Re: [PATCH V3 1/2] mm/mmap: Restrict generic protection_map[] array visibility

[Christophe Leroy]

Le 20/06/2022 à 06:45, Anshuman Khandual a écrit :
> 
> On 6/16/22 18:14, kernel test robot wrote:
>> Hi Anshuman,
>>
>> Thank you for the patch! Yet something to improve:
>>
>> [auto build test ERROR on akpm-mm/mm-everything]
>>
>> url:    https://github.com/intel-lab-lkp/linux/commits/Anshuman-Khandual/mm-mmap-Drop-__SXXX-__PXXX-macros-from-across-platforms/20220616-121132
>> base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
>> config: x86_64-allyesconfig (https://download.01.org/0day-ci/archive/20220616/202206162004.ak9KTfMD-lkp@xxxxxxxxx/config)
>> compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
>> reproduce (this is a W=1 build):
>>          # https://github.com/intel-lab-lkp/linux/commit/4eb89368b130fe235d5e587bcc2eec18bb688e2d
>>          git remote add linux-review https://github.com/intel-lab-lkp/linux
>>          git fetch --no-tags linux-review Anshuman-Khandual/mm-mmap-Drop-__SXXX-__PXXX-macros-from-across-platforms/20220616-121132
>>          git checkout 4eb89368b130fe235d5e587bcc2eec18bb688e2d
>>          # save the config file
>>          mkdir build_dir && cp config build_dir/.config
>>          make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash arch/x86/
>>
>> If you fix the issue, kindly add following tag where applicable
>> Reported-by: kernel test robot <lkp@xxxxxxxxx>
>>
>> All errors (new ones prefixed by >>):
>>
>>     In file included from arch/x86/include/asm/percpu.h:27,
>>                      from arch/x86/include/asm/preempt.h:6,
>>                      from include/linux/preempt.h:78,
>>                      from include/linux/spinlock.h:55,
>>                      from include/linux/mmzone.h:8,
>>                      from include/linux/gfp.h:6,
>>                      from include/linux/mm.h:7,
>>                      from arch/x86/mm/mem_encrypt_amd.c:14:
>>     arch/x86/mm/mem_encrypt_amd.c: In function 'sme_early_init':
>>>> arch/x86/mm/mem_encrypt_amd.c:499:36: error: 'protection_map' undeclared (first use in this function)
>>       499 |         for (i = 0; i < ARRAY_SIZE(protection_map); i++)
>>           |                                    ^~~~~~~~~~~~~~
>>     include/linux/kernel.h:55:33: note: in definition of macro 'ARRAY_SIZE'
>>        55 | #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
>>           |                                 ^~~
>>     arch/x86/mm/mem_encrypt_amd.c:499:36: note: each undeclared identifier is reported only once for each function it appears in
>>       499 |         for (i = 0; i < ARRAY_SIZE(protection_map); i++)
>>           |                                    ^~~~~~~~~~~~~~
>>     include/linux/kernel.h:55:33: note: in definition of macro 'ARRAY_SIZE'
>>        55 | #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
>>           |                                 ^~~
>>     In file included from include/linux/bits.h:22,
>>                      from include/linux/ratelimit_types.h:5,
>>                      from include/linux/printk.h:9,
>>                      from include/asm-generic/bug.h:22,
>>                      from arch/x86/include/asm/bug.h:87,
>>                      from include/linux/bug.h:5,
>>                      from include/linux/mmdebug.h:5,
>>                      from include/linux/mm.h:6,
>>                      from arch/x86/mm/mem_encrypt_amd.c:14:
>>     include/linux/build_bug.h:16:51: error: bit-field '<anonymous>' width not an integer constant
>>        16 | #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
>>           |                                                   ^
>>     include/linux/compiler.h:240:33: note: in expansion of macro 'BUILD_BUG_ON_ZERO'
>>       240 | #define __must_be_array(a)      BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
>>           |                                 ^~~~~~~~~~~~~~~~~
>>     include/linux/kernel.h:55:59: note: in expansion of macro '__must_be_array'
>>        55 | #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
>>           |                                                           ^~~~~~~~~~~~~~~
>>     arch/x86/mm/mem_encrypt_amd.c:499:25: note: in expansion of macro 'ARRAY_SIZE'
>>       499 |         for (i = 0; i < ARRAY_SIZE(protection_map); i++)
>>           |                         ^~~~~~~~~~
> 
> This patch fixes the build failure here.
> 
> diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
> index f6d038e2cd8e..d0c2ec1bb659 100644
> --- a/arch/x86/mm/mem_encrypt_amd.c
> +++ b/arch/x86/mm/mem_encrypt_amd.c
> @@ -484,6 +484,8 @@ void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages, boo
>          enc_dec_hypercall(vaddr, npages, enc);
>   }
>   
> +extern pgprot_t protection_map[16];

Adding extern declaration in C files is not the best solution. Isn't 
there a H header with that declaration ?

> +
>   void __init sme_early_init(void)
>   {
>          unsigned int i;
> diff --git a/arch/x86/mm/pgprot.c b/arch/x86/mm/pgprot.c
> index 7eca1b009af6..96eca0b2ec90 100644
> --- a/arch/x86/mm/pgprot.c
> +++ b/arch/x86/mm/pgprot.c
> @@ -4,7 +4,7 @@
>   #include <linux/mm.h>
>   #include <asm/pgtable.h>
>   
> -static pgprot_t protection_map[16] __ro_after_init = {
> +pgprot_t protection_map[16] __ro_after_init = {
>          [VM_NONE]                                       = PAGE_NONE,
>          [VM_READ]                                       = PAGE_READONLY,
>          [VM_WRITE]                                      = PAGE_COPY,
>