by Chao Fan

[permalink] [raw]

Subject: Re: [PATCH v11 4/5] x86/boot: Dig out SRAT table from RSDP and find immovable memory

Hi Boris,

On Fri, Nov 16, 2018 at 12:16:54PM +0100, Borislav Petkov wrote:
>On Mon, Nov 12, 2018 at 05:46:44PM +0800, Chao Fan wrote:
>> To avoid KASLR extracting kernel on movable memory, slove the
> ^^^^^
>
>Please introduce a spellchecker into your patch creation workflow.
>
>> conflict between KASLR and movable_node feature, dig the SRAT tables
>
>s/dig/determine/ or "compute SRAT table's address" or so.
>
>Also, replace "dig" with a more suitable verb in all your patches.
>
>> from RSDP pointer. Walk the SRAT tables and store the immovable
>> memory regions in immovable_mem[].
>
> "... in an array called immovable_mem[]."
>
>> There are three methods to get RSDP pointer: KEXEC condition,
>> EFI confition, BIOS condition.
>
>"condition" is not the right word here.
>
>> If KEXEC add 'acpi_rsdp' to cmdline, use it.
>> Otherwise, parse EFI table for RSDP.
>> Then, search memory for RSDP.
>>
>> Imitate from ACPI code, based on acpi_os_get_root_pointer().
>> Process: RSDP->RSDT/XSDT->ACPI root table->SRAT.
>
>What?!
>
>This looks like a comment you've added as a note for yourself but not
>part of the final commit message. If you wanna explain the process, then
>write it out in plain english as if you're explaining it to someone who
>doesn't know what you're doing.
>
>>
>> Signed-off-by: Chao Fan <[email protected]>
>> ---
>> arch/x86/boot/compressed/Makefile | 4 +
>> arch/x86/boot/compressed/acpitb.c | 139 ++++++++++++++++++++++++++++++
>> arch/x86/boot/compressed/kaslr.c | 4 -
>> arch/x86/boot/compressed/misc.h | 15 ++++
>> 4 files changed, 158 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
>> index 466f66c8a7f8..b51f7629b8ef 100644
>> --- a/arch/x86/boot/compressed/Makefile
>> +++ b/arch/x86/boot/compressed/Makefile
>> @@ -84,6 +84,10 @@ ifdef CONFIG_X86_64
>> vmlinux-objs-y += $(obj)/pgtable_64.o
>> endif
>>
>> +#if (defined CONFIG_MEMORY_HOTREMOVE) && (defined CONFIG_RANDOMIZE_BASE)
>> +vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/acpitb.o
>> +#endif
>
>Right, as previously pointed out, this needs that CONFIG_ symbol and
>then you can save yourself most (if not all) of the ifdeffery in the
>rest of the patchset.
>
>> +
>> $(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone
>>
>> vmlinux-objs-$(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
>> index 5cfb4efa5a19..161f21a7fb3b 100644
>> --- a/arch/x86/boot/compressed/acpitb.c
>> +++ b/arch/x86/boot/compressed/acpitb.c
>> @@ -14,6 +14,11 @@
>> #define BOOT_STRING
>> #include "../string.h"
>>
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +/* Store the immovable memory regions */
>> +struct mem_vector immovable_mem[MAX_NUMNODES*2];
>> +#endif
>> +
>> /* Search EFI table for RSDP table. */
>> static void efi_get_rsdp_addr(acpi_physical_address *rsdp_addr)
>> {
>> @@ -226,3 +231,137 @@ static void get_acpi_rsdp(acpi_physical_address *rsdp_addr)
>> }
>> #endif
>> }
>> +
>> +/*
>> + * Used to dig RSDP table from EFI table or BIOS.
>> + * 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;
>> +
>> + get_acpi_rsdp(&pa);
>> +
>> + if (!pa)
>> + efi_get_rsdp_addr(&pa);
>> +
>> + if (!pa)
>> + bios_get_rsdp_addr(&pa);
>> +
>> + return pa;
>> +}
>> +
>> +static struct acpi_table_header *get_acpi_srat_table(void)
>> +{
>> + acpi_physical_address acpi_table;
>> + acpi_physical_address root_table;
>> + struct acpi_table_header *header;
>> + struct acpi_table_rsdp *rsdp;
>> + bool acpi_use_rsdt = false;
>> + char *signature;
>> + char arg[10];
>> + u8 *entry;
>> + u32 count;
>> + u32 size;
>> + int i, j;
>> + int ret;
>> + u32 len;
>> +
>> + rsdp = (struct acpi_table_rsdp *)get_rsdp_addr();
>> + if (!rsdp)
>> + return NULL;
>> +
>> + ret = cmdline_find_option("acpi", arg, sizeof(arg));
>> + if (ret == 4 && !strncmp(arg, "rsdt", 4))
>> + acpi_use_rsdt = true;
>> +
>> + /* Get RSDT or XSDT from RSDP. */
>> + if (!acpi_use_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;
>> + }
>
>Reorganize that code here to get rid of acpi_use_rsdt.
>
>> +
>> + /* Get ACPI root table from RSDT or XSDT.*/
>> + header = (struct acpi_table_header *)root_table;
>> + len = header->length;
>
>No checking of that header pointer before dereffing it?
>
>If it is NUL, that gives you a very nasty bug to try to debug in the
>early code.
>
>> + count = (u32)((len - sizeof(struct acpi_table_header)) / size);
>
>Uuh, no checking for count wrapping around here due to wrong len? That
>would give you a *lot* of looping below if it wraps.
>
>IOW, you need to verify all those values before doing arithmetic with
>them - it is early code and it is BIOS - there's no trusting it.
>
>Also, it is not "count" but "num_entries" or so.
>
>> + entry = ACPI_ADD_PTR(u8, header, sizeof(struct acpi_table_header));
>> +
>> + for (i = 0; i < count; i++) {
>
>That variable i is not needed, right?
>
> while (num_entries--)
>
>?
>
>> + 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) {
>
>Now can acpi_table be NUL here?

