Messages in this thread | | | Date | Sun, 5 Aug 2012 10:03:45 -0400 | From | Cyril Chemparathy <> | Subject | Re: [PATCH 02/22] ARM: use late patch framework for phys-virt patching |
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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
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