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Message-ID: <955d3fda-fe94-44c1-8479-d1b46e2f1140@ghiti.fr>
Date: Tue, 9 Jan 2024 13:54:38 +0100
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User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH 2/4] arm64, powerpc, riscv, s390, x86: Refactor
 CONFIG_DEBUG_WX
Content-Language: en-US
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
 linux-hardening@vger.kernel.org, Russell King <linux@armlinux.org.uk>,
 Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>,
 Michael Ellerman <mpe@ellerman.id.au>, Nicholas Piggin <npiggin@gmail.com>,
 "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>,
 "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
 Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt
 <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>,
 Heiko Carstens <hca@linux.ibm.com>, Vasily Gorbik <gor@linux.ibm.com>,
 Alexander Gordeev <agordeev@linux.ibm.com>,
 Christian Borntraeger <borntraeger@linux.ibm.com>,
 Sven Schnelle <svens@linux.ibm.com>,
 Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
 Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
 Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>,
 x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
 Andy Lutomirski <luto@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
 Andrew Morton <akpm@linux-foundation.org>, Kees Cook <keescook@chromium.org>
Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
 linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
 linux-s390@vger.kernel.org, linux-mm@kvack.org, steven.price@arm.com,
 Phong Tran <tranmanphong@gmail.com>, mark.rutland@arm.com,
 Greg KH <greg@kroah.com>
References: <cover.1704800524.git.christophe.leroy@csgroup.eu>
 <b1e2171587806648500fd305918bc7e90abdeeb5.1704800524.git.christophe.leroy@csgroup.eu>
From: Alexandre Ghiti <alex@ghiti.fr>
In-Reply-To: <b1e2171587806648500fd305918bc7e90abdeeb5.1704800524.git.christophe.leroy@csgroup.eu>
Content-Type: text/plain; charset=UTF-8; format=flowed
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Hi Christophe,

On 09/01/2024 13:14, Christophe Leroy 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>
> ---
>   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 15f6347d23b6..e011beb2e5e3 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -635,8 +635,6 @@ 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 2e011cbddf3a..55c4deb1b332 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>
> @@ -720,8 +719,6 @@ 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>
>   


For riscv, you can add:

Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>

Thanks,

Alex


> 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 57bab91bbf50..036ce63f3b95 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 a190aae8ceaf..16e248769338 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");