In iacpi_tb_parse_root_table() of drivers/acpi/acpica/tbutils.c:
/* Skip NULL entries in RSDT/XSDT */

if (!address) {
goto next_table;
}
So I think the table might be NULL and did the similar operation.

Thanks,
Chao Fan

>
>> + header = (struct acpi_table_header *)acpi_table;
>> + signature = header->signature;
>> +
>> + if (ACPI_COMPARE_NAME(header->signature, ACPI_SIG_SRAT))
>> + return header;
>> + }
>> + entry += size;
>> + }
>> + return NULL;
>> +}
>> +
>> +/*
>> + * According to ACPI table, filter the immvoable memory regions
> ^^^^^^^^^
>Typo.
>
>> + * and store them in immovable_mem[].
>> + */
>> +void get_immovable_mem(void)
>> +{
>> + struct acpi_table_header *table_header;
>> + struct acpi_subtable_header *table;
>> + struct acpi_srat_mem_affinity *ma;
>> + unsigned long table_end;
>> + char arg[10];
>> + int i = 0;
>> + int ret;
>> +
>> + ret = cmdline_find_option("acpi", arg, sizeof(arg));
>> + if (ret == 3 && !strncmp(arg, "off", 3))
>> + return;
>> +
>> + if (!cmdline_find_option_bool("movable_node"))
>> + return;
>> +
>> + 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) +
>> + sizeof(struct acpi_subtable_header) < table_end) {
>> + if (table->type == ACPI_SRAT_TYPE_MEMORY_AFFINITY) {
>> + 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) {
>> + debug_putstr("Too many immovable memory regions, aborted.\n");
>
>"..., aborting."
>
>> + break;
>> + }
>> + }
>> + table = (struct acpi_subtable_header *)
>> + ((unsigned long)table + table->length);
>> + }
>> + num_immovable_mem = i;
>> +}
>> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
>> index 9ed9709d9947..b251572e77af 100644
>> --- a/arch/x86/boot/compressed/kaslr.c
>> +++ b/arch/x86/boot/compressed/kaslr.c
>> @@ -87,10 +87,6 @@ static unsigned long get_boot_seed(void)
>> #define KASLR_COMPRESSED_BOOT
>> #include "../../lib/kaslr.c"
>>
>> -struct mem_vector {
>> - unsigned long long start;
>> - unsigned long long size;
>> -};
>>
>> /* Only supporting at most 4 unusable memmap regions with kaslr */
>> #define MAX_MEMMAP_REGIONS 4
>> diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
>> index a1d5918765f3..4a3645fda0ed 100644
>> --- a/arch/x86/boot/compressed/misc.h
>> +++ b/arch/x86/boot/compressed/misc.h
>> @@ -77,6 +77,11 @@ void choose_random_location(unsigned long input,
>> unsigned long *output,
>> unsigned long output_size,
>> unsigned long *virt_addr);
>> +struct mem_vector {
>> + unsigned long long start;
>> + unsigned long long size;
>> +};
>> +
>> /* cpuflags.c */
>> bool has_cpuflag(int flag);
>> #else
>> @@ -116,3 +121,13 @@ static inline void console_init(void)
>> void set_sev_encryption_mask(void);
>>
>> #endif
>> +
>> +/* acpitb.c */
>> +#ifdef CONFIG_RANDOMIZE_BASE
>> +int num_immovable_mem;
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +/* Store the amount of immovable memory regions */
>
>Above says "regions" but define below is "TABLES". Hmmm?
>
>> +#define ACPI_MAX_TABLES 128
>> +void get_immovable_mem(void);
>> +#endif
>> +#endif
>> --
>
>--
>Regards/Gruss,
> Boris.
>
>Good mailing practices for 400: avoid top-posting and trim the reply.
>
>