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From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Borislav Petkov <bp@alien8.de>,
	David Woodhouse <dwmw@amazon.co.uk>
Subject: [PATCH] x86/mce: Make machine check speculation protected
Date: Thu, 18 Jan 2018 16:28:26 +0100 (CET)
Message-ID: <alpine.DEB.2.20.1801181626290.1847@nanos> (raw)

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>
---
 arch/x86/entry/entry_64.S        |    2 +-
 arch/x86/include/asm/traps.h     |    1 +
 arch/x86/kernel/cpu/mcheck/mce.c |    5 +++++
 3 files changed, 7 insertions(+), 1 deletion(-)

--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1264,7 +1264,7 @@ idtentry async_page_fault	do_async_page_
 #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
 
 /*
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -88,6 +88,7 @@ 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
@@ -1785,6 +1785,11 @@ 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:

             reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-18 15:28 Thomas Gleixner [this message]
2018-01-18 15:46 ` Peter Zijlstra
2018-01-18 15:53 ` Borislav Petkov
2018-01-18 15:55 ` David Woodhouse
2018-01-19  8:46 ` Woodhouse, David
2018-01-19 15:46 ` [tip:x86/pti] " tip-bot for Thomas Gleixner

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