x86/mce: Make machine check speculation protected
CVE-2017-5715 (Spectre v2 retpoline) commit 6f41c34d 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@nanosSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> (cherry picked from commit 64d0fe7072138d34d60b903edf597161ac3d05b9) Signed-off-by: Andy Whitcroft <apw@canonical.com> Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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