* [PATCH 1/3] arm64/boot: Move init_pgdir[] into __pi_ namespace
2025-05-03 11:21 [PATCH 0/3] arm64/boot: Forbid the use of BSS symbols in startup code Ard Biesheuvel
@ 2025-05-03 11:21 ` Ard Biesheuvel
2025-05-03 11:28 ` Ard Biesheuvel
` (2 more replies)
2025-05-03 11:21 ` [PATCH 3/3] arm64/boot: Disallow BSS exports to startup code Ard Biesheuvel
` (2 subsequent siblings)
3 siblings, 3 replies; 9+ messages in thread
From: Ard Biesheuvel @ 2025-05-03 11:21 UTC (permalink / raw)
To: linux-arm-kernel
Cc: linux-kernel, will, catalin.marinas, mark.rutland, Ard Biesheuvel,
Yeoreum Yun
From: Ard Biesheuvel <ardb@kernel.org>
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.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm64/include/asm/pgtable.h | 2 --
arch/arm64/kernel/image-vars.h | 2 --
arch/arm64/kernel/pi/pi.h | 1 +
arch/arm64/kernel/vmlinux.lds.S | 4 ++--
4 files changed, 3 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.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
-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/image-vars.h b/arch/arm64/kernel/image-vars.h
index 5e3c4b58f279..a0977f7cd3ec 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -56,8 +56,6 @@ 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_init_pg_dir = init_pg_dir);
-PROVIDE(__pi_init_pg_end = init_pg_end);
PROVIDE(__pi_swapper_pg_dir = swapper_pg_dir);
PROVIDE(__pi__text = _text);
diff --git a/arch/arm64/kernel/pi/pi.h b/arch/arm64/kernel/pi/pi.h
index c91e5e965cd3..38a908d048e8 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 *offset)
extern bool dynamic_scs_is_enabled;
extern pgd_t init_idmap_pg_dir[], init_idmap_pg_end[];
+extern pgd_t init_pg_dir[];
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.lds.S
index e73326bd3ff7..73fa57f341b0 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -321,9 +321,9 @@ SECTIONS
BSS_SECTION(SBSS_ALIGN, 0, 0)
. = ALIGN(PAGE_SIZE);
- init_pg_dir = .;
+ __pi_init_pg_dir = .;
. += INIT_DIR_SIZE;
- init_pg_end = .;
+ __pi_init_pg_end = .;
/* end of zero-init region */
. += SZ_4K; /* stack for the early C runtime */
--
2.49.0.906.g1f30a19c02-goog
^ permalink raw reply related [flat|nested] 9+ messages in thread* Re: [PATCH 1/3] arm64/boot: Move init_pgdir[] into __pi_ namespace
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
2 siblings, 0 replies; 9+ messages in thread
From: Ard Biesheuvel @ 2025-05-03 11:28 UTC (permalink / raw)
Cc: linux-arm-kernel, linux-kernel, will, catalin.marinas,
mark.rutland, Yeoreum Yun
On Sat, 3 May 2025 at 13:22, Ard Biesheuvel <ardb+git@google.com> wrote:
>
> From: Ard Biesheuvel <ardb@kernel.org>
>
> 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.
>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> arch/arm64/include/asm/pgtable.h | 2 --
> arch/arm64/kernel/image-vars.h | 2 --
> arch/arm64/kernel/pi/pi.h | 1 +
> arch/arm64/kernel/vmlinux.lds.S | 4 ++--
> 4 files changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.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
>
> -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/image-vars.h b/arch/arm64/kernel/image-vars.h
> index 5e3c4b58f279..a0977f7cd3ec 100644
> --- a/arch/arm64/kernel/image-vars.h
> +++ b/arch/arm64/kernel/image-vars.h
> @@ -56,8 +56,6 @@ 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_init_pg_dir = init_pg_dir);
> -PROVIDE(__pi_init_pg_end = init_pg_end);
> PROVIDE(__pi_swapper_pg_dir = swapper_pg_dir);
>
> PROVIDE(__pi__text = _text);
> diff --git a/arch/arm64/kernel/pi/pi.h b/arch/arm64/kernel/pi/pi.h
> index c91e5e965cd3..38a908d048e8 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 *offset)
> extern bool dynamic_scs_is_enabled;
>
> extern pgd_t init_idmap_pg_dir[], init_idmap_pg_end[];
> +extern pgd_t init_pg_dir[];
>
Apologies, I hit send too quickly - init_pg_end[] is missing here.
