From: Ard Biesheuvel <ardb+git@google.com>
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 <ardb@kernel.org>,
Yeoreum Yun <yeoreum.yun@arm.com>
Subject: [PATCH 3/3] arm64/boot: Disallow BSS exports to startup code
Date: Sat, 3 May 2025 13:21:40 +0200 [thread overview]
Message-ID: <20250503112137.1962910-7-ardb+git@google.com> (raw)
In-Reply-To: <20250503112137.1962910-5-ardb+git@google.com>
From: Ard Biesheuvel <ardb@kernel.org>
BSS might be uninitialized when entering the startup code, so forbid the
use of any variables that live after __bss_start in the linker map.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/kernel/image-vars.h | 66 +++++++++++---------
arch/arm64/kernel/vmlinux.lds.S | 2 +
2 files changed, 37 insertions(+), 31 deletions(-)
diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index a0977f7cd3ec..a70244d1aa2a 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
+#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 < __bss_start, #msg)
+
PROVIDE(__efistub_primary_entry = primary_entry);
/*
@@ -36,39 +42,37 @@ 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_memstart_offset_seed = memstart_offset_seed);
-
-PROVIDE(__pi_init_idmap_pg_dir = init_idmap_pg_dir);
-PROVIDE(__pi_init_idmap_pg_end = init_idmap_pg_end);
-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(memstart_offset_seed);
+
+PI_EXPORT_SYM(init_idmap_pg_dir);
+PI_EXPORT_SYM(init_idmap_pg_end);
+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
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 73fa57f341b0..bd7626b8c7a3 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -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
--
2.49.0.906.g1f30a19c02-goog
next prev parent reply other threads:[~2025-05-03 11:22 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-03 11:21 [PATCH 0/3] arm64/boot: Forbid the use of BSS symbols in " Ard Biesheuvel
2025-05-03 11:21 ` [PATCH 1/3] arm64/boot: Move init_pgdir[] into __pi_ namespace Ard Biesheuvel
2025-05-03 11:28 ` Ard Biesheuvel
2025-05-05 13:54 ` kernel test robot
2025-05-05 23:50 ` kernel test robot
2025-05-03 11:21 ` Ard Biesheuvel [this message]
2025-05-03 11:45 ` [PATCH 3/3] arm64/boot: Disallow BSS exports to startup code Ard Biesheuvel
2025-05-03 11:21 ` [PATCH 2/3] arm64/boot: Move global CPU override variables out of BSS Ard Biesheuvel
2025-05-08 11:14 ` [PATCH 0/3] arm64/boot: Forbid the use of BSS symbols in startup code Yeoreum Yun
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