Re: [RFC PATCH v4 14/28] Add support to access boot related data in the clear

Borislav Petkov
2017-02-21T15:06:56Z

On Thu, Feb 16, 2017 at 09:45:09AM -0600, Tom Lendacky wrote:
> Boot data (such as EFI related data) is not encrypted when the system is
> booted and needs to be mapped decrypted. Add support to apply the proper
> attributes to the EFI page tables and to the early_memremap and memremap
> APIs to identify the type of data being accessed so that the proper
> encryption attribute can be applied.

So this doesn't even begin to explain *why* we need this. The emphasis
being on *why*.

Lemme guess? kexec? And because of efi_reuse_config?

If so, then that whole ad-hoc caching in parse_setup_data() needs to go.
Especially if efi_reuse_config() already sees those addresses so while
we're there, we could save them somewhere or whatnot. But not doing the
whole thing again in parse_setup_data().

> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
> arch/x86/include/asm/io.h | 3 +
> arch/x86/include/asm/setup.h | 8 +++
> arch/x86/kernel/setup.c | 33 ++++++++++++
> arch/x86/mm/ioremap.c | 111 ++++++++++++++++++++++++++++++++++++++++
> arch/x86/platform/efi/efi_64.c | 16 ++++--
> kernel/memremap.c | 11 ++++
> mm/early_ioremap.c | 18 +++++-
> 7 files changed, 192 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
> index 7afb0e2..833f7cc 100644
> --- a/arch/x86/include/asm/io.h
> +++ b/arch/x86/include/asm/io.h
> @@ -381,4 +381,7 @@ extern int __must_check arch_phys_wc_add(unsigned long base,
> #define arch_io_reserve_memtype_wc arch_io_reserve_memtype_wc
> #endif
>
> +extern bool arch_memremap_do_ram_remap(resource_size_t offset, size_t size);
> +#define arch_memremap_do_ram_remap arch_memremap_do_ram_remap
> +
> #endif /* _ASM_X86_IO_H */
> diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
> index ac1d5da..99998d9 100644
> --- a/arch/x86/include/asm/setup.h
> +++ b/arch/x86/include/asm/setup.h
> @@ -63,6 +63,14 @@ static inline void x86_ce4100_early_setup(void) { }
> #include <asm/espfix.h>
> #include <linux/kernel.h>
>
> +struct setup_data_attrs {
> + u64 paddr;
> + unsigned long size;
> +};
> +
> +extern struct setup_data_attrs setup_data_list[];
> +extern unsigned int setup_data_list_count;
> +
> /*
> * This is set up by the setup-routine at boot-time
> */
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index bd5b9a7..d2234bf 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -148,6 +148,9 @@ int default_check_phys_apicid_present(int phys_apicid)
>
> struct boot_params boot_params;
>
> +struct setup_data_attrs setup_data_list[32];
> +unsigned int setup_data_list_count;
> +
> /*
> * Machine setup..
> */
> @@ -419,6 +422,32 @@ static void __init reserve_initrd(void)
> }
> #endif /* CONFIG_BLK_DEV_INITRD */
>
> +static void __init update_setup_data_list(u64 pa_data, unsigned long size)
> +{
> + unsigned int i;
> +
> + for (i = 0; i < setup_data_list_count; i++) {
> + if (setup_data_list[i].paddr != pa_data)
> + continue;
> +
> + setup_data_list[i].size = size;
> + break;
> + }
> +}
> +
> +static void __init add_to_setup_data_list(u64 pa_data, unsigned long size)
> +{
> + if (!sme_active())
> + return;
> +
> + if (!WARN(setup_data_list_count == ARRAY_SIZE(setup_data_list),
> + "exceeded maximum setup data list slots")) {
> + setup_data_list[setup_data_list_count].paddr = pa_data;
> + setup_data_list[setup_data_list_count].size = size;
> + setup_data_list_count++;
> + }
> +}
> +
> static void __init parse_setup_data(void)
> {
> struct setup_data *data;
> @@ -428,12 +457,16 @@ static void __init parse_setup_data(void)
> while (pa_data) {
> u32 data_len, data_type;
>
> + add_to_setup_data_list(pa_data, sizeof(*data));
> +
> data = early_memremap(pa_data, sizeof(*data));
> data_len = data->len + sizeof(struct setup_data);
> data_type = data->type;
> pa_next = data->next;
> early_memunmap(data, sizeof(*data));
>
> + update_setup_data_list(pa_data, data_len);
> +
> switch (data_type) {
> case SETUP_E820_EXT:
> e820__memory_setup_extended(pa_data, data_len);
> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> index 2385e70..b0ff6bc 100644
> --- a/arch/x86/mm/ioremap.c
> +++ b/arch/x86/mm/ioremap.c
> @@ -13,6 +13,7 @@
> #include <linux/slab.h>
> #include <linux/vmalloc.h>
> #include <linux/mmiotrace.h>
> +#include <linux/efi.h>
>
> #include <asm/cacheflush.h>
> #include <asm/e820/api.h>
> @@ -21,6 +22,7 @@
> #include <asm/tlbflush.h>
> #include <asm/pgalloc.h>
> #include <asm/pat.h>
> +#include <asm/setup.h>
>
> #include "physaddr.h"
>
> @@ -419,6 +421,115 @@ void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
> iounmap((void __iomem *)((unsigned long)addr & PAGE_MASK));
> }
>
> +/*
> + * Examine the physical address to determine if it is boot data. Check
> + * it against the boot params structure and EFI tables.
> + */
> +static bool memremap_is_setup_data(resource_size_t phys_addr,
> + unsigned long size)
> +{
> + unsigned int i;
> + u64 paddr;
> +
> + for (i = 0; i < setup_data_list_count; i++) {
> + if (phys_addr < setup_data_list[i].paddr)
> + continue;
> +
> + if (phys_addr >= (setup_data_list[i].paddr +
> + setup_data_list[i].size))
> + continue;
> +
> + /* Address is within setup data range */
> + return true;
> + }
> +
> + paddr = boot_params.efi_info.efi_memmap_hi;
> + paddr <<= 32;
> + paddr |= boot_params.efi_info.efi_memmap;
> + if (phys_addr == paddr)
> + return true;
> +
> + paddr = boot_params.efi_info.efi_systab_hi;
> + paddr <<= 32;
> + paddr |= boot_params.efi_info.efi_systab;
> + if (phys_addr == paddr)
> + return true;
> +
> + if (efi_table_address_match(phys_addr))
> + return true;
> +
> + return false;
> +}
> +
> +/*
> + * This function determines if an address should be mapped encrypted.
> + * Boot setup data, EFI data and E820 areas are checked in making this
> + * determination.
> + */
> +static bool memremap_should_map_encrypted(resource_size_t phys_addr,
> + unsigned long size)
> +{
> + /*
> + * SME is not active, return true:
> + * - For early_memremap_pgprot_adjust(), returning true or false
> + * results in the same protection value
> + * - For arch_memremap_do_ram_remap(), returning true will allow
> + * the RAM remap to occur instead of falling back to ioremap()
> + */
> + if (!sme_active())
> + return true;
> +
> + /* Check if the address is part of the setup data */
> + if (memremap_is_setup_data(phys_addr, size))
> + return false;
> +
> + /* Check if the address is part of EFI boot/runtime data */
> + switch (efi_mem_type(phys_addr)) {

