Re: [PATCH v11 3/5] x86/boot: Add get_acpi_rsdp() to parse RSDP in cmdlien from kexec

Borislav Petkov
2018-11-13T17:51:50Z

On Mon, Nov 12, 2018 at 05:46:43PM +0800, Chao Fan wrote:
> Imitate setup_acpi_rsdp() for the early_param of 'acpi_rsdp'.
> KEXEC writes the RSDP pointer to cmdline for EFI booting.
> So if 'acpi_rsdp' found in cmdline, use it directely.
>
> Since function kstrtoull() is needed, include it in
> arch/x86/boot/string.h. To solve the definition conflict
> problem, set BOOT_STRING tag to expose only kstrtoull() and
> functions used by it. Other functions in lib/kstrtox.c will
> be covered.
>
> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
> ---
> arch/x86/boot/compressed/acpitb.c | 26 ++++++++++++++++++++++++++
> arch/x86/boot/string.h | 4 ++++
> lib/kstrtox.c | 4 ++++
> 3 files changed, 34 insertions(+)
>
> diff --git a/arch/x86/boot/compressed/acpitb.c b/arch/x86/boot/compressed/acpitb.c
> index 50fa65cf824d..5cfb4efa5a19 100644
> --- a/arch/x86/boot/compressed/acpitb.c
> +++ b/arch/x86/boot/compressed/acpitb.c
> @@ -8,6 +8,12 @@
> #include <linux/numa.h>
> #include <linux/acpi.h>
>
> +#define STATIC
> +#include <linux/decompress/mm.h>
> +
> +#define BOOT_STRING
> +#include "../string.h"
> +
> /* Search EFI table for RSDP table. */
> static void efi_get_rsdp_addr(acpi_physical_address *rsdp_addr)
> {
> @@ -200,3 +206,23 @@ static void bios_get_rsdp_addr(acpi_physical_address *rsdp_addr)
> *rsdp_addr = (acpi_physical_address)address;
> }
> }
> +
> +static void get_acpi_rsdp(acpi_physical_address *rsdp_addr)
> +{
> +#ifdef CONFIG_KEXEC

Ok, why is that CONFIG_KEXEC dependency needed now too?

Ok, let's recap: so far, for your use case you need:

CONFIG_MEMORY_HOTREMOVE
CONFIG_RANDOMIZE_BASE
and now
CONFIG_KEXEC

So, you can clean up all that ifdeffery by defining a new config item
CONFIG_EARLY_PARSE_RSDP or so which depends on all those three items and
then you can do

vmlinux-objs-$(CONFIG_EARLY_PARSE_RSDP) += $(obj)/acpitb.o

and get rid of the most of the ifdeffery.

Yes?

> + unsigned long long res;
> + int len = 0;
> + char *val;
> +
> + val = malloc(19);
> + len = cmdline_find_option("acpi_rsdp", val, 19);
> +

^ Superfluous newline.

> + if (len == -1)
> + return;

That check is not needed since you do > 0 below.

> +
> + if (len > 0) {
> + val[len] = 0;
> + *rsdp_addr = (acpi_physical_address)kstrtoull(val, 16, &res);
> + }
> +#endif
> +}
> diff --git a/arch/x86/boot/string.h b/arch/x86/boot/string.h
> index 3d78e27077f4..0ff3edb888e4 100644
> --- a/arch/x86/boot/string.h
> +++ b/arch/x86/boot/string.h
> @@ -30,3 +30,7 @@ extern unsigned long long simple_strtoull(const char *cp, char **endp,
> unsigned int base);
>
> #endif /* BOOT_STRING_H */
> +
> +#ifdef BOOT_STRING
> +#include "../../../lib/kstrtox.c"
> +#endif
> diff --git a/lib/kstrtox.c b/lib/kstrtox.c
> index 1006bf70bf74..3804db9eed56 100644
> --- a/lib/kstrtox.c
> +++ b/lib/kstrtox.c
> @@ -126,6 +126,8 @@ int kstrtoull(const char *s, unsigned int base, unsigned long long *res)
> }
> EXPORT_SYMBOL(kstrtoull);

This needs a comment to explain what is that guard used for.

> +#ifndef BOOT_STRING
> +
> /**
> * kstrtoll - convert a string to a long long
> * @s: The start of the string. The string must be null-terminated, and may also
> @@ -408,3 +410,5 @@ kstrto_from_user(kstrtou16_from_user, kstrtou16, u16);
> kstrto_from_user(kstrtos16_from_user, kstrtos16, s16);
> kstrto_from_user(kstrtou8_from_user, kstrtou8, u8);
> kstrto_from_user(kstrtos8_from_user, kstrtos8, s8);
> +
> +#endif

#endif /* BOOT_STRING */

--
Regards/Gruss,
Boris.

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