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arm64/boot: Disallow BSS exports to startup code

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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: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Yeoreum Yun <yeoreum.yun@arm.com>
Reviewed-by: Yeoreum 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: Will Deacon <will@kernel.org>
This commit is contained in:
Ard Biesheuvel 2025-05-08 13:43:32 +02:00 committed by Will Deacon
parent 4afff6cc9a
commit 9053052107
2 changed files with 32 additions and 26 deletions
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56
arch/arm64/kernel/image-vars.h
View File

@ -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);
PI_EXPORT_SYM(_ctype);
PROVIDE(__pi_swapper_pg_dir = swapper_pg_dir);
PI_EXPORT_SYM(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(_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

2
arch/arm64/kernel/vmlinux.lds.S
View File

@ -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