* Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
> 0-day reported this build error:
>
> arch/x86/boot/compressed/pgtable_64.o: In function `l5_paging_required':
> pgtable_64.c:(.text+0x22): undefined reference to `__force_order'
>
> The issue is only with GCC < 5 and when KASLR is disabled. Newer GCC
> works fine.
>
> __force_order is used by special_insns.h asm code to force instruction
> serialization.
s/is used by special_insns.h asm code
/is used by the special_insns.h asm code
> It doesn't actually referenced from the code, but GCC < 5 with -fPIE
> would still generate undefined symbol.
s/It doesn't actually referenced from the code
/It isn't actually referenced from the code
s/would still generate undefined symbol.
/would still generate an undefined symbol.
> I didn't noticed this before and failed to move __force_order definition
> from pagetable.c (which compiles only with KASLR enabled) to
> pgtable_64.c.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Fixes: 10c9a5346f72 ("x86/boot/compressed/64: Detect and handle 5-level paging at boot-time")
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> arch/x86/boot/compressed/pagetable.c | 3 ---
> arch/x86/boot/compressed/pgtable_64.c | 11 +++++++++++
> 2 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/pagetable.c b/arch/x86/boot/compressed/pagetable.c
> index 6bd51de4475c..250826ac216e 100644
> --- a/arch/x86/boot/compressed/pagetable.c
> +++ b/arch/x86/boot/compressed/pagetable.c
> @@ -38,9 +38,6 @@
> #define __PAGE_OFFSET __PAGE_OFFSET_BASE
> #include "../../mm/ident_map.c"
>
> -/* Used by pgtable.h asm code to force instruction serialization. */
> -unsigned long __force_order;
> -
> /* Used to track our page table allocation area. */
> struct alloc_pgt_data {
> unsigned char *pgt_buf;
> diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c
> index 7bcf03b376da..491fa2d08bca 100644
> --- a/arch/x86/boot/compressed/pgtable_64.c
> +++ b/arch/x86/boot/compressed/pgtable_64.c
> @@ -1,5 +1,16 @@
> #include <asm/processor.h>
>
> +/*
> + * __force_order is used by special_insns.h asm code to force instruction
> + * serialization.
s/is used by special_insns.h asm code
/is used by the special_insns.h asm code
> + *
> + * It doesn't actually referenced from the code, but GCC < 5 with -fPIE
> + * would still generate undefined symbol.
s/It doesn't actually referenced from the code
/It isn't actually referenced from the code
s/would still generate undefined symbol.
/would still generate an undefined symbol.
> + *
> + * Let's workaround this by defining the variable.
s/Let's workaround
/Let's work around
Also, for the title:
s/Fix build with GCC < 5
/Fix the build with GCC < 5
Thanks,
Ingo