Re: [PATCH v2 2/5] arm64, powerpc, riscv, s390, x86: ptdump: Refactor CONFIG_DEBUG_WX

Palmer Dabbelt
2024-03-27T14:38:34Z

On Tue, 30 Jan 2024 02:34:33 PST (-0800), christophe.leroy@csgroup.eu wrote:
> All architectures using the core ptdump functionality also implement
> CONFIG_DEBUG_WX, and they all do it more or less the same way, with a
> function called debug_checkwx() that is called by mark_rodata_ro(),
> which is a substitute to ptdump_check_wx() when CONFIG_DEBUG_WX is
> set and a no-op otherwise.
>
> Refactor by centraly defining debug_checkwx() in linux/ptdump.h and
> call debug_checkwx() immediately after calling mark_rodata_ro()
> instead of calling it at the end of every mark_rodata_ro().
>
> On x86_32, mark_rodata_ro() first checks __supported_pte_mask has
> _PAGE_NX before calling debug_checkwx(). Now the check is inside the
> callee ptdump_walk_pgd_level_checkwx().
>
> On powerpc_64, mark_rodata_ro() bails out early before calling
> ptdump_check_wx() when the MMU doesn't have KERNEL_RO feature. The
> check is now also done in ptdump_check_wx() as it is called outside
> mark_rodata_ro().
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> ---
> v2: For x86 change macro ptdump_check_wx() to ptdump_check_wx
> ---
> arch/arm64/include/asm/ptdump.h | 7 -------
> arch/arm64/mm/mmu.c | 2 --
> arch/powerpc/mm/mmu_decl.h | 6 ------
> arch/powerpc/mm/pgtable_32.c | 4 ----
> arch/powerpc/mm/pgtable_64.c | 3 ---
> arch/powerpc/mm/ptdump/ptdump.c | 3 +++
> arch/riscv/include/asm/ptdump.h | 22 ----------------------
> arch/riscv/mm/init.c | 3 ---
> arch/riscv/mm/ptdump.c | 1 -
> arch/s390/include/asm/ptdump.h | 14 --------------
> arch/s390/mm/dump_pagetables.c | 1 -
> arch/s390/mm/init.c | 2 --
> arch/x86/include/asm/pgtable.h | 3 +--
> arch/x86/mm/dump_pagetables.c | 3 +++
> arch/x86/mm/init_32.c | 2 --
> arch/x86/mm/init_64.c | 2 --
> include/linux/ptdump.h | 7 +++++++
> init/main.c | 2 ++
> 18 files changed, 16 insertions(+), 71 deletions(-)
> delete mode 100644 arch/riscv/include/asm/ptdump.h
> delete mode 100644 arch/s390/include/asm/ptdump.h
>
> diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> index 581caac525b0..5b1701c76d1c 100644
> --- a/arch/arm64/include/asm/ptdump.h
> +++ b/arch/arm64/include/asm/ptdump.h
> @@ -29,13 +29,6 @@ void __init ptdump_debugfs_register(struct ptdump_info *info, const char *name);
> static inline void ptdump_debugfs_register(struct ptdump_info *info,
> const char *name) { }
> #endif
> -void ptdump_check_wx(void);
> #endif /* CONFIG_PTDUMP_CORE */
>
> -#ifdef CONFIG_DEBUG_WX
> -#define debug_checkwx() ptdump_check_wx()
> -#else
> -#define debug_checkwx() do { } while (0)
> -#endif
> -
> #endif /* __ASM_PTDUMP_H */
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 1ac7467d34c9..3a27d887f7dd 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -632,8 +632,6 @@ void mark_rodata_ro(void)
> section_size = (unsigned long)__init_begin - (unsigned long)__start_rodata;
> update_mapping_prot(__pa_symbol(__start_rodata), (unsigned long)__start_rodata,
> section_size, PAGE_KERNEL_RO);
> -
> - debug_checkwx();
> }
>
> static void __init map_kernel_segment(pgd_t *pgdp, void *va_start, void *va_end,
> diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
> index 72341b9fb552..90dcc2844056 100644
> --- a/arch/powerpc/mm/mmu_decl.h
> +++ b/arch/powerpc/mm/mmu_decl.h
> @@ -171,12 +171,6 @@ static inline void mmu_mark_rodata_ro(void) { }
> void __init mmu_mapin_immr(void);
> #endif
>
> -#ifdef CONFIG_DEBUG_WX
> -void ptdump_check_wx(void);
> -#else
> -static inline void ptdump_check_wx(void) { }
> -#endif
> -
> static inline bool debug_pagealloc_enabled_or_kfence(void)
> {
> return IS_ENABLED(CONFIG_KFENCE) || debug_pagealloc_enabled();
> diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
