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efi capsule loader fixes

PATCH New Ard Biesheuvel 1 participant 3 messages Dec 7, 2020

Subsystems (3)
Arm (32-bit) arm64 EFI
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Ard Biesheuvel

author maintainer
#0 lore raw

cover efi capsule loader fixes

A couple of fixes for the EFI capsule loader. Patch #1 switches from kmap() to kmap_atomic(). Patch #2 adds cache maintenance of the scatter gather list entries passed to UpdateCapsule.

Cc Samer El-Haj-Mahmoud <[email protected]>

Ard Biesheuvel (2):
efi: capsule: use atomic kmap for transient sglist mappings
efi: capsule: clean scatter-gather entries from the D-cache

 arch/arm/include/asm/efi.h     |  5 +++++
 arch/arm64/include/asm/efi.h   |  5 +++++
 drivers/firmware/efi/capsule.c | 16 ++++++++++++++--
 3 files changed, 24 insertions(+), 2 deletions(-)
Signature · 1 line
2.17.1
author maintainer
#1 lore raw

PATCH 1/2 efi: capsule: use atomic kmap for transient sglist mappings

Don't use the heavy-weight kmap() API to create short-lived mappings of the scatter-gather list entries that are released as soon as the entries are written. Instead, use kmap_atomic(), which is more suited to this purpose.

Signed-off-by Ard Biesheuvel <[email protected]>
---
 drivers/firmware/efi/capsule.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
drivers/firmware/efi/capsule.c +2 -2
index 598b7800d14e..43f6fe7bfe80 100644
@@ -244,7 +244,7 @@ int efi_capsule_update(efi_capsule_header_t *capsule, phys_addr_t *pages)
 	for (i = 0; i < sg_count; i++) {
 		efi_capsule_block_desc_t *sglist;
 
-		sglist = kmap(sg_pages[i]);
+		sglist = kmap_atomic(sg_pages[i]);
 
 		for (j = 0; j < SGLIST_PER_PAGE && count > 0; j++) {
 			u64 sz = min_t(u64, imagesize,

@@ -265,7 +265,7 @@ int efi_capsule_update(efi_capsule_header_t *capsule, phys_addr_t *pages)
 		else
 			sglist[j].data = page_to_phys(sg_pages[i + 1]);
 
-		kunmap(sg_pages[i]);
+		kunmap_atomic(sglist);
 	}
 
 	mutex_lock(&capsule_mutex);
Signature · 1 line
2.17.1
author maintainer
#2 lore raw

PATCH 2/2 efi: capsule: clean scatter-gather entries from the D-cache

In reply to Ard Biesheuvel

The UEFI spec 2.9 has recently been updated to include a requirement that scatter-gather lists passed to UpdateCapsule() should be cleaned from the D-cache to ensure that they are visible to the CPU after a warm reboot before it enables the MMU. On ARM and arm64 systems, this implies a D-cache clean by virtual address to the point of coherency.

Signed-off-by Ard Biesheuvel <[email protected]>
---
 arch/arm/include/asm/efi.h     |  5 +++++
 arch/arm64/include/asm/efi.h   |  5 +++++
 drivers/firmware/efi/capsule.c | 12 ++++++++++++
 3 files changed, 22 insertions(+)
arch/arm/include/asm/efi.h +5 -0
index 3ee4f4381985..e9a06e164e06 100644
@@ -93,4 +93,9 @@ struct efi_arm_entry_state {
 	u32	sctlr_after_ebs;
 };
 
+static inline void efi_capsule_flush_cache_range(void *addr, int size)
+{
+	__cpuc_flush_dcache_area(addr, size);
+}
+
 #endif /* _ASM_ARM_EFI_H */
arch/arm64/include/asm/efi.h +5 -0
index 973b14415271..00bd1e179d36 100644
@@ -141,4 +141,9 @@ static inline void efi_set_pgd(struct mm_struct *mm)
 void efi_virtmap_load(void);
 void efi_virtmap_unload(void);
 
+static inline void efi_capsule_flush_cache_range(void *addr, int size)
+{
+	__flush_dcache_area(addr, size);
+}
+
 #endif /* _ASM_EFI_H */
drivers/firmware/efi/capsule.c +12 -0
index 43f6fe7bfe80..768430293669 100644
@@ -12,6 +12,7 @@
 #include <linux/highmem.h>
 #include <linux/efi.h>
 #include <linux/vmalloc.h>
+#include <asm/efi.h>
 #include <asm/io.h>
 
 typedef struct {

@@ -265,6 +266,17 @@ int efi_capsule_update(efi_capsule_header_t *capsule, phys_addr_t *pages)
 		else
 			sglist[j].data = page_to_phys(sg_pages[i + 1]);
 
+#if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
+		/*
+		 * At runtime, the firmware has no way to find out where the
+		 * sglist elements are mapped, if they are mapped in the first
+		 * place. Therefore, on architectures that can only perform
+		 * cache maintenance by virtual address, the firmware is unable
+		 * to perform this maintenance, and so it is up to the OS to do
+		 * it instead.
+		 */
+		efi_capsule_flush_cache_range(sglist, PAGE_SIZE);
+#endif
 		kunmap_atomic(sglist);
 	}
Signature · 1 line
2.17.1