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Date: Sat, 11 Mar 2023 17:34:32 +0300
From: Evgeniy Baskov <baskov@...ras.ru>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>, Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Alexey Khoroshilov <khoroshilov@...ras.ru>,
Peter Jones <pjones@...hat.com>,
"Limonciello, Mario" <mario.limonciello@....com>,
joeyli <jlee@...e.com>, lvc-project@...uxtesting.org,
x86@...nel.org, linux-efi@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v4 12/26] x86/boot: Make kernel_add_identity_map() a
pointer
On 2023-03-10 17:52, Ard Biesheuvel wrote:
> On Thu, 15 Dec 2022 at 13:40, Evgeniy Baskov <baskov@...ras.ru> wrote:
>>
>> Convert kernel_add_identity_map() into a function pointer to be able
>> to provide alternative implementations of this function. Required
>> to enable calling the code using this function from EFI environment.
>>
>> Tested-by: Mario Limonciello <mario.limonciello@....com>
>> Tested-by: Peter Jones <pjones@...hat.com>
>> Signed-off-by: Evgeniy Baskov <baskov@...ras.ru>
>> ---
>> arch/x86/boot/compressed/ident_map_64.c | 7 ++++---
>> arch/x86/boot/compressed/misc.c | 24 ++++++++++++++++++++++++
>> arch/x86/boot/compressed/misc.h | 15 +++------------
>> 3 files changed, 31 insertions(+), 15 deletions(-)
>>
>> diff --git a/arch/x86/boot/compressed/ident_map_64.c
>> b/arch/x86/boot/compressed/ident_map_64.c
>> index ba5108c58a4e..1aee524d3c2b 100644
>> --- a/arch/x86/boot/compressed/ident_map_64.c
>> +++ b/arch/x86/boot/compressed/ident_map_64.c
>> @@ -92,9 +92,9 @@ bool has_nx; /* set in head_64.S */
>> /*
>> * Adds the specified range to the identity mappings.
>> */
>> -unsigned long kernel_add_identity_map(unsigned long start,
>> - unsigned long end,
>> - unsigned int flags)
>> +unsigned long kernel_add_identity_map_(unsigned long start,
>
> Please use a more discriminating name here - the trailing _ is rather
> hard to spot.
Got it. The kernel_add_identity_map_impl() will fit better, I think.
>
>> + unsigned long end,
>> + unsigned int flags)
>> {
>> int ret;
>>
>> @@ -142,6 +142,7 @@ void initialize_identity_maps(void *rmode)
>> struct setup_data *sd;
>>
>> boot_params = rmode;
>> + kernel_add_identity_map = kernel_add_identity_map_;
>>
>> /* Exclude the encryption mask from __PHYSICAL_MASK */
>> physical_mask &= ~sme_me_mask;
>> diff --git a/arch/x86/boot/compressed/misc.c
>> b/arch/x86/boot/compressed/misc.c
>> index aa4a22bc9cf9..c9c235d65d16 100644
>> --- a/arch/x86/boot/compressed/misc.c
>> +++ b/arch/x86/boot/compressed/misc.c
>> @@ -275,6 +275,22 @@ static void parse_elf(void *output, unsigned long
>> output_len,
>> free(phdrs);
>> }
>>
>> +/*
>> + * This points to actual implementation of mapping function
>> + * for current environment: either EFI API wrapper,
>> + * own implementation or dummy implementation below.
>> + */
>> +unsigned long (*kernel_add_identity_map)(unsigned long start,
>> + unsigned long end,
>> + unsigned int flags);
>> +
>> +static inline unsigned long kernel_add_identity_map_dummy(unsigned
>> long start,
>
> This function is never called, it only has its address taken, so the
> 'inline' makes no sense here.
>
Indeed. I'll remove the inline.
>> + unsigned
>> long end,
>> + unsigned int
>> flags)
>> +{
>> + return start;
>> +}
>> +
>> /*
>> * The compressed kernel image (ZO), has been moved so that its
>> position
>> * is against the end of the buffer used to hold the uncompressed
>> kernel
>> @@ -312,6 +328,14 @@ asmlinkage __visible void *extract_kernel(void
>> *rmode, memptr heap,
>>
>> init_default_io_ops();
>>
>> + /*
>> + * On 64-bit this pointer is set during page table
>> uninitialization,
>
> initialization
Thanks!
>
>> + * but on 32-bit it remains uninitialized, since paging is
>> disabled.
>> + */
>> + if (IS_ENABLED(CONFIG_X86_32))
>> + kernel_add_identity_map =
>> kernel_add_identity_map_dummy;
>> +
>> +
>> /*
>> * Detect TDX guest environment.
>> *
>> diff --git a/arch/x86/boot/compressed/misc.h
>> b/arch/x86/boot/compressed/misc.h
>> index 38d31bec062d..0076b2845b4b 100644
>> --- a/arch/x86/boot/compressed/misc.h
>> +++ b/arch/x86/boot/compressed/misc.h
>> @@ -180,18 +180,9 @@ static inline int
>> count_immovable_mem_regions(void) { return 0; }
>> #ifdef CONFIG_X86_5LEVEL
>> extern unsigned int __pgtable_l5_enabled, pgdir_shift, ptrs_per_p4d;
>> #endif
>> -#ifdef CONFIG_X86_64
>> -extern unsigned long kernel_add_identity_map(unsigned long start,
>> - unsigned long end,
>> - unsigned int flags);
>> -#else
>> -static inline unsigned long kernel_add_identity_map(unsigned long
>> start,
>> - unsigned long end,
>> - unsigned int
>> flags)
>> -{
>> - return start;
>> -}
>> -#endif
>> +extern unsigned long (*kernel_add_identity_map)(unsigned long start,
>> + unsigned long end,
>> + unsigned int flags);
>> /* Used by PAGE_KERN* macros: */
>> extern pteval_t __default_kernel_pte_mask;
>>
>> --
>> 2.37.4
>>
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