linux-kernel - Re: arm-linux-gnueabihf-ld: kernel/rcu/update.o:update.c:(.text+0x1cc4): more undefined references to `__bad

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <583e2476-50c5-4f9c-85af-f4489a53083b@paulmck-laptop>
Date: Thu, 30 May 2024 15:05:21 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>, Russell King <linux@...linux.org.uk>,
	Naresh Kamboju <naresh.kamboju@...aro.org>,
	open list <linux-kernel@...r.kernel.org>,
	Linux ARM <linux-arm-kernel@...ts.infradead.org>,
	lkft-triage@...ts.linaro.org,
	Linux Regressions <regressions@...ts.linux.dev>,
	rcu <rcu@...r.kernel.org>, Dan Carpenter <dan.carpenter@...aro.org>,
	Joel Fernandes <joel@...lfernandes.org>, neeraj.upadhyay@...nel.org,
	John Ogness <john.ogness@...utronix.de>, broonie@...nel.org
Subject: Re: arm-linux-gnueabihf-ld:
 kernel/rcu/update.o:update.c:(.text+0x1cc4): more undefined references to
 `__bad_cmpxchg' follow

On Thu, May 30, 2024 at 02:52:48PM -0700, Nathan Chancellor wrote:
> On Thu, May 30, 2024 at 10:24:05AM -0700, Paul E. McKenney wrote:
> > And for an untested first attempt at a fix.
> > 
> > What did I mess up this time?  ;-)
> 
> An include for cmpxchg-emu.h ;)
> 
>   In file included from arch/arm/include/asm/atomic.h:16,
>                    from include/linux/atomic.h:7,
>                    from include/asm-generic/bitops/lock.h:5,
>                    from arch/arm/include/asm/bitops.h:245,
>                    from include/linux/bitops.h:63,
>                    from include/linux/log2.h:12,
>                    from kernel/bounds.c:13:
>   arch/arm/include/asm/cmpxchg.h: In function '__cmpxchg':
>   arch/arm/include/asm/cmpxchg.h:167:26: error: implicit declaration of function 'cmpxchg_emu_u8' [-Werror=implicit-function-declaration]
>     167 |                 oldval = cmpxchg_emu_u8((volatile u8 *)ptr, old, new);
>         |                          ^~~~~~~~~~~~~~
>   cc1: some warnings being treated as errors

Good catch, and thank you for testing this!  Does the updated version
shown below do better?

							Thanx, Paul

------------------------------------------------------------------------

commit 74e3470afacaa9d2f37db4773a5fef887ac4ef56
Author: Paul E. McKenney <paulmck@...nel.org>
Date:   Thu May 30 10:11:31 2024 -0700

    ARM: Emulate one-byte cmpxchg
    
    Use the new cmpxchg_emu_u8() to emulate one-byte cmpxchg() on ARM systems
    with ARCH < ARMv6K.
    
    [ paulmck: Apply Arnd Bergmann and Nathan Chancellor feedback. ]
    
    Reported-by: Mark Brown <broonie@...nel.org>
    Closes: https://lore.kernel.org/all/54798f68-48f7-4c65-9cba-47c0bf175143@sirena.org.uk/
    Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
    Closes: https://lore.kernel.org/all/CA+G9fYuZ+pf6p8AXMZWtdFtX-gbG8HMaBKp=XbxcdzA_QeLkxQ@mail.gmail.com/
    Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
    Cc: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
    Cc: Arnd Bergmann <arnd@...db.de>
    Cc: Andrew Davis <afd@...com>
    Cc: Andrew Morton <akpm@...ux-foundation.org>
    Cc: Linus Walleij <linus.walleij@...aro.org>
    Cc: Eric DeVolder <eric.devolder@...cle.com>
    Cc: Rob Herring <robh@...nel.org>
    Cc: <linux-arm-kernel@...ts.infradead.org>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index ee5115252aac4..a867a7d967aa5 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -34,6 +34,7 @@ config ARM
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7
+	select ARCH_NEED_CMPXCHG_1_EMU if CPU_V6
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_SUPPORTS_CFI_CLANG
 	select ARCH_SUPPORTS_HUGETLBFS if ARM_LPAE
diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h
index 44667bdb4707a..a428e06fe94ee 100644
--- a/arch/arm/include/asm/cmpxchg.h
+++ b/arch/arm/include/asm/cmpxchg.h
@@ -5,6 +5,7 @@
 #include <linux/irqflags.h>
 #include <linux/prefetch.h>
 #include <asm/barrier.h>
+#include <linux/cmpxchg-emu.h>
 
 #if defined(CONFIG_CPU_SA1100) || defined(CONFIG_CPU_SA110)
 /*
@@ -162,7 +163,11 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
 	prefetchw((const void *)ptr);
 
 	switch (size) {
-#ifndef CONFIG_CPU_V6	/* min ARCH >= ARMv6K */
+#ifdef CONFIG_CPU_V6	/* min ARCH < ARMv6K */
+	case 1:
+		oldval = cmpxchg_emu_u8((volatile u8 *)ptr, old, new);
+		break;
+#else /* min ARCH >= ARMv6K */
 	case 1:
 		do {
 			asm volatile("@ __cmpxchg1\n"