x86/mm/pti: Force entry through trampoline when PTI active

Force the entry through the trampoline only when PTI is active. Otherwise
go through the normal entry code.

Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Borislav Petkov <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Laight <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: Eduardo Valentin <[email protected]>
Cc: Greg KH <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a9210f9b7cf842c46f976ff72bfefab16b5e5171..f2a94dfb434e9a7c61d6eacc28dd0129f6e844e1 100644 (file)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1339,7 +1339,10 @@ void syscall_init(void)
                (entry_SYSCALL_64_trampoline - _entry_trampoline);
 
        wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS);
-       wrmsrl(MSR_LSTAR, SYSCALL64_entry_trampoline);
+       if (static_cpu_has(X86_FEATURE_PTI))
+               wrmsrl(MSR_LSTAR, SYSCALL64_entry_trampoline);
+       else
+               wrmsrl(MSR_LSTAR, (unsigned long)entry_SYSCALL_64);
 
 #ifdef CONFIG_IA32_EMULATION
        wrmsrl(MSR_CSTAR, (unsigned long)entry_SYSCALL_compat);