Commit a799c2bd authored by Mike Rapoport's avatar Mike Rapoport Committed by Borislav Petkov
Browse files

x86/setup: Consolidate early memory reservations 



The early reservations of memory areas used by the firmware, bootloader,
kernel text and data are spread over setup_arch(). Moreover, some of them
happen *after* memblock allocations, e.g trim_platform_memory_ranges() and
trim_low_memory_range() are called after reserve_real_mode() that allocates
memory.

There was no corruption of these memory regions because memblock always
allocates memory either from the end of memory (in top-down mode) or above
the kernel image (in bottom-up mode). However, the bottom up mode is going
to be updated to span the entire memory [1] to avoid limitations caused by
KASLR.

Consolidate early memory reservations in a dedicated function to improve
robustness against future changes. Having the early reservations in one
place also makes it clearer what memory must be reserved before memblock
allocations are allowed.

Signed-off-by: default avatarMike Rapoport <rppt@linux.ibm.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarBaoquan He <bhe@redhat.com>
Acked-by: default avatarBorislav Petkov <bp@suse.de>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Link: [1] https://lore.kernel.org/lkml/20201217201214.3414100-2-guro@fb.com
Link: https://lkml.kernel.org/r/20210302100406.22059-2-rppt@kernel.org
parent e14cfb3b

arch/x86/kernel/setup.c

+44 −48
Original line number Diff line number Diff line
@@ -645,18 +645,6 @@ static void __init trim_snb_memory(void) 
	}

}



/*

 * Here we put platform-specific memory range workarounds, i.e.

 * memory known to be corrupt or otherwise in need to be reserved on

 * specific platforms.

 *

 * If this gets used more widely it could use a real dispatch mechanism.

 */

static void __init trim_platform_memory_ranges(void)

{

	trim_snb_memory();

}



static void __init trim_bios_range(void)

{

	/*
@@ -730,6 +718,37 @@ static void __init trim_low_memory_range(void) 
	memblock_reserve(0, ALIGN(reserve_low, PAGE_SIZE));

}



static void __init early_reserve_memory(void)

{

	/*

	 * Reserve the memory occupied by the kernel between _text and

	 * __end_of_kernel_reserve symbols. Any kernel sections after the

	 * __end_of_kernel_reserve symbol must be explicitly reserved with a

	 * separate memblock_reserve() or they will be discarded.

	 */

	memblock_reserve(__pa_symbol(_text),

			 (unsigned long)__end_of_kernel_reserve - (unsigned long)_text);



	/*

	 * Make sure page 0 is always reserved because on systems with

	 * L1TF its contents can be leaked to user processes.

	 */

	memblock_reserve(0, PAGE_SIZE);



	early_reserve_initrd();



	if (efi_enabled(EFI_BOOT))

		efi_memblock_x86_reserve_range();



	memblock_x86_reserve_range_setup_data();



	reserve_ibft_region();

	reserve_bios_regions();



	trim_snb_memory();

	trim_low_memory_range();

}



/*

 * Dump out kernel offset information on panic.

 */
@@ -764,29 +783,6 @@ dump_kernel_offset(struct notifier_block *self, unsigned long v, void *p) 


void __init setup_arch(char **cmdline_p)

{

	/*

	 * Reserve the memory occupied by the kernel between _text and

	 * __end_of_kernel_reserve symbols. Any kernel sections after the

	 * __end_of_kernel_reserve symbol must be explicitly reserved with a

	 * separate memblock_reserve() or they will be discarded.

	 */

	memblock_reserve(__pa_symbol(_text),

			 (unsigned long)__end_of_kernel_reserve - (unsigned long)_text);



	/*

	 * Make sure page 0 is always reserved because on systems with

	 * L1TF its contents can be leaked to user processes.

	 */

	memblock_reserve(0, PAGE_SIZE);



	early_reserve_initrd();



	/*

	 * At this point everything still needed from the boot loader

	 * or BIOS or kernel text should be early reserved or marked not

	 * RAM in e820. All other memory is free game.

	 */



#ifdef CONFIG_X86_32

	memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
@@ -910,8 +906,18 @@ void __init setup_arch(char **cmdline_p) 


	parse_early_param();



	if (efi_enabled(EFI_BOOT))

		efi_memblock_x86_reserve_range();

	/*

	 * Do some memory reservations *before* memory is added to

	 * memblock, so memblock allocations won't overwrite it.

	 * Do it after early param, so we could get (unlikely) panic from

	 * serial.

	 *

	 * After this point everything still needed from the boot loader or

	 * firmware or kernel text should be early reserved or marked not

	 * RAM in e820. All other memory is free game.

	 */

	early_reserve_memory();



#ifdef CONFIG_MEMORY_HOTPLUG

	/*

	 * Memory used by the kernel cannot be hot-removed because Linux
@@ -938,9 +944,6 @@ void __init setup_arch(char **cmdline_p) 


	x86_report_nx();



	/* after early param, so could get panic from serial */

	memblock_x86_reserve_range_setup_data();



	if (acpi_mps_check()) {

#ifdef CONFIG_X86_LOCAL_APIC

		disable_apic = 1;
@@ -1032,8 +1035,6 @@ void __init setup_arch(char **cmdline_p) 
	 */

	find_smp_config();



	reserve_ibft_region();



	early_alloc_pgt_buf();



	/*
@@ -1054,8 +1055,6 @@ void __init setup_arch(char **cmdline_p) 
	 */

	sev_setup_arch();



	reserve_bios_regions();



	efi_fake_memmap();

	efi_find_mirror();

	efi_esrt_init();
@@ -1081,9 +1080,6 @@ void __init setup_arch(char **cmdline_p) 


	reserve_real_mode();



	trim_platform_memory_ranges();

	trim_low_memory_range();



	init_mem_mapping();



	idt_setup_early_pf();