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[v2,4/5] efi: implement generic support for the Memory Attributes table

Message ID CAKv+Gu-ncY=edbP0tD13m_Fogqrh+BFKW+ACSwGTu+7JtuKGWA@mail.gmail.com
State New
Headers show

Commit Message

Ard Biesheuvel April 1, 2016, 12:36 p.m. UTC 
On 30 March 2016 at 18:38, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> This implements shared support for discovering the presence of the

> Memory Attributes table, and for parsing and validating its contents.

>

> The table is validated against the construction rules in the UEFI spec.

> Since this is a new table, it makes sense to complain if we encounter

> a table that does not follow those rules.

>

> The parsing and validation routine takes a callback that can be specified

> per architecture, that gets passed each unique validated region, with the

> virtual address retrieved from the ordinary memory map.

>

> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---

>  drivers/firmware/efi/Makefile  |   2 +-

>  drivers/firmware/efi/memattr.c | 170 ++++++++++++++++++++

>  include/linux/efi.h            |  13 ++

>  3 files changed, 184 insertions(+), 1 deletion(-)

>

> diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile

> index 62e654f255f4..d5be62399130 100644

> --- a/drivers/firmware/efi/Makefile

> +++ b/drivers/firmware/efi/Makefile

> @@ -9,7 +9,7 @@

>  #

>  KASAN_SANITIZE_runtime-wrappers.o      := n

>

> -obj-$(CONFIG_EFI)                      += efi.o vars.o reboot.o

> +obj-$(CONFIG_EFI)                      += efi.o vars.o reboot.o memattr.o

>  obj-$(CONFIG_EFI_VARS)                 += efivars.o

>  obj-$(CONFIG_EFI_ESRT)                 += esrt.o

>  obj-$(CONFIG_EFI_VARS_PSTORE)          += efi-pstore.o

> diff --git a/drivers/firmware/efi/memattr.c b/drivers/firmware/efi/memattr.c

> new file mode 100644

> index 000000000000..c55683937f4a

> --- /dev/null

> +++ b/drivers/firmware/efi/memattr.c

> @@ -0,0 +1,170 @@

> +/*

> + * Copyright (C) 2016 Linaro Ltd. <ard.biesheuvel@linaro.org>

> + *

> + * This program is free software; you can redistribute it and/or modify

> + * it under the terms of the GNU General Public License version 2 as

> + * published by the Free Software Foundation.

> + */

> +

> +#define pr_fmt(fmt)    "efi: " fmt

> +

> +#include <linux/efi.h>

> +#include <linux/init.h>

> +#include <linux/io.h>

> +#include <linux/memblock.h>

> +

> +#include <asm/early_ioremap.h>

> +

> +static int __initdata tbl_size;

> +

> +/*

> + * Reserve the memory associated with the Memory Attributes configuration

> + * table, if it exists.

> + */

> +int __init efi_memattr_init(void)

> +{

> +       efi_memory_attributes_table_t *tbl;

> +

> +       if (efi.mem_attr_table == EFI_INVALID_TABLE_ADDR)

> +               return 0;

> +

> +       tbl = early_memremap(efi.mem_attr_table, sizeof(*tbl));

> +       if (!tbl) {

> +               pr_err("Failed to map EFI Memory Attribute table @ 0x%lx\n",

> +                      efi.mem_attr_table);

> +               return -ENOMEM;

> +       }

> +

> +       if (tbl->version > 1) {

> +               pr_warn("Unexpected EFI Memory Attribute table version %d\n",

> +                       tbl->version);

> +               tbl_size = 0;

> +               goto unmap;

> +       }

> +

> +       tbl_size = sizeof(*tbl) + tbl->num_entries * tbl->desc_size;

> +       memblock_reserve(efi.mem_attr_table, tbl_size);

> +

> +unmap:

> +       early_memunmap(tbl, sizeof(*tbl));

> +       return 0;

> +}

> +

> +/*

> + * Returns a copy @out of the UEFI memory descriptor @in if it is covered

> + * entirely by a UEFI memory map entry with matching attributes. The virtual

> + * address of @out is set according to the matching entry that was found.

> + */

> +static bool entry_is_valid(const efi_memory_desc_t *in, efi_memory_desc_t *out)

> +{

> +       u64 in_paddr = in->phys_addr;

> +       u64 in_size = in->num_pages << EFI_PAGE_SHIFT;

> +       efi_memory_desc_t *md;

> +

> +       if (in->type != EFI_RUNTIME_SERVICES_CODE &&

> +           in->type != EFI_RUNTIME_SERVICES_DATA) {

> +               pr_warn("MEMATTR table entry type should be RuntimeServiceCode/Data\n");

> +               return false;

> +       }

> +

> +       if (!(in->attribute & (EFI_MEMORY_RO | EFI_MEMORY_XP))) {

> +               pr_warn("MEMATTR table entry attributes invalid: RO and XP bits both cleared\n");

> +               return false;

> +       }

> +

> +       if (PAGE_SIZE > EFI_PAGE_SIZE &&

> +           (!PAGE_ALIGNED(in->phys_addr) ||

> +            !PAGE_ALIGNED(in->num_pages << EFI_PAGE_SHIFT))) {

> +               /*

> +                * Since arm64 may execute with page sizes of up to 64 KB, the

> +                * UEFI spec mandates that RuntimeServices memory regions must

> +                * be 64 KB aligned. We need to validate this here since we will

> +                * not be able to tighten permissions on such regions without

> +                * affecting adjacent regions.

