linux-kernel - [patch V4 part 2 11/18] x86/entry/64: Mark ___preempt_schedule

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Date:   Tue, 05 May 2020 15:41:23 +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 2 11/18] x86/entry/64: Mark
 ___preempt_schedule_notrace() thunk noinstr

Code calling this from noinstr sections, e.g. entry code, has interrupts
disabled, so the actual call into the scheduler code does not happen.

The objtool section check complains nevertheless, so mark the call "safe".

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/entry/thunk_64.S |   18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

--- a/arch/x86/entry/thunk_64.S
+++ b/arch/x86/entry/thunk_64.S
@@ -12,6 +12,7 @@
 #include <asm/irqflags.h>
 
 .code64
+.section .noinstr.text, "ax"
 
 	/* rdi:	arg1 ... normal C conventions. rax is saved/restored. */
 	.macro THUNK name, func, put_ret_addr_in_rdi=0, check_if=0
@@ -49,10 +50,24 @@ SYM_FUNC_START_NOALIGN(\name)
 	movq 8(%rbp), %rdi
 	.endif
 
+	/*
+	 * noinstr callers will have interrupts disabled and will thus
+	 * not get here. Annotate the call as objtool does not know about
+	 * this and would complain about leaving the noinstr section.
+	 */
+1:
+	.pushsection .discard.instr_begin
+	.long 1b - .
+	.popsection
+
 	call \func
+2:
+	.pushsection .discard.instr_end
+	.long 2b - .
+	.popsection
+
 	jmp  .L_restore
 SYM_FUNC_END(\name)
-	_ASM_NOKPROBE(\name)
 	.endm
 
 #ifdef CONFIG_TRACE_IRQFLAGS
@@ -82,6 +97,5 @@ SYM_CODE_START_LOCAL_NOALIGN(.L_restore)
 	popq %rdi
 	popq %rbp
 	ret
-	_ASM_NOKPROBE(.L_restore)
 SYM_CODE_END(.L_restore)
 #endif