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH 1/3] arm64/boot: Move init_pgdir[] into __pi_ namespace
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
2 siblings, 0 replies; 9+ messages in thread
From: kernel test robot @ 2025-05-05 13:54 UTC (permalink / raw)
To: Ard Biesheuvel, linux-arm-kernel
Cc: llvm, oe-kbuild-all, linux-kernel, will, catalin.marinas,
mark.rutland, Ard Biesheuvel, Yeoreum Yun
Hi Ard,
kernel test robot noticed the following build errors:
[auto build test ERROR on soc/for-next]
[also build test ERROR on linus/master v6.15-rc5 next-20250505]
[cannot apply to arm64/for-next/core kvmarm/next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Ard-Biesheuvel/arm64-boot-Move-init_pgdir-into-__pi_-namespace/20250503-192534
base: https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git for-next
patch link: https://lore.kernel.org/r/20250503112137.1962910-6-ardb%2Bgit%40google.com
patch subject: [PATCH 1/3] arm64/boot: Move init_pgdir[] into __pi_ namespace
config: arm64-randconfig-001-20250505 (https://download.01.org/0day-ci/archive/20250505/202505052102.U2NQHrS4-lkp@intel.com/config)
compiler: clang version 21.0.0git (https://github.com/llvm/llvm-project f819f46284f2a79790038e1f6649172789734ae8)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250505/202505052102.U2NQHrS4-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202505052102.U2NQHrS4-lkp@intel.com/
All errors (new ones prefixed by >>):
>> arch/arm64/kernel/pi/map_kernel.c:191:30: error: use of undeclared identifier 'init_pg_end'
191 | memset(init_pg_dir, 0, (u64)init_pg_end - (u64)init_pg_dir);
| ^
arch/arm64/kernel/pi/map_kernel.c:222:30: error: use of undeclared identifier 'init_pg_end'
222 | memset(__bss_start, 0, (u64)init_pg_end - (u64)__bss_start);
| ^
2 errors generated.
vim +/init_pg_end +191 arch/arm64/kernel/pi/map_kernel.c
9684ec186f8fadd Ard Biesheuvel 2024-02-14 158
9684ec186f8fadd Ard Biesheuvel 2024-02-14 159 static void __init remap_idmap_for_lpa2(void)
9684ec186f8fadd Ard Biesheuvel 2024-02-14 160 {
9684ec186f8fadd Ard Biesheuvel 2024-02-14 161 /* clear the bits that change meaning once LPA2 is turned on */
9684ec186f8fadd Ard Biesheuvel 2024-02-14 162 pteval_t mask = PTE_SHARED;
9684ec186f8fadd Ard Biesheuvel 2024-02-14 163
9684ec186f8fadd Ard Biesheuvel 2024-02-14 164 /*
9684ec186f8fadd Ard Biesheuvel 2024-02-14 165 * We have to clear bits [9:8] in all block or page descriptors in the
9684ec186f8fadd Ard Biesheuvel 2024-02-14 166 * initial ID map, as otherwise they will be (mis)interpreted as
9684ec186f8fadd Ard Biesheuvel 2024-02-14 167 * physical address bits once we flick the LPA2 switch (TCR.DS). Since
9684ec186f8fadd Ard Biesheuvel 2024-02-14 168 * we cannot manipulate live descriptors in that way without creating
9684ec186f8fadd Ard Biesheuvel 2024-02-14 169 * potential TLB conflicts, let's create another temporary ID map in a
9684ec186f8fadd Ard Biesheuvel 2024-02-14 170 * LPA2 compatible fashion, and update the initial ID map while running
9684ec186f8fadd Ard Biesheuvel 2024-02-14 171 * from that.
9684ec186f8fadd Ard Biesheuvel 2024-02-14 172 */
9684ec186f8fadd Ard Biesheuvel 2024-02-14 173 create_init_idmap(init_pg_dir, mask);
9684ec186f8fadd Ard Biesheuvel 2024-02-14 174 dsb(ishst);
9684ec186f8fadd Ard Biesheuvel 2024-02-14 175 set_ttbr0_for_lpa2((u64)init_pg_dir);
9684ec186f8fadd Ard Biesheuvel 2024-02-14 176
9684ec186f8fadd Ard Biesheuvel 2024-02-14 177 /*
9684ec186f8fadd Ard Biesheuvel 2024-02-14 178 * Recreate the initial ID map with the same granularity as before.
