On Fri, 29 May 2026, at 10:27, Kevin Brodsky wrote: > On 26/05/2026 19:58, Ard Biesheuvel wrote: >> From: Ard Biesheuvel <[email protected]> >> >> Move the fixmap and kasan page tables out of the BSS section, and place >> them at the end of the image, right before the init_pg_dir section where >> some of the other statically allocated page tables live. >> >> These page tables are currently the only data objects in vmlinux that >> are meant to be accessed via the kernel image's linear alias, and so >> placing them together allows the remainder of the data/bss section to be >> remapped read-only or unmapped entirely. >> >> Reviewed-by: Kevin Brodsky <[email protected]> >> Signed-off-by: Ard Biesheuvel <[email protected]> >> --- >> arch/arm64/include/asm/mmu.h | 2 ++ >> arch/arm64/kernel/vmlinux.lds.S | 8 +++++++- >> arch/arm64/mm/fixmap.c | 6 +++--- >> arch/arm64/mm/kasan_init.c | 2 +- >> 4 files changed, 13 insertions(+), 5 deletions(-) >> >> diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h >> index 5e1211c540ab..fb95754f2876 100644 >> --- a/arch/arm64/include/asm/mmu.h >> +++ b/arch/arm64/include/asm/mmu.h >> @@ -13,6 +13,8 @@ >> >> #ifndef __ASSEMBLER__ >> >> +#define __pgtbl_bss __section(".pgdir.bss") __aligned(PAGE_SIZE) >> + >> #include <linux/refcount.h> >> #include <asm/cpufeature.h> >> >> diff --git a/arch/arm64/kernel/vmlinux.lds.S >> b/arch/arm64/kernel/vmlinux.lds.S >> index e1ac876200a3..2b0ebfb30c63 100644 >> --- a/arch/arm64/kernel/vmlinux.lds.S >> +++ b/arch/arm64/kernel/vmlinux.lds.S >> @@ -349,9 +349,15 @@ SECTIONS >> _edata = .; >> >> /* start of zero-init region */ >> - BSS_SECTION(SBSS_ALIGN, 0, 0) >> + BSS_SECTION(SBSS_ALIGN, 0, PAGE_SIZE) >> __pi___bss_start = __bss_start; >> >> + /* fixmap BSS starts here - preceding data/BSS is omitted from the >> linear map */ >> + .pgdir.bss (NOLOAD) : ALIGN(PAGE_SIZE) { > > Do we actually need the NOLOAD type here?
Yes, otherwise it is emitted as PROGBITS, resulting in all of BSS to be emitted into Image.
