linux-kernel - Re: [RFC] arm64:use set_fixmap

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Date:	Fri, 24 Jul 2015 19:53:14 +0800
From:	yalin wang <yalin.wang2010@...il.com>
To:	Mark Rutland <mark.rutland@....com>
Cc:	yalin wang <yalin.wang2010@...il.com>,
	"lauraa@...eaurora.org" <lauraa@...eaurora.org>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Punit Agrawal <Punit.Agrawal@....com>,
	Will Deacon <Will.Deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"zlim.lnx@...il.com" <zlim.lnx@...il.com>,
	"wcohen@...hat.com" <wcohen@...hat.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC] arm64:use set_fixmap_offset to make it more clear


> 在 2015年7月24日，18:07，Mark Rutland <mark.rutland@....com> 写道：
> 
> On Fri, Jul 24, 2015 at 10:56:18AM +0100, Mark Rutland wrote:
>> On Fri, Jul 24, 2015 at 04:56:59AM +0100, yalin wang wrote:
>>> 
>>>> On Jul 23, 2015, at 21:03, Catalin Marinas <catalin.marinas@....com> wrote:
>>>> 
>>>> On Thu, Jul 23, 2015 at 07:45:53PM +0800, yalin wang wrote:
>>>>> A little change to patch_map() function,
>>>>> use set_fixmap_offset() to make code more clear.
>>>>> 
>>>>> Signed-off-by: yalin wang <yalin.wang2010@...il.com>
>>>>> ---
>>>>> arch/arm64/kernel/insn.c | 5 ++---
>>>>> 1 file changed, 2 insertions(+), 3 deletions(-)
>>>>> 
>>>>> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
>>>>> index dd9671c..7dafd5a 100644
>>>>> --- a/arch/arm64/kernel/insn.c
>>>>> +++ b/arch/arm64/kernel/insn.c
>>>>> @@ -101,9 +101,8 @@ static void __kprobes *patch_map(void *addr, int fixmap)
>>>>> 		return addr;
>>>>> 
>>>>> 	BUG_ON(!page);
>>>>> -	set_fixmap(fixmap, page_to_phys(page));
>>>>> -
>>>>> -	return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
>>>>> +	return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
>>>>> +			(addr & ~PAGE_MASK));
>>>> 
>>>> It looks fine. Do you get any compiler warning for the automatic pointer
>>>> to long conversion? You may want to add some explicit casts, otherwise:
>>>> 
>>>> Acked-by: Catalin Marinas <catalin.marinas@....com>
>>> i have build it, there is no warning about this change. :)
>> 
>> I see no warnings with defconfig, but there's an (unrelated) set of warnings if
>> CONFIG_DEBUG_SET_MODULE_RONX or CONFIG_DEBUG_RODATA are enabled:
> 
> Actually they aren't unrelated after all. the unsigned long addr in
> __set_fixmap_offset shadows the void* addr from patch_map making the
> types match.
> 
> With a few underscores addrd to __set_fixmap_offset's addr, I get the
> following regarding patch_map:
> 
> ----
> In file included from ./arch/arm64/include/asm/fixmap.h:85:0,
>                 from arch/arm64/kernel/insn.c:32:
> arch/arm64/kernel/insn.c: In function ‘patch_map’:
> arch/arm64/kernel/insn.c:105:10: error: invalid operands to binary & (have ‘void *’ and ‘long unsigned int’)
>    (addr & ~PAGE_MASK));
>          ^
> include/asm-generic/fixmap.h:73:20: note: in definition of macro ‘__set_fixmap_offset’
>  __set_fixmap(idx, phys, flags);         \
>                    ^
> arch/arm64/kernel/insn.c:104:17: note: in expansion of macro ‘set_fixmap_offset’
>  return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
>                 ^
> arch/arm64/kernel/insn.c:105:10: error: invalid operands to binary & (have ‘void *’ and ‘long unsigned int’)
>    (addr & ~PAGE_MASK));
>          ^
> include/asm-generic/fixmap.h:74:32: note: in definition of macro ‘__set_fixmap_offset’
>  __addr = fix_to_virt(idx) + ((phys) & (PAGE_SIZE - 1)); \
>                                ^
> arch/arm64/kernel/insn.c:104:17: note: in expansion of macro ‘set_fixmap_offset’
>  return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
>                 ^
> make[1]: *** [arch/arm64/kernel/insn.o] Error 1
> make: *** [arch/arm64/kernel/insn.o] Error 2
> ----
> 
> we need both the cast in patch_map, and an update to __set_fixmap_offset to
> prevent the name clash.
> 
> Thanks,
> Mark.
i see, i will send V2 to solve this.

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