Re: [PATCH v13 2/6] x86/boot: Introduce get_acpi_rsdp() to parse RSDP in cmdline from KEXEC

[Masayoshi Mizuma <msys.mizuma@gmail.com>]

Hi Chao,

Great work! Let me say some trivial comments.

On Wed, Dec 12, 2018 at 11:10:49AM +0800, Chao Fan wrote:
> Memory information in SRAT is necessary to fix the conflict between
> KASLR and memory-hotremove.
> 
> ACPI SRAT (System/Static Resource Affinity Table) shows the details
> about memory ranges, including ranges of memory provided by hot-added
> memory devices. SRAT is introduced by Root System Description
> Pointer(RSDP). So RSDP should be found firstly.
> 
> When booting form KEXEC/EFI/BIOS, the methods to find RSDP
> are different. When booting from KEXEC, 'acpi_rsdp' may have been
> added to cmdline, so parse cmdline to find RSDP.
> 
> Since 'RANDOMIZE_BASE' && 'MEMORY_HOTREMOVE' is needed, introduce
> 'CONFIG_EARLY_PARSE_RSDP' to make ifdeffery clear.
> 
> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
> ---
>  arch/x86/Kconfig                | 10 ++++++++++
>  arch/x86/boot/compressed/acpi.c | 30 ++++++++++++++++++++++++++++++
>  arch/x86/boot/compressed/misc.h |  6 ++++++
>  3 files changed, 46 insertions(+)
>  create mode 100644 arch/x86/boot/compressed/acpi.c
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index ba7e3464ee92..455da382fa9e 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2149,6 +2149,16 @@ config X86_NEED_RELOCS
>  	def_bool y
>  	depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
>  
> +config EARLY_PARSE_RSDP
> +	bool "Parse RSDP pointer on compressed period for KASLR"
> +	def_bool y
> +	depends on RANDOMIZE_BASE && MEMORY_HOTREMOVE
> +	help
> +	  This option parses RSDP in compressed period. Works
> +	  for KASLR to get memory information from 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/acpi.c b/arch/x86/boot/compressed/acpi.c
> new file mode 100644
> index 000000000000..cad15686f82c
> --- /dev/null
> +++ b/arch/x86/boot/compressed/acpi.c
> @@ -0,0 +1,30 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define BOOT_CTYPE_H
> +#include "misc.h"
> +#include "error.h"
> +
> +#include <linux/efi.h>
> +#include <linux/numa.h>
> +#include <linux/acpi.h>
> +#include <asm/efi.h>
> +
> +#define STATIC
> +#include <linux/decompress/mm.h>
> +
> +#include "../string.h"
> +
> +static acpi_physical_address get_acpi_rsdp(void)
> +{
> +#ifdef CONFIG_KEXEC
> +	unsigned long long res;
> +	int len = 0;
> +	char val[MAX_ADDRESS_LENGTH+1];
> +

> +	len = cmdline_find_option("acpi_rsdp", val, MAX_ADDRESS_LENGTH+1);

sizeof() is better here.

	len = cmdline_find_option("acpi_rsdp", val, sizeof(var));

> +	if (len > 0) {
> +		val[len] = 0;

'\0' should be fine here not 0.

		val[len] = '\0';

> +		return (acpi_physical_address)kstrtoull(val, 16, &res);
> +	}
> +	return 0;
> +#endif
> +}
> diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
> index a1d5918765f3..72fcfbfec3c6 100644
> --- a/arch/x86/boot/compressed/misc.h
> +++ b/arch/x86/boot/compressed/misc.h
> @@ -116,3 +116,9 @@ static inline void console_init(void)
>  void set_sev_encryption_mask(void);
>  
>  #endif
> +
> +/* acpi.c */
> +#ifdef CONFIG_EARLY_PARSE_RSDP
> +/* Max length of 64-bit hex address string is 18, prefix "0x" + 16 hex digit. */
> +#define MAX_ADDRESS_LENGTH 18
> +#endif
> -- 
> 2.19.2
> 
>