[RFC PATCH v1 44/57] arm64: Align sections to PAGE_SIZE_MAX

Ryan Roberts
2024-10-14T12:26:07Z

Increase alignment of sections in nvhe hyp, vdso and final vmlinux image
from PAGE_SIZE to PAGE_SIZE_MAX. For compile-time PAGE_SIZE,
PAGE_SIZE_MAX == PAGE_SIZE so there is no change. For boot-time
PAGE_SIZE, PAGE_SIZE_MAX is the largest selectable page size.

For a boot-time page size build, image size is comparable to a 64K page
size compile-time build. In future, it may be desirable to optimize
run-time memory consumption by freeing unused padding pages when the
boot-time selected page size is less than PAGE_SIZE_MAX.

Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
---

***NOTE***
Any confused maintainers may want to read the cover note here for context:
https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/

arch/arm64/include/asm/memory.h | 4 +--
arch/arm64/kernel/vdso-wrap.S | 4 +--
arch/arm64/kernel/vdso.c | 7 +++---
arch/arm64/kernel/vdso/vdso.lds.S | 4 +--
arch/arm64/kernel/vdso32-wrap.S | 4 +--
arch/arm64/kernel/vdso32/vdso.lds.S | 4 +--
arch/arm64/kernel/vmlinux.lds.S | 38 ++++++++++++++---------------
arch/arm64/kvm/hyp/nvhe/hyp.lds.S | 2 +-
8 files changed, 34 insertions(+), 33 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 6aa97fa22dc30..5393a859183f7 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -195,13 +195,13 @@
* Open-coded (swapper_pg_dir - reserved_pg_dir) as this cannot be calculated
* until link time.
*/
-#define RESERVED_SWAPPER_OFFSET (PAGE_SIZE)
+#define RESERVED_SWAPPER_OFFSET (PAGE_SIZE_MAX)

/*
* Open-coded (swapper_pg_dir - tramp_pg_dir) as this cannot be calculated
* until link time.
*/
-#define TRAMP_SWAPPER_OFFSET (2 * PAGE_SIZE)
+#define TRAMP_SWAPPER_OFFSET (2 * PAGE_SIZE_MAX)

#ifndef __ASSEMBLY__

diff --git a/arch/arm64/kernel/vdso-wrap.S b/arch/arm64/kernel/vdso-wrap.S
index c4b1990bf2be0..79fa77628199b 100644
--- a/arch/arm64/kernel/vdso-wrap.S
+++ b/arch/arm64/kernel/vdso-wrap.S
@@ -13,10 +13,10 @@

.globl vdso_start, vdso_end
.section .rodata
- .balign PAGE_SIZE
+ .balign PAGE_SIZE_MAX
vdso_start:
.incbin "arch/arm64/kernel/vdso/vdso.so"
- .balign PAGE_SIZE
+ .balign PAGE_SIZE_MAX
vdso_end:

.previous
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 89b6e78400023..1efe98909a2e0 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -195,7 +195,7 @@ static int __setup_additional_pages(enum vdso_abi abi,

vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
/* Be sure to map the data page */
- vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
+ vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE_MAX;

vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
if (IS_ERR_VALUE(vdso_base)) {
@@ -203,7 +203,8 @@ static int __setup_additional_pages(enum vdso_abi abi,
goto up_fail;
}

- ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
+ ret = _install_special_mapping(mm, vdso_base,
+ VVAR_NR_PAGES * PAGE_SIZE_MAX,
VM_READ|VM_MAYREAD|VM_PFNMAP,
vdso_info[abi].dm);
if (IS_ERR(ret))
@@ -212,7 +213,7 @@ static int __setup_additional_pages(enum vdso_abi abi,
if (system_supports_bti_kernel())
gp_flags = VM_ARM64_BTI;

- vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
+ vdso_base += VVAR_NR_PAGES * PAGE_SIZE_MAX;
mm->context.vdso = (void *)vdso_base;
ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
VM_READ|VM_EXEC|gp_flags|
diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S
index 45354f2ddf706..f7d1537a689e8 100644
--- a/arch/arm64/kernel/vdso/vdso.lds.S
+++ b/arch/arm64/kernel/vdso/vdso.lds.S
@@ -18,9 +18,9 @@ OUTPUT_ARCH(aarch64)