9684ec186f8fadd Ard Biesheuvel 2024-02-14 179 * Don't bother with the FDT, we no longer need it after this.
9684ec186f8fadd Ard Biesheuvel 2024-02-14 180 */
9684ec186f8fadd Ard Biesheuvel 2024-02-14 181 memset(init_idmap_pg_dir, 0,
ecc54006f158ae0 Zenghui Yu 2024-06-21 182 (u64)init_idmap_pg_end - (u64)init_idmap_pg_dir);
9684ec186f8fadd Ard Biesheuvel 2024-02-14 183
9684ec186f8fadd Ard Biesheuvel 2024-02-14 184 create_init_idmap(init_idmap_pg_dir, mask);
9684ec186f8fadd Ard Biesheuvel 2024-02-14 185 dsb(ishst);
9684ec186f8fadd Ard Biesheuvel 2024-02-14 186
9684ec186f8fadd Ard Biesheuvel 2024-02-14 187 /* switch back to the updated initial ID map */
9684ec186f8fadd Ard Biesheuvel 2024-02-14 188 set_ttbr0_for_lpa2((u64)init_idmap_pg_dir);
9684ec186f8fadd Ard Biesheuvel 2024-02-14 189
9684ec186f8fadd Ard Biesheuvel 2024-02-14 190 /* wipe the temporary ID map from memory */
9684ec186f8fadd Ard Biesheuvel 2024-02-14 @191 memset(init_pg_dir, 0, (u64)init_pg_end - (u64)init_pg_dir);
9684ec186f8fadd Ard Biesheuvel 2024-02-14 192 }
9684ec186f8fadd Ard Biesheuvel 2024-02-14 193
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH 1/3] arm64/boot: Move init_pgdir[] into __pi_ namespace
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
2 siblings, 0 replies; 9+ messages in thread
From: kernel test robot @ 2025-05-05 23:50 UTC (permalink / raw)
To: Ard Biesheuvel, linux-arm-kernel
Cc: oe-kbuild-all, linux-kernel, will, catalin.marinas, mark.rutland,
Ard Biesheuvel, Yeoreum Yun
Hi Ard,
kernel test robot noticed the following build errors:
[auto build test ERROR on soc/for-next]
[also build test ERROR on arm/for-next arm/fixes linus/master v6.15-rc5 next-20250505]
[cannot apply to arm64/for-next/core kvmarm/next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Ard-Biesheuvel/arm64-boot-Move-init_pgdir-into-__pi_-namespace/20250503-192534
base: https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git for-next
patch link: https://lore.kernel.org/r/20250503112137.1962910-6-ardb%2Bgit%40google.com
patch subject: [PATCH 1/3] arm64/boot: Move init_pgdir[] into __pi_ namespace
config: arm64-allnoconfig (https://download.01.org/0day-ci/archive/20250506/202505060740.OIkWGFVZ-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250506/202505060740.OIkWGFVZ-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202505060740.OIkWGFVZ-lkp@intel.com/
All errors (new ones prefixed by >>):
arch/arm64/kernel/pi/map_kernel.c: In function 'remap_idmap_for_lpa2':
>> arch/arm64/kernel/pi/map_kernel.c:191:37: error: 'init_pg_end' undeclared (first use in this function); did you mean 'init_pg_dir'?
191 | memset(init_pg_dir, 0, (u64)init_pg_end - (u64)init_pg_dir);
| ^~~~~~~~~~~
| init_pg_dir
arch/arm64/kernel/pi/map_kernel.c:191:37: note: each undeclared identifier is reported only once for each function it appears in
arch/arm64/kernel/pi/map_kernel.c: In function 'early_map_kernel':
arch/arm64/kernel/pi/map_kernel.c:222:37: error: 'init_pg_end' undeclared (first use in this function); did you mean 'init_pg_dir'?
