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Date:   Thu, 29 Nov 2018 12:55:21 -0500
From:   Masayoshi Mizuma <msys.mizuma@gmail.com>
To:     Chao Fan <fanc.fnst@cn.fujitsu.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org, bp@alien8.de,
        tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
        keescook@chromium.org, bhe@redhat.com, indou.takao@jp.fujitsu.com,
        caoj.fnst@cn.fujitsu.com
Subject: Re: [PATCH v12 4/5] x86/boot: Parse SRAT table from RSDP and store
 immovable memory
Message-ID: <20181129175520.xcmj3bv4yhdr7kk3@gabell>
References: <20181129081631.11139-1-fanc.fnst@cn.fujitsu.com>
 <20181129081631.11139-5-fanc.fnst@cn.fujitsu.com>
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On Thu, Nov 29, 2018 at 04:16:30PM +0800, Chao Fan wrote:
> To fix the conflict between KASLR and memory-hotremove, SRAT table
> should be parsed by RSDP pointer, then find the immovable
> memory regions and store them in an array called immovable_mem[].
> The array called immovable_mem[] will extern to KASLR, then
> KASLR will avoid to extract kernel to these regions.
> 
> Add 'CONFIG_EARLY_PARSE_RSDP' which depends on RANDOMIZE_BASE &&
> MEMORY_HOTREMOVE, cause only when both KASLR and memory-hotremove
> are enabled, RSDP needs to be parsed in compressed period.
> 
> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
> ---
>  arch/x86/Kconfig                  |  10 +++
>  arch/x86/boot/compressed/Makefile |   2 +
>  arch/x86/boot/compressed/acpitb.c | 125 ++++++++++++++++++++++++++++++
>  arch/x86/boot/compressed/kaslr.c  |   4 -
>  arch/x86/boot/compressed/misc.h   |  20 +++++
>  5 files changed, 157 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index a29d49ef4d56..bc775968557b 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2146,6 +2146,16 @@ config X86_NEED_RELOCS
>  	def_bool y
>  	depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
>  

> +config CONFIG_EARLY_PARSE_RSDP

config EARLY_PARSE_RSDP

> +	bool "Parse RSDP pointer on compressed period for KASLR"
> +	def_bool n

Should be def_bool y?
It is better to enable EARLY_PARSE_RSDP by default if 
RANDOMIZE_BASE and MEMORY_HOTREMOVE are enabled.

> +	depends on RANDOMIZE_BASE && MEMORY_HOTREMOVE
> +	help
> +	  This option parses RSDP pointer in compressed period. Works
> +	  for KASLR to get memory information by SRAT table and choose
> +	  immovable memory to extract kernel.
> +	  Say Y if you want to use both KASLR and memory-hotremove.
> +
>  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..4cbfb58bf083 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_PARSE_RSDP) += $(obj)/acpitb.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/acpitb.c b/arch/x86/boot/compressed/acpitb.c
> index 82d27c4b8978..023b33d0cd3b 100644
> --- a/arch/x86/boot/compressed/acpitb.c
> +++ b/arch/x86/boot/compressed/acpitb.c
> @@ -195,3 +195,128 @@ static acpi_physical_address bios_get_rsdp_addr(void)
>  		return (acpi_physical_address)address;
>  	}
>  }
> +
> +/* Used to determine RSDP table, based on acpi_os_get_root_pointer(). */
> +static acpi_physical_address get_rsdp_addr(void)
> +{
> +	acpi_physical_address pa = 0;
> +
> +	pa = get_acpi_rsdp();
> +
> +	if (!pa)
> +		pa = efi_get_rsdp_addr();
> +
> +	if (!pa)
> +		pa = bios_get_rsdp_addr();
> +
> +	return pa;
> +}
> +
> +/* Compute SRAT table 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;
> +	int num_entries;
> +	char arg[10];
> +	u8 *entry;
> +	u32 size;
> +	u32 len;
> +
> +	rsdp = (struct acpi_table_rsdp *)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.*/
> +	header = (struct acpi_table_header *)root_table;
> +	if (!header)
> +		return NULL;
> +
> +	len = header->length;
> +	num_entries = (u32)((len - sizeof(struct acpi_table_header)) / size);

> +	if (num_entries > MAX_ACPI_SIG)
> +		return NULL;

I think this check isn't needed...

> +
> +	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_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;
> +
> +			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;
> +	unsigned long table_end;
> +	char arg[10];
> +	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);
> +	}
> +	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 809c31effa4b..d94e2a419c13 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
> @@ -118,5 +123,20 @@ void set_sev_encryption_mask(void);
>  #endif
>  
>  /* acpitb.c */
> +#ifdef CONFIG_RANDOMIZE_BASE
> +/* Store the amount of immovable memory regions */
> +int num_immovable_mem;
> +#endif
> +
> +#ifdef CONFIG_EARLY_PARSE_RSDP
> +void get_immovable_mem(void);

> +/* There are 72 kinds of ACPI_SIG in head file of ACPI. */
> +#define MAX_ACPI_SIG	72

The 72 isn't the specification of ACPI, right? So the number
of SIG may increase and decrease in the future.
This macro and the check I commented above isn't needed...

Thanks,
Masa

> +#else
> +static void get_immovable_mem(void)
> +{
> +}
> +#endif
> +
>  #define BOOT_STRING
>  extern int kstrtoull(const char *s, unsigned int base, unsigned long long *res);
> -- 
> 2.19.1
> 
> 
>