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.
> Signed-off-by: Cyril Chemparathy <[email protected]>
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.
> 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.
> 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.
Nicolas
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 <[email protected]>
>
> 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
On Sun, 5 Aug 2012, Cyril Chemparathy wrote:
> 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?
This has nothing to do with LPAe. This is about
CONFIG_ARM_PATCH_PHYS_VIRT only. If not selected, those global
vaariables have no need to exist.
> > 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?
Just initialize them explicitly to zero. They will end up in .ddata
section.
>
> > > 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?
Maybe, but at the moment this is not the case.
> 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.
Let's cross that bridge in time.
FWIW, I don't like "init patch" much. I feel like the "runtime"
qualifier more pricisely describe this code than "init".
Nicolas