Re: [PATCH v8 1/3] x86/boot: Add acpitb.c to parse acpi tables

[Chao Fan <fanc.fnst@cn.fujitsu.com>]

On Thu, Oct 11, 2018 at 12:57:08PM +0200, Borislav Petkov wrote:
>On Wed, Oct 10, 2018 at 04:41:17PM +0800, Chao Fan wrote:
>> There is a bug that kaslr may randomly chooses some positions
>> which are located in movable memory regions. This will break memory
>> hotplug feature and make the movable memory chosen by KASLR can't be
>> removed. So dig SRAT table from ACPI tables to get memory information.
>> 
>> Imitate the ACPI code of parsing ACPI tables to dig and read ACPI
>> tables. Since some operations are not needed here, functions are
>> simplified. Functions will be used to dig only SRAT tables to get
>> information of memory, so that KASLR can the memory in immovable node.
>> 
>> And also, these functions won't influence the initialization of
>> ACPI after start_kernel().
>> 
>> Since use physical address directely, so acpi_os_map_memory()
>> and acpi_os_unmap_memory() are not needed.
>> 
>> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
>> ---
>>  arch/x86/boot/compressed/Makefile |   2 +
>>  arch/x86/boot/compressed/acpitb.c | 405 ++++++++++++++++++++++++++++++
>>  arch/x86/boot/compressed/misc.h   |   8 +
>>  3 files changed, 415 insertions(+)
>>  create mode 100644 arch/x86/boot/compressed/acpitb.c
>> 
>> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
>> index 28764dacf018..1609e4efcaed 100644
>> --- a/arch/x86/boot/compressed/Makefile
>> +++ b/arch/x86/boot/compressed/Makefile
>> @@ -83,6 +83,8 @@ ifdef CONFIG_X86_64
>>  	vmlinux-objs-y += $(obj)/pgtable_64.o
>>  endif
>>  
>> +vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/acpitb.o
>

So many thanks for your review.

>This should be CONFIG_MEMORY_HOTREMOVE *and* CONFIG_RANDOMIZE_BASE.
>Otherwise we don't need all that code.

Thanks, I will add CONFIG_RANDOMIZE_BASE.
In V7, I ever added CONFIG_MEMORY_HOTREMOVE, then I need add in kaslr.c:

+#ifdef CONFIG_MEMORY_HOTREMOVE
+       /* Mark the immovable regions we need to choose */
+       get_immovable_mem();
+#endif

Then in V8, follow Kees Cook's suggestion, change the #ifdef to the
definition of get_immovable_mem() in acpitb.c
So I drop the CONFIG_MEMORY_HOTREMOVE.

I will splite it to more patch in next version.

Thanks,
Chao Fan

>
>>  $(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone
>>  
>>  vmlinux-objs-$(CONFIG_EFI_STUB) += $(obj)/eboot.o $(obj)/efi_stub_$(BITS).o \
>> diff --git a/arch/x86/boot/compressed/acpitb.c b/arch/x86/boot/compressed/acpitb.c
>> new file mode 100644
>> index 000000000000..6b869e3f9780
>> --- /dev/null
>> +++ b/arch/x86/boot/compressed/acpitb.c
>> @@ -0,0 +1,405 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +#define BOOT_CTYPE_H
>> +#include "misc.h"
>> +#include "error.h"
>> +
>> +#include <linux/efi.h>
>> +#include <asm/efi.h>
>> +#include <linux/numa.h>
>> +#include <linux/acpi.h>
>> +
>> +extern unsigned long get_cmd_line_ptr(void);
>> +
>> +#define STATIC
>> +#include <linux/decompress/mm.h>
>> +
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +struct mem_vector {
>> +	unsigned long long start;
>> +	unsigned long long size;
>> +};
>> +/* Store the immovable memory regions */
>> +struct mem_vector immovable_mem[MAX_NUMNODES*2];
>> +#endif
>> +
>> +#ifdef CONFIG_EFI
>> +/* Search EFI table for rsdp table. */
>> +static bool efi_get_rsdp_addr(acpi_physical_address *rsdp_addr)
>> +{
>> +	efi_system_table_t *systab;
>> +	bool find_rsdp = false;
>> +	bool efi_64 = false;
>> +	void *config_tables;
>> +	struct efi_info *e;
>> +	char *sig;
>> +	int size;
>> +	int i;
>> +
>> +	e = &boot_params->efi_info;
>> +	sig = (char *)&e->efi_loader_signature;
>> +
>> +	if (!strncmp(sig, EFI64_LOADER_SIGNATURE, 4))
>> +		efi_64 = true;
>> +	else if (!strncmp(sig, EFI32_LOADER_SIGNATURE, 4))
>> +		efi_64 = false;
>> +	else {
>> +		debug_putstr("Wrong EFI loader signature.\n");
>> +		return false;
>> +	}
>> +
>> +	/* Get systab from boot params. Based on efi_init(). */
>> +#ifdef CONFIG_X86_32
>
>Why the efi_64 detection above but the ifdeffery here? Why not test
>efi_64 instead?

