Changeset ca8f84f in mainline for kernel/arch/amd64/src/asm.S

Timestamp:

2010-07-02T19:59:57Z (14 years ago)

Author:

Martin Decky <martin@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

fef504a

Parents:

bbfdf62

Message:

it might be handy for early_putchar to also interpret backspace
(i.e. for printing numeric updates and avoiding a time-consuming scrolling)

File:

• kernel/arch/amd64/src/asm.S (modified) (4 diffs)

kernel/arch/amd64/src/asm.S

@@ -347 +347 @@
  * Since the EGA can only display Extended ASCII (usually
  * ISO Latin 1) characters, some of the Unicode characters
- * can be displayed in a wrong way. Only the newline character
- * is interpreted, all other characters (even unprintable) are
+ * can be displayed in a wrong way. Only newline and backspace
+ * are interpreted, all other characters (even unprintable) are
  * printed verbatim.
  *
@@ -399 +399 @@
         
         cmp $0x0a, %al
-        jne early_putchar_print
+        jne early_putchar_backspace
         
                 /* Interpret newline */
@@ -413 +413 @@
                 subw %dx, %bx
                 
-                jmp early_putchar_newline
+                jmp early_putchar_skip
+        
+        early_putchar_backspace:
+        
+                cmp $0x08, %al
+                jne early_putchar_print
+                
+                /* Interpret backspace */
+                
+                cmp $0x0000, %bx
+                je early_putchar_skip
+                
+                dec %bx
+                jmp early_putchar_skip
         
         early_putchar_print:
@@ -423 +436 @@
                 inc %bx
         
-        early_putchar_newline:
+        early_putchar_skip:
         
         /* Sanity check for the cursor on the last line */