linux-kernel - [patch V4 part 4 22/24] x86/mce: Address objtools noinstr complaints

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Date:   Tue, 05 May 2020 15:49:48 +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>
Subject: [patch V4 part 4 22/24] x86/mce: Address objtools noinstr complaints

Mark the relevant functions noinstr, use the plain non-instrumented MSR
accessors. The only odd part is the instr_begin()/end() pair around the
indirect machine_check_vector() call as objtool can't figure that out. The
possible invoked functions are annotated correctly.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/cpu/mce/core.c    |   20 +++++++++++++++-----
 arch/x86/kernel/cpu/mce/p5.c      |    4 +++-
 arch/x86/kernel/cpu/mce/winchip.c |    4 +++-
 kernel/time/timekeeping.c         |    2 +-
 4 files changed, 22 insertions(+), 8 deletions(-)

--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -130,7 +130,7 @@ static void (*quirk_no_way_out)(int bank
 BLOCKING_NOTIFIER_HEAD(x86_mce_decoder_chain);
 
 /* Do initial initialization of a struct mce */
-void mce_setup(struct mce *m)
+noinstr void mce_setup(struct mce *m)
 {
 	memset(m, 0, sizeof(struct mce));
 	m->cpu = m->extcpu = smp_processor_id();
@@ -140,12 +140,12 @@ void mce_setup(struct mce *m)
 	m->cpuid = cpuid_eax(1);
 	m->socketid = cpu_data(m->extcpu).phys_proc_id;
 	m->apicid = cpu_data(m->extcpu).initial_apicid;
-	rdmsrl(MSR_IA32_MCG_CAP, m->mcgcap);
+	m->mcgcap = __rdmsr(MSR_IA32_MCG_CAP);
 
 	if (this_cpu_has(X86_FEATURE_INTEL_PPIN))
-		rdmsrl(MSR_PPIN, m->ppin);
+		m->ppin = __rdmsr(MSR_PPIN);
 	else if (this_cpu_has(X86_FEATURE_AMD_PPIN))
-		rdmsrl(MSR_AMD_PPIN, m->ppin);
+		m->ppin = __rdmsr(MSR_AMD_PPIN);
 
 	m->microcode = boot_cpu_data.microcode;
 }
@@ -1895,10 +1895,12 @@ bool filter_mce(struct mce *m)
 }
 
 /* Handle unconfigured int18 (should never happen) */
-static void unexpected_machine_check(struct pt_regs *regs)
+static noinstr void unexpected_machine_check(struct pt_regs *regs)
 {
+	instr_begin();
 	pr_err("CPU#%d: Unexpected int18 (Machine Check)\n",
 	       smp_processor_id());
+	instr_end();
 }
 
 /* Call the installed machine check handler for this CPU setup. */
@@ -1915,14 +1917,22 @@ static __always_inline void exc_machine_
 		return;
 
 	nmi_enter();
+	/*
+	 * The call targets are marked noinstr, but objtool can't figure
+	 * that out because it's an indirect call. Annotate it.
+	 */
+	instr_begin();
 	machine_check_vector(regs);
+	instr_end();
 	nmi_exit();
 }
 
 static __always_inline void exc_machine_check_user(struct pt_regs *regs)
 {
 	idtentry_enter(regs);
+	instr_begin();
 	machine_check_vector(regs);
+	instr_end();
 	idtentry_exit(regs);
 }
 
--- a/arch/x86/kernel/cpu/mce/p5.c
+++ b/arch/x86/kernel/cpu/mce/p5.c
@@ -21,10 +21,11 @@
 int mce_p5_enabled __read_mostly;
 
 /* Machine check handler for Pentium class Intel CPUs: */
-static void pentium_machine_check(struct pt_regs *regs)
+static noinstr void pentium_machine_check(struct pt_regs *regs)
 {
 	u32 loaddr, hi, lotype;
 
+	instr_begin();
 	rdmsr(MSR_IA32_P5_MC_ADDR, loaddr, hi);
 	rdmsr(MSR_IA32_P5_MC_TYPE, lotype, hi);
 
@@ -37,6 +38,7 @@ static void pentium_machine_check(struct
 	}
 
 	add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
+	instr_end();
 }
 
 /* Set up machine check reporting for processors with Intel style MCE: */
--- a/arch/x86/kernel/cpu/mce/winchip.c
+++ b/arch/x86/kernel/cpu/mce/winchip.c
@@ -17,10 +17,12 @@
 #include "internal.h"
 
 /* Machine check handler for WinChip C6: */
-static void winchip_machine_check(struct pt_regs *regs)
+static noinstr void winchip_machine_check(struct pt_regs *regs)
 {
+	instr_begin();
 	pr_emerg("CPU0: Machine Check Exception.\n");
 	add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
+	instr_end();
 }
 
 /* Set up machine check reporting on the Winchip C6 series */
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -953,7 +953,7 @@ EXPORT_SYMBOL_GPL(ktime_get_real_seconds
  * but without the sequence counter protect. This internal function
  * is called just when timekeeping lock is already held.
  */
-time64_t __ktime_get_real_seconds(void)
+noinstr time64_t __ktime_get_real_seconds(void)
 {
 	struct timekeeper *tk = &tk_core.timekeeper;