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Message-Id: <20200505134058.863038566@linutronix.de>
Date: Tue, 05 May 2020 15:16:10 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: x86@...nel.org, "Paul E. McKenney" <paulmck@...nel.org>,
Andy Lutomirski <luto@...nel.org>,
Alexandre Chartre <alexandre.chartre@...cle.com>,
Frederic Weisbecker <frederic@...nel.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Petr Mladek <pmladek@...e.com>,
Steven Rostedt <rostedt@...dmis.org>,
Joel Fernandes <joel@...lfernandes.org>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Juergen Gross <jgross@...e.com>,
Brian Gerst <brgerst@...il.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Will Deacon <will@...nel.org>, Borislav Petkov <bp@...en8.de>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: [patch V4 part 1 08/36] x86/doublefault: Remove memmove() call
Use of memmove() in #DF is problematic considered tracing and other
instrumentation.
Remove the memmove() call and simply write out what needs doing; this
even clarifies the code, win-win! The code copies from the espfix64
stack to the normal task stack, there is no possible way for that to
overlap.
Survives selftests/x86, specifically sigreturn_64.
Suggested-by: Borislav Petkov <bp@...en8.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Andy Lutomirski <luto@...nel.org>
Link: https://lkml.kernel.org/r/20200220121727.GB507@zn.tnic
---
arch/x86/kernel/traps.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -278,6 +278,7 @@ dotraplinkage void do_double_fault(struc
regs->ip == (unsigned long)native_irq_return_iret)
{
struct pt_regs *gpregs = (struct pt_regs *)this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;
+ unsigned long *p = (unsigned long *)regs->sp;
/*
* regs->sp points to the failing IRET frame on the
@@ -285,7 +286,11 @@ dotraplinkage void do_double_fault(struc
* in gpregs->ss through gpregs->ip.
*
*/
- memmove(&gpregs->ip, (void *)regs->sp, 5*8);
+ gpregs->ip = p[0];
+ gpregs->cs = p[1];
+ gpregs->flags = p[2];
+ gpregs->sp = p[3];
+ gpregs->ss = p[4];
gpregs->orig_ax = 0; /* Missing (lost) #GP error code */
/*
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