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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Thu, 1 Nov 2012 15:17:44 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r242433 - head/sys/amd64/amd64
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Author: kib
Date: Thu Nov  1 15:17:43 2012
New Revision: 242433
URL: http://svn.freebsd.org/changeset/base/242433

Log:
  Enable the new instructions for reading and writing bases for %fs,
  %gs, when supported.  Note that WRFSBASE and WRGSBASE are not very
  useful on FreeBSD right now, because a return from the kernel mode to
  userspace reloads the bases specified by the sysarch(2) syscall, most
  likely.
  
  Enable the Supervisor Mode Execution Prevention (SMEP) when
  supported. Since the loader(8) performs hand-off to the kernel with
  the page tables which contradict the SMEP, postpone enabling the SMEP
  on BSP until pmap switched for the proper kernel tables.
  
  Debugged with the help from:	avg
  Tested by:	avg, Michael Moll <kvedulv@kvedulv.de>
  MFC after:	1 month

Modified:
  head/sys/amd64/amd64/initcpu.c
  head/sys/amd64/amd64/pmap.c

Modified: head/sys/amd64/amd64/initcpu.c
==============================================================================
--- head/sys/amd64/amd64/initcpu.c	Thu Nov  1 15:14:37 2012	(r242432)
+++ head/sys/amd64/amd64/initcpu.c	Thu Nov  1 15:17:43 2012	(r242433)
@@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
+#include <sys/pcpu.h>
 #include <sys/systm.h>
 #include <sys/sysctl.h>
 
@@ -153,11 +154,25 @@ void
 initializecpu(void)
 {
 	uint64_t msr;
+	uint32_t cr4;
 
+	cr4 = rcr4();
 	if ((cpu_feature & CPUID_XMM) && (cpu_feature & CPUID_FXSR)) {
-		load_cr4(rcr4() | CR4_FXSR | CR4_XMM);
+		cr4 |= CR4_FXSR | CR4_XMM;
 		cpu_fxsr = hw_instruction_sse = 1;
 	}
+	if (cpu_stdext_feature & CPUID_STDEXT_FSGSBASE)
+		cr4 |= CR4_FSGSBASE;
+
+	/*
+	 * Postpone enabling the SMEP on the boot CPU until the page
+	 * tables are switched from the boot loader identity mapping
+	 * to the kernel tables.  The boot loader enables the U bit in
+	 * its tables.
+	 */
+	if (!IS_BSP() && (cpu_stdext_feature & CPUID_STDEXT_SMEP))
+		cr4 |= CR4_SMEP;
+	load_cr4(cr4);
 	if ((amd_feature & AMDID_NX) != 0) {
 		msr = rdmsr(MSR_EFER) | EFER_NXE;
 		wrmsr(MSR_EFER, msr);

Modified: head/sys/amd64/amd64/pmap.c
==============================================================================
--- head/sys/amd64/amd64/pmap.c	Thu Nov  1 15:14:37 2012	(r242432)
+++ head/sys/amd64/amd64/pmap.c	Thu Nov  1 15:17:43 2012	(r242433)
@@ -622,6 +622,8 @@ pmap_bootstrap(vm_paddr_t *firstaddr)
 	/* XXX do %cr0 as well */
 	load_cr4(rcr4() | CR4_PGE | CR4_PSE);
 	load_cr3(KPML4phys);
+	if (cpu_stdext_feature & CPUID_STDEXT_SMEP)
+		load_cr4(rcr4() | CR4_SMEP);
 
 	/*
 	 * Initialize the kernel pmap (which is statically allocated).