SECTIONS
{
- PROVIDE(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE);
+ PROVIDE(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE_MAX);
#ifdef CONFIG_TIME_NS
- PROVIDE(_timens_data = _vdso_data + PAGE_SIZE);
+ PROVIDE(_timens_data = _vdso_data + PAGE_SIZE_MAX);
#endif
. = VDSO_LBASE + SIZEOF_HEADERS;

diff --git a/arch/arm64/kernel/vdso32-wrap.S b/arch/arm64/kernel/vdso32-wrap.S
index e72ac7bc4c04f..1c6069d6c457e 100644
--- a/arch/arm64/kernel/vdso32-wrap.S
+++ b/arch/arm64/kernel/vdso32-wrap.S
@@ -10,10 +10,10 @@

.globl vdso32_start, vdso32_end
.section .rodata
- .balign PAGE_SIZE
+ .balign PAGE_SIZE_MAX
vdso32_start:
.incbin "arch/arm64/kernel/vdso32/vdso.so"
- .balign PAGE_SIZE
+ .balign PAGE_SIZE_MAX
vdso32_end:

.previous
diff --git a/arch/arm64/kernel/vdso32/vdso.lds.S b/arch/arm64/kernel/vdso32/vdso.lds.S
index 8d95d7d35057d..c46d18a69d1ce 100644
--- a/arch/arm64/kernel/vdso32/vdso.lds.S
+++ b/arch/arm64/kernel/vdso32/vdso.lds.S
@@ -18,9 +18,9 @@ OUTPUT_ARCH(arm)

SECTIONS
{
- PROVIDE_HIDDEN(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE);
+ PROVIDE_HIDDEN(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE_MAX);
#ifdef CONFIG_TIME_NS
- PROVIDE_HIDDEN(_timens_data = _vdso_data + PAGE_SIZE);
+ PROVIDE_HIDDEN(_timens_data = _vdso_data + PAGE_SIZE_MAX);
#endif
. = VDSO_LBASE + SIZEOF_HEADERS;

diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 7f3f6d709ae73..1ef6dea13b57c 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -15,16 +15,16 @@

#define HYPERVISOR_DATA_SECTIONS \
HYP_SECTION_NAME(.rodata) : { \
- . = ALIGN(PAGE_SIZE); \
+ . = ALIGN(PAGE_SIZE_MAX); \
__hyp_rodata_start = .; \
*(HYP_SECTION_NAME(.data..ro_after_init)) \
*(HYP_SECTION_NAME(.rodata)) \
- . = ALIGN(PAGE_SIZE); \
+ . = ALIGN(PAGE_SIZE_MAX); \
__hyp_rodata_end = .; \
}

#define HYPERVISOR_PERCPU_SECTION \
- . = ALIGN(PAGE_SIZE); \
+ . = ALIGN(PAGE_SIZE_MAX); \
HYP_SECTION_NAME(.data..percpu) : { \
*(HYP_SECTION_NAME(.data..percpu)) \
}
@@ -39,7 +39,7 @@
#define BSS_FIRST_SECTIONS \
__hyp_bss_start = .; \
*(HYP_SECTION_NAME(.bss)) \
- . = ALIGN(PAGE_SIZE); \
+ . = ALIGN(PAGE_SIZE_MAX); \
__hyp_bss_end = .;

/*
@@ -48,7 +48,7 @@
* between them, which can in some cases cause the linker to misalign them. To
* work around the issue, force a page alignment for __bss_start.
*/
-#define SBSS_ALIGN PAGE_SIZE
+#define SBSS_ALIGN PAGE_SIZE_MAX
#else /* CONFIG_KVM */
#define HYPERVISOR_EXTABLE
#define HYPERVISOR_DATA_SECTIONS
@@ -75,14 +75,14 @@ ENTRY(_text)
jiffies = jiffies_64;

#define HYPERVISOR_TEXT \
- . = ALIGN(PAGE_SIZE); \
+ . = ALIGN(PAGE_SIZE_MAX); \
__hyp_idmap_text_start = .; \
*(.hyp.idmap.text) \
__hyp_idmap_text_end = .; \
__hyp_text_start = .; \
*(.hyp.text) \
HYPERVISOR_EXTABLE \
- . = ALIGN(PAGE_SIZE); \
+ . = ALIGN(PAGE_SIZE_MAX); \
__hyp_text_end = .;

