[PATCH v2 4/5] efi: implement generic support for the Memory Attributes table
Ard Biesheuvel
ard.biesheuvel at linaro.org
Fri Apr 1 05:36:33 PDT 2016
On 30 March 2016 at 18:38, Ard Biesheuvel <ard.biesheuvel at 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 at 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 at 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
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) {
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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