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charset="utf-8" From: Ard Biesheuvel init_pgdir[] is only referenced from the startup code, but lives after BSS in the linker map. Before tightening the rules about accessing BSS from startup code, move init_pgdir[] into the __pi_ namespace, so it does not need to be exported explicitly. For symmetry, do the same with init_idmap_pgdir[], although it lives before BSS. Signed-off-by: Ard Biesheuvel Reviewed-by: Yeoreum Yun Tested-by: Yeoreum Yun --- arch/arm64/include/asm/pgtable.h | 2 -- arch/arm64/kernel/head.S | 6 +++--- arch/arm64/kernel/image-vars.h | 4 ---- arch/arm64/kernel/pi/pi.h | 1 + arch/arm64/kernel/vmlinux.lds.S | 8 ++++---- 5 files changed, 8 insertions(+), 13 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgta= ble.h index d3b538be1500..6a040f0bbfe1 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -754,8 +754,6 @@ static inline bool pud_table(pud_t pud) { return true; } PUD_TYPE_TABLE) #endif =20 -extern pgd_t init_pg_dir[]; -extern pgd_t init_pg_end[]; extern pgd_t swapper_pg_dir[]; extern pgd_t idmap_pg_dir[]; extern pgd_t tramp_pg_dir[]; diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 2ce73525de2c..ca04b338cb0d 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -89,7 +89,7 @@ SYM_CODE_START(primary_entry) adrp x1, early_init_stack mov sp, x1 mov x29, xzr - adrp x0, init_idmap_pg_dir + adrp x0, __pi_init_idmap_pg_dir mov x1, xzr bl __pi_create_init_idmap =20 @@ -101,7 +101,7 @@ SYM_CODE_START(primary_entry) cbnz x19, 0f dmb sy mov x1, x0 // end of used region - adrp x0, init_idmap_pg_dir + adrp x0, __pi_init_idmap_pg_dir adr_l x2, dcache_inval_poc blr x2 b 1f @@ -507,7 +507,7 @@ SYM_FUNC_END(__no_granule_support) =20 SYM_FUNC_START_LOCAL(__primary_switch) adrp x1, reserved_pg_dir - adrp x2, init_idmap_pg_dir + adrp x2, __pi_init_idmap_pg_dir bl __enable_mmu =20 adrp x1, early_init_stack diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h index 5e3c4b58f279..c3b4c0479d5c 100644 --- a/arch/arm64/kernel/image-vars.h +++ b/arch/arm64/kernel/image-vars.h @@ -54,10 +54,6 @@ PROVIDE(__pi_is_midr_in_range_list =3D is_midr_in_range_= list); PROVIDE(__pi__ctype =3D _ctype); PROVIDE(__pi_memstart_offset_seed =3D memstart_offset_seed); =20 -PROVIDE(__pi_init_idmap_pg_dir =3D init_idmap_pg_dir); -PROVIDE(__pi_init_idmap_pg_end =3D init_idmap_pg_end); -PROVIDE(__pi_init_pg_dir =3D init_pg_dir); -PROVIDE(__pi_init_pg_end =3D init_pg_end); PROVIDE(__pi_swapper_pg_dir =3D swapper_pg_dir); =20 PROVIDE(__pi__text =3D _text); diff --git a/arch/arm64/kernel/pi/pi.h b/arch/arm64/kernel/pi/pi.h index c91e5e965cd3..1f4731a4e17e 100644 --- a/arch/arm64/kernel/pi/pi.h +++ b/arch/arm64/kernel/pi/pi.h @@ -22,6 +22,7 @@ static inline void *prel64_to_pointer(const prel64_t *off= set) extern bool dynamic_scs_is_enabled; =20 extern pgd_t init_idmap_pg_dir[], init_idmap_pg_end[]; +extern pgd_t init_pg_dir[], init_pg_end[]; =20 void init_feature_override(u64 boot_status, const void *fdt, int chosen); u64 kaslr_early_init(void *fdt, int chosen); diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.ld= s.S index e73326bd3ff7..466544c47dca 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -249,9 +249,9 @@ SECTIONS __inittext_end =3D .; 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charset="utf-8" From: Ard Biesheuvel Accessing BSS will no longer be permitted from the startup code in arch/arm64/kernel/pi, as some of it executes before BSS is cleared. Clearing BSS earlier would involve managing cache coherency explicitly in software, which is a hassle we prefer to avoid. So move some variables that are assigned by the startup code out of BSS and into .data. Signed-off-by: Ard Biesheuvel Reviewed-by: Yeoreum Yun Tested-by: Yeoreum Yun --- arch/arm64/kernel/cpufeature.c | 22 ++++++++++---------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 4c46d80aa64b..2cac5e5ca94d 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -765,17 +765,17 @@ static const struct arm64_ftr_bits ftr_raz[] =3D { #define ARM64_FTR_REG(id, table) \ __ARM64_FTR_REG_OVERRIDE(#id, id, table, &no_override) =20 -struct arm64_ftr_override id_aa64mmfr0_override; -struct arm64_ftr_override id_aa64mmfr1_override; -struct arm64_ftr_override id_aa64mmfr2_override; -struct arm64_ftr_override id_aa64pfr0_override; -struct arm64_ftr_override id_aa64pfr1_override; -struct arm64_ftr_override