Re: [PATCH v7 12/14] x86/vsyscall/64: Fixup shadow stack and branch tracking for vsyscall

When emulating a RET, also unwind the task's shadow stack and cancel
the current branch tracking status.

Signed-off-by: Yu-cheng Yu <redacted>
---
 arch/x86/entry/vsyscall/vsyscall_64.c | 28 +++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index d9d81ad7a400..6869ef9d1e8b 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c

@@ -38,6 +38,8 @@
 #include <asm/fixmap.h>
 #include <asm/traps.h>
 #include <asm/paravirt.h>
+#include <asm/fpu/xstate.h>
+#include <asm/fpu/types.h>

 #define CREATE_TRACE_POINTS
 #include "vsyscall_trace.h"

@@ -92,6 +94,30 @@ static int addr_to_vsyscall_nr(unsigned long addr)
        return nr;
 }

+void fixup_shstk(void)
+{
+#ifdef CONFIG_X86_INTEL_SHADOW_STACK_USER
+       u64 r;
+
+       if (current->thread.cet.shstk_enabled) {
+               rdmsrl(MSR_IA32_PL3_SSP, r);
+               wrmsrl(MSR_IA32_PL3_SSP, r + 8);
+       }
+#endif
+}
+
+void fixup_ibt(void)
+{
+#ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER
+       u64 r;
+
+       if (current->thread.cet.ibt_enabled) {
+               rdmsrl(MSR_IA32_U_CET, r);
+               wrmsrl(MSR_IA32_U_CET, r & ~MSR_IA32_CET_WAIT_ENDBR);
+       }
+#endif
+}