222 | memset(__bss_start, 0, (u64)init_pg_end - (u64)__bss_start);
| ^~~~~~~~~~~
| init_pg_dir
vim +191 arch/arm64/kernel/pi/map_kernel.c
9684ec186f8fad Ard Biesheuvel 2024-02-14 158
9684ec186f8fad Ard Biesheuvel 2024-02-14 159 static void __init remap_idmap_for_lpa2(void)
9684ec186f8fad Ard Biesheuvel 2024-02-14 160 {
9684ec186f8fad Ard Biesheuvel 2024-02-14 161 /* clear the bits that change meaning once LPA2 is turned on */
9684ec186f8fad Ard Biesheuvel 2024-02-14 162 pteval_t mask = PTE_SHARED;
9684ec186f8fad Ard Biesheuvel 2024-02-14 163
9684ec186f8fad Ard Biesheuvel 2024-02-14 164 /*
9684ec186f8fad Ard Biesheuvel 2024-02-14 165 * We have to clear bits [9:8] in all block or page descriptors in the
9684ec186f8fad Ard Biesheuvel 2024-02-14 166 * initial ID map, as otherwise they will be (mis)interpreted as
9684ec186f8fad Ard Biesheuvel 2024-02-14 167 * physical address bits once we flick the LPA2 switch (TCR.DS). Since
9684ec186f8fad Ard Biesheuvel 2024-02-14 168 * we cannot manipulate live descriptors in that way without creating
9684ec186f8fad Ard Biesheuvel 2024-02-14 169 * potential TLB conflicts, let's create another temporary ID map in a
9684ec186f8fad Ard Biesheuvel 2024-02-14 170 * LPA2 compatible fashion, and update the initial ID map while running
9684ec186f8fad Ard Biesheuvel 2024-02-14 171 * from that.
9684ec186f8fad Ard Biesheuvel 2024-02-14 172 */
9684ec186f8fad Ard Biesheuvel 2024-02-14 173 create_init_idmap(init_pg_dir, mask);
9684ec186f8fad Ard Biesheuvel 2024-02-14 174 dsb(ishst);
9684ec186f8fad Ard Biesheuvel 2024-02-14 175 set_ttbr0_for_lpa2((u64)init_pg_dir);
9684ec186f8fad Ard Biesheuvel 2024-02-14 176
9684ec186f8fad Ard Biesheuvel 2024-02-14 177 /*
9684ec186f8fad Ard Biesheuvel 2024-02-14 178 * Recreate the initial ID map with the same granularity as before.
9684ec186f8fad Ard Biesheuvel 2024-02-14 179 * Don't bother with the FDT, we no longer need it after this.
9684ec186f8fad Ard Biesheuvel 2024-02-14 180 */
9684ec186f8fad Ard Biesheuvel 2024-02-14 181 memset(init_idmap_pg_dir, 0,
ecc54006f158ae Zenghui Yu 2024-06-21 182 (u64)init_idmap_pg_end - (u64)init_idmap_pg_dir);
9684ec186f8fad Ard Biesheuvel 2024-02-14 183
9684ec186f8fad Ard Biesheuvel 2024-02-14 184 create_init_idmap(init_idmap_pg_dir, mask);
9684ec186f8fad Ard Biesheuvel 2024-02-14 185 dsb(ishst);
9684ec186f8fad Ard Biesheuvel 2024-02-14 186
9684ec186f8fad Ard Biesheuvel 2024-02-14 187 /* switch back to the updated initial ID map */
9684ec186f8fad Ard Biesheuvel 2024-02-14 188 set_ttbr0_for_lpa2((u64)init_idmap_pg_dir);
9684ec186f8fad Ard Biesheuvel 2024-02-14 189
9684ec186f8fad Ard Biesheuvel 2024-02-14 190 /* wipe the temporary ID map from memory */
9684ec186f8fad Ard Biesheuvel 2024-02-14 @191 memset(init_pg_dir, 0, (u64)init_pg_end - (u64)init_pg_dir);
9684ec186f8fad Ard Biesheuvel 2024-02-14 192 }
9684ec186f8fad Ard Biesheuvel 2024-02-14 193
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH 3/3] arm64/boot: Disallow BSS exports to startup code
2025-05-03 11:21 [PATCH 0/3] arm64/boot: Forbid the use of BSS symbols in startup code Ard Biesheuvel
2025-05-03 11:21 ` [PATCH 1/3] arm64/boot: Move init_pgdir[] into __pi_ namespace Ard Biesheuvel
@ 2025-05-03 11:21 ` Ard Biesheuvel
2025-05-03 11:45 ` 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
3 siblings, 1 reply; 9+ messages in thread
From: Ard Biesheuvel @ 2025-05-03 11:21 UTC (permalink / raw)
To: linux-arm-kernel
Cc: linux-kernel, will, catalin.marinas, mark.rutland, Ard Biesheuvel,
Yeoreum Yun
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
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH 3/3] arm64/boot: Disallow BSS exports to startup code
2025-05-03 11:21 ` [PATCH 3/3] arm64/boot: Disallow BSS exports to startup code Ard Biesheuvel