> index 5c02fd08d61e..12498017da8e 100644
> --- a/arch/powerpc/mm/pgtable_32.c
> +++ b/arch/powerpc/mm/pgtable_32.c
> @@ -153,7 +153,6 @@ void mark_rodata_ro(void)
>
> if (v_block_mapped((unsigned long)_stext + 1)) {
> mmu_mark_rodata_ro();
> - ptdump_check_wx();
> return;
> }
>
> @@ -166,9 +165,6 @@ void mark_rodata_ro(void)
> PFN_DOWN((unsigned long)_stext);
>
> set_memory_ro((unsigned long)_stext, numpages);
> -
> - // mark_initmem_nx() should have already run by now
> - ptdump_check_wx();
> }
> #endif
>
> diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
> index 5ac1fd30341b..1b366526f4f2 100644
> --- a/arch/powerpc/mm/pgtable_64.c
> +++ b/arch/powerpc/mm/pgtable_64.c
> @@ -150,9 +150,6 @@ void mark_rodata_ro(void)
> radix__mark_rodata_ro();
> else
> hash__mark_rodata_ro();
> -
> - // mark_initmem_nx() should have already run by now
> - ptdump_check_wx();
> }
>
> void mark_initmem_nx(void)
> diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
> index 2313053fe679..620d4917ebe8 100644
> --- a/arch/powerpc/mm/ptdump/ptdump.c
> +++ b/arch/powerpc/mm/ptdump/ptdump.c
> @@ -343,6 +343,9 @@ void ptdump_check_wx(void)
> }
> };
>
> + if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && !mmu_has_feature(MMU_FTR_KERNEL_RO))
> + return;
> +
> ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
>
> if (st.wx_pages)
> diff --git a/arch/riscv/include/asm/ptdump.h b/arch/riscv/include/asm/ptdump.h
> deleted file mode 100644
> index 3c9ea6dd5af7..000000000000
> --- a/arch/riscv/include/asm/ptdump.h
> +++ /dev/null
> @@ -1,22 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0 */
> -/*
> - * Copyright (C) 2019 SiFive
> - */
> -
> -#ifndef _ASM_RISCV_PTDUMP_H
> -#define _ASM_RISCV_PTDUMP_H
> -
> -void ptdump_check_wx(void);
> -
> -#ifdef CONFIG_DEBUG_WX
> -static inline void debug_checkwx(void)
> -{
> - ptdump_check_wx();
> -}
> -#else
> -static inline void debug_checkwx(void)
> -{
> -}
> -#endif
> -
> -#endif /* _ASM_RISCV_PTDUMP_H */
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 32cad6a65ccd..c5c69f38d11e 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -29,7 +29,6 @@
> #include <asm/io.h>
> #include <asm/numa.h>
> #include <asm/pgtable.h>
> -#include <asm/ptdump.h>
> #include <asm/sections.h>
> #include <asm/soc.h>
> #include <asm/tlbflush.h>
> @@ -723,8 +722,6 @@ void mark_rodata_ro(void)
> if (IS_ENABLED(CONFIG_64BIT))
> set_kernel_memory(lm_alias(__start_rodata), lm_alias(_data),
> set_memory_ro);
> -
> - debug_checkwx();
> }
> #else
> static __init pgprot_t pgprot_from_va(uintptr_t va)
> diff --git a/arch/riscv/mm/ptdump.c b/arch/riscv/mm/ptdump.c
> index 657c27bc07a7..075265603313 100644
> --- a/arch/riscv/mm/ptdump.c
> +++ b/arch/riscv/mm/ptdump.c
> @@ -9,7 +9,6 @@
> #include <linux/seq_file.h>
> #include <linux/ptdump.h>
>
> -#include <asm/ptdump.h>
> #include <linux/pgtable.h>
> #include <asm/kasan.h>
>
> diff --git a/arch/s390/include/asm/ptdump.h b/arch/s390/include/asm/ptdump.h
> deleted file mode 100644
> index f960b2896606..000000000000
> --- a/arch/s390/include/asm/ptdump.h
> +++ /dev/null
> @@ -1,14 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0 */
> -
> -#ifndef _ASM_S390_PTDUMP_H
> -#define _ASM_S390_PTDUMP_H
> -
> -void ptdump_check_wx(void);
> -
> -static inline void debug_checkwx(void)
> -{
> - if (IS_ENABLED(CONFIG_DEBUG_WX))
> - ptdump_check_wx();
> -}
> -
> -#endif /* _ASM_S390_PTDUMP_H */
> diff --git a/arch/s390/mm/dump_pagetables.c b/arch/s390/mm/dump_pagetables.c
> index d37a8f607b71..8dcb4e0c71bd 100644
> --- a/arch/s390/mm/dump_pagetables.c
> +++ b/arch/s390/mm/dump_pagetables.c
> @@ -6,7 +6,6 @@
> #include <linux/mm.h>
> #include <linux/kfence.h>
> #include <linux/kasan.h>
> -#include <asm/ptdump.h>
> #include <asm/kasan.h>
> #include <asm/abs_lowcore.h>