The efi_64 is used for the efi table size.

>
>> +	if (e->efi_systab_hi || e->efi_memmap_hi) {
>> +		debug_putstr("Table located above 4GB, disabling EFI.\n");
>
>Are you disabling EFI? Where?
>
>Ah, I see, this code is copied from arch/x86/platform/efi/efi.c.
>
>So when copying, fix the user-visible strings too.

Will change it.

>
>> +		return false;
>> +	}
>> +	systab = (efi_system_table_t *)e->efi_systab;
>> +#else
>> +	systab = (efi_system_table_t *)(
>> +			e->efi_systab | ((__u64)e->efi_systab_hi<<32));
>> +#endif
>> +
>> +	if (systab == NULL)
>
>	if (!systab)
>
>Fix all other occurrences.
>
>> +		return false;
>> +
>> +	/*
>> +	 * Get EFI tables from systab. Based on efi_config_init() and
>> +	 * efi_config_parse_tables(). Only dig the config_table.
>
>					dig out
>
>> +	 */
>> +	size = efi_64 ? sizeof(efi_config_table_64_t) :
>> +			sizeof(efi_config_table_32_t);
>> +
>> +	for (i = 0; i < systab->nr_tables; i++) {
>> +		efi_guid_t guid;
>> +		unsigned long table;
>> +
>> +		config_tables = (void *)(systab->tables + size * i);
>> +		if (efi_64) {
>> +			efi_config_table_64_t *tmp_table;
>> +
>> +			tmp_table = (efi_config_table_64_t *)config_tables;
>> +			guid = tmp_table->guid;
>> +			table = tmp_table->table;
>> +#ifndef CONFIG_64BIT
>> +			if (table >> 32) {
>> +				debug_putstr("Table located above 4G, disabling EFI.\n");
>
>Fix that.
>
>> +				return false;
>> +			}
>> +#endif
>> +		} else {
>> +			efi_config_table_32_t *tmp_table;
>> +
>> +			tmp_table = (efi_config_table_32_t *)config_tables;
>> +			guid = tmp_table->guid;
>> +			table = tmp_table->table;
>> +		}
>> +
>> +		/*
>> +		 * Get rsdp from EFI tables.
>> +		 * If ACPI20 table found, use it and return true.
>
>You don't have to say "return true" in the comment - that is in the code
>already.
>
>Also, this function - just like get_acpi_rsdp() doesn't need to return
>bool but the pa directly.
>
>> +		 * If ACPI20 table not found, but ACPI table found,
>> +		 * use the ACPI table and return true.
>> +		 * If neither ACPI table nor ACPI20 table found,
>> +		 * return false.
>> +		 */
>> +		if (!(efi_guidcmp(guid, ACPI_TABLE_GUID))) {
>> +			*rsdp_addr = (acpi_physical_address)table;
>> +			find_rsdp = true;
>> +		} else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID))) {
>> +			*rsdp_addr = (acpi_physical_address)table;
>> +			return true;
>> +		}
>> +	}
>> +	return find_rsdp;
>> +}
>> +#else
>> +static bool efi_get_rsdp_addr(acpi_physical_address *rsdp_addr)
>> +{
>> +	return false;
>> +}
>> +#endif
>
>Instead of doing this, move the ifdef inside the function:
>
>static bool efi_get_rsdp_addr(acpi_physical_address *rsdp_addr)
>{
>#ifdef CONFIG_EFI
>
>	/* function body */
>#endif
>}
>
>
>> +
>> +static u8 checksum(u8 *buffer, u32 length)
>
>compute_checksum(...)
>
>> +{
>> +	u8 sum = 0;
>> +	u8 *end = buffer + length;
>> +
>> +	while (buffer < end)
>> +		sum = (u8)(sum + *(buffer++));
>> +
>> +	return sum;
>> +}
>> +
>> +/*
>> + * Used to search a block of memory for the RSDP signature.
>> + * Return Pointer to the RSDP if found, otherwise NULL.
