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

Borislav Petkov
2022-05-10T11:04:09Z

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.