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Ard BiesheuvelIngo Molnar
Ard Biesheuvel
authored and
Ingo Molnar
committed
efi: Implement generic support for the Memory Attributes table
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> [ Trim pr_*() strings to 80 cols and use EFI consistently. ] Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Leif Lindholm <leif.lindholm@linaro.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Peter Jones <pjones@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/1461614832-17633-14-git-send-email-matt@codeblueprint.co.uk Signed-off-by: Ingo Molnar <mingo@kernel.org>
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‎drivers/firmware/efi/Makefile

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
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#
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KASAN_SANITIZE_runtime-wrappers.o := n
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12-
obj-$(CONFIG_EFI) += efi.o vars.o reboot.o
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obj-$(CONFIG_EFI) += efi.o vars.o reboot.o memattr.o
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obj-$(CONFIG_EFI_VARS) += efivars.o
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obj-$(CONFIG_EFI_ESRT) += esrt.o
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obj-$(CONFIG_EFI_VARS_PSTORE) += efi-pstore.o

‎drivers/firmware/efi/memattr.c

Lines changed: 182 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,182 @@
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/*
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* Copyright (C) 2016 Linaro Ltd. <ard.biesheuvel@linaro.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#define pr_fmt(fmt) "efi: memattr: " fmt
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#include <linux/efi.h>
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#include <linux/init.h>
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#include <linux/io.h>
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#include <linux/memblock.h>
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#include <asm/early_ioremap.h>
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static int __initdata tbl_size;
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/*
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* Reserve the memory associated with the Memory Attributes configuration
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* table, if it exists.
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*/
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int __init efi_memattr_init(void)
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{
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efi_memory_attributes_table_t *tbl;
27+
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if (efi.mem_attr_table == EFI_INVALID_TABLE_ADDR)
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return 0;
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tbl = early_memremap(efi.mem_attr_table, sizeof(*tbl));
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if (!tbl) {
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pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
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efi.mem_attr_table);
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return -ENOMEM;
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}
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if (tbl->version > 1) {
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pr_warn("Unexpected EFI Memory Attributes table version %d\n",
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tbl->version);
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goto unmap;
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}
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tbl_size = sizeof(*tbl) + tbl->num_entries * tbl->desc_size;
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memblock_reserve(efi.mem_attr_table, tbl_size);
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unmap:
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early_memunmap(tbl, sizeof(*tbl));
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return 0;
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}
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/*
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* Returns a copy @out of the UEFI memory descriptor @in if it is covered
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* entirely by a UEFI memory map entry with matching attributes. The virtual
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* address of @out is set according to the matching entry that was found.
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*/
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static bool entry_is_valid(const efi_memory_desc_t *in, efi_memory_desc_t *out)
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{
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u64 in_paddr = in->phys_addr;
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u64 in_size = in->num_pages << EFI_PAGE_SHIFT;
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efi_memory_desc_t *md;
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*out = *in;
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if (in->type != EFI_RUNTIME_SERVICES_CODE &&
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in->type != EFI_RUNTIME_SERVICES_DATA) {
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pr_warn("Entry type should be RuntimeServiceCode/Data\n");
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return false;
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}
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if (!(in->attribute & (EFI_MEMORY_RO | EFI_MEMORY_XP))) {
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pr_warn("Entry attributes invalid: RO and XP bits both cleared\n");
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return false;
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}
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if (PAGE_SIZE > EFI_PAGE_SIZE &&
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(!PAGE_ALIGNED(in->phys_addr) ||
