lkml.org 
[lkml]   [2012]   [Aug]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 02/22] ARM: use late patch framework for phys-virt patching
Hi Nicolas,

On 8/4/2012 2:15 AM, Nicolas Pitre wrote:
> On Tue, 31 Jul 2012, Cyril Chemparathy wrote:
>
>> This patch replaces the original physical offset patching implementation
>> with one that uses the newly added patching framework. In the process, we now
>> unconditionally initialize the __pv_phys_offset and __pv_offset globals in the
>> head.S code.
>
> Why unconditionally initializing those? There is no reason for that.
>

We could keep this conditional on LPAE, but do you see any specific need
for keeping it conditional?

>> Signed-off-by: Cyril Chemparathy <cyril@ti.com>
>
> Comments below.
>
>> diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
>> index 835898e..d165896 100644
>> --- a/arch/arm/kernel/head.S
>> +++ b/arch/arm/kernel/head.S
> [...]
>> .data
>> .globl __pv_phys_offset
>> .type __pv_phys_offset, %object
>> __pv_phys_offset:
>> .long 0
>> .size __pv_phys_offset, . - __pv_phys_offset
>> +
>> + .globl __pv_offset
>> + .type __pv_offset, %object
>> __pv_offset:
>> .long 0
>> -#endif
>> + .size __pv_offset, . - __pv_offset
>
> Please move those to C code. They aren't of much use in this file
> anymore. This will allow you to use pphys_addr_t for them as well in
> your subsequent patch. And more importantly get rid of that ugly
> pv_offset_high that you introduced iin another patch.
>

Moving it to C-code caused problems because these get filled in prior to
BSS being cleared.

We could potentially have this initialized in C with a mystery dummy
value to prevent it from landing in BSS. Would that be acceptable?

>> diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
>> index df5e897..39f8fce 100644
>> --- a/arch/arm/kernel/module.c
>> +++ b/arch/arm/kernel/module.c
>> @@ -317,11 +317,6 @@ int module_finalize(const Elf32_Ehdr *hdr, const Elf_Shdr *sechdrs,
>> maps[i].txt_sec->sh_addr,
>> maps[i].txt_sec->sh_size);
>> #endif
>> -#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
>> - s = find_mod_section(hdr, sechdrs, ".pv_table");
>> - if (s)
>> - fixup_pv_table((void *)s->sh_addr, s->sh_size);
>> -#endif
>> s = find_mod_section(hdr, sechdrs, ".patch.table");
>> if (s)
>> patch_kernel((void *)s->sh_addr, s->sh_size);
>
> The patch_kernel code and its invokation should still be conditional on
> CONFIG_ARM_PATCH_PHYS_VIRT. This ability may still be configured out
> irrespective of the implementation used.
>

Maybe CONFIG_ARM_PATCH_PHYS_VIRT is not quite appropriate if this is
used to patch up other things in addition to phys-virt stuff?

I could have this dependent on CONFIG_ARM_INIT_PATCH (or whatever
nomenclature we chose for this) and have CONFIG_ARM_PATCH_PHYS_VIRT
depend on it.

>> diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
>> index bacb275..13731e3 100644
>> --- a/arch/arm/kernel/vmlinux.lds.S
>> +++ b/arch/arm/kernel/vmlinux.lds.S
>> @@ -162,11 +162,6 @@ SECTIONS
>> __smpalt_end = .;
>> }
>> #endif
>> - .init.pv_table : {
>> - __pv_table_begin = .;
>> - *(.pv_table)
>> - __pv_table_end = .;
>> - }
>> .init.patch_table : {
>> __patch_table_begin = .;
>> *(.patch.table)
>
> Since you're changing the module ABI,it is important to also modify the
> module vermagic string in asm/module.h to prevent the loading of
> incompatible kernel modules.
>

Absolutely. Thanks.

>
> Nicolas
>

--
Thanks
- Cyril


\
 
 \ /
  Last update: 2012-08-05 16:21    [W:0.053 / U:1.416 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site