VeraCrypt
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authorMounir IDRASSI <mounir.idrassi@idrix.fr>2017-08-02 15:25:06 (GMT)
committerMounir IDRASSI <mounir.idrassi@idrix.fr>2017-08-02 15:31:19 (GMT)
commit2fde7f0b4738494ff58bf2bc3fe5810c1d2546d8 (patch)
tree611061f0962e0d424cd7f266af149371c45fafa6
parent21fc5a8750f5dfbb33f6830d7520cd799cd2b930 (diff)
downloadVeraCrypt-2fde7f0b4738494ff58bf2bc3fe5810c1d2546d8.zip
VeraCrypt-2fde7f0b4738494ff58bf2bc3fe5810c1d2546d8.tar.gz
Windows MBR bootloader: reduce CPU usage during password prompt (Credit: Jason Pyeron of CipherShed project https://github.com/CipherShed/CipherShed/commit/00ea00e8e6a23a4243316f860aa07ed59203ab97)
-rw-r--r--src/Boot/Windows/BootConsoleIo.cpp23
1 files changed, 22 insertions, 1 deletions
diff --git a/src/Boot/Windows/BootConsoleIo.cpp b/src/Boot/Windows/BootConsoleIo.cpp
index b03098f..9148f5c 100644
--- a/src/Boot/Windows/BootConsoleIo.cpp
+++ b/src/Boot/Windows/BootConsoleIo.cpp
@@ -238,11 +238,32 @@ byte GetKeyboardChar ()
return GetKeyboardChar (nullptr);
}
+/*
+inline void Sleep ()
+{
+ __asm
+ {
+ mov al, 0
+ mov ah, 0x86
+ // Sleep for 250 milliseconds = 250 000 microseconds = 0x0003D090
+ mov cx, 0x0003
+ mov dx, 0xD090
+ int 0x15
+ }
+}
+*/
byte GetKeyboardChar (byte *scanCode)
{
// Work around potential BIOS bugs (Windows boot manager polls the keystroke buffer)
- while (!IsKeyboardCharAvailable());
+ while (!IsKeyboardCharAvailable())
+ {
+ // reduce CPU usage by halting CPU until the next external interrupt is fired
+ __asm
+ {
+ hlt
+ }
+ }
byte asciiCode;
byte scan;