Commit 90530521 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Will Deacon
Browse files

arm64/boot: Disallow BSS exports to startup code 



BSS might be uninitialized when entering the startup code, so forbid the
use by the startup code of any variables that live after __bss_start in
the linker map.

Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Tested-by: default avatarYeoreum Yun <yeoreum.yun@arm.com>
Reviewed-by: default avatarYeoreum Yun <yeoreum.yun@arm.com>
Link: https://lore.kernel.org/r/20250508114328.2460610-8-ardb+git@google.com


[will: Drop export of 'memstart_offset_seed', as this has been removed]
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 4afff6cc

arch/arm64/kernel/image-vars.h

+32 −28
Original line number Diff line number Diff line
@@ -10,6 +10,12 @@ 
#error This file should only be included in vmlinux.lds.S

#endif



#define PI_EXPORT_SYM(sym)		\

	__PI_EXPORT_SYM(sym, __pi_ ## sym, Cannot export BSS symbol sym to startup code)

#define __PI_EXPORT_SYM(sym, pisym, msg)\

	PROVIDE(pisym = sym);		\

	ASSERT((sym - KIMAGE_VADDR) < (__bss_start - KIMAGE_VADDR), #msg)



PROVIDE(__efistub_primary_entry		= primary_entry);



/*
@@ -36,36 +42,34 @@ PROVIDE(__pi___memcpy = __pi_memcpy); 
PROVIDE(__pi___memmove			= __pi_memmove);

PROVIDE(__pi___memset			= __pi_memset);



PROVIDE(__pi_id_aa64isar1_override	= id_aa64isar1_override);

PROVIDE(__pi_id_aa64isar2_override	= id_aa64isar2_override);

PROVIDE(__pi_id_aa64mmfr0_override	= id_aa64mmfr0_override);

PROVIDE(__pi_id_aa64mmfr1_override	= id_aa64mmfr1_override);

PROVIDE(__pi_id_aa64mmfr2_override	= id_aa64mmfr2_override);

PROVIDE(__pi_id_aa64pfr0_override	= id_aa64pfr0_override);

PROVIDE(__pi_id_aa64pfr1_override	= id_aa64pfr1_override);

PROVIDE(__pi_id_aa64smfr0_override	= id_aa64smfr0_override);

PROVIDE(__pi_id_aa64zfr0_override	= id_aa64zfr0_override);

PROVIDE(__pi_arm64_sw_feature_override	= arm64_sw_feature_override);

PROVIDE(__pi_arm64_use_ng_mappings	= arm64_use_ng_mappings);

PI_EXPORT_SYM(id_aa64isar1_override);

PI_EXPORT_SYM(id_aa64isar2_override);

PI_EXPORT_SYM(id_aa64mmfr0_override);

PI_EXPORT_SYM(id_aa64mmfr1_override);

PI_EXPORT_SYM(id_aa64mmfr2_override);

PI_EXPORT_SYM(id_aa64pfr0_override);

PI_EXPORT_SYM(id_aa64pfr1_override);

PI_EXPORT_SYM(id_aa64smfr0_override);

PI_EXPORT_SYM(id_aa64zfr0_override);

PI_EXPORT_SYM(arm64_sw_feature_override);

PI_EXPORT_SYM(arm64_use_ng_mappings);

#ifdef CONFIG_CAVIUM_ERRATUM_27456

PROVIDE(__pi_cavium_erratum_27456_cpus	= cavium_erratum_27456_cpus);

PROVIDE(__pi_is_midr_in_range_list	= is_midr_in_range_list);

PI_EXPORT_SYM(cavium_erratum_27456_cpus);

PI_EXPORT_SYM(is_midr_in_range_list);

#endif

PROVIDE(__pi__ctype			= _ctype);



PROVIDE(__pi_swapper_pg_dir		= swapper_pg_dir);



PROVIDE(__pi__text			= _text);

PROVIDE(__pi__stext               	= _stext);

PROVIDE(__pi__etext               	= _etext);

PROVIDE(__pi___start_rodata       	= __start_rodata);

PROVIDE(__pi___inittext_begin     	= __inittext_begin);

PROVIDE(__pi___inittext_end       	= __inittext_end);

PROVIDE(__pi___initdata_begin     	= __initdata_begin);

PROVIDE(__pi___initdata_end       	= __initdata_end);

PROVIDE(__pi__data                	= _data);

PROVIDE(__pi___bss_start		= __bss_start);

PROVIDE(__pi__end			= _end);

PI_EXPORT_SYM(_ctype);



PI_EXPORT_SYM(swapper_pg_dir);



PI_EXPORT_SYM(_text);

PI_EXPORT_SYM(_stext);

PI_EXPORT_SYM(_etext);

PI_EXPORT_SYM(__start_rodata);

PI_EXPORT_SYM(__inittext_begin);

PI_EXPORT_SYM(__inittext_end);

PI_EXPORT_SYM(__initdata_begin);

PI_EXPORT_SYM(__initdata_end);

PI_EXPORT_SYM(_data);



#ifdef CONFIG_KVM

arch/arm64/kernel/vmlinux.lds.S

+2 −0
Original line number Diff line number Diff line
@@ -319,6 +319,7 @@ SECTIONS 


	/* start of zero-init region */

	BSS_SECTION(SBSS_ALIGN, 0, 0)

	__pi___bss_start = __bss_start;



	. = ALIGN(PAGE_SIZE);

	__pi_init_pg_dir = .;
@@ -332,6 +333,7 @@ SECTIONS 
	. = ALIGN(SEGMENT_ALIGN);

	__pecoff_data_size = ABSOLUTE(. - __initdata_begin);

	_end = .;

	__pi__end = .;



	STABS_DEBUG

	DWARF_DEBUG