Re: [PATCH 2/4] arm64, powerpc, riscv, s390, x86: Refactor CONFIG_DEBUG_WX

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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@xxxxxxxxxx>
---
  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@xxxxxxxxxxxx>

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");




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