x86/efi: Drop support for fake EFI memory maps

Between kexec and confidential VM support, handling the EFI memory maps
correctly on x86 is already proving to be rather difficult (as opposed
to other EFI architectures which manage to never modify the EFI memory
map to begin with)

EFI fake memory map support is essentially a development hack (for
testing new support for the 'special purpose' and 'more reliable' EFI
memory attributes) that leaked into production code. The regions marked
in this manner are not actually recognized as such by the firmware
itself or the EFI stub (and never have), and marking memory as 'more
reliable' seems rather futile if the underlying memory is just ordinary
RAM.

Marking memory as 'special purpose' in this way is also dubious, but may
be in use in production code nonetheless. However, the same should be
achievable by using the memmap= command line option with the ! operator.

EFI fake memmap support is not enabled by any of the major distros
(Debian, Fedora, SUSE, Ubuntu) and does not exist on other
architectures, so let's drop support for it.

Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

4 files changed, 1 insertions, 200 deletions

diff --git a/arch/x86/platform/efi/Makefile b/arch/x86/platform/efi/Makefile
index 543df9a1379d..500cab4a7f7c 100644
--- a/arch/x86/platform/efi/Makefile
+++ b/arch/x86/platform/efi/Makefile
@@ -5,5 +5,4 @@ GCOV_PROFILE := n
 obj-$(CONFIG_EFI) 		+= memmap.o quirks.o efi.o efi_$(BITS).o \
 				   efi_stub_$(BITS).o
 obj-$(CONFIG_EFI_MIXED)		+= efi_thunk_$(BITS).o
-obj-$(CONFIG_EFI_FAKE_MEMMAP)	+= fake_mem.o
 obj-$(CONFIG_EFI_RUNTIME_MAP)	+= runtime-map.o
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index f090ec972d7b..88a96816de9a 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -226,8 +226,6 @@ int __init efi_memblock_x86_reserve_range(void)
 	if (add_efi_memmap || do_efi_soft_reserve())
 		do_add_efi_memmap();
 
