[PATCH 3.16 222/254] x86/mce: Make machine check speculation protected

Ben Hutchings
2018-02-28T16:14:30Z

From: Thomas Gleixner <tglx@linutronix.de>

commit 6f41c34d69eb005e7848716bbcafc979b35037d5 upstream.

The machine check idtentry uses an indirect branch directly from the low
level code. This evades the speculation protection.

Replace it by a direct call into C code and issue the indirect call there
so the compiler can apply the proper speculation protection.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by:Borislav Petkov <bp@alien8.de>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Niced-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801181626290.1847@nanos
[bwh: Backported to 3.16
- #include <asm/traps.h> in mce.c
- Adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -91,6 +91,7 @@ dotraplinkage void do_simd_coprocessor_e
#ifdef CONFIG_X86_32
dotraplinkage void do_iret_error(struct pt_regs *, long);
#endif
+dotraplinkage void do_mce(struct pt_regs *, long);

static inline int get_si_code(unsigned long condition)
{
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -46,6 +46,7 @@
#include <asm/tlbflush.h>
#include <asm/mce.h>
#include <asm/msr.h>
+#include <asm/traps.h>

#include "mce-internal.h"

@@ -1693,6 +1694,11 @@ static void unexpected_machine_check(str
void (*machine_check_vector)(struct pt_regs *, long error_code) =
unexpected_machine_check;

+dotraplinkage void do_mce(struct pt_regs *regs, long error_code)
+{
+ machine_check_vector(regs, error_code);
+}
+
/*
* Called for each booted CPU to set up machine checks.
* Must be called with preempt off:
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1320,7 +1320,7 @@ trace_idtentry page_fault do_page_fault
idtentry async_page_fault do_async_page_fault has_error_code=1
#endif
#ifdef CONFIG_X86_MCE
-idtentry machine_check has_error_code=0 paranoid=1 do_sym=*machine_check_vector(%rip)
+idtentry machine_check do_mce has_error_code=0 paranoid=1
#endif

/*