@ 2025-05-03 11:45 ` Ard Biesheuvel
0 siblings, 0 replies; 9+ messages in thread
From: Ard Biesheuvel @ 2025-05-03 11:45 UTC (permalink / raw)
To: Ard Biesheuvel
Cc: linux-arm-kernel, linux-kernel, will, catalin.marinas,
mark.rutland, Yeoreum Yun
On Sat, 3 May 2025 at 13:22, Ard Biesheuvel <ardb+git@google.com> wrote:
>
> 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)
LLD doesn't seem to love this. I'll replace this with
ASSERT((sym - KIMAGE_VADDR) < (__bss_start - KIMAGE_VADDR), #msg)
which appears to work for both LLD and ld.bfd
> +
> 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
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH 2/3] arm64/boot: Move global CPU override variables out of BSS
2025-05-03 11:21 [PATCH 0/3] arm64/boot: Forbid the use of BSS symbols in startup code Ard Biesheuvel
2025-05-03 11:21 ` [PATCH 1/3] arm64/boot: Move init_pgdir[] into __pi_ namespace Ard Biesheuvel
2025-05-03 11:21 ` [PATCH 3/3] arm64/boot: Disallow BSS exports to startup code Ard Biesheuvel
@ 2025-05-03 11:21 ` Ard Biesheuvel
2025-05-08 11:14 ` [PATCH 0/3] arm64/boot: Forbid the use of BSS symbols in startup code Yeoreum Yun
3 siblings, 0 replies; 9+ messages in thread
From: Ard Biesheuvel @ 2025-05-03 11:21 UTC (permalink / raw)
To: linux-arm-kernel
Cc: linux-kernel, will, catalin.marinas, mark.rutland, Ard Biesheuvel,
Yeoreum Yun
From: Ard Biesheuvel <ardb@kernel.org>
Accessing BSS will no longer be permitted form 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 <ardb@kernel.org>
---
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 9c4d6d552b25..4f7a8050ab85 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -758,17 +758,17 @@ static const struct arm64_ftr_bits ftr_raz[] = {
#define ARM64_FTR_REG(id, table) \
__ARM64_FTR_REG_OVERRIDE(#id, id, table, &no_override)
-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;
+struct arm64_ftr_override __section(".data") id_aa64mmfr0_override;
+struct arm64_ftr_override __section(".data") id_aa64mmfr1_override;
+struct arm64_ftr_override __section(".data") id_aa64mmfr2_override;
+struct arm64_ftr_override __section(".data") id_aa64pfr0_override;
+struct arm64_ftr_override __section(".data") id_aa64pfr1_override;
+struct arm64_ftr_override __section(".data") id_aa64zfr0_override;
+struct arm64_ftr_override __section(".data") id_aa64smfr0_override;
+struct arm64_ftr_override __section(".data") id_aa64isar1_override;
+struct arm64_ftr_override __section(".data") id_aa64isar2_override;
+
+struct arm64_ftr_override __section(".data") arm64_sw_feature_override;
static const struct __ftr_reg_entry {
u32 sys_id;
--
2.49.0.906.g1f30a19c02-goog
^ permalink raw reply related [flat|nested] 9+ messages in thread* Re: [PATCH 0/3] arm64/boot: Forbid the use of BSS symbols in startup code
2025-05-03 11:21 [PATCH 0/3] arm64/boot: Forbid the use of BSS symbols in startup code Ard Biesheuvel
` (2 preceding siblings ...)
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 ` Yeoreum Yun
3 siblings, 0 replies; 9+ messages in thread
From: Yeoreum Yun @ 2025-05-08 11:14 UTC (permalink / raw)
To: Ard Biesheuvel
Cc: linux-arm-kernel, linux-kernel, will, catalin.marinas,
mark.rutland, Ard Biesheuvel
Hi Ard,
> From: Ard Biesheuvel <ardb@kernel.org>
>
> Move any variables accessed or assigned by the startup code out of BSS,
> and into .data, so that we can forbid the use of BSS variables
> altogether, by ASSERT()'ing in the linker script that each symbol made
> available to the startup code lives before __bss_start in the linker
> map.
>
> Cc: Yeoreum Yun <yeoreum.yun@arm.com>
Thanks for ccing me and with the your fix it looks good to me.
When you send the patch with fix, I'll test it.
Thanks.
--
Sincerely,
Yeoreum Yun
^ permalink raw reply [flat|nested] 9+ messages in thread