* [PATCH] arm64: head: remove __PHYS_OFFSET
@ 2022-06-28 4:57 Anshuman Khandual
2022-06-28 7:25 ` Ard Biesheuvel
0 siblings, 1 reply; 3+ messages in thread
From: Anshuman Khandual @ 2022-06-28 4:57 UTC (permalink / raw)
To: linux-arm-kernel
Cc: Mark Rutland, Ard Biesheuvel, Catalin Marinas, Will Deacon,
Anshuman Khandual
From: Mark Rutland <mark.rutland@arm.com>
It's very easy to confuse __PHYS_OFFSET and PHYS_OFFSET. To clarify
things, let's remove __PHYS_OFFSET and use KERNEL_START directly, with
comments to show that we're using physical address, as we do for other
objects.
At the same time, update the comment regarding the kernel entry address
to mention __pa(KERNEL_START) rather than __pa(PAGE_OFFSET).
There should be no functional change as a result of this patch.
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
This applies on latest arm64 kernel (for-next/boot).
arch/arm64/kernel/head.S | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 6bf685f988f1..763f11a394a7 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -37,8 +37,6 @@
#include "efi-header.S"
-#define __PHYS_OFFSET KERNEL_START
-
#if (PAGE_OFFSET & 0x1fffff) != 0
#error PAGE_OFFSET must be at least 2MB aligned
#endif
@@ -52,7 +50,7 @@
* x0 = physical address to the FDT blob.
*
* This code is mostly position independent so you call this at
- * __pa(PAGE_OFFSET).
+ * __pa(KERNEL_START).
*
* Note that the callee-saved registers are used for storing variables
* that are useful before the MMU is enabled. The allocations are described
@@ -409,7 +407,7 @@ SYM_FUNC_END(create_kernel_mapping)
/*
* The following fragment of code is executed with the MMU enabled.
*
- * x0 = __PHYS_OFFSET
+ * x0 = __pa(KERNEL_START)
*/
SYM_FUNC_START_LOCAL(__primary_switched)
adr_l x4, init_task
@@ -793,7 +791,7 @@ SYM_FUNC_START_LOCAL(__primary_switch)
adrp x2, init_idmap_pg_dir
bl __enable_mmu
#ifdef CONFIG_RELOCATABLE
- adrp x23, __PHYS_OFFSET
+ adrp x23, KERNEL_START
and x23, x23, MIN_KIMG_ALIGN - 1
#ifdef CONFIG_RANDOMIZE_BASE
mov x0, x22
@@ -815,6 +813,6 @@ SYM_FUNC_START_LOCAL(__primary_switch)
bl __relocate_kernel
#endif
ldr x8, =__primary_switched
- adrp x0, __PHYS_OFFSET
+ adrp x0, KERNEL_START // __pa(KERNEL_START)
br x8
SYM_FUNC_END(__primary_switch)
--
2.20.1
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^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] arm64: head: remove __PHYS_OFFSET
2022-06-28 4:57 [PATCH] arm64: head: remove __PHYS_OFFSET Anshuman Khandual
@ 2022-06-28 7:25 ` Ard Biesheuvel
2022-06-28 7:43 ` Anshuman Khandual
0 siblings, 1 reply; 3+ messages in thread
From: Ard Biesheuvel @ 2022-06-28 7:25 UTC (permalink / raw)
To: Anshuman Khandual; +Cc: Linux ARM, Mark Rutland, Catalin Marinas, Will Deacon
On Tue, 28 Jun 2022 at 06:57, Anshuman Khandual
<anshuman.khandual@arm.com> wrote:
>
> From: Mark Rutland <mark.rutland@arm.com>
>
> It's very easy to confuse __PHYS_OFFSET and PHYS_OFFSET. To clarify
> things, let's remove __PHYS_OFFSET and use KERNEL_START directly, with
> comments to show that we're using physical address, as we do for other
> objects.
>
> At the same time, update the comment regarding the kernel entry address
> to mention __pa(KERNEL_START) rather than __pa(PAGE_OFFSET).
>
> There should be no functional change as a result of this patch.
>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Acked-by: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> This applies on latest arm64 kernel (for-next/boot).
>
> arch/arm64/kernel/head.S | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index 6bf685f988f1..763f11a394a7 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -37,8 +37,6 @@
>
> #include "efi-header.S"
>
> -#define __PHYS_OFFSET KERNEL_START
> -
> #if (PAGE_OFFSET & 0x1fffff) != 0
> #error PAGE_OFFSET must be at least 2MB aligned
> #endif
> @@ -52,7 +50,7 @@
> * x0 = physical address to the FDT blob.
