From: Ian.Campbell@xensource.com <Ian.Campbell@xensource.com>
Date: Fri, 21 Apr 2006 16:19:31 +0000 (+0100)
Subject: Linux support for sysenter/exit on x86_32.
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~16117^2~33
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/success//%22http:/www.example.com/cgi/success/?a=commitdiff_plain;h=dadf394db4b56349c0aea6f72e406e5d3e2e80ac;p=xen.git

Linux support for sysenter/exit on x86_32.

This support is only active when supervisor_mode_kernel is enabled
in the Xen build (and when the hardware supports sysenter).

Signed-off-by: Ian Campbell <ian.campbell@xensource.com>
---

diff --git a/linux-2.6-xen-sparse/arch/i386/kernel/entry-xen.S b/linux-2.6-xen-sparse/arch/i386/kernel/entry-xen.S
index 78ad19ef2b..770d2e1fb4 100644
--- a/linux-2.6-xen-sparse/arch/i386/kernel/entry-xen.S
+++ b/linux-2.6-xen-sparse/arch/i386/kernel/entry-xen.S
@@ -239,7 +239,7 @@ sysenter_past_esp:
 	jae syscall_badsys
 	call *sys_call_table(,%eax,4)
 	movl %eax,EAX(%esp)
-	cli
+	DISABLE_INTERRUPTS
 	movl TI_flags(%ebp), %ecx
 	testw $_TIF_ALLWORK_MASK, %cx
 	jne syscall_exit_work
@@ -247,8 +247,23 @@ sysenter_past_esp:
 	movl EIP(%esp), %edx
 	movl OLDESP(%esp), %ecx
 	xorl %ebp,%ebp
+#ifdef CONFIG_XEN
+	__ENABLE_INTERRUPTS
+sysexit_scrit:	/**** START OF SYSEXIT CRITICAL REGION ****/
+	__TEST_PENDING
+	jnz  14f			# process more events if necessary...
+	movl ESI(%esp), %esi
+	sysexit
+14:	__DISABLE_INTERRUPTS
+sysexit_ecrit:	/**** END OF SYSEXIT CRITICAL REGION ****/
+	push %esp
+	call evtchn_do_upcall
+	add  $4,%esp
+	jmp  ret_from_intr
+#else
 	sti
 	sysexit
+#endif /* !CONFIG_XEN */
 
 
 	# system call handler stub
@@ -530,6 +545,11 @@ error_code:
 # So, on entry to the handler we detect whether we interrupted an
 # existing activation in its critical region -- if so, we pop the current
 # activation and restart the handler using the previous one.
+#
+# The sysexit critical region is slightly different. sysexit
+# atomically removes the entire stack frame. If we interrupt in the
+# critical region we know that the entire frame is present and correct
+# so we can simply throw away the new one.
 ENTRY(hypervisor_callback)
 	pushl %eax
 	SAVE_ALL
@@ -538,6 +558,11 @@ ENTRY(hypervisor_callback)
 	jb   11f
 	cmpl $ecrit,%eax
 	jb   critical_region_fixup
+	cmpl $sysexit_scrit,%eax
+	jb   11f
+	cmpl $sysexit_ecrit,%eax
+	ja   11f
+	addl $0x34,%esp			# Remove cs...ebx from stack frame.
 11:	push %esp
 	call evtchn_do_upcall
 	add  $4,%esp
diff --git a/linux-2.6-xen-sparse/arch/i386/kernel/sysenter.c b/linux-2.6-xen-sparse/arch/i386/kernel/sysenter.c
index 32e44f0f01..844c87e78c 100644
--- a/linux-2.6-xen-sparse/arch/i386/kernel/sysenter.c
+++ b/linux-2.6-xen-sparse/arch/i386/kernel/sysenter.c
@@ -20,6 +20,10 @@
 #include <asm/pgtable.h>
 #include <asm/unistd.h>
 
+#ifdef CONFIG_XEN
+#include <xen/interface/callback.h>
+#endif
+
 extern asmlinkage void sysenter_entry(void);
 
 void enable_sep_cpu(void)
@@ -54,6 +58,18 @@ int __init sysenter_setup(void)
 {
 	syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
 
+#ifdef CONFIG_XEN
+	if (boot_cpu_has(X86_FEATURE_SEP)) {
+		struct callback_register sysenter = {
+			.type = CALLBACKTYPE_sysenter,
+			.address = { __KERNEL_CS, (unsigned long)sysenter_entry },
+		};
+
+		if (HYPERVISOR_callback_op(CALLBACKOP_register, &sysenter) < 0)
+			clear_bit(X86_FEATURE_SEP, boot_cpu_data.x86_capability);
+	}
+#endif
+
 	if (boot_cpu_has(X86_FEATURE_SEP)) {
 		memcpy(syscall_page,
 		       &vsyscall_sysenter_start,