Changeset 0cd21bf in mainline for kernel/arch/ia32/src/asm.S

Timestamp:

2010-07-13T10:01:39Z (14 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

80c9416

Parents:

1b6c058

Message:

Sanitize EFLAGS in sysenter_handler.

File:

• kernel/arch/ia32/src/asm.S (modified) (3 diffs)

kernel/arch/ia32/src/asm.S

@@ -32 +32 @@
 
 #include <arch/pm.h>
+#include <arch/cpu.h>
 #include <arch/mm/page.h>
 
@@ -190 +191 @@
 .global sysenter_handler
 sysenter_handler:
-        sti
         subl $(ISTATE_REAL_SIZE), %esp
 
@@ -231 +231 @@
         movw %ax, %es
         
-        cld
+        /*
+         * Sanitize EFLAGS.
+         *
+         * SYSENTER does not clear the NT flag, which could thus proliferate
+         * from here to the IRET instruction via a context switch and result
+         * in crash.
+         *
+         * SYSENTER does not clear DF, which the ABI assumes to be cleared.
+         *
+         * SYSENTER clears IF, which we would like to be set for syscalls.
+         *
+         */
+        pushl $(EFLAGS_IF)  /* specify EFLAGS bits that we want to set */
+        popfl               /* set bits from the mask, clear or ignore others */
+
         call syscall_handler