[PATCH v5 1/2] x86/kexec: Build identity mapping for EFI systab and ACPI tables

Borislav Petkov bp at alien8.de
Sat Apr 27 09:11:21 PDT 2019


On Wed, Apr 24, 2019 at 05:29:43PM +0800, Baoquan He wrote:
> From: Kairui Song <kasong at redhat.com>
> 
> The current code only builds identity mapping for physical memory during
> kexec-type loading. The regions reserved by firmware are not covered.
> In the next patch, the boot decompressing code of kexec-ed kernel tries

There's no guarantee that when this patch gets applied, the next patch
will be the one you mean. So explain what you mean here instead.

> to access EFI systab and ACPI tables, lacking identity mapping for them
> will cause error and reset system to firmware.
> 
> This error doesn't happen on all systems. Because kexec enables gbpages
> to build identity mapping, the EFI systab and ACPI tables could have been
> covered if they share the same 1 GB area with physical memory. To make
> sure, we should map them always.
> 
> So here add mapping for them.
> 
> Signed-off-by: Kairui Song <kasong at redhat.com>

When you send someone else's patch, you need to add your SOB. Lemme
point you to

  Documentation/process/submitting-patches.rst

again. Please have a deeper look.

> ---
>  arch/x86/kernel/machine_kexec_64.c | 86 ++++++++++++++++++++++++++++++
>  1 file changed, 86 insertions(+)
> 
> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> index ceba408ea982..77b40c3e28d7 100644
> --- a/arch/x86/kernel/machine_kexec_64.c
> +++ b/arch/x86/kernel/machine_kexec_64.c
> @@ -18,6 +18,7 @@
>  #include <linux/io.h>
>  #include <linux/suspend.h>
>  #include <linux/vmalloc.h>
> +#include <linux/efi.h>
>  
>  #include <asm/init.h>
>  #include <asm/pgtable.h>
> @@ -29,6 +30,48 @@
>  #include <asm/setup.h>
>  #include <asm/set_memory.h>
>  
> +#ifdef CONFIG_ACPI
> +/**

Two stars '**' are kernel-doc style but this comment is implementation
detail and is irrelevant for kernel-doc ouput.

> + * Used while adding mapping for ACPI tables.
> + * Can be reused when other iomem regions need be mapped
> + */
> +struct init_pgtable_data {
> +	struct x86_mapping_info *info;
> +	pgd_t *level4p;
> +};
> +
> +static int mem_region_callback(struct resource *res, void *arg)
> +{
> +	struct init_pgtable_data *data = arg;
> +	unsigned long mstart, mend;
> +
> +	mstart = res->start;
> +	mend = mstart + resource_size(res) - 1;
> +
> +	return kernel_ident_mapping_init(data->info,
> +			data->level4p, mstart, mend);

Do not break that line.

> +}
> +
> +static int init_acpi_pgtable(struct x86_mapping_info *info,
> +				   pgd_t *level4p)

static int
map_acpi_tables(...)

> +{
> +	unsigned long flags = IORESOURCE_MEM | IORESOURCE_BUSY;
> +	struct init_pgtable_data data;
> +
> +	data.info = info;
> +	data.level4p = level4p;
> +	flags = IORESOURCE_MEM | IORESOURCE_BUSY;
> +	return walk_iomem_res_desc(IORES_DESC_ACPI_TABLES, flags, 0, -1,
> +				   &data, mem_region_callback);
> +}
> +#else
> +static int init_acpi_pgtable(struct x86_mapping_info *info,
> +				   pgd_t *level4p)
> +{
> +	return 0;
> +}
> +#endif
> +
>  #ifdef CONFIG_KEXEC_FILE
>  const struct kexec_file_ops * const kexec_file_loaders[] = {
>  		&kexec_bzImage64_ops,
> @@ -36,6 +79,37 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
>  };
>  #endif
>  
> +#ifdef CONFIG_EFI
> +static int init_efi_systab_pgtable(struct x86_mapping_info *info,
> +				   pgd_t *level4p)

This function's name is wrong. Make it like this:

static int
map_efi_systab(struct x86_mapping_info *info, pgd_t *level4p)
{
#ifdef CONFIG_EFI

	...

#endif

	return 0;
}

and drop the #else ifdeffery.


> +{
> +	unsigned long mstart, mend;
> +
> +	if (!efi_enabled(EFI_BOOT))
> +		return 0;
> +
> +	mstart = (boot_params.efi_info.efi_systab |
> +			((u64)boot_params.efi_info.efi_systab_hi<<32));
> +
> +	if (efi_enabled(EFI_64BIT))
> +		mend = mstart + sizeof(efi_system_table_64_t);
> +	else
> +		mend = mstart + sizeof(efi_system_table_32_t);
> +
> +	if (mstart)
> +		return kernel_ident_mapping_init(info,
> +				level4p, mstart, mend);

Flip that logic:

	if (!mstart)
		return 0;

	return kernel_ident_mapping_init(info, level4p, mstart, mend);

and let the function stick out.

> +
> +	return 0;
> +}
> +#else
> +static inline int init_efi_systab_pgtable(struct x86_mapping_info *info,
> +					  pgd_t *level4p)
> +{
> +	return 0;
> +}
> +#endif
> +
>  static void free_transition_pgtable(struct kimage *image)
>  {
>  	free_page((unsigned long)image->arch.p4d);
> @@ -159,6 +233,18 @@ static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
>  			return result;
>  	}
>  
> +	/**

Two stars '**' are kernel-doc style comments above function names but
not here.

> +	 * Prepare EFI systab and ACPI table mapping for kexec kernel,
> +	 * since they are not covered by pfn_mapped.
> +	 */
> +	result = init_efi_systab_pgtable(&info, level4p);
> +	if (result)
> +		return result;
> +
> +	result = init_acpi_pgtable(&info, level4p);
> +	if (result)
> +		return result;
> +
>  	return init_transition_pgtable(image, level4p);
>  }
>  
> -- 
> 2.17.2
> 

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.



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