-	efi_fake_memmap_early();
-
 	WARN(efi.memmap.desc_version != 1,
 	     "Unexpected EFI_MEMORY_DESCRIPTOR version %ld",
 	     efi.memmap.desc_version);
diff --git a/arch/x86/platform/efi/fake_mem.c b/arch/x86/platform/efi/fake_mem.c
deleted file mode 100644
index 41d57cad3d84..000000000000
--- a/arch/x86/platform/efi/fake_mem.c
+++ /dev/null
@@ -1,197 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * fake_mem.c
- *
- * Copyright (C) 2015 FUJITSU LIMITED
- * Author: Taku Izumi <izumi.taku@jp.fujitsu.com>
- *
- * This code introduces new boot option named "efi_fake_mem"
- * By specifying this parameter, you can add arbitrary attribute to
- * specific memory range by updating original (firmware provided) EFI
- * memmap.
- */
-
-#include <linux/kernel.h>
-#include <linux/efi.h>
-#include <linux/init.h>
-#include <linux/memblock.h>
-#include <linux/types.h>
-#include <linux/sort.h>
-#include <asm/e820/api.h>
-#include <asm/efi.h>
-
-#define EFI_MAX_FAKEMEM CONFIG_EFI_MAX_FAKE_MEM
-
-static struct efi_mem_range efi_fake_mems[EFI_MAX_FAKEMEM];
-static int nr_fake_mem;
-
-static int __init cmp_fake_mem(const void *x1, const void *x2)
-{
-	const struct efi_mem_range *m1 = x1;
-	const struct efi_mem_range *m2 = x2;
-
-	if (m1->range.start < m2->range.start)
-		return -1;
-	if (m1->range.start > m2->range.start)
-		return 1;
-	return 0;
-}
-
-static void __init efi_fake_range(struct efi_mem_range *efi_range)
-{
-	struct efi_memory_map_data data = { 0 };
-	int new_nr_map = efi.memmap.nr_map;
-	efi_memory_desc_t *md;
-	void *new_memmap;
-
-	/* count up the number of EFI memory descriptor */
-	for_each_efi_memory_desc(md)
-		new_nr_map += efi_memmap_split_count(md, &efi_range->range);
-
-	/* allocate memory for new EFI memmap */
-	if (efi_memmap_alloc(new_nr_map, &data) != 0)
-		return;
-
-	/* create new EFI memmap */
-	new_memmap = early_memremap(data.phys_map, data.size);
-	if (!new_memmap) {
-		__efi_memmap_free(data.phys_map, data.size, data.flags);
-		return;
-	}
-
-	efi_memmap_insert(&efi.memmap, new_memmap, efi_range);
-
-	/* swap into new EFI memmap */
-	early_memunmap(new_memmap, data.size);
-
-	efi_memmap_install(&data);
-}
-
-void __init efi_fake_memmap(void)
-{
-	int i;
-
-	if (!efi_enabled(EFI_MEMMAP) || !nr_fake_mem)
-		return;
-
-	for (i = 0; i < nr_fake_mem; i++)
-		efi_fake_range(&efi_fake_mems[i]);
-
-	/* print new EFI memmap */
-	efi_print_memmap();
-}
-
-static int __init setup_fake_mem(char *p)
-{
-	u64 start = 0, mem_size = 0, attribute = 0;
-	int i;
-
-	if (!p)
-		return -EINVAL;
-
-	while (*p != '\0') {
-		mem_size = memparse(p, &p);
-		if (*p == '@')
-			start = memparse(p+1, &p);
-		else
-			break;
-
-		if (*p == ':')
-			attribute = simple_strtoull(p+1, &p, 0);
-		else
-			break;
-
-		if (nr_fake_mem >= EFI_MAX_FAKEMEM)
-			break;
-
-		efi_fake_mems[nr_fake_mem].range.start = start;
-		efi_fake_mems[nr_fake_mem].range.end = start + mem_size - 1;
-		efi_fake_mems[nr_fake_mem].attribute = attribute;
-		nr_fake_mem++;
-
-		if (*p == ',')
-			p++;
-	}
-
-	sort(efi_fake_mems, nr_fake_mem, sizeof(struct efi_mem_range),
-	     cmp_fake_mem, NULL);
-
-	for (i = 0; i < nr_fake_mem; i++)
-		pr_info("efi_fake_mem: add attr=0x%016llx to [mem 0x%016llx-0x%016llx]",
-			efi_fake_mems[i].attribute, efi_fake_mems[i].range.start,
-			efi_fake_mems[i].range.end);
-
-	return *p == '\0' ? 0 : -EINVAL;
-}
-
-early_param("efi_fake_mem", setup_fake_mem);
-
-void __init efi_fake_memmap_early(void)
-{
-	int i;
-
-	/*
-	 * The late efi_fake_mem() call can handle all requests if
-	 * EFI_MEMORY_SP support is disabled.
-	 */
-	if (!efi_soft_reserve_enabled())
-		return;
-
-	if (!efi_enabled(EFI_MEMMAP) || !nr_fake_mem)
-		return;
-
-	/*
-	 * Given that efi_fake_memmap() needs to perform memblock
-	 * allocations it needs to run after e820__memblock_setup().
-	 * However, if efi_fake_mem specifies EFI_MEMORY_SP for a given
-	 * address range that potentially needs to mark the memory as
-	 * reserved prior to e820__memblock_setup(). Update e820
-	 * directly if EFI_MEMORY_SP is specified for an
-	 * EFI_CONVENTIONAL_MEMORY descriptor.
-	 */
-	for (i = 0; i < nr_fake_mem; i++) {
-		struct efi_mem_range *mem = &efi_fake_mems[i];
-		efi_memory_desc_t *md;
-		u64 m_start, m_end;
-
-		if ((mem->attribute & EFI_MEMORY_SP) == 0)
-			continue;
-
-		m_start = mem->range.start;
-		m_end = mem->range.end;
-		for_each_efi_memory_desc(md) {
-			u64 start, end, size;
-
-			if (md->type != EFI_CONVENTIONAL_MEMORY)
-				continue;
-
-			start = md->phys_addr;
-			end = md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT) - 1;
-
-			if (m_start <= end && m_end >= start)
-				/* fake range overlaps descriptor */;
-			else
-				continue;
-
-			/*
-			 * Trim the boundary of the e820 update to the
-			 * descriptor in case the fake range overlaps
-			 * !EFI_CONVENTIONAL_MEMORY
-			 */
-			start = max(start, m_start);
-			end = min(end, m_end);
-			size = end - start + 1;
-
-			if (end <= start)
-				continue;
-
-			/*
-			 * Ensure each efi_fake_mem instance results in
-			 * a unique e820 resource
-			 */
-			e820__range_remove(start, size, E820_TYPE_RAM, 1);
-			e820__range_add(start, size, E820_TYPE_SOFT_RESERVED);
-			e820__update_table(e820_table);
-		}
-	}
-}
diff --git a/arch/x86/platform/efi/memmap.c b/arch/x86/platform/efi/memmap.c
index 6ed1935504b9..061b8ecc71a1 100644
--- a/arch/x86/platform/efi/memmap.c
+++ b/arch/x86/platform/efi/memmap.c
@@ -30,6 +30,7 @@ static phys_addr_t __init __efi_memmap_alloc_late(unsigned long size)
 	return PFN_PHYS(page_to_pfn(p));
 }
 
+static
 void __init __efi_memmap_free(u64 phys, unsigned long size, unsigned long flags)
 {
 	if (flags & EFI_MEMMAP_MEMBLOCK) {