> +                */

> +               pr_warn("MEMATTR table entry misaligned\n");

> +               return false;

> +       }

> +

> +       for_each_efi_memory_desc(&memmap, md) {

> +               u64 md_paddr = md->phys_addr;

> +               u64 md_size = md->num_pages << EFI_PAGE_SHIFT;

> +

> +               if (!(md->attribute & EFI_MEMORY_RUNTIME))

> +                       continue;

> +               if (md->virt_addr == 0) {

> +                       /* no virtual mapping has been installed by the stub */

> +                       break;

> +               }

> +

> +               if (md_paddr > in_paddr || (in_paddr - md_paddr) >= md_size)

> +                       continue;

> +

> +               /*

> +                * This entry covers the start of @in, check whether

> +                * it covers the end as well.

> +                */

> +               if (md_paddr + md_size < in_paddr + in_size) {

> +                       pr_warn("MEMATTR table entry covers multiple UEFI memory map regions\n");

> +                       return false;

> +               }

> +

> +               if (md->type != in->type) {

> +                       pr_warn("MEMATTR table entry type deviates from UEFI memory map region type\n");

> +                       return false;

> +               }

> +

> +               *out = *in;

> +               out->virt_addr = in_paddr +

> +                                (md->virt_addr - md->phys_addr);

> +               return true;

> +       }

> +       return false;

> +}

> +

> +/*

> + * To be called after the EFI page tables have been populated. If a memory

> + * attributes table is available, its contents will be used to update the

> + * mappings with tightened permissions as described by the table.

> + * This requires the UEFI memory map to have already been populated with

> + * virtual addresses.

> + */

> +int __init efi_memattr_apply_permissions(struct mm_struct *mm,

> +                                        efi_memattr_perm_setter fn)

> +{

> +       efi_memory_attributes_table_t *tbl;

> +       int i, ret;

> +

> +       if (tbl_size <= sizeof(*tbl))

> +               return 0;

> +

> +       tbl = memremap(efi.mem_attr_table, tbl_size, MEMREMAP_WB);

> +       if (!tbl) {

> +               pr_err("Failed to map EFI Memory Attribute table @ 0x%lx\n",

> +                      efi.mem_attr_table);

> +               return -ENOMEM;

> +       }

> +

> +       if (efi_enabled(EFI_DBG))

> +               pr_info("Processing UEFI Memory Attributes table:\n");

> +

> +       for (i = ret = 0; ret == 0 && i < tbl->num_entries; i++) {

> +               efi_memory_desc_t md;

> +               unsigned long size;

> +               bool valid;

> +               char buf[64];

> +

> +               valid = entry_is_valid((void *)tbl->entry + i * tbl->desc_size,

> +                                      &md);

> +               size = md.num_pages << EFI_PAGE_SHIFT;

> +               if (efi_enabled(EFI_DBG) || !valid)

> +                       pr_info("  0x%012llx-0x%012llx %s\n", md.phys_addr,

> +                               md.phys_addr + size - 1,

> +                               efi_md_typeattr_format(buf, sizeof(buf), &md));

> +

> +               if (valid)

> +                       ret = fn(mm, &md);

> +       }

> +       memunmap(tbl);

> +       return ret;

> +}

> diff --git a/include/linux/efi.h b/include/linux/efi.h

> index 346d01ad7cca..277a9bb4e587 100644

> --- a/include/linux/efi.h

> +++ b/include/linux/efi.h

> @@ -970,6 +970,19 @@ extern void __init efi_fake_memmap(void);

>  static inline void efi_fake_memmap(void) { }

>  #endif

>

> +/*

> + * efi_memattr_perm_setter - arch specific callback function passed into

> + *                           efi_memattr_apply_permissions() that updates the

> + *                           mapping permissions described by the second

> + *                           argument in the page tables referrred to by the

> + *                           first argument

> + */

> +typedef int (*efi_memattr_perm_setter)(struct mm_struct *, efi_memory_desc_t *);

> +

> +extern int efi_memattr_init(void);

> +extern int efi_memattr_apply_permissions(struct mm_struct *mm,

> +                                        efi_memattr_perm_setter fn);

> +

>  /* Iterate through an efi_memory_map */

>  #define for_each_efi_memory_desc(m, md)                                           \

>         for ((md) = (m)->map;                                              \

> --

> 2.5.0

>


This patch needs the following folded on top to deal with tables where
the memory attribute table entry has not counterpart in the memory map

                pr_warn("MEMATTR table entry type should be
RuntimeServiceCode/Data\n");
@@ -114,11 +116,11 @@ static bool entry_is_valid(const
efi_memory_desc_t *in, efi_memory_desc_t *out)
                        return false;
                }

-               *out = *in;
                out->virt_addr = in_paddr +
                                 (md->virt_addr - md->phys_addr);
                return true;
        }
+       pr_warn("MEMATTR table entry does not having a matching entry
in the memory map\n");
        return false;
 }

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diff mbox

Patch

diff --git a/drivers/firmware/efi/memattr.c b/drivers/firmware/efi/memattr.c
index c55683937f4a..4dfef78e64d8 100644
--- a/drivers/firmware/efi/memattr.c
+++ b/drivers/firmware/efi/memattr.c
@@ -61,6 +61,8 @@  static bool entry_is_valid(const efi_memory_desc_t
*in, efi_memory_desc_t *out)
        u64 in_size = in->num_pages << EFI_PAGE_SHIFT;
        efi_memory_desc_t *md;

+       *out = *in;
+
        if (in->type != EFI_RUNTIME_SERVICES_CODE &&
            in->type != EFI_RUNTIME_SERVICES_DATA) {