Re: [PATCHv5 06/12] x86/boot/compressed: Handle unaccepted memory

[Borislav Petkov]

On Fri, May 06, 2022 at 06:30:13PM +0300, Kirill A. Shutemov wrote:
> I find it harder to follow.

If in doubt, always consider using a helper function:

---

diff --git a/arch/x86/boot/compressed/efi.h b/arch/x86/boot/compressed/efi.h
index 7db2f41b54cd..cf475243b6d5 100644
--- a/arch/x86/boot/compressed/efi.h
+++ b/arch/x86/boot/compressed/efi.h
@@ -32,6 +32,7 @@ typedef	struct {
 } efi_table_hdr_t;
 
 #define EFI_CONVENTIONAL_MEMORY		 7
+#define EFI_UNACCEPTED_MEMORY		15
 
 #define EFI_MEMORY_MORE_RELIABLE \
 				((u64)0x0000000000010000ULL)	/* higher reliability */
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 28b91df9d31e..39bb4c319dfc 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -671,6 +671,23 @@ static bool process_mem_region(struct mem_vector *region,
 }
 
 #ifdef CONFIG_EFI
+
+/*
+ * Only EFI_CONVENTIONAL_MEMORY and EFI_UNACCEPTED_MEMORY (if supported) are guaranteed
+ * to be free.
+ */
+static inline bool memory_type_is_free(efi_memory_desc_t *md)
+{
+	if (md->type == EFI_CONVENTIONAL_MEMORY)
+		return true;
+
+	if (IS_ENABLED(CONFIG_UNACCEPTED_MEMORY))
+		if (md->type == EFI_UNACCEPTED_MEMORY)
+			return true;
+
+	return false;
+}
+
 /*
  * Returns true if we processed the EFI memmap, which we prefer over the E820
  * table if it is available.
@@ -723,21 +740,9 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)
 		 * free memory and thus available to place the kernel image into,
 		 * but in practice there's firmware where using that memory leads
 		 * to crashes.
-		 *
-		 * Only EFI_CONVENTIONAL_MEMORY and EFI_UNACCEPTED_MEMORY (if
-		 * supported) are guaranteed to be free.
 		 */
-
-		switch (md->type) {
-		case EFI_CONVENTIONAL_MEMORY:
-			break;
-		case EFI_UNACCEPTED_MEMORY:
-			if (IS_ENABLED(CONFIG_UNACCEPTED_MEMORY))
-				break;
+		if (!memory_type_is_free(md))
 			continue;
-		default:
-			continue;
-		}
 
 		if (efi_soft_reserve_enabled() &&
 		    (md->attribute & EFI_MEMORY_SP))
-- 
Regards/Gruss,
    Boris.

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