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SubjectRe: [PATCH v4 06/26] x86/boot: Setup memory protection for bzImage code
On 2023-03-08 13:47, Ard Biesheuvel wrote:
> On Thu, 15 Dec 2022 at 13:38, Evgeniy Baskov <baskov@ispras.ru> wrote:
>>
>> Use previously added code to use 4KB pages for mapping. Map compressed
>> and uncompressed kernel with appropriate memory protection attributes.
>> For compressed kernel set them up manually. For uncompressed kernel
>> used flags specified in ELF header.
>>
>> Tested-by: Mario Limonciello <mario.limonciello@amd.com>
>> Tested-by: Peter Jones <pjones@redhat.com>
>> Signed-off-by: Evgeniy Baskov <baskov@ispras.ru>
>>
>
> This patch breaks the 'nokaslr' command line option (at least with
> SeaBIOS) unless I apply the hunk below:
>

Oh, I didn't think of that option.. Thanks!
I will also add the check to the identity mapping,
so the warning won't be emitted with 'nokaslr'.

>
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -329,7 +329,8 @@ static size_t parse_elf(void *output, unsigned
> long output_len,
>
> handle_relocations(output, output_len, virt_addr);
>
> - if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE))
> + if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE) ||
> + cmdline_find_option_bool("nokaslr"))
> goto skip_protect;
>
> for (i = 0; i < ehdr.e_phnum; i++) {
> @@ -481,8 +482,10 @@ asmlinkage __visible void *extract_kernel(void
> *rmode, memptr heap,
> * If KASLR is disabled input and output regions may overlap.
> * In this case we need to map region excutable as well.
> */
> - unsigned long map_flags = MAP_ALLOC | MAP_WRITE |
> - (IS_ENABLED(CONFIG_RANDOMIZE_BASE) ? 0 :
> MAP_EXEC);
> + unsigned long map_flags = MAP_ALLOC | MAP_WRITE;
> + if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE) ||
> + cmdline_find_option_bool("nokaslr"))
> + map_flags |= MAP_EXEC;
> phys_addr = kernel_add_identity_map(phys_addr,
> phys_addr + needed_size,
> map_flags);

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