Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

Christophe Leroy
2021-10-15T06:24:37Z

Le 15/10/2021 à 08:16, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
>> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
>> HAVE_FUNCTION_DESCRIPTORS and use it instead of
>> 'dereference_function_descriptor' macro to know
>> whether an arch has function descriptors.
>>
>> To limit churn in one of the following patches, use
>> an #ifdef/#else construct with empty first part
>> instead of an #ifndef in asm-generic/sections.h
>
> Is it worth putting this into Kconfig if you're going to
> change it? In any case

That was what I wanted to do in the begining but how can I do that in
Kconfig ?

#ifdef __powerpc64__
#if defined(_CALL_ELF) && _CALL_ELF = 2
#define PPC64_ELF_ABI_v2
#else
#define PPC64_ELF_ABI_v1
#endif
#endif /* __powerpc64__ */

#ifdef PPC64_ELF_ABI_v1
#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1

Christophe

>
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
>
>>
>> Reviewed-by: Kees Cook <keescook@chromium.org>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>> arch/ia64/include/asm/sections.h | 5 +++--
>> arch/parisc/include/asm/sections.h | 6 ++++--
>> arch/powerpc/include/asm/sections.h | 6 ++++--
>> include/asm-generic/sections.h | 3 ++-
>> include/linux/kallsyms.h | 2 +-
>> 5 files changed, 14 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
>> index 35f24e52149a..6e55e545bf02 100644
>> --- a/arch/ia64/include/asm/sections.h
>> +++ b/arch/ia64/include/asm/sections.h
>> @@ -9,6 +9,9 @@
>>
>> #include <linux/elf.h>
>> #include <linux/uaccess.h>
>> +
>> +#define HAVE_FUNCTION_DESCRIPTORS 1
>> +
>> #include <asm-generic/sections.h>
>>
>> extern char __phys_per_cpu_start[];
>> @@ -27,8 +30,6 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
>> extern char __start_unwind[], __end_unwind[];
>> extern char __start_ivt_text[], __end_ivt_text[];
>>
>> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
>> -
>> #undef dereference_function_descriptor
>> static inline void *dereference_function_descriptor(void *ptr)
>> {
>> diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
>> index bb52aea0cb21..85149a89ff3e 100644
>> --- a/arch/parisc/include/asm/sections.h
>> +++ b/arch/parisc/include/asm/sections.h
>> @@ -2,6 +2,10 @@
>> #ifndef _PARISC_SECTIONS_H
>> #define _PARISC_SECTIONS_H
>>
>> +#ifdef CONFIG_64BIT
>> +#define HAVE_FUNCTION_DESCRIPTORS 1
>> +#endif
>> +
>> /* nothing to see, move along */
>> #include <asm-generic/sections.h>
>>
>> @@ -9,8 +13,6 @@ extern char __alt_instructions[], __alt_instructions_end[];
>>
>> #ifdef CONFIG_64BIT
>>
>> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
>> -
>> #undef dereference_function_descriptor
>> void *dereference_function_descriptor(void *);
>>
>> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
>> index 32e7035863ac..bba97b8c38cf 100644
>> --- a/arch/powerpc/include/asm/sections.h
>> +++ b/arch/powerpc/include/asm/sections.h
>> @@ -8,6 +8,10 @@
>>
>> #define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
>>
>> +#ifdef PPC64_ELF_ABI_v1
>> +#define HAVE_FUNCTION_DESCRIPTORS 1
>> +#endif
>> +
>> #include <asm-generic/sections.h>
>>
>> extern bool init_mem_is_free;
>> @@ -69,8 +73,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
>>
>> #ifdef PPC64_ELF_ABI_v1
>>
>> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
>> -
>> #undef dereference_function_descriptor
>> static inline void *dereference_function_descriptor(void *ptr)
>> {
>> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
>> index d16302d3eb59..b677e926e6b3 100644
>> --- a/include/asm-generic/sections.h
>> +++ b/include/asm-generic/sections.h
>> @@ -59,7 +59,8 @@ extern char __noinstr_text_start[], __noinstr_text_end[];
>> extern __visible const void __nosave_begin, __nosave_end;
>>
>> /* Function descriptor handling (if any). Override in asm/sections.h */
>> -#ifndef dereference_function_descriptor
>> +#ifdef HAVE_FUNCTION_DESCRIPTORS
>> +#else
>> #define dereference_function_descriptor(p) ((void *)(p))
>> #define dereference_kernel_function_descriptor(p) ((void *)(p))
>> #endif
>> diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
>> index a1d6fc82d7f0..9f277baeb559 100644
>> --- a/include/linux/kallsyms.h
>> +++ b/include/linux/kallsyms.h
>> @@ -57,7 +57,7 @@ static inline int is_ksym_addr(unsigned long addr)
>>
>> static inline void *dereference_symbol_descriptor(void *ptr)
>> {
>> -#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
>> +#ifdef HAVE_FUNCTION_DESCRIPTORS
>> struct module *mod;
>>
>> ptr = dereference_kernel_function_descriptor(ptr);
>> --
>> 2.31.1
>>
>>
>>