Thread (21 messages) 21 messages, 2 authors, 2021-05-05

Re: [PATCH v11 3/9] powerpc: Always define MODULES_{VADDR,END}

From: Christophe Leroy <hidden>
Date: 2021-04-29 05:04:35


Le 29/04/2021 à 05:15, Jordan Niethe a écrit :
quoted hunk ↗ jump to hunk
If MODULES_{VADDR,END} are not defined set them to VMALLOC_START and
VMALLOC_END respectively. This reduces the need for special cases. For
example, powerpc's module_alloc() was previously predicated on
MODULES_VADDR being defined but now is unconditionally defined.

This will be useful reducing conditional code in other places that need
to allocate from the module region (i.e., kprobes).

Signed-off-by: Jordan Niethe <redacted>
---
v10: New to series
v11: - Consider more places MODULES_VADDR was being used
---
  arch/powerpc/include/asm/pgtable.h    | 11 +++++++++++
  arch/powerpc/kernel/module.c          |  5 +----
  arch/powerpc/mm/kasan/kasan_init_32.c | 10 +++++-----
  arch/powerpc/mm/ptdump/ptdump.c       |  4 ++--
  4 files changed, 19 insertions(+), 11 deletions(-)
diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index c6a676714f04..882fda779648 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -39,6 +39,17 @@ struct mm_struct;
  #define __S110	PAGE_SHARED_X
  #define __S111	PAGE_SHARED_X
  
+#ifndef MODULES_VADDR
+#define MODULES_VADDR VMALLOC_START
+#define MODULES_END VMALLOC_END
+#endif
+
+#if defined(CONFIG_PPC_BOOK3S_32) && defined(CONFIG_STRICT_KERNEL_RWX)
No no.

TASK_SIZE > MODULES_VADDR is ALWAYS wrong, for any target, in any configuration.

Why is it a problem to leave the test as a BUILD_BUG_ON() in module_alloc() ?
quoted hunk ↗ jump to hunk
+#if TASK_SIZE > MODULES_VADDR
+#error TASK_SIZE > MODULES_VADDR
+#endif
+#endif
+
  #ifndef __ASSEMBLY__
  
  /* Keep these as a macros to avoid include dependency mess */
diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
index fab84024650c..c60c7457ff47 100644
--- a/arch/powerpc/kernel/module.c
+++ b/arch/powerpc/kernel/module.c
@@ -15,6 +15,7 @@
  #include <linux/sort.h>
  #include <asm/setup.h>
  #include <asm/sections.h>
+#include <linux/mm.h>
  
  static LIST_HEAD(module_bug_list);
  
@@ -88,7 +89,6 @@ int module_finalize(const Elf_Ehdr *hdr,
  	return 0;
  }
  
-#ifdef MODULES_VADDR
  static __always_inline void *
  __module_alloc(unsigned long size, unsigned long start, unsigned long end)
  {
@@ -102,8 +102,6 @@ void *module_alloc(unsigned long size)
  	unsigned long limit = (unsigned long)_etext - SZ_32M;
  	void *ptr = NULL;
  
-	BUILD_BUG_ON(TASK_SIZE > MODULES_VADDR);
-
  	/* First try within 32M limit from _etext to avoid branch trampolines */
  	if (MODULES_VADDR < PAGE_OFFSET && MODULES_END > limit)
  		ptr = __module_alloc(size, limit, MODULES_END);
@@ -113,4 +111,3 @@ void *module_alloc(unsigned long size)
  
  	return ptr;
  }
-#endif
diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c
index cf8770b1a692..42c057366ac7 100644
--- a/arch/powerpc/mm/kasan/kasan_init_32.c
+++ b/arch/powerpc/mm/kasan/kasan_init_32.c
@@ -116,11 +116,11 @@ static void __init kasan_unmap_early_shadow_vmalloc(void)
  
  	kasan_update_early_region(k_start, k_end, __pte(0));
  
-#ifdef MODULES_VADDR
-	k_start = (unsigned long)kasan_mem_to_shadow((void *)MODULES_VADDR);
-	k_end = (unsigned long)kasan_mem_to_shadow((void *)MODULES_END);
-	kasan_update_early_region(k_start, k_end, __pte(0));
-#endif
+	if (MODULES_VADDR != VMALLOC_START && MODULES_END != VMALLOC_END) {
Shouldn't it be an || ?

As soon as either MODULES_VADDR or MODULES_END differs from the vmalloc boundaries, it needs to be 
done I think.
quoted hunk ↗ jump to hunk
+		k_start = (unsigned long)kasan_mem_to_shadow((void *)MODULES_VADDR);
+		k_end = (unsigned long)kasan_mem_to_shadow((void *)MODULES_END);
+		kasan_update_early_region(k_start, k_end, __pte(0));
+	}
  }
  
  void __init kasan_mmu_init(void)
diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
index aca354fb670b..0431457f668f 100644
--- a/arch/powerpc/mm/ptdump/ptdump.c
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -73,7 +73,7 @@ struct addr_marker {
  
  static struct addr_marker address_markers[] = {
  	{ 0,	"Start of kernel VM" },
-#ifdef MODULES_VADDR
+#if defined(CONFIG_BOOK32_32) && defined(CONFIG_STRICT_KERNEL_RWX)
Not valid anymore, see https://github.com/linuxppc/linux/commit/80edc68e0479 and 
https://github.com/linuxppc/linux/commit/9132a2e82adc

The best would be to be able to do something like:

#if MODULES_VADDR != VMALLOC_START

If it doesn't work, then it has to be

#if defined(CONFIG_BOOK32_32) || defined(CONFIG_PPC_8xx)
quoted hunk ↗ jump to hunk
  	{ 0,	"modules start" },
  	{ 0,	"modules end" },
  #endif
@@ -359,7 +359,7 @@ static void populate_markers(void)
  #else
  	address_markers[i++].start_address = TASK_SIZE;
  #endif
-#ifdef MODULES_VADDR
+#if defined(CONFIG_BOOK32_32) && defined(CONFIG_STRICT_KERNEL_RWX)
Same.
  	address_markers[i++].start_address = MODULES_VADDR;
  	address_markers[i++].start_address = MODULES_END;
  #endif
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