linux-kernel - Re: [PATCH] x86: make SMP locks handling interact properly with CONFIG_DEBUG

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Message-Id: <200707171954.34541.ak@suse.de>
Date:	Tue, 17 Jul 2007 19:54:34 +0200
From:	Andi Kleen <ak@...e.de>
To:	"Jan Beulich" <jbeulich@...ell.com>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, patches@...-64.org
Subject: Re: [PATCH] x86: make SMP locks handling interact properly with CONFIG_DEBUG_RODATA (2nd try)

On Wednesday 04 July 2007 08:33:24 Jan Beulich wrote:

Sorry for late feedback.


> +#ifdef CONFIG_DEBUG_RODATA
> +
> +#ifdef CONFIG_X86_32
> +#include <asm/highmem.h>
> +#define MODULES_VADDR VMALLOC_START
> +#endif
> +
> +static inline void make_writable(const void *instr, unsigned int len)
> +{
> +	unsigned long va = (unsigned long)instr;
> +
> +	if (va < MODULES_VADDR) {
> +		change_page_attr(virt_to_page(instr),
> +				 PFN_UP(va + len) - PFN_DOWN(va),
> +				 PAGE_KERNEL_EXEC);
> +		global_flush_tlb();
> +	}
> +}
> +
> +static inline void make_readonly(const void *instr, unsigned int len)
> +{
> +	unsigned long va = (unsigned long)instr;
> +
> +	if (va < MODULES_VADDR) {
> +		change_page_attr(virt_to_page(instr),
> +				 PFN_UP(va + len) - PFN_DOWN(va),
> +#ifdef CONFIG_X86_64
> +				 PAGE_KERNEL_RO);
> +#else
> +				 PAGE_KERNEL_RX);
> +#endif
> +		global_flush_tlb();
> +	}
> +}

Can you please move those into the respective pageattr.cs without ifdefs? 
Also the va < MODULES_VADDR test seems overly magic; while it may work right now
it seems fragile. It would be better to test the exact ranges in the respective
architectures

>  void alternatives_smp_module_del(struct module *mod)
>  {
>  	struct smp_alt_module *item;
> -	unsigned long flags;
>  
>  	if (smp_alt_once || noreplace_smp)
>  		return;
>  
> -	spin_lock_irqsave(&smp_alt, flags);
> +	spin_lock(&smp_alt);

Unrelated change?  Why? Should probably be separate patch.

> --- linux-2.6.22-rc7/arch/x86_64/kernel/vmlinux.lds.S	2007-07-03 10:57:39.000000000 +0200
> +++ 2.6.22-rc7-x86-alt-page-attr/arch/x86_64/kernel/vmlinux.lds.S	2007-07-02 14:40:15.000000000 +0200
> @@ -131,20 +131,11 @@ SECTIONS
>    /* might get freed after init */
>    . = ALIGN(4096);
>    __smp_alt_begin = .;
> -  __smp_alt_instructions = .;
> -  .smp_altinstructions : AT(ADDR(.smp_altinstructions) - LOAD_OFFSET) {
> -	*(.smp_altinstructions)
> -  }
> -  __smp_alt_instructions_end = .;
> -  . = ALIGN(8);
>    __smp_locks = .;
>    .smp_locks : AT(ADDR(.smp_locks) - LOAD_OFFSET) {
>  	*(.smp_locks)
>    }
>    __smp_locks_end = .;
> -  .smp_altinstr_replacement : AT(ADDR(.smp_altinstr_replacement) - LOAD_OFFSET) {
> -	*(.smp_altinstr_replacement)
> -  }

While ok too it should be also separate please.

-Andi
-
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