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

Chao Fan
2018-11-14T01:59:45Z

On Wed, Nov 14, 2018 at 09:54:50AM +0800, Chao Fan wrote:
>On Tue, Nov 13, 2018 at 06:51:50PM +0100, Borislav Petkov wrote:
>>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?
>>
>
>CONFIG_KEXEC is only needed in this function.
>
>When searching RSDP, there are three methods in order:
>1. When booting from KEXEC, 'acpi_rsdp' is added to cmdline by KEXEC,
> so it can be parsed and used. CONFIG_KEXEC is needed here.
>2. When booting from EFI, parse EFI table and find RSDP.
>3. When booting from BIOS, search memory for RSDP just like
> acpi_find_root_pointer() in drivers/acpi/acpica/tbxfroot.c did.
>
>So, CONFIG_KEXEC is only needed in 1, exactly in this function
>get_acpi_rsdp() of my PATCH.
>
>Thanks,
>Chao Fan
>

That means, CONFIG_KEXEC is needed by a little part of the whole PATCHSET.
Without CONFIG_KEXEC, RSDP can only be found in other methods.

Thanks,
Chao Fan

>>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.
>>
>>Good mailing practices for 400: avoid top-posting and trim the reply.
>>
>>