#define IDMAP_TEXT \
@@ -113,11 +113,11 @@ jiffies = jiffies_64;

#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
#define TRAMP_TEXT \
- . = ALIGN(PAGE_SIZE); \
+ . = ALIGN(PAGE_SIZE_MAX); \
__entry_tramp_text_start = .; \
*(.entry.tramp.text) \
- . = ALIGN(PAGE_SIZE); \
__entry_tramp_text_end = .; \
+ . = ALIGN(PAGE_SIZE_MAX); \
*(.entry.tramp.rodata)
#else
#define TRAMP_TEXT
@@ -187,7 +187,7 @@ SECTIONS
_etext = .; /* End of text section */

/* everything from this point to __init_begin will be marked RO NX */
- RO_DATA(PAGE_SIZE)
+ RO_DATA(PAGE_SIZE_MAX)

HYPERVISOR_DATA_SECTIONS

@@ -206,22 +206,22 @@ SECTIONS
HIBERNATE_TEXT
KEXEC_TEXT
IDMAP_TEXT
- . = ALIGN(PAGE_SIZE);
+ . = ALIGN(PAGE_SIZE_MAX);
}

idmap_pg_dir = .;
- . += PAGE_SIZE;
+ . += PAGE_SIZE_MAX;

#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
tramp_pg_dir = .;
- . += PAGE_SIZE;
+ . += PAGE_SIZE_MAX;
#endif

reserved_pg_dir = .;
- . += PAGE_SIZE;
+ . += PAGE_SIZE_MAX;

swapper_pg_dir = .;
- . += PAGE_SIZE;
+ . += PAGE_SIZE_MAX;

. = ALIGN(SEGMENT_ALIGN);
__init_begin = .;
@@ -290,7 +290,7 @@ SECTIONS

_data = .;
_sdata = .;
- RW_DATA(L1_CACHE_BYTES, PAGE_SIZE, THREAD_ALIGN)
+ RW_DATA(L1_CACHE_BYTES, PAGE_SIZE_MAX, THREAD_ALIGN)

/*
* Data written with the MMU off but read with the MMU on requires
@@ -317,7 +317,7 @@ SECTIONS
/* start of zero-init region */
BSS_SECTION(SBSS_ALIGN, 0, 0)

- . = ALIGN(PAGE_SIZE);
+ . = ALIGN(PAGE_SIZE_MAX);
init_pg_dir = .;
. += INIT_DIR_SIZE_MAX;
init_pg_end = .;
@@ -356,7 +356,7 @@ SECTIONS
* former is page-aligned, but the latter may not be with 16K or 64K pages, so
* it should also not cross a page boundary.
*/
-ASSERT(__hyp_idmap_text_end - __hyp_idmap_text_start <= PAGE_SIZE,
+ASSERT(__hyp_idmap_text_end - __hyp_idmap_text_start <= SZ_4K,
"HYP init code too big")
ASSERT(__idmap_text_end - (__idmap_text_start & ~(SZ_4K - 1)) <= SZ_4K,
"ID map text too big or misaligned")
@@ -367,7 +367,7 @@ ASSERT(__hibernate_exit_text_start == swsusp_arch_suspend_exit,
"Hibernate exit text does not start with swsusp_arch_suspend_exit")
#endif
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
-ASSERT((__entry_tramp_text_end - __entry_tramp_text_start) <= 3*PAGE_SIZE,
+ASSERT((__entry_tramp_text_end - __entry_tramp_text_start) <= 3 * SZ_4K,
"Entry trampoline text too big")
#endif
#ifdef CONFIG_KVM
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp.lds.S b/arch/arm64/kvm/hyp/nvhe/hyp.lds.S
index f4562f417d3fc..74c7c21626270 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp.lds.S
+++ b/arch/arm64/kvm/hyp/nvhe/hyp.lds.S
@@ -21,7 +21,7 @@ SECTIONS {
* .hyp..data..percpu needs to be page aligned to maintain the same
* alignment for when linking into vmlinux.
*/
- . = ALIGN(PAGE_SIZE);
+ . = ALIGN(PAGE_SIZE_MAX);
BEGIN_HYP_SECTION(.data..percpu)
PERCPU_INPUT(L1_CACHE_BYTES)
END_HYP_SECTION
--
2.43.0