linux-kernel - [PATCH 1/6] x86/entry: Fix noinstr fail

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Message-ID: <20210106144017.472696632@infradead.org>
Date:   Wed, 06 Jan 2021 15:36:20 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        rdunlap@...radead.org, jpoimboe@...hat.com, sfr@...b.auug.org.au,
        tony.luck@...el.com
Subject: [PATCH 1/6] x86/entry: Fix noinstr fail

  vmlinux.o: warning: objtool: __do_fast_syscall_32()+0x47: call to syscall_enter_from_user_mode_work() leaves .noinstr.text section

Fixes: 4facb95b7ada ("x86/entry: Unbreak 32bit fast syscall")
Reported-by: Randy Dunlap <rdunlap@...radead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/entry/common.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -73,10 +73,8 @@ static __always_inline void do_syscall_3
 						  unsigned int nr)
 {
 	if (likely(nr < IA32_NR_syscalls)) {
-		instrumentation_begin();
 		nr = array_index_nospec(nr, IA32_NR_syscalls);
 		regs->ax = ia32_sys_call_table[nr](regs);
-		instrumentation_end();
 	}
 }
 
@@ -91,8 +89,11 @@ __visible noinstr void do_int80_syscall_
 	 * or may not be necessary, but it matches the old asm behavior.
 	 */
 	nr = (unsigned int)syscall_enter_from_user_mode(regs, nr);
+	instrumentation_begin();
 
 	do_syscall_32_irqs_on(regs, nr);
+
+	instrumentation_end();
 	syscall_exit_to_user_mode(regs);
 }
 
@@ -121,11 +122,12 @@ static noinstr bool __do_fast_syscall_32
 		res = get_user(*(u32 *)&regs->bp,
 		       (u32 __user __force *)(unsigned long)(u32)regs->sp);
 	}
-	instrumentation_end();
 
 	if (res) {
 		/* User code screwed up. */
 		regs->ax = -EFAULT;
+
+		instrumentation_end();
 		syscall_exit_to_user_mode(regs);
 		return false;
 	}
@@ -135,6 +137,8 @@ static noinstr bool __do_fast_syscall_32
 
 	/* Now this is just like a normal syscall. */
 	do_syscall_32_irqs_on(regs, nr);
+
+	instrumentation_end();
 	syscall_exit_to_user_mode(regs);
 	return true;
 }