>> + * Based on acpi_tb_scan_memory_for_rsdp().
>> + */
>> +static u8 *scan_mem_for_rsdp(u8 *start_address, u32 length)
>> +{
>> +	struct acpi_table_rsdp *rsdp;
>> +	u8 *end_address;
>> +	u8 *mem_rover;
>> +
>> +	end_address = start_address + length;
>> +
>> +	/* Search from given start address for the requested length */
>> +	for (mem_rover = start_address; mem_rover < end_address;
>> +	     mem_rover += ACPI_RSDP_SCAN_STEP) {
>
>Shorten those variable names so that the loop fits on one line.
>
>> +		/*
>> +		 * The RSDP signature and checksum must both be correct
>> +		 * Note: Sometimes there exists more than one RSDP in memory;
>> +		 * the valid RSDP has a valid checksum, all others have an
>> +		 * invalid checksum.
>> +		 */
>> +		rsdp = (struct acpi_table_rsdp *)mem_rover;
>> +
>> +		/* Nope, BAD Signature */
>> +		if (!ACPI_VALIDATE_RSDP_SIG(rsdp->signature))
>> +			continue;
>> +
>> +		/* Check the standard checksum */
>> +		if (checksum((u8 *) rsdp, ACPI_RSDP_CHECKSUM_LENGTH) != 0)
>
>No need for "!= 0" at the end. Fix all other tests too.
>
>> +			continue;
>> +
>> +		/* Check extended checksum if table version >= 2 */
>> +		if ((rsdp->revision >= 2) &&
>> +		    (checksum((u8 *) rsdp, ACPI_RSDP_XCHECKSUM_LENGTH) != 0))
>> +			continue;
>> +
>> +		/* Sig and checksum valid, we have found a real RSDP */
>> +		return mem_rover;
>> +	}
>> +	return NULL;
>> +}
>> +
>> +/*
>> + * Used to search RSDP physical address.
>> + * Based on acpi_find_root_pointer(). Since only use physical address
>> + * in this period, so there is no need to do the memory map jobs.
>> + */
>> +static void bios_get_rsdp_addr(acpi_physical_address *rsdp_addr)
>> +{
>> +	struct acpi_table_rsdp *rsdp;
>> +	u8 *table_ptr;
>> +	u8 *mem_rover;
>> +	u32 address;
>> +
>> +	/*
>> +	 * Get the location of the Extended BIOS Data Area (EBDA)
>> +	 * Since we use physical address directely, so
>> +	 * acpi_os_map_memory() and acpi_os_unmap_memory() are
>> +	 * not needed here.
>> +	 */
>> +	table_ptr = (u8 *)ACPI_EBDA_PTR_LOCATION;
>> +	*(u32 *)(void *)&address = *(u16 *)(void *)table_ptr;
>> +	address <<= 4;
>> +	table_ptr = (u8 *)address;
>> +
>> +	/*
>> +	 * Search EBDA paragraphs (EBDA is required to be a minimum of
>> +	 * 1K length)
>> +	 */
>> +	if (address > 0x400) {
>> +		mem_rover = scan_mem_for_rsdp(table_ptr, ACPI_EBDA_WINDOW_SIZE);
>> +
>> +		if (mem_rover) {
>> +			address += (u32)ACPI_PTR_DIFF(mem_rover, table_ptr);
>> +			*rsdp_addr = (acpi_physical_address)address;
>> +			return;
>> +		}
>> +	}
>> +
>> +	table_ptr = (u8 *)ACPI_HI_RSDP_WINDOW_BASE;
>> +	mem_rover = scan_mem_for_rsdp(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);
>> +
>> +	/*
>> +	 * Search upper memory: 16-byte boundaries in E0000h-FFFFFh
>> +	 * Since we use physical address directely, so
>> +	 * acpi_os_map_memory() and acpi_os_unmap_memory() are
>> +	 * not needed here.
>> +	 */
>> +	if (mem_rover) {
>> +		address = (u32)(ACPI_HI_RSDP_WINDOW_BASE +
>> +				ACPI_PTR_DIFF(mem_rover, table_ptr));
>> +		*rsdp_addr = (acpi_physical_address)address;
