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SubjectRe: [PATCH] x86: Fix boot protocol KEEP_SEGMENTS check.
Eric W. Biederman wrote:
> The kernel only ever supports 1 version of the boot protocol
> so there is no need to check the boot protocol revision to
> see if a feature is supported.
>
> Both x86 and x86_64 support the same boot protocol so we need
> to implement the KEEP_SEGMENTS on x86_64 as well. It isn't
> just paravirt bootloaders that could use this functionality.
>

Ack. I was planning on sending this patch out today...

J
> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
> Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Vivek Goyal <vgoyal@in.ibm.com>
> Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
> Cc: Zachary Amsden <zach@vmware.com>
> Cc: Andi Kleen <ak@suse.de>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@elte.hu>
> ---
> arch/x86/boot/compressed/head_32.S | 12 ++++--------
> arch/x86/boot/compressed/head_64.S | 7 +++++++
> arch/x86/kernel/asm-offsets_64.c | 10 ++++++++++
> 3 files changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
> index a0ae2e7..036e635 100644
> --- a/arch/x86/boot/compressed/head_32.S
> +++ b/arch/x86/boot/compressed/head_32.S
> @@ -33,24 +33,20 @@
> .globl startup_32
>
> startup_32:
> - /* check to see if KEEP_SEGMENTS flag is meaningful */
> - cmpw $0x207, BP_version(%esi)
> - jb 1f
> -
> + cld
> /* test KEEP_SEGMENTS flag to see if the bootloader is asking
> * us to not reload segments */
> testb $(1<<6), BP_loadflags(%esi)
> - jnz 2f
> + jnz 1f
>
> -1: cli
> + cli
> movl $(__BOOT_DS),%eax
> movl %eax,%ds
> movl %eax,%es
> movl %eax,%fs
> movl %eax,%gs
> movl %eax,%ss
> -
> -2: cld
> +1:
>
> /* Calculate the delta between where we were compiled to run
> * at and where we were actually loaded at. This can only be done
> diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
> index 4946764..1ccb38a 100644
> --- a/arch/x86/boot/compressed/head_64.S
> +++ b/arch/x86/boot/compressed/head_64.S
> @@ -29,6 +29,7 @@
> #include <asm/pgtable.h>
> #include <asm/page.h>
> #include <asm/msr.h>
> +#include <asm/asm-offsets.h>
>
> .section ".text.head"
> .code32
> @@ -36,11 +37,17 @@
>
> startup_32:
> cld
> + /* test KEEP_SEGMENTS flag to see if the bootloader is asking
> + * us to not reload segments */
> + testb $(1<<6), BP_loadflags(%esi)
> + jnz 1f
> +
> cli
> movl $(__KERNEL_DS), %eax
> movl %eax, %ds
> movl %eax, %es
> movl %eax, %ss
> +1:
>
> /* Calculate the delta between where we were compiled to run
> * at and where we were actually loaded at. This can only be done
> diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
> index 7e50bda..d1b6ed9 100644
> --- a/arch/x86/kernel/asm-offsets_64.c
> +++ b/arch/x86/kernel/asm-offsets_64.c
> @@ -15,12 +15,16 @@
> #include <asm/segment.h>
> #include <asm/thread_info.h>
> #include <asm/ia32.h>
> +#include <asm/bootparam.h>
>
> #define DEFINE(sym, val) \
> asm volatile("\n->" #sym " %0 " #val : : "i" (val))
>
> #define BLANK() asm volatile("\n->" : : )
>
> +#define OFFSET(sym, str, mem) \
> + DEFINE(sym, offsetof(struct str, mem))
> +
> #define __NO_STUBS 1
> #undef __SYSCALL
> #undef _ASM_X86_64_UNISTD_H_
> @@ -109,5 +113,11 @@ int main(void)
> DEFINE(crypto_tfm_ctx_offset, offsetof(struct crypto_tfm, __crt_ctx));
> BLANK();
> DEFINE(__NR_syscall_max, sizeof(syscalls) - 1);
> +
> + BLANK();
> + OFFSET(BP_scratch, boot_params, scratch);
> + OFFSET(BP_loadflags, boot_params, hdr.loadflags);
> + OFFSET(BP_hardware_subarch, boot_params, hdr.hardware_subarch);
> + OFFSET(BP_version, boot_params, hdr.version);
> return 0;
> }
>

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