %ds:(%rsi), %es:(%rdi)