* Chao Fan <fanc.f...@cn.fujitsu.com> 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.
What is the nature of the basic conflict? Should the kernel only allow
hot-removing memory ranges that are explicitly marked as such in the
SRAT? I presume that's already so, correct? Or should the kernel avoiding
KASLR-randomizing into hot-removable memory areas?
Some minor nits:
> Signed-off-by: Chao Fan <fanc.f...@cn.fujitsu.com>
> ---
> arch/x86/boot/compressed/acpi.c | 30 ++++++++++++++++++++++++++++++
> 1 file changed, 30 insertions(+)
> create mode 100644 arch/x86/boot/compressed/acpi.c
>
> diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
> new file mode 100644
> index 000000000000..44f19546c169
> --- /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>
> +
> +/* Max length of 64-bit hex address string is 18, prefix "0x" + 16 hex
> digits */
> +#define MAX_ADDRESS_LENGTH 18
I'd suggest adding the +1 for the string termination \0 as well, and use
that below.
Also, 'max address length' is way too generic (and hence pretty
meaningless) - how about MAX_HEX_ADDRESS_STRING_LEN or so?
> +
> +static acpi_physical_address get_acpi_rsdp(void)
> +{
> +#ifdef CONFIG_KEXEC
> + char val[MAX_ADDRESS_LENGTH+1];
> + unsigned long long res;
> + int len;
> +
> + len = cmdline_find_option("acpi_rsdp", val, MAX_ADDRESS_LENGTH+1);
> + if (len > 0) {
> + char *e;
> +
> + val[len] = '\0';
> + return (acpi_physical_address)simple_strtoull(val, &e, 16);
'return' is not a function - no need for the parenthesis.
Thanks,
Ingo