>> +		return;
>
>We will return anyway, without that statement. :)
>
>> +	}
>> +}
>> +
>> +#ifdef CONFIG_KEXEC
>> +static bool get_acpi_rsdp(acpi_physical_address *rsdp_addr)
>> +{
>> +	char *args = (char *)get_cmd_line_ptr();
>> +	size_t len = strlen((char *)args);
>> +	char *tmp_cmdline, *param, *val;
>> +	unsigned long long addr = 0;
>> +	char *endptr;
>> +
>> +	if (!strstr(args, "acpi_rsdp="))
>> +		return false;
>> +
>> +	tmp_cmdline = malloc(len+1);
>> +	if (!tmp_cmdline)
>> +		error("Failed to allocate space for tmp_cmdline");
>
>Why do you even need to allocate a tmp cmdline?
>
>Ah, I see what you've done - you've copied handle_mem_options() in
>kaslr.c. Well no, not really.
>
>That functionality needs to get extracted into a separate facility. Oh
>look, there's arch/x86/boot/compressed/cmdline.c which is begging to get
>extended.
>
>:-)
>
>> +
>> +	memcpy(tmp_cmdline, args, len);
>> +	tmp_cmdline[len] = 0;
>> +	args = tmp_cmdline;
>> +
>> +	args = skip_spaces(args);
>> +
>> +	while (*args) {
>> +		args = next_arg(args, &param, &val);
>> +
>> +		if (!val && strcmp(param, "--") == 0) {
>> +			warn("Only '--' specified in cmdline");
>> +			free(tmp_cmdline);
>> +			return false;
>> +		}
>> +
>> +		if (!strcmp(param, "acpi_rsdp")) {
>> +			addr = simple_strtoull(val, &endptr, 0);
>
>WARNING: simple_strtoull is obsolete, use kstrtoull instead
>#321: FILE: arch/x86/boot/compressed/acpitb.c:262:
>+                       addr = simple_strtoull(val, &endptr, 0);
>
>
>Please integrate scripts/checkpatch.pl into your patch creation
>workflow. Some of the warnings/errors *actually* make sense.
>
>> +
>> +			if (addr == 0)
>> +				return false;
>> +
>> +			*rsdp_addr = (acpi_physical_address)addr;
>> +			return true;
>> +		}
>> +	}
>> +	return false;
>> +}
>> +#else
>> +static bool get_acpi_rsdp(acpi_physical_address *rsdp_addr)
>> +{
>> +	return false;
>> +}
>> +#endif
>> +
>> +/*
>> + * Used to dig rsdp table from EFI table or BIOS.
>
>Write "rsdp" in all caps in all comments.
>
>> + * If rsdp table found in EFI table, use it. Or search BIOS.
>> + * Based on acpi_os_get_root_pointer().
>> + */
>> +static acpi_physical_address get_rsdp_addr(void)
>> +{
>> +	acpi_physical_address pa = 0;
>> +	bool status = false;
>> +
>> +	status = get_acpi_rsdp(&pa);
>
>Why does this function return bool if pa == 0 is already an invalid
>address. You don't need the initialization to 0 above either.
>
>> +
>> +	if (!status || pa == 0)
>
>	if (!status || !pa)
>
>Fix all other tests.
>
>> +		status = efi_get_rsdp_addr(&pa);
>> +
>> +	if (!status || pa == 0)
>> +		bios_get_rsdp_addr(&pa);
>> +
>> +	return pa;
>> +}
>> +
>> +static struct acpi_table_header *get_acpi_srat_table(void)
>> +{
>> +	char *args = (char *)get_cmd_line_ptr();
>> +	acpi_physical_address acpi_table;
>> +	acpi_physical_address root_table;
>> +	struct acpi_table_header *header;
>> +	struct acpi_table_rsdp *rsdp;
>> +	char *signature;
>> +	u8 *entry;
>> +	u32 count;
>> +	u32 size;
>> +	int i, j;
>> +	u32 len;
>> +
>> +	rsdp = (struct acpi_table_rsdp *)get_rsdp_addr();