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!PAGE_ALIGNED(in->num_pages << EFI_PAGE_SHIFT))) {
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/*
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* Since arm64 may execute with page sizes of up to 64 KB, the
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* UEFI spec mandates that RuntimeServices memory regions must
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* be 64 KB aligned. We need to validate this here since we will
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* not be able to tighten permissions on such regions without
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* affecting adjacent regions.
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*/
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pr_warn("Entry address region misaligned\n");
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return false;
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}
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for_each_efi_memory_desc(md) {
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u64 md_paddr = md->phys_addr;
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u64 md_size = md->num_pages << EFI_PAGE_SHIFT;
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if (!(md->attribute & EFI_MEMORY_RUNTIME))
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continue;
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if (md->virt_addr == 0) {
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/* no virtual mapping has been installed by the stub */
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break;
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}
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if (md_paddr > in_paddr || (in_paddr - md_paddr) >= md_size)
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continue;
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/*
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* This entry covers the start of @in, check whether
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* it covers the end as well.
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*/
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if (md_paddr + md_size < in_paddr + in_size) {
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pr_warn("Entry covers multiple EFI memory map regions\n");
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return false;
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}
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if (md->type != in->type) {
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pr_warn("Entry type deviates from EFI memory map region type\n");
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return false;
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}
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out->virt_addr = in_paddr + (md->virt_addr - md_paddr);
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return true;
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}
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pr_warn("No matching entry found in the EFI memory map\n");
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return false;
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}
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/*
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* To be called after the EFI page tables have been populated. If a memory
129+
* attributes table is available, its contents will be used to update the
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* mappings with tightened permissions as described by the table.
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* This requires the UEFI memory map to have already been populated with
132+
* virtual addresses.
133+
*/
134+
int __init efi_memattr_apply_permissions(struct mm_struct *mm,
135+
efi_memattr_perm_setter fn)
136+
{
137+
efi_memory_attributes_table_t *tbl;
138+
int i, ret;
139+
140+
if (tbl_size <= sizeof(*tbl))
141+
return 0;
142+
143+
/*
144+
* We need the EFI memory map to be setup so we can use it to
145+
* lookup the virtual addresses of all entries in the of EFI
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* Memory Attributes table. If it isn't available, this
147+
* function should not be called.
148+
*/
149+
if (WARN_ON(!efi_enabled(EFI_MEMMAP)))
150+
return 0;
151+
152+
tbl = memremap(efi.mem_attr_table, tbl_size, MEMREMAP_WB);
153+
if (!tbl) {
154+
pr_err("Failed to map EFI Memory Attributes table @ 0x%lx\n",
155+
efi.mem_attr_table);
156+
return -ENOMEM;
157+
}
158+
159+
if (efi_enabled(EFI_DBG))
160+
pr_info("Processing EFI Memory Attributes table:\n");
161+
162+
for (i = ret = 0; ret == 0 && i < tbl->num_entries; i++) {
163+
efi_memory_desc_t md;
164+
unsigned long size;
165+
bool valid;
166+
char buf[64];
167+
168+
valid = entry_is_valid((void *)tbl->entry + i * tbl->desc_size,
169+
&md);
170+
size = md.num_pages << EFI_PAGE_SHIFT;
171+
if (efi_enabled(EFI_DBG) || !valid)
172+
pr_info("%s 0x%012llx-0x%012llx %s\n",
173+
valid ? "" : "!", md.phys_addr,
174+
md.phys_addr + size - 1,
175+
efi_md_typeattr_format(buf, sizeof(buf), &md));
176+
177+
if (valid)
178+
ret = fn(mm, &md);
179+
}
180+
memunmap(tbl);
181+
return ret;
182+
}

‎include/linux/efi.h

Lines changed: 13 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -969,6 +969,19 @@ extern void __init efi_fake_memmap(void);
969969
static inline void efi_fake_memmap(void) { }
970970
#endif
971971

972+
/*
973+
* efi_memattr_perm_setter - arch specific callback function passed into
974+
* efi_memattr_apply_permissions() that updates the
975+
* mapping permissions described by the second
976+
* argument in the page tables referred to by the
977+
* first argument.
978+
*/
979+
typedef int (*efi_memattr_perm_setter)(struct mm_struct *, efi_memory_desc_t *);
980+
981+
extern int efi_memattr_init(void);
982+
extern int efi_memattr_apply_permissions(struct mm_struct *mm,
983+
efi_memattr_perm_setter fn);
984+
972985
/* Iterate through an efi_memory_map */
973986
#define for_each_efi_memory_desc_in_map(m, md) \
974987
for ((md) = (m)->map; \

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