> #include <asm/nospec-branch.h>
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index 43e612bc2bcd..d2e5eff9d1de 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -37,7 +37,6 @@
> #include <asm/pgalloc.h>
> #include <asm/ctlreg.h>
> #include <asm/kfence.h>
> -#include <asm/ptdump.h>
> #include <asm/dma.h>
> #include <asm/abs_lowcore.h>
> #include <asm/tlb.h>
> @@ -109,7 +108,6 @@ void mark_rodata_ro(void)
>
> __set_memory_ro(__start_ro_after_init, __end_ro_after_init);
> pr_info("Write protected read-only-after-init data: %luk\n", size >> 10);
> - debug_checkwx();
> }
>
> int set_memory_encrypted(unsigned long vaddr, int numpages)
> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
> index 9d077bca6a10..6c979028e521 100644
> --- a/arch/x86/include/asm/pgtable.h
> +++ b/arch/x86/include/asm/pgtable.h
> @@ -32,6 +32,7 @@ void ptdump_walk_pgd_level(struct seq_file *m, struct mm_struct *mm);
> void ptdump_walk_pgd_level_debugfs(struct seq_file *m, struct mm_struct *mm,
> bool user);
> void ptdump_walk_pgd_level_checkwx(void);
> +#define ptdump_check_wx ptdump_walk_pgd_level_checkwx
> void ptdump_walk_user_pgd_level_checkwx(void);
>
> /*
> @@ -41,10 +42,8 @@ void ptdump_walk_user_pgd_level_checkwx(void);
> #define pgprot_decrypted(prot) __pgprot(cc_mkdec(pgprot_val(prot)))
>
> #ifdef CONFIG_DEBUG_WX
> -#define debug_checkwx() ptdump_walk_pgd_level_checkwx()
> #define debug_checkwx_user() ptdump_walk_user_pgd_level_checkwx()
> #else
> -#define debug_checkwx() do { } while (0)
> #define debug_checkwx_user() do { } while (0)
> #endif
>
> diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
> index e1b599ecbbc2..0008524eebe9 100644
> --- a/arch/x86/mm/dump_pagetables.c
> +++ b/arch/x86/mm/dump_pagetables.c
> @@ -433,6 +433,9 @@ void ptdump_walk_user_pgd_level_checkwx(void)
>
> void ptdump_walk_pgd_level_checkwx(void)
> {
> + if (!(__supported_pte_mask & _PAGE_NX))
> + return;
> +
> ptdump_walk_pgd_level_core(NULL, &init_mm, INIT_PGD, true, false);
> }
>
> diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
> index b63403d7179d..5c736b707cae 100644
> --- a/arch/x86/mm/init_32.c
> +++ b/arch/x86/mm/init_32.c
> @@ -800,6 +800,4 @@ void mark_rodata_ro(void)
> set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);
> #endif
> mark_nxdata_nx();
> - if (__supported_pte_mask & _PAGE_NX)
> - debug_checkwx();
> }
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index a0dffaca6d2b..ebdbcae48011 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -1412,8 +1412,6 @@ void mark_rodata_ro(void)
> (void *)text_end, (void *)rodata_start);
> free_kernel_image_pages("unused kernel image (rodata/data gap)",
> (void *)rodata_end, (void *)_sdata);
> -
> - debug_checkwx();
> }
>
> /*
> diff --git a/include/linux/ptdump.h b/include/linux/ptdump.h
> index 2a3a95586425..c10513739bf9 100644
> --- a/include/linux/ptdump.h
> +++ b/include/linux/ptdump.h
> @@ -19,5 +19,12 @@ struct ptdump_state {
> };
>
> void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd);
> +void ptdump_check_wx(void);
> +
> +static inline void debug_checkwx(void)
> +{
> + if (IS_ENABLED(CONFIG_DEBUG_WX))
> + ptdump_check_wx();
> +}
>
> #endif /* _LINUX_PTDUMP_H */
> diff --git a/init/main.c b/init/main.c
> index e24b0780fdff..749a9f8d2c9b 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -99,6 +99,7 @@
> #include <linux/init_syscalls.h>
> #include <linux/stackdepot.h>
> #include <linux/randomize_kstack.h>
> +#include <linux/ptdump.h>
> #include <net/net_namespace.h>
>
> #include <asm/io.h>
> @@ -1408,6 +1409,7 @@ static void mark_readonly(void)
> */
> rcu_barrier();
> mark_rodata_ro();
> + debug_checkwx();
> rodata_test();
> } else
> pr_info("Kernel memory protection disabled.\n");

Acked-by: Palmer Dabbelt <palmer@rivosinc.com> # RISC-V