> *
> * This code is mostly position independent so you call this at
> - * __pa(PAGE_OFFSET).
> + * __pa(KERNEL_START).
> *
I'm now wondering whether we should just drop this comment - it is no
longer accurate, and of dubious value even when it was.
> * Note that the callee-saved registers are used for storing variables
> * that are useful before the MMU is enabled. The allocations are described
> @@ -409,7 +407,7 @@ SYM_FUNC_END(create_kernel_mapping)
> /*
> * The following fragment of code is executed with the MMU enabled.
> *
> - * x0 = __PHYS_OFFSET
> + * x0 = __pa(KERNEL_START)
> */
> SYM_FUNC_START_LOCAL(__primary_switched)
> adr_l x4, init_task
> @@ -793,7 +791,7 @@ SYM_FUNC_START_LOCAL(__primary_switch)
> adrp x2, init_idmap_pg_dir
> bl __enable_mmu
> #ifdef CONFIG_RELOCATABLE
> - adrp x23, __PHYS_OFFSET
> + adrp x23, KERNEL_START
> and x23, x23, MIN_KIMG_ALIGN - 1
> #ifdef CONFIG_RANDOMIZE_BASE
> mov x0, x22
> @@ -815,6 +813,6 @@ SYM_FUNC_START_LOCAL(__primary_switch)
> bl __relocate_kernel
> #endif
> ldr x8, =__primary_switched
> - adrp x0, __PHYS_OFFSET
> + adrp x0, KERNEL_START // __pa(KERNEL_START)
> br x8
> SYM_FUNC_END(__primary_switch)
> --
> 2.20.1
>
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] arm64: head: remove __PHYS_OFFSET
2022-06-28 7:25 ` Ard Biesheuvel
@ 2022-06-28 7:43 ` Anshuman Khandual
0 siblings, 0 replies; 3+ messages in thread
From: Anshuman Khandual @ 2022-06-28 7:43 UTC (permalink / raw)
To: Ard Biesheuvel; +Cc: Linux ARM, Mark Rutland, Catalin Marinas, Will Deacon
On 6/28/22 12:55, Ard Biesheuvel wrote:
> On Tue, 28 Jun 2022 at 06:57, Anshuman Khandual
> <anshuman.khandual@arm.com> wrote:
>> From: Mark Rutland <mark.rutland@arm.com>
>>
>> It's very easy to confuse __PHYS_OFFSET and PHYS_OFFSET. To clarify
>> things, let's remove __PHYS_OFFSET and use KERNEL_START directly, with
>> comments to show that we're using physical address, as we do for other
>> objects.
>>
>> At the same time, update the comment regarding the kernel entry address
>> to mention __pa(KERNEL_START) rather than __pa(PAGE_OFFSET).
>>
>> There should be no functional change as a result of this patch.
>>
>> Cc: Ard Biesheuvel <ardb@kernel.org>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will@kernel.org>
>> Acked-by: Ard Biesheuvel <ardb@kernel.org>
>> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> ---
>> This applies on latest arm64 kernel (for-next/boot).
>>
>> arch/arm64/kernel/head.S | 10 ++++------
>> 1 file changed, 4 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
>> index 6bf685f988f1..763f11a394a7 100644
>> --- a/arch/arm64/kernel/head.S
>> +++ b/arch/arm64/kernel/head.S
>> @@ -37,8 +37,6 @@
>>
>> #include "efi-header.S"
>>
>> -#define __PHYS_OFFSET KERNEL_START
>> -
>> #if (PAGE_OFFSET & 0x1fffff) != 0
>> #error PAGE_OFFSET must be at least 2MB aligned
>> #endif
>> @@ -52,7 +50,7 @@
>> * x0 = physical address to the FDT blob.
>> *
>> * This code is mostly position independent so you call this at
>> - * __pa(PAGE_OFFSET).
>> + * __pa(KERNEL_START).
>> *
> I'm now wondering whether we should just drop this comment - it is no
> longer accurate, and of dubious value even when it was.
Sure, will drop those two comment lines.
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-06-28 4:57 [PATCH] arm64: head: remove __PHYS_OFFSET Anshuman Khandual
2022-06-28 7:25 ` Ard Biesheuvel
2022-06-28 7:43 ` Anshuman Khandual
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