>> +	if (!rsdp)
>> +		return NULL;
>> +
>> +	/* Get rsdt or xsdt from rsdp. */
>> +	if (!strstr(args, "acpi=rsdt") &&
>> +	    rsdp->xsdt_physical_address && rsdp->revision > 1) {
>> +		root_table = rsdp->xsdt_physical_address;
>> +		size = ACPI_XSDT_ENTRY_SIZE;
>> +	} else {
>> +		root_table = rsdp->rsdt_physical_address;
>> +		size = ACPI_RSDT_ENTRY_SIZE;
>> +	}
>
>Please rework the cmdline parsing so that the functions can call helpers
>only.
>
>> +
>> +	/* Get ACPI root table from rsdt or xsdt.*/
>> +	header = (struct acpi_table_header *)root_table;
>> +	len = header->length;
>> +	count = (u32)((len - sizeof(struct acpi_table_header)) / size);
>> +	entry = ACPI_ADD_PTR(u8, header, sizeof(struct acpi_table_header));
>> +
>> +	for (i = 0; i < count; i++) {
>> +		u64 address64;
>> +
>> +		if (size == ACPI_RSDT_ENTRY_SIZE)
>> +			acpi_table = ((acpi_physical_address)
>> +				      (*ACPI_CAST_PTR(u32, entry)));
>> +		else {
>> +			*(u64 *)(void *)&address64 = *(u64 *)(void *)entry;
>> +			acpi_table = (acpi_physical_address) address64;
>> +		}
>> +
>> +		if (acpi_table) {
>> +			header = (struct acpi_table_header *)acpi_table;
>> +			signature = header->signature;
>> +
>> +			if (!strncmp(signature, "SRAT", 4))
>> +				return header;
>> +		}
>> +		entry += size;
>> +	}
>> +	return NULL;
>> +}
>> +
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +/*
>> + * According to ACPI table, filter the immvoable memory regions
>> + * and store them in immovable_mem[].
>> + */
>> +void get_immovable_mem(void)
>> +{
>> +	char *args = (char *)get_cmd_line_ptr();
>> +	struct acpi_table_header *table_header;
>> +	struct acpi_subtable_header *table;
>> +	struct acpi_srat_mem_affinity *ma;
>> +	unsigned long table_end;
>> +	int i = 0;
>> +
>> +	if (!strstr(args, "movable_node") || strstr(args, "acpi=off"))
>> +		return;
>
>Ditto.
>
>> +
>> +	table_header = get_acpi_srat_table();
>> +	if (!table_header)
>> +		return;
>> +
>> +	table_end = (unsigned long)table_header + table_header->length;
>> +
>> +	table = (struct acpi_subtable_header *)
>> +		((unsigned long)table_header + sizeof(struct acpi_table_srat));
>> +
>> +	while (((unsigned long)table) + table->length < table_end) {
>> +		if (table->type == 1) {
>> +			ma = (struct acpi_srat_mem_affinity *)table;
>> +			if (!(ma->flags & ACPI_SRAT_MEM_HOT_PLUGGABLE)) {
>> +				immovable_mem[i].start = ma->base_address;
>> +				immovable_mem[i].size = ma->length;
>> +				i++;
>> +			}
>> +
>> +			if (i >= MAX_NUMNODES*2)
>> +				break;
>> +		}
>> +		table = (struct acpi_subtable_header *)
>> +			((unsigned long)table + table->length);
>> +	}
>> +	num_immovable_mem = i;
>> +}
>> +#else
>> +void get_immovable_mem(void)
>> +{
>> +}
>> +#endif
>
>This patch is a pain to review - pls split it into patches adding:
>
>* get_acpi_rsdp
>* efi_get_rsdp_addr
>* bios_get_rsdp_addr
>
>and the needed functionality.
>
>As a prepatch refactor the cmdline parsing pls.
>
>Thx.
>
>-- 
>Regards/Gruss,
>    Boris.
>
>Good mailing practices for 400: avoid top-posting and trim the reply.
>
>