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Date: Fri, 15 Mar 2024 00:57:37 +0000
From: Wei Yang <richard.weiyang@...il.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: Wei Yang <richard.weiyang@...il.com>, tglx@...utronix.de,
mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] x86/boot: replace __PHYSICAL_START with
LOAD_PHYSICAL_ADDR
On Thu, Mar 14, 2024 at 10:25:53AM +0100, Ingo Molnar wrote:
>
>* Wei Yang <richard.weiyang@...il.com> wrote:
>
>> On Wed, Mar 13, 2024 at 11:29:33AM +0100, Ingo Molnar wrote:
>> >
>> >* Wei Yang <richard.weiyang@...il.com> wrote:
>> >
>> >> Both __PHYSICAL_START and LOAD_PHYSICAL_ADDR are defined to get aligned
>> >> CONFIG_PHYSICAL_START, so we can replace __PHYSICAL_START with
>> >> LOAD_PHYSICAL_ADDR. And then remove the definition of __PHYSICAL_START,
>> >> which is only used to define __START_KERNEL.
>> >>
>> >> Since <asm/boot.h> includes <asm/pgtable_types.h>, which includes
>> >> <asm/page_types.h>, it is fine to move definition from <asm/boot.h> to
>> >> <asm/page_types.h>.
>> >>
>> >> Signed-off-by: Wei Yang <richard.weiyang@...il.com>
>> >> ---
>> >> arch/x86/include/asm/boot.h | 5 -----
>> >> arch/x86/include/asm/page_types.h | 8 +++++---
>> >> 2 files changed, 5 insertions(+), 8 deletions(-)
>> >>
>> >> diff --git a/arch/x86/include/asm/boot.h b/arch/x86/include/asm/boot.h
>> >> index a38cc0afc90a..12cbc57d0128 100644
>> >> --- a/arch/x86/include/asm/boot.h
>> >> +++ b/arch/x86/include/asm/boot.h
>> >> @@ -6,11 +6,6 @@
>> >> #include <asm/pgtable_types.h>
>> >> #include <uapi/asm/boot.h>
>> >>
>> >> -/* Physical address where kernel should be loaded. */
>> >> -#define LOAD_PHYSICAL_ADDR ((CONFIG_PHYSICAL_START \
>> >> - + (CONFIG_PHYSICAL_ALIGN - 1)) \
>> >> - & ~(CONFIG_PHYSICAL_ALIGN - 1))
>> >> -
>> >> /* Minimum kernel alignment, as a power of two */
>> >> #ifdef CONFIG_X86_64
>> >> # define MIN_KERNEL_ALIGN_LG2 PMD_SHIFT
>> >> diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h
>> >> index 86bd4311daf8..acc1620fd121 100644
>> >> --- a/arch/x86/include/asm/page_types.h
>> >> +++ b/arch/x86/include/asm/page_types.h
>> >> @@ -31,10 +31,12 @@
>> >>
>> >> #define VM_DATA_DEFAULT_FLAGS VM_DATA_FLAGS_TSK_EXEC
>> >>
>> >> -#define __PHYSICAL_START ALIGN(CONFIG_PHYSICAL_START, \
>> >> - CONFIG_PHYSICAL_ALIGN)
>> >> +/* Physical address where kernel should be loaded. */
>> >> +#define LOAD_PHYSICAL_ADDR ((CONFIG_PHYSICAL_START \
>> >> + + (CONFIG_PHYSICAL_ALIGN - 1)) \
>> >> + & ~(CONFIG_PHYSICAL_ALIGN - 1))
>> >
>> >I agree with this simplification, but the ALIGN() expression is far easier
>> >to read, so please keep that one instead of the open-coded version.
>> >
>>
>> I just tried to define LOAD_PHYSICAL_ADDR by ALIGN, but face a compile error
>> on compressed/head_[32|64].o.
