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authorH. Peter Anvin <hpa@linux.intel.com>2012-09-21 12:43:12 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2012-09-21 12:45:27 -0700
commit63bcff2a307b9bcc712a8251eb27df8b2e117967 (patch)
tree0a23a378d2c967edf63e9bb2b5df2288bf30859c /arch/x86/ia32
parenta052858fabb376b695f2c125633daa6728e0f284 (diff)
downloadlinux-63bcff2a307b9bcc712a8251eb27df8b2e117967.tar.bz2
x86, smap: Add STAC and CLAC instructions to control user space access
When Supervisor Mode Access Prevention (SMAP) is enabled, access to userspace from the kernel is controlled by the AC flag. To make the performance of manipulating that flag acceptable, there are two new instructions, STAC and CLAC, to set and clear it. This patch adds those instructions, via alternative(), when the SMAP feature is enabled. It also adds X86_EFLAGS_AC unconditionally to the SYSCALL entry mask; there is simply no reason to make that one conditional. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Link: http://lkml.kernel.org/r/1348256595-29119-9-git-send-email-hpa@linux.intel.com
Diffstat (limited to 'arch/x86/ia32')
-rw-r--r--arch/x86/ia32/ia32entry.S6
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 20e5f7ba0e6b..9c289504e680 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -14,6 +14,7 @@
#include <asm/segment.h>
#include <asm/irqflags.h>
#include <asm/asm.h>
+#include <asm/smap.h>
#include <linux/linkage.h>
#include <linux/err.h>
@@ -146,8 +147,10 @@ ENTRY(ia32_sysenter_target)
SAVE_ARGS 0,1,0
/* no need to do an access_ok check here because rbp has been
32bit zero extended */
+ ASM_STAC
1: movl (%rbp),%ebp
_ASM_EXTABLE(1b,ia32_badarg)
+ ASM_CLAC
orl $TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP-ARGOFFSET)
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
CFI_REMEMBER_STATE
@@ -301,8 +304,10 @@ ENTRY(ia32_cstar_target)
/* no need to do an access_ok check here because r8 has been
32bit zero extended */
/* hardware stack frame is complete now */
+ ASM_STAC
1: movl (%r8),%r9d
_ASM_EXTABLE(1b,ia32_badarg)
+ ASM_CLAC
orl $TS_COMPAT,TI_status+THREAD_INFO(%rsp,RIP-ARGOFFSET)
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
CFI_REMEMBER_STATE
@@ -365,6 +370,7 @@ cstar_tracesys:
END(ia32_cstar_target)
ia32_badarg:
+ ASM_CLAC
movq $-EFAULT,%rax
jmp ia32_sysret
CFI_ENDPROC