Changeset f2ef7fd in mainline for kernel/arch/ia32/src/asm.S

Timestamp:

2008-10-05T21:20:13Z (16 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

6198611

Parents:

1d132ae

Message:

Support for SYSENTER on ia32.

File:

• kernel/arch/ia32/src/asm.S (modified) (1 diff)

kernel/arch/ia32/src/asm.S

@@ -147 +147 @@
         popfl
 .endm   
+
+/*
+ * The SYSENTER syscall mechanism can be used for syscalls with
+ * four or fewer arguments. To pass these four arguments, we
+ * use four registers: EDX, ECX, EBX, ESI. The syscall number
+ * is passed in EAX. We use EDI to remember the return address
+ * and EBP to remember the stack. The INT-based syscall mechanism
+ * can actually handle six arguments plus the syscall number
+ * entirely in registers.
+ */
+.global sysenter_handler
+sysenter_handler:
+        pushl %ebp      # remember user stack
+        pushl %edi      # remember return user address
+
+        pushl %gs       # remember TLS
+
+        pushl %eax      # syscall number
+        subl $8, %esp   # unused sixth and fifth argument
+        pushl %esi      # fourth argument
+        pushl %ebx      # third argument
+        pushl %ecx      # second argument
+        pushl %edx      # first argument
+
+        movw $16, %ax
+        movw %ax, %ds
+        movw %ax, %es
+
+        cld
+        call syscall_handler
+        addl $28, %esp  # remove arguments from stack
+
+        pop %gs         # restore TLS
+
+        pop %edx        # prepare return EIP for SYSEXIT
+        pop %ecx        # prepare userspace ESP for SYSEXIT
+
+        sysexit         # return to userspace
+
 
 ## Declare interrupt handlers