linux-kernel - Re: [PATCH v12 1/5] x86/boot: Add get_acpi_rsdp() to parse RSDP in cmdline from KEXEC

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Message-ID: <20181129211003.saxfvyboxpsn5mdr@gabell>
Date:   Thu, 29 Nov 2018 16:10:03 -0500
From:   Masayoshi Mizuma <msys.mizuma@...il.com>
To:     Chao Fan <fanc.fnst@...fujitsu.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, bp@...en8.de,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        keescook@...omium.org, bhe@...hat.com, indou.takao@...fujitsu.com,
        caoj.fnst@...fujitsu.com
Subject: Re: [PATCH v12 1/5] x86/boot: Add get_acpi_rsdp() to parse RSDP in
 cmdline from KEXEC

On Thu, Nov 29, 2018 at 04:16:27PM +0800, Chao Fan wrote:
> To fix the conflict between KASLR and memory-hotremove, memory
> information in SRAT table is necessary.
> 
> ACPI SRAT (System/Static Resource Affinity Table) can show the details
> about memory ranges, including ranges of memory provided by hot-added
> memory devices. SRAT table must be introduced by RSDP pointer (Root
> System Description Pointer). So RSDP should be found firstly.
> 
> When booting form KEXEC/EFI/BIOS, the methods to find RSDP pointer
> are different. When booting from KEXEC, 'acpi_rsdp' may have been
> added to cmdline, so parse the cmdline and find the RSDP pointer.
> 
> Signed-off-by: Chao Fan <fanc.fnst@...fujitsu.com>
> ---
>  arch/x86/boot/compressed/acpitb.c | 33 +++++++++++++++++++++++++++++++
>  arch/x86/boot/compressed/misc.c   |  5 +++++
>  arch/x86/boot/compressed/misc.h   |  4 ++++
>  lib/kstrtox.c                     |  5 +++++
>  4 files changed, 47 insertions(+)
>  create mode 100644 arch/x86/boot/compressed/acpitb.c
> 
> diff --git a/arch/x86/boot/compressed/acpitb.c b/arch/x86/boot/compressed/acpitb.c
> new file mode 100644
> index 000000000000..614c45655cff
> --- /dev/null
> +++ b/arch/x86/boot/compressed/acpitb.c
> @@ -0,0 +1,33 @@
> +// 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>
> +
> +#define STATIC
> +#include <linux/decompress/mm.h>
> +
> +/* Store the immovable memory regions. */
> +struct mem_vector immovable_mem[MAX_NUMNODES*2];
> +#endif
> +
> +static acpi_physical_address get_acpi_rsdp(void)
> +{
> +#ifdef CONFIG_KEXEC
> +	unsigned long long res;
> +	int len = 0;
> +	char *val;
> +
> +	val = malloc(19);
> +	len = cmdline_find_option("acpi_rsdp", val, 19);
> +	if (len > 0) {
> +		val[len] = 0;
> +		return (acpi_physical_address)kstrtoull(val, 16, &res);
> +	}
> +	return 0;
> +#endif
> +}
> diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
> index 8dd1d5ccae58..e51713fe3add 100644
> --- a/arch/x86/boot/compressed/misc.c
> +++ b/arch/x86/boot/compressed/misc.c
> @@ -12,6 +12,7 @@
>   * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
>   */
>  
> +#define BOOT_CTYPE_H
>  #include "misc.h"
>  #include "error.h"
>  #include "pgtable.h"
> @@ -426,3 +427,7 @@ void fortify_panic(const char *name)
>  {
>  	error("detected buffer overflow");
>  }
> +
> +#ifdef BOOT_STRING
> +#include "../../../../lib/kstrtox.c"
> +#endif
> diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
> index a1d5918765f3..809c31effa4b 100644
> --- a/arch/x86/boot/compressed/misc.h
> +++ b/arch/x86/boot/compressed/misc.h
> @@ -116,3 +116,7 @@ static inline void console_init(void)
>  void set_sev_encryption_mask(void);
>  
>  #endif
> +
> +/* acpitb.c */
> +#define BOOT_STRING
> +extern int kstrtoull(const char *s, unsigned int base, unsigned long long *res);
> diff --git a/lib/kstrtox.c b/lib/kstrtox.c
> index 1006bf70bf74..a0ac1b2257b8 100644
> --- a/lib/kstrtox.c
> +++ b/lib/kstrtox.c
> @@ -126,6 +126,9 @@ int kstrtoull(const char *s, unsigned int base, unsigned long long *res)
>  }
>  EXPORT_SYMBOL(kstrtoull);
>  
> +/* Make compressed period code be able to use kstrtoull(). */
> +#ifndef BOOT_STRING

I got the following build error.

]$ make arch/x86/boot/compressed/misc.o
  CALL    scripts/checksyscalls.sh
  DESCEND  objtool
  CC      arch/x86/boot/compressed/misc.o
ld: -r and -pie may not be used together
make[1]: *** [scripts/Makefile.build:294: arch/x86/boot/compressed/misc.o] Error 1
make: *** [Makefile:1715: arch/x86/boot/compressed/misc.o] Error 2
]$

I think this error gets fixed by changing the BOOT_STRING ifndef
order before the EXPORT_SYMBOL, like this:

#ifndef BOOT_STRING
EXPORT_SYMBOL(kstrtoull);

I'm not sure this change is a good way...

Thanks,
Masa