shellcraft: fix and optimize itoa

Fixes #2073
Gallopsled · Aug 7, 2022 · b825e97 · b825e97
1 parent 0533ba0
commit b825e97
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Showing 2 changed files with 11 additions and 13 deletions.
diff --git a/pwnlib/shellcraft/templates/amd64/itoa.asm b/pwnlib/shellcraft/templates/amd64/itoa.asm
@@ -35,14 +35,16 @@ assert v in registers.amd64
     ${mov('rdi', buffer)}
     ${mov('rax', v)}
     push rax /* save for later */
+    ${mov('rcx', 10)}
 ${size_loop}:
     ${mov('rdx', 0)}
-    ${mov('rcx', 10)}
     div rcx
-    inc rdi
+    stosb
     test rax, rax
     jnz ${size_loop}
-    dec rdi
+## null terminate
+    std
+    stosb
 ## Now we begin the actual division process
     pop rax
  ${itoa_loop}:
@@ -54,7 +56,4 @@ ${size_loop}:
     dec  rdi
     test rax, rax
     jnz  ${itoa_loop}
-## null terminate
-    ${mov('rdx', 0)}
-    mov  BYTE PTR [rdi], dl
-    inc  rdi
+    cld
diff --git a/pwnlib/shellcraft/templates/i386/itoa.asm b/pwnlib/shellcraft/templates/i386/itoa.asm
@@ -36,14 +36,16 @@ assert v in registers.i386
     ${mov('edi', buffer)}
     ${mov('eax', v)}
     push eax /* save for later */
+    ${mov('ecx', 10)}
 ${size_loop}:
     ${mov('edx', 0)}
-    ${mov('ecx', 10)}
     div ecx
     inc edi
     test eax, eax
     jnz ${size_loop}
-    dec edi
+## null terminate
+    std
+    stosb
 ## Now we begin the actual division process
     pop eax
  ${itoa_loop}:
@@ -55,7 +57,4 @@ ${size_loop}:
     dec  edi
     test eax, eax
     jnz  ${itoa_loop}
-## null terminate
-    ${mov('edx', 0)}
-    mov  BYTE PTR [edi], dl
-    inc  edi
+    cld