Re: [PATCH v15 5/6] x86/boot: Parse SRAT address from RSDP and store immovable memory

Borislav Petkov
2019-01-16T11:02:09Z

On Mon, Jan 07, 2019 at 11:22:42AM +0800, Chao Fan wrote:
> SRAT should be parsed by RSDP to fix the conflict between KASLR and
> memory-hotremove, then find the immovable memory regions and store
> them in an array called immovable_mem[]. With immovable_mem[], KASLR
> can avoid to extract kernel to specific regions.
>
> Since 'RANDOMIZE_BASE' && 'MEMORY_HOTREMOVE' is needed, introduce
> 'CONFIG_EARLY_SRAT_PARSE' to make ifdeffery clear.
>
> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
> ---
> arch/x86/Kconfig | 12 +++
> arch/x86/boot/compressed/Makefile | 2 +
> arch/x86/boot/compressed/acpi.c | 138 ++++++++++++++++++++++++++++++
> arch/x86/boot/compressed/kaslr.c | 4 -
> arch/x86/boot/compressed/misc.h | 19 ++++
> 5 files changed, 171 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index ba7e3464ee92..c1457609f2e3 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2149,6 +2149,18 @@ config X86_NEED_RELOCS
> def_bool y
> depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
>
> +config EARLY_SRAT_PARSE
> + bool "EARLY SRAT parsing"
> + def_bool y
> + depends on RANDOMIZE_BASE && MEMORY_HOTREMOVE
> + help
> + This option enables early SRAT parsing in compressed boot stage
> + so that memory hot-remove ranges do not overlap with KASLR
> + chosen ranges. Kernel won't be extracted in hot-removable
> + memory, so that make sure memory-hotremove works well with
> + KASLR enabled.
> + Say Y if you want to use both KASLR and memory-hotremove.
> +

One argument for Ingo's suggestion to have this enabled unconditionally
is all the other code needing RSDP. It might be easier to have it always
built-in instead of a long "depends on" line in Kconfig. We'll see.

> config PHYSICAL_ALIGN
> hex "Alignment value to which kernel should be aligned"
> default "0x200000"
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index 466f66c8a7f8..23491d74939d 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -84,6 +84,8 @@ ifdef CONFIG_X86_64
> vmlinux-objs-y += $(obj)/pgtable_64.o
> endif
>
> +vmlinux-objs-$(CONFIG_EARLY_SRAT_PARSE) += $(obj)/acpi.o
> +
> $(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone
>
> vmlinux-objs-$(CONFIG_EFI_STUB) += $(obj)/eboot.o $(obj)/efi_stub_$(BITS).o \
> diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
> index e9dd84f459ed..f7a9e9cbd254 100644
> --- a/arch/x86/boot/compressed/acpi.c
> +++ b/arch/x86/boot/compressed/acpi.c
> @@ -5,6 +5,7 @@
> #include "../string.h"
>
> #include <linux/acpi.h>
> +#include <linux/numa.h>
> #include <linux/efi.h>
> #include <asm/efi.h>
>
> @@ -14,6 +15,19 @@
> */
> #define MAX_HEX_ADDRESS_STRING_LEN 19
>
> +/*
> + * Longest parameter of 'acpi=' in cmldine is 'copy_dsdt', so max length
> + * is 10, which contains '\0' for termination.
> + */
> +#define MAX_ACPI_ARG_LENGTH 10
> +
> +/*
> + * Information of immovable memory regions.
> + * Max amount of memory regions is MAX_NUMNODES*2, so need such array
> + * to place immovable memory regions if all of the memory is immovable.
> + */
> +struct mem_vector immovable_mem[MAX_NUMNODES*2];
> +
> static acpi_physical_address get_acpi_rsdp(void)
> {
> #ifdef CONFIG_KEXEC
> @@ -197,3 +211,127 @@ static acpi_physical_address bios_get_rsdp_addr(void)
> }
> return 0;
> }
> +
> +/* Determine RSDP, based on acpi_os_get_root_pointer(). */
> +static acpi_physical_address get_rsdp_addr(void)
> +{
> + acpi_physical_address pa;
> +
> + pa = get_acpi_rsdp();
> +
> + if (!pa)
> + pa = efi_get_rsdp_addr();
> +
> + if (!pa)
> + pa = bios_get_rsdp_addr();
> +
> + return pa;
> +}
> +
> +/* Compute SRAT address from RSDP. */
> +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;
> + u32 num_entries;
> + char arg[10];
> + u8 *entry;
> + u32 size;
> + u32 len;
> +
> + rsdp = (struct acpi_table_rsdp *)(long)get_rsdp_addr();
> + if (!rsdp)
> + return NULL;
> +
> + /* Get RSDT or XSDT from RSDP. */
> + if (!(cmdline_find_option("acpi", arg, sizeof(arg)) == 4 &&
> + !strncmp(arg, "rsdt", 4)) &&
> + 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;
> + }
> +
> + /* Get ACPI root table from RSDT or XSDT.*/

This comment is wrong here - should be above.

> + if (!root_table)
> + return NULL;

<---- newline here.

> + header = (struct acpi_table_header *)(long)root_table;
> +
> + len = header->length;
> + if (len < sizeof(struct acpi_table_header) + size)
> + return NULL;
> +
> + num_entries = (u32)((len - sizeof(struct acpi_table_header)) / size);
> + entry = ACPI_ADD_PTR(u8, header, sizeof(struct acpi_table_header));
> +
> + while (num_entries--) {
> + u64 address64;
> +
> + if (size == ACPI_RSDT_ENTRY_SIZE)
> + acpi_table = *ACPI_CAST_PTR(u32, entry);
> + else {
> + address64 = *(u64 *)entry;
> + acpi_table = address64;

The same thing as in the previous patch - get rid of address64.

> + }
> +
> + if (acpi_table) {
> + header = (struct acpi_table_header *)(long)acpi_table;
> +
> + if (ACPI_COMPARE_NAME(header->signature, ACPI_SIG_SRAT))
> + return header;
> + }
> + entry += size;
> + }
> + return NULL;
> +}
> +
> +/*
> + * According to ACPI table, filter the immovable memory regions
> + * 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;
> + char arg[MAX_ACPI_ARG_LENGTH];
> + unsigned long table_end;
> + int i = 0;
> +
> + if (cmdline_find_option("acpi", arg, sizeof(arg)) == 3 &&
> + !strncmp(arg, "off", 3))
> + 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, aborting.\n");
> + return;
> + }
> + }
> + table = (struct acpi_subtable_header *)
> + ((unsigned long)table + table->length);

That's a lot of unnecessary casting AFAICT. You can return an unsigned
long from get_acpi_srat_table() and get rid of all that casting here.

> + }
> + 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..b49748366a5b 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 +121,17 @@ static inline void console_init(void)
> void set_sev_encryption_mask(void);
>
> #endif
> +
> +/* acpi.c */
> +#ifdef CONFIG_RANDOMIZE_BASE
> +/* Amount of immovable memory regions */
> +int num_immovable_mem;
> +#endif
> +
> +#ifdef CONFIG_EARLY_SRAT_PARSE
> +void get_immovable_mem(void);
> +#else
> +static void get_immovable_mem(void)
> +{
> +}

Put those on a single line:

static void get_immovable_mem(void) {}

> +#endif
> --
> 2.20.1
>
>
>

--
Regards/Gruss,
Boris.

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