diff mbox

[1/5] ARM: efi: apply strict permissons for UEFI Runtime Services regions

Message ID 1456151158-25849-2-git-send-email-ard.biesheuvel@linaro.org
State Superseded
Headers show

Commit Message

Ard Biesheuvel Feb. 22, 2016, 2:25 p.m. UTC 
Recent UEFI versions expose permission attributes for runtime services
memory regions, either in the UEFI memory map or in the separate memory
attributes table.  This allows the kernel to map these regions with
stricter permissions, rather than the RWX permissions that are used by
default. So wire this up in our mapping routine.

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

---
 arch/arm/include/asm/efi.h |  1 +
 arch/arm/kernel/efi.c      | 41 ++++++++++++++++++++
 2 files changed, 42 insertions(+)

-- 
2.5.0


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Comments

Ard Biesheuvel March 2, 2016, 1:07 p.m. UTC | #1 
On 2 March 2016 at 12:49, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> On Mon, 22 Feb, at 03:25:54PM, Ard Biesheuvel wrote:

>> Recent UEFI versions expose permission attributes for runtime services

>> memory regions, either in the UEFI memory map or in the separate memory

>> attributes table.  This allows the kernel to map these regions with

>> stricter permissions, rather than the RWX permissions that are used by

>> default. So wire this up in our mapping routine.

>>

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

>> ---

>>  arch/arm/include/asm/efi.h |  1 +

>>  arch/arm/kernel/efi.c      | 41 ++++++++++++++++++++

>>  2 files changed, 42 insertions(+)

>

> Looks fine from an EFI perspective, but it would be nice for somebody

> else with ARM knowledge to ACK it.


I agree.

Note that the whole memory attribute series needs to wait for some
memremap() changes that I proposed for ARM (or at least the bits where
we wire it up for arm64+ARM)

Thanks,
Ard.

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diff mbox

Patch

diff --git a/arch/arm/include/asm/efi.h b/arch/arm/include/asm/efi.h
index e0eea72deb87..b0c341d7ceee 100644
--- a/arch/arm/include/asm/efi.h
+++ b/arch/arm/include/asm/efi.h
@@ -22,6 +22,7 @@ 
 void efi_init(void);
 
 int efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md);
+int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
 
 #define efi_call_virt(f, ...)						\
 ({									\
diff --git a/arch/arm/kernel/efi.c b/arch/arm/kernel/efi.c
index ff8a9d8acfac..9f43ba012d10 100644
--- a/arch/arm/kernel/efi.c
+++ b/arch/arm/kernel/efi.c
@@ -11,6 +11,41 @@ 
 #include <asm/mach/map.h>
 #include <asm/mmu_context.h>
 
+static int __init set_permissions(pte_t *ptep, pgtable_t token,
+				  unsigned long addr, void *data)
+{
+	efi_memory_desc_t *md = data;
+	pte_t pte = *ptep;
+
+	if (md->attribute & EFI_MEMORY_RO)
+		pte = set_pte_bit(pte, __pgprot(L_PTE_RDONLY));
+	if (md->attribute & EFI_MEMORY_XP)
+		pte = set_pte_bit(pte, __pgprot(L_PTE_XN));
+	set_pte_ext(ptep, pte, PTE_EXT_NG);
+	return 0;
+}
+
+int __init efi_set_mapping_permissions(struct mm_struct *mm,
+				       efi_memory_desc_t *md)
+{
+	unsigned long base, size;
+
+	base = md->virt_addr;
+	size = md->num_pages << EFI_PAGE_SHIFT;
+
+	/*
+	 * We can only use apply_to_page_range() if we can guarantee that the
+	 * entire region was mapped using pages. This should be the case if the
+	 * region does not cover any naturally aligned SECTION_SIZE sized
+	 * blocks.
+	 */
+	if (round_down(base + size, SECTION_SIZE) <
+	    round_up(base, SECTION_SIZE) + SECTION_SIZE)
+		return apply_to_page_range(mm, base, size, set_permissions, md);
+
+	return 0;
+}
+
 int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
 {
 	struct map_desc desc = {
@@ -34,5 +69,11 @@  int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
 		desc.type = MT_DEVICE;
 
 	create_mapping_late(mm, &desc, true);
+
+	/*
+	 * If stricter permissions were specified, apply them now.
+	 */
+	if (md->attribute & (EFI_MEMORY_RO | EFI_MEMORY_XP))
+		return efi_set_mapping_permissions(mm, md);
 	return 0;
 }