linux-kernel - Re: [PATCH v2] um: Avoid longjmp/setjmp symbol clashes with libpthread.a

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Date:   Mon, 5 Jun 2017 12:32:18 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Jeff Dike <jdike@...toit.com>, Richard Weinberger <richard@....at>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "open list:USER-MODE LINUX (UML)" 
        <user-mode-linux-devel@...ts.sourceforge.net>,
        "open list:USER-MODE LINUX (UML)" 
        <user-mode-linux-user@...ts.sourceforge.net>
Subject: Re: [PATCH v2] um: Avoid longjmp/setjmp symbol clashes with
 libpthread.a

On 05/23/2017 05:32 PM, Florian Fainelli wrote:
> Building a statically linked UML kernel on a Centos 6.9 host resulted in
> the following linking failure (GCC 4.4, glibc-2.12):
> 
> /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../lib64/libpthread.a(libpthread.o):
> In function `siglongjmp':
> (.text+0x8490): multiple definition of `longjmp'
> arch/x86/um/built-in.o:/local/users/fainelli/openwrt/trunk/build_dir/target-x86_64_musl/linux-uml/linux-4.4.69/arch/x86/um/setjmp_64.S:44:
> first defined here
> /usr/lib/gcc/x86_64-redhat-linux/4.4.7/../../../../lib64/libpthread.a(libpthread.o):
> In function `sem_open':
> (.text+0x77cd): warning: the use of `mktemp' is dangerous, better use
> `mkstemp'
> collect2: ld returned 1 exit status
> make[4]: *** [vmlinux] Error 1
> 
> Adopt a solution similar to the one done for vmap where we define
> longjmp/setjmp to be kernel_longjmp/setjmp. In the process, make sure we
> do rename the functions in arch/x86/um/setjmp_*.S accordingly.
> 
> Fixes: a7df4716d195 ("um: link with -lpthread")
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>

Richard, we are kind of hijacking this thread now that was originally
about statically linking UML, is this particular patch okay?

> ---
> Changes in v2:
> - fix typo introduced on longjmp
> 
>  arch/um/Makefile        |  4 ++++
>  arch/x86/um/setjmp_32.S | 16 ++++++++--------
>  arch/x86/um/setjmp_64.S | 16 ++++++++--------
>  3 files changed, 20 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/um/Makefile b/arch/um/Makefile
> index 0ca46ededfc7..6ca4f66085c1 100644
> --- a/arch/um/Makefile
> +++ b/arch/um/Makefile
> @@ -59,10 +59,14 @@ KBUILD_CPPFLAGS += -I$(srctree)/$(HOST_DIR)/um
>  # Same things for in6addr_loopback and mktime - found in libc. For these two we
>  # only get link-time error, luckily.
>  #
> +# -Dlongjmp=kernel_longjmp prevents anything from referencing the libpthread.a
> +# embedded copy of longjmp, same thing for setjmp.
> +#
>  # These apply to USER_CFLAGS to.
>  
>  KBUILD_CFLAGS += $(CFLAGS) $(CFLAGS-y) -D__arch_um__ \
>  	$(ARCH_INCLUDE) $(MODE_INCLUDE) -Dvmap=kernel_vmap	\
> +	-Dlongjmp=kernel_longjmp -Dsetjmp=kernel_setjmp \
>  	-Din6addr_loopback=kernel_in6addr_loopback \
>  	-Din6addr_any=kernel_in6addr_any -Dstrrchr=kernel_strrchr
>  
> diff --git a/arch/x86/um/setjmp_32.S b/arch/x86/um/setjmp_32.S
> index b766792c9933..39053192918d 100644
> --- a/arch/x86/um/setjmp_32.S
> +++ b/arch/x86/um/setjmp_32.S
> @@ -16,9 +16,9 @@
>  
>  	.text
>  	.align 4
> -	.globl setjmp
> -	.type setjmp, @function
> -setjmp:
> +	.globl kernel_setjmp
> +	.type kernel_setjmp, @function
> +kernel_setjmp:
>  #ifdef _REGPARM
>  	movl %eax,%edx
>  #else
> @@ -35,13 +35,13 @@ setjmp:
>  	movl %ecx,20(%edx)		# Return address
>  	ret
>  
> -	.size setjmp,.-setjmp
> +	.size kernel_setjmp,.-kernel_setjmp
>  
>  	.text
>  	.align 4
> -	.globl longjmp
> -	.type longjmp, @function
> -longjmp:
> +	.globl kernel_longjmp
> +	.type kernel_longjmp, @function
> +kernel_longjmp:
>  #ifdef _REGPARM
>  	xchgl %eax,%edx
>  #else
> @@ -55,4 +55,4 @@ longjmp:
>  	movl 16(%edx),%edi
>  	jmp *20(%edx)
>  
> -	.size longjmp,.-longjmp
> +	.size kernel_longjmp,.-kernel_longjmp
> diff --git a/arch/x86/um/setjmp_64.S b/arch/x86/um/setjmp_64.S
> index 45f547b4043e..c56942e1a38c 100644
> --- a/arch/x86/um/setjmp_64.S
> +++ b/arch/x86/um/setjmp_64.S
> @@ -18,9 +18,9 @@
>  
>  	.text
>  	.align 4
> -	.globl setjmp
> -	.type setjmp, @function
> -setjmp:
> +	.globl kernel_setjmp
> +	.type kernel_setjmp, @function
> +kernel_setjmp:
>  	pop  %rsi			# Return address, and adjust the stack
>  	xorl %eax,%eax			# Return value
>  	movq %rbx,(%rdi)
> @@ -34,13 +34,13 @@ setjmp:
>  	movq %rsi,56(%rdi)		# Return address
>  	ret
>  
> -	.size setjmp,.-setjmp
> +	.size kernel_setjmp,.-kernel_setjmp
>  
>  	.text
>  	.align 4
> -	.globl longjmp
> -	.type longjmp, @function
> -longjmp:
> +	.globl kernel_longjmp
> +	.type kernel_longjmp, @function
> +kernel_longjmp:
>  	movl %esi,%eax			# Return value (int)
>  	movq (%rdi),%rbx
>  	movq 8(%rdi),%rsp
> @@ -51,4 +51,4 @@ longjmp:
>  	movq 48(%rdi),%r15
>  	jmp *56(%rdi)
>  
> -	.size longjmp,.-longjmp
> +	.size kernel_longjmp,.-kernel_longjmp
> 


-- 
Florian