linux-kernel - [RFC PATCH 1/2] modules: Make module_enable_x() independant of CONFIG_ARCH_HAS_STRICT_MODULE

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Date:   Thu, 3 Feb 2022 20:23:25 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     "atomlin@...hat.com" <atomlin@...hat.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        "linux-modules@...r.kernel.org" <linux-modules@...r.kernel.org>
CC:     Christophe Leroy <christophe.leroy@...roup.eu>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH 1/2] modules: Make module_enable_x() independant of
 CONFIG_ARCH_HAS_STRICT_MODULE_RWX

module_enable_x() has nothing to do with CONFIG_ARCH_HAS_STRICT_MODULE_RWX
allthough by coincidence architectures who need module_enable_x() are
selection CONFIG_ARCH_HAS_STRICT_MODULE_RWX.

Enable module_enable_x() for everyone everytime. If an architecture
already has module text set executable, it's a no-op.

Only check end boundary if CONFIG_STRICT_MODULE_RWX is set, and
make sure we entirely get the last page when the boundary is not
aligned. When CONFIG_STRICT_MODULE_RWX is not selected, it is not
a big deal to have the start of data as executable.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 kernel/module.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 24dab046e16c..44ed39cbbd17 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -70,9 +70,9 @@
 /*
  * Modules' sections will be aligned on page boundaries
  * to ensure complete separation of code and data, but
- * only when CONFIG_ARCH_HAS_STRICT_MODULE_RWX=y
+ * only when CONFIG_STRICT_MODULE_RWX=y
  */
-#ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX
+#ifdef CONFIG_STRICT_MODULE_RWX
 # define debug_align(X) ALIGN(X, PAGE_SIZE)
 #else
 # define debug_align(X) (X)
@@ -1955,14 +1955,15 @@ static void mod_sysfs_teardown(struct module *mod)
  * CONFIG_STRICT_MODULE_RWX block below because they are needed regardless of
  * whether we are strict.
  */
-#ifdef CONFIG_ARCH_HAS_STRICT_MODULE_RWX
 static void frob_text(const struct module_layout *layout,
 		      int (*set_memory)(unsigned long start, int num_pages))
 {
 	BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1));
+#ifdef CONFIG_STRICT_MODULE_RWX
 	BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1));
+#endif
 	set_memory((unsigned long)layout->base,
-		   layout->text_size >> PAGE_SHIFT);
+		   ((layout->text_size - 1) >> PAGE_SHIFT) + 1);
 }
 
 static void module_enable_x(const struct module *mod)
@@ -1970,9 +1971,6 @@ static void module_enable_x(const struct module *mod)
 	frob_text(&mod->core_layout, set_memory_x);
 	frob_text(&mod->init_layout, set_memory_x);
 }
-#else /* !CONFIG_ARCH_HAS_STRICT_MODULE_RWX */
-static void module_enable_x(const struct module *mod) { }
-#endif /* CONFIG_ARCH_HAS_STRICT_MODULE_RWX */
 
 #ifdef CONFIG_STRICT_MODULE_RWX
 static void frob_rodata(const struct module_layout *layout,
-- 
2.33.1