[PATCH] x86/efi: Handle errors for efi_map_region_fixed()

[Eshaan Deshmukh]

The function efi_map_region_fixed() ignores the errors returned from
kernel_map_pages_in_pgd(). If mapping failes, this can cause page
faults. Update __map_region() and efi_map_region_fixed() to return the
error code from kernel_map_pages_in_pgd(). If there is an error,
efi_map_region_fixed() logs an error message using pr_err(), disables
EFI runtime services, and returns.

Signed-off-by: Eshaan Deshmukh <eshaan2031@xxxxxxxxxx>
---
 arch/x86/include/asm/efi.h     |  2 +-
 arch/x86/platform/efi/efi.c    | 10 ++++++++--
 arch/x86/platform/efi/efi_32.c |  6 +++++-
 arch/x86/platform/efi/efi_64.c | 20 ++++++++++++++------
 4 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index be58b7f5c..04952e064 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -128,7 +128,7 @@ extern bool efi_disable_ibt_for_runtime;
 extern int __init efi_memblock_x86_reserve_range(void);
 extern void __init efi_print_memmap(void);
 extern void __init efi_map_region(efi_memory_desc_t *md);
-extern void __init efi_map_region_fixed(efi_memory_desc_t *md);
+extern int __init efi_map_region_fixed(efi_memory_desc_t *md);
 extern void efi_sync_low_kernel_mappings(void);
 extern int __init efi_alloc_page_tables(void);
 extern int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages);
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 0c39adb96..4b875843a 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -735,8 +735,14 @@ static void __init kexec_enter_virtual_mode(void)
 	* Map efi regions which were passed via setup_data. The virt_addr is a
 	* fixed addr which was used in first kernel of a kexec boot.
 	*/
-	for_each_efi_memory_desc(md)
-		efi_map_region_fixed(md); /* FIXME: add error handling */
+	for_each_efi_memory_desc(md) {
+		if (efi_map_region_fixed(md)) {
+			pr_err("Failed to map fixed EFI region\n");
+			clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
+			return;
+		}
+
+	}
 
 	/*
 	 * Unregister the early EFI memmap from efi_init() and install
diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c
index b2cc7b455..9307999b9 100644
--- a/arch/x86/platform/efi/efi_32.c
+++ b/arch/x86/platform/efi/efi_32.c
@@ -84,7 +84,11 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
 	return 0;
 }
 
-void __init efi_map_region_fixed(efi_memory_desc_t *md) {}
+int __init efi_map_region_fixed(efi_memory_desc_t *md)
+{
+	return 0;
+}
+
 void __init parse_efi_setup(u64 phys_addr, u32 data_len) {}
 
 efi_status_t efi_call_svam(efi_runtime_services_t * const *,
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 5861008ea..05f1df6ca 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -269,12 +269,12 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
 	return 0;
 }
 
-static void __init __map_region(efi_memory_desc_t *md, u64 va)
+static int __init __map_region(efi_memory_desc_t *md, u64 va)
 {
 	unsigned long flags = _PAGE_RW;
 	unsigned long pfn;
 	pgd_t *pgd = efi_mm.pgd;
-
+	int error;
 	/*
 	 * EFI_RUNTIME_SERVICES_CODE regions typically cover PE/COFF
 	 * executable images in memory that consist of both R-X and
@@ -299,9 +299,11 @@ static void __init __map_region(efi_memory_desc_t *md, u64 va)
 		flags |= _PAGE_ENC;
 
 	pfn = md->phys_addr >> PAGE_SHIFT;
-	if (kernel_map_pages_in_pgd(pgd, pfn, va, md->num_pages, flags))
+	error = kernel_map_pages_in_pgd(pgd, pfn, va, md->num_pages, flags);
+	if (error)
 		pr_warn("Error mapping PA 0x%llx -> VA 0x%llx!\n",
 			   md->phys_addr, va);
+	return error;
 }
 
 void __init efi_map_region(efi_memory_desc_t *md)
@@ -357,10 +359,16 @@ void __init efi_map_region(efi_memory_desc_t *md)
  * md->virt_addr is the original virtual address which had been mapped in kexec
  * 1st kernel.
  */
-void __init efi_map_region_fixed(efi_memory_desc_t *md)
+int __init efi_map_region_fixed(efi_memory_desc_t *md)
 {
-	__map_region(md, md->phys_addr);
-	__map_region(md, md->virt_addr);
+	int error;
+
+	error = __map_region(md, md->phys_addr);
+
+	if (error)
+		return error;
+
+	return __map_region(md, md->virt_addr);
 }
 
 void __init parse_efi_setup(u64 phys_addr, u32 data_len)
-- 
2.55.0