linux-kernel - Re: [PATCH v2 3/4] x86: Patch alternatives in the 32-bit vDSO

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Message-ID: <1393682667.982.28.camel@wall-e.seibold.net>
Date:	Sat, 01 Mar 2014 15:04:27 +0100
From:	Stefani Seibold <stefani@...bold.net>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	John Stultz <john.stultz@...aro.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	andriy.shevchenko@...ux.intel.com, Martin.Runge@...de-schwarz.com,
	Andreas.Brief@...de-schwarz.com
Subject: Re: [PATCH v2 3/4] x86: Patch alternatives in the 32-bit vDSO

Am Donnerstag, den 27.02.2014, 16:18 -0800 schrieb Andy Lutomirski:
> rdtsc_barrier() needs this.
> 
> Signed-off-by: Andy Lutomirski <luto@...capital.net>
> ---
>  arch/x86/include/asm/vdso.h  |  2 ++
>  arch/x86/vdso/vdso32-setup.c | 25 +++++++++++++------------
>  arch/x86/vdso/vma.c          |  9 ++++++---
>  3 files changed, 21 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h
> index 6db8b23..a844f90 100644
> --- a/arch/x86/include/asm/vdso.h
> +++ b/arch/x86/include/asm/vdso.h
> @@ -40,4 +40,6 @@ extern const char vdso32_int80_start, vdso32_int80_end;
>  extern const char vdso32_syscall_start, vdso32_syscall_end;
>  extern const char vdso32_sysenter_start, vdso32_sysenter_end;
>  
> +void __init patch_vdso32(void *vdso, size_t len);
> +
>  #endif /* _ASM_X86_VDSO_H */
> diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c
> index 6b74a46..b37aa1d 100644
> --- a/arch/x86/vdso/vdso32-setup.c
> +++ b/arch/x86/vdso/vdso32-setup.c
> @@ -273,29 +273,30 @@ static void map_compat_vdso(int map)
>  
>  int __init sysenter_setup(void)
>  {
> -	void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
> -	const void *vsyscall;
> -	size_t vsyscall_len;
> +	void *vdso_page = (void *)get_zeroed_page(GFP_ATOMIC);
> +	const void *vdso;
> +	size_t vdso_len;
>  
> -	vdso32_pages[0] = virt_to_page(syscall_page);
> +	vdso32_pages[0] = virt_to_page(vdso_page);
>  
>  #ifdef CONFIG_X86_32
>  	gate_vma_init();
>  #endif
>  
>  	if (vdso32_syscall()) {
> -		vsyscall = &vdso32_syscall_start;
> -		vsyscall_len = &vdso32_syscall_end - &vdso32_syscall_start;
> +		vdso = &vdso32_syscall_start;
> +		vdso_len = &vdso32_syscall_end - &vdso32_syscall_start;
>  	} else if (vdso32_sysenter()){
> -		vsyscall = &vdso32_sysenter_start;
> -		vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
> +		vdso = &vdso32_sysenter_start;
> +		vdso_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
>  	} else {
> -		vsyscall = &vdso32_int80_start;
> -		vsyscall_len = &vdso32_int80_end - &vdso32_int80_start;
> +		vdso = &vdso32_int80_start;
> +		vdso_len = &vdso32_int80_end - &vdso32_int80_start;
>  	}
>  
> -	memcpy(syscall_page, vsyscall, vsyscall_len);
> -	relocate_vdso(syscall_page);
> +	memcpy(vdso_page, vdso, vdso_len);
> +	patch_vdso32(vdso_page, vdso_len);

This will fail with 32 bit kernels since vma.c is only build for 64 bit
kernel. I have fixed this.

> +	relocate_vdso(vdso_page);
>  
>  	return 0;
>  }
> diff --git a/arch/x86/vdso/vma.c b/arch/x86/vdso/vma.c
> index 431e875..149caa1 100644
> --- a/arch/x86/vdso/vma.c
> +++ b/arch/x86/vdso/vma.c
> @@ -28,8 +28,11 @@ static unsigned vdso_size;
>  extern char vdsox32_start[], vdsox32_end[];
>  extern struct page *vdsox32_pages[];
>  static unsigned vdsox32_size;
> +#endif
>  
> -static void __init patch_vdsox32(void *vdso, size_t len)
> +#if defined(CONFIG_X86_32) || defined(CONFIG_X86_X32_ABI) || \
> +	defined(CONFIG_COMPAT)
> +void __init patch_vdso32(void *vdso, size_t len)
>  {
>  	Elf32_Ehdr *hdr = vdso;
>  	Elf32_Shdr *sechdrs, *alt_sec = 0;
> @@ -52,7 +55,7 @@ static void __init patch_vdsox32(void *vdso, size_t len)
>  	}
>  
>  	/* If we get here, it's probably a bug. */
> -	pr_warning("patch_vdsox32: .altinstructions not found\n");
> +	pr_warning("patch_vdso32: .altinstructions not found\n");
>  	return;  /* nothing to patch */
>  
>  found:
> @@ -104,7 +107,7 @@ static int __init init_vdso(void)
>  		vdso_pages[i] = virt_to_page(vdso_start + i*PAGE_SIZE);
>  
>  #ifdef CONFIG_X86_X32_ABI
> -	patch_vdsox32(vdsox32_start, vdsox32_end - vdsox32_start);
> +	patch_vdso32(vdsox32_start, vdsox32_end - vdsox32_start);
>  	npages = (vdsox32_end - vdsox32_start + PAGE_SIZE - 1) / PAGE_SIZE;
>  	vdsox32_size = npages << PAGE_SHIFT;
>  	for (i = 0; i < npages; i++)


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