>>
>> $ make arch/x86/boot/compressed/head_64.o
>> CALL scripts/checksyscalls.sh
>> DESCEND objtool
>> INSTALL libsubcmd_headers
>> AS arch/x86/boot/compressed/head_64.o
>> arch/x86/boot/compressed/head_64.S: Assembler messages:
>> arch/x86/boot/compressed/head_64.S:154: Error: junk (0x1000000,0x200000)' after expression
>> arch/x86/boot/compressed/head_64.S:154: Error: number of operands mismatch for 16' after expression
>> arch/x86/boot/compressed/head_64.S:157: Error: junk mov'
>> arch/x86/boot/compressed/head_64.S:330: Error: junk (0x1000000,0x200000)' after expression
>> arch/x86/boot/compressed/head_64.S:330: Error: number of operands mismatch for 16' after expression
>> arch/x86/boot/compressed/head_64.S:333: Error: junk movq'
>>
>> If my understanding is correct, the reason is linkage.h defines ALIGN, which
>> is ".balign xxx". Maybe this is why original LOAD_PHYSICAL_ADDR doesn't use
>> ALIGN.
>
>linkage.h defines __ALIGN, which is different from ALIGN().
>
linkage.h defines ALIGN to __ALIGN which is different from what we expect.
>Also, a number of .S files seem to be using some sort of ALIGN() method
>within arch/x86/, according to:
>
> git grep 'ALIGN(' -- 'arch/x86/*.S'
I tried below command by append '\<' to ALIGN
git grep '\<ALIGN(' -- 'arch/x86/*.S'
>
>> So is this ok to keep the open-coded definition?
>
>It would be nice to figure out why ALIGN() appears to be working in other
>cases in .S files, while not in this case.
>
Here is grep result
arch/x86/boot/compressed/vmlinux.lds.S: .data : ALIGN(0x1000) {
arch/x86/boot/compressed/vmlinux.lds.S: . = ALIGN(. + 4, 0x200);
arch/x86/boot/compressed/vmlinux.lds.S: . = ALIGN(L1_CACHE_BYTES);
arch/x86/boot/compressed/vmlinux.lds.S: . = ALIGN(8); /* For convenience during zeroing */
arch/x86/boot/compressed/vmlinux.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/boot/compressed/vmlinux.lds.S: . = ALIGN(PAGE_SIZE); /* keep ZO size page aligned */
arch/x86/kernel/vmlinux.lds.S:#define X86_ALIGN_RODATA_BEGIN . = ALIGN(HPAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(HPAGE_SIZE); \
arch/x86/kernel/vmlinux.lds.S:#define ALIGN_ENTRY_TEXT_BEGIN . = ALIGN(PMD_SIZE);
arch/x86/kernel/vmlinux.lds.S:#define ALIGN_ENTRY_TEXT_END . = ALIGN(PMD_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PMD_SIZE); \
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE); \
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PMD_SIZE); \
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE); \
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(__vvar_page + PAGE_SIZE, PAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(8);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(8);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(8);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(8);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(8);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(8);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(8);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(8);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(PAGE_SIZE); /* keep VO_INIT_SIZE page aligned */
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(HPAGE_SIZE);
arch/x86/kernel/vmlinux.lds.S: . = ALIGN(HPAGE_SIZE);
arch/x86/realmode/rm/realmode.lds.S: . = ALIGN(4);
arch/x86/realmode/rm/realmode.lds.S: . = ALIGN(16);
arch/x86/realmode/rm/realmode.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/realmode/rm/realmode.lds.S: . = ALIGN(PAGE_SIZE);
arch/x86/realmode/rm/realmode.lds.S: . = ALIGN(128);
arch/x86/realmode/rm/realmode.lds.S: . = ALIGN(4);
arch/x86/um/vdso/vdso-layout.lds.S: . = ALIGN(0x100);
It looks all happens in link script, not assembly source code.
And other grep result with "ALIGN" are:
SYM_CODE_START_NOALIGN
SYM_CODE_START_LOCAL_NOALIGN
SYM_FUNC_START_NOALIGN
SYM_FUNC_START_LOCAL_NOALIGN
SYM_INNER_LABEL_ALIGN
which are defined in linkage.h.
>Thanks,
>
> Ingo
--
Wei Yang
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