arch/x86/built-in.o: In function `memremap_should_map_encrypted':
/home/boris/kernel/alt-linux/arch/x86/mm/ioremap.c:487: undefined reference to `efi_mem_type'
make: *** [vmlinux] Error 1

That's a !CONFIG_EFI .config.

> + case EFI_BOOT_SERVICES_DATA:
> + case EFI_RUNTIME_SERVICES_DATA:
> + return false;
> + default:
> + break;
> + }
> +
> + /* Check if the address is outside kernel usable area */
> + switch (e820__get_entry_type(phys_addr, phys_addr + size - 1)) {
> + case E820_TYPE_RESERVED:
> + case E820_TYPE_ACPI:
> + case E820_TYPE_NVS:
> + case E820_TYPE_UNUSABLE:
> + return false;
> + default:
> + break;
> + }
> +
> + return true;
> +}
> +
> +/*
> + * Architecure function to determine if RAM remap is allowed.
> + */
> +bool arch_memremap_do_ram_remap(resource_size_t phys_addr, unsigned long size)
> +{
> + return memremap_should_map_encrypted(phys_addr, size);
> +}
> +
> +/*
> + * Architecure override of __weak function to adjust the protection attributes
> + * used when remapping memory.
> + */
> +pgprot_t __init early_memremap_pgprot_adjust(resource_size_t phys_addr,
> + unsigned long size,
> + pgprot_t prot)
> +{
> + if (memremap_should_map_encrypted(phys_addr, size))
> + prot = pgprot_encrypted(prot);
> + else
> + prot = pgprot_decrypted(prot);
> +
> + return prot;
> +}
> +
> #ifdef CONFIG_ARCH_USE_MEMREMAP_PROT
> /* Remap memory with encryption */
> void __init *early_memremap_encrypted(resource_size_t phys_addr,
> diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
> index 2ee7694..2d8674d 100644
> --- a/arch/x86/platform/efi/efi_64.c
> +++ b/arch/x86/platform/efi/efi_64.c
> @@ -243,7 +243,7 @@ void efi_sync_low_kernel_mappings(void)
>
> int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
> {
> - unsigned long pfn, text;
> + unsigned long pfn, text, pf;
> struct page *page;
> unsigned npages;
> pgd_t *pgd;
> @@ -251,7 +251,13 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
> if (efi_enabled(EFI_OLD_MEMMAP))
> return 0;
>
> - efi_scratch.efi_pgt = (pgd_t *)__pa(efi_pgd);
> + /*
> + * Since the PGD is encrypted, set the encryption mask so that when
> + * this value is loaded into cr3 the PGD will be decrypted during
> + * the pagetable walk.
> + */
> + efi_scratch.efi_pgt = (pgd_t *)__sme_pa(efi_pgd);
> +
> pgd = efi_pgd;
>
> /*
> @@ -261,7 +267,8 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
> * phys_efi_set_virtual_address_map().
> */
> pfn = pa_memmap >> PAGE_SHIFT;
> - if (kernel_map_pages_in_pgd(pgd, pfn, pa_memmap, num_pages, _PAGE_NX | _PAGE_RW)) {
> + pf = _PAGE_NX | _PAGE_RW | _PAGE_ENC;
> + if (kernel_map_pages_in_pgd(pgd, pfn, pa_memmap, num_pages, pf)) {
> pr_err("Error ident-mapping new memmap (0x%lx)!\n", pa_memmap);
> return 1;
> }
> @@ -304,7 +311,8 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
> text = __pa(_text);
> pfn = text >> PAGE_SHIFT;
>
> - if (kernel_map_pages_in_pgd(pgd, pfn, text, npages, _PAGE_RW)) {
> + pf = _PAGE_RW | _PAGE_ENC;
> + if (kernel_map_pages_in_pgd(pgd, pfn, text, npages, pf)) {
> pr_err("Failed to map kernel text 1:1\n");
> return 1;
> }

Those changes should be in a separate patch IMHO.

--
Regards/Gruss,
Boris.

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