id_aa64zfr0_override; -struct arm64_ftr_override id_aa64smfr0_override; -struct arm64_ftr_override id_aa64isar1_override; -struct arm64_ftr_override id_aa64isar2_override; - -struct arm64_ftr_override arm64_sw_feature_override; 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Thu, 08 May 2025 04:43:43 -0700 (PDT) Date: Thu, 8 May 2025 13:43:32 +0200 In-Reply-To: <20250508114328.2460610-5-ardb+git@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250508114328.2460610-5-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=4218; i=ardb@kernel.org; h=from:subject; bh=j8k/j5lLwOtOO5g2RunsS1a0UPrHZPgoaoPHRVCj0HU=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JIUNmxtNDLXyH4vbP5Hn2N3xteLLlH9mFD+alrm7kKly3W eLd4e+rO0pZGMQ4GGTFFFkEZv99t/P0RKla51myMHNYmUCGMHBxCsBEbi9lZGh+6vuo8tplgY66 2R3/RSr/Fy7eV5byx/cO7yFOxgb98iWMDHdPm57KuGFZE86venruP3lRDoPFOk/SGjfantBpO/x /FxcA X-Mailer: git-send-email 2.49.0.987.g0cc8ee98dc-goog Message-ID: <20250508114328.2460610-8-ardb+git@google.com> Subject: [PATCH v2 3/3] arm64/boot: Disallow BSS exports to startup code From: Ard Biesheuvel To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, Ard Biesheuvel , Yeoreum Yun Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Ard Biesheuvel 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 Reviewed-by: Yeoreum Yun Tested-by: Yeoreum Yun --- arch/arm64/kernel/image-vars.h | 62 +++++++++++--------- arch/arm64/kernel/vmlinux.lds.S | 2 + 2 files changed, 35 insertions(+), 29 deletions(-) diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h index c3b4c0479d5c..a928e0c0b45a 100644 --- a/arch/arm64/kernel/image-vars.h +++ b/arch/arm64/kernel/image-vars.h @@ -10,6 +10,12 @@ #error This file should only be included in vmlinux.lds.S #endif =20 +#define PI_EXPORT_SYM(sym) \ + __PI_EXPORT_SYM(sym, __pi_ ## sym, Cannot export BSS symbol sym to startu= p code) +#define __PI_EXPORT_SYM(sym, pisym, msg)\ + PROVIDE(pisym =3D sym); \ + ASSERT((sym - KIMAGE_VADDR) < (__bss_start - KIMAGE_VADDR), #msg) + PROVIDE(__efistub_primary_entry =3D primary_entry); =20 /* @@ -36,37 +42,35 @@ PROVIDE(__pi___memcpy =3D __pi_memcpy); PROVIDE(__pi___memmove =3D __pi_memmove); PROVIDE(__pi___memset =3D __pi_memset); =20 -PROVIDE(__pi_id_aa64isar1_override =3D id_aa64isar1_override); -PROVIDE(__pi_id_aa64isar2_override =3D id_aa64isar2_override); -PROVIDE(__pi_id_aa64mmfr0_override =3D id_aa64mmfr0_override); -PROVIDE(__pi_id_aa64mmfr1_override =3D id_aa64mmfr1_override); -PROVIDE(__pi_id_aa64mmfr2_override =3D id_aa64mmfr2_override); -PROVIDE(__pi_id_aa64pfr0_override =3D id_aa64pfr0_override); -PROVIDE(__pi_id_aa64pfr1_override =3D id_aa64pfr1_override); -PROVIDE(__pi_id_aa64smfr0_override =3D id_aa64smfr0_override); -PROVIDE(__pi_id_aa64zfr0_override =3D id_aa64zfr0_override); -PROVIDE(__pi_arm64_sw_feature_override =3D arm64_sw_feature_override); -PROVIDE(__pi_arm64_use_ng_mappings =3D 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 =3D cavium_erratum_27456_cpus); -PROVIDE(__pi_is_midr_in_range_list =3D is_midr_in_range_list); +PI_EXPORT_SYM(cavium_erratum_27456_cpus); +PI_EXPORT_SYM(is_midr_in_range_list); #endif -PROVIDE(__pi__ctype =3D _ctype); -PROVIDE(__pi_memstart_offset_seed =3D memstart_offset_seed); - -PROVIDE(__pi_swapper_pg_dir =3D swapper_pg_dir); - -PROVIDE(__pi__text =3D _text); -PROVIDE(__pi__stext =3D _stext); -PROVIDE(__pi__etext =3D _etext); -PROVIDE(__pi___start_rodata =3D __start_rodata); -PROVIDE(__pi___inittext_begin =3D __inittext_begin); -PROVIDE(__pi___inittext_end =3D __inittext_end); -PROVIDE(__pi___initdata_begin =3D __initdata_begin); -PROVIDE(__pi___initdata_end =3D __initdata_end); -PROVIDE(__pi__data =3D _data); -PROVIDE(__pi___bss_start =3D __bss_start); -PROVIDE(__pi__end =3D _end); +PI_EXPORT_SYM(_ctype); +PI_EXPORT_SYM(memstart_offset_seed); + +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); =20 #ifdef CONFIG_KVM =20 diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.ld= s.S index 466544c47dca..e4a525a865c1 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -319,6 +319,7 @@ SECTIONS =20 /* start of zero-init region */ BSS_SECTION(SBSS_ALIGN, 0, 0) + __pi___bss_start =3D __bss_start; =20 . =3D ALIGN(PAGE_SIZE); __pi_init_pg_dir =3D .; @@ -332,6 +333,7 @@ SECTIONS . =3D ALIGN(SEGMENT_ALIGN); __pecoff_data_size =3D ABSOLUTE(. - __initdata_begin); _end =3D .; + __pi__end =3D .; =20 STABS_DEBUG DWARF_DEBUG --=20 2.49.0.987.g0cc8ee98dc-goog