Message-ID: <20250429113242.998312-24-vschneid@redhat.com>
Date: Tue, 29 Apr 2025 13:32:40 +0200
From: Valentin Schneider <vschneid@...hat.com>
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Subject: [PATCH v5 23/25] module: Add MOD_NOINSTR_TEXT mem_type

As pointed out by Sean [1], is_kernel_noinstr_text() will return false for
an address contained within a module's .noinstr.text section. A later patch
will require checking whether a text address is noinstr, and this can
unfortunately be the case of modules - KVM is one such case.

A module's .noinstr.text section is already tracked as of commit
  66e9b0717102 ("kprobes: Prevent probes in .noinstr.text section")
for kprobe blacklisting purposes, but via an ad-hoc mechanism.

Add a MOD_NOINSTR_TEXT mem_type, and reorganize __layout_sections() so that
it maps all the sections in a single invocation.

[1]: http://lore.kernel.org/r/Z4qQL89GZ_gk0vpu@google.com
Signed-off-by: Valentin Schneider <vschneid@...hat.com>
---
 include/linux/module.h |  6 ++--
 kernel/kprobes.c       |  8 ++---
 kernel/module/main.c   | 76 ++++++++++++++++++++++++++++++++----------
 3 files changed, 66 insertions(+), 24 deletions(-)

diff --git a/include/linux/module.h b/include/linux/module.h
index d94b196d5a34e..193d8d34eeee0 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -332,6 +332,7 @@ struct mod_tree_node {
 
 enum mod_mem_type {
 	MOD_TEXT = 0,
+	MOD_NOINSTR_TEXT,
 	MOD_DATA,
 	MOD_RODATA,
 	MOD_RO_AFTER_INIT,
@@ -502,8 +503,6 @@ struct module {
 	void __percpu *percpu;
 	unsigned int percpu_size;
 #endif
-	void *noinstr_text_start;
-	unsigned int noinstr_text_size;
 
 #ifdef CONFIG_TRACEPOINTS
 	unsigned int num_tracepoints;
@@ -622,12 +621,13 @@ static inline bool module_is_coming(struct module *mod)
         return mod->state == MODULE_STATE_COMING;
 }
 
-struct module *__module_text_address(unsigned long addr);
 struct module *__module_address(unsigned long addr);
+struct module *__module_text_address(unsigned long addr);
 bool is_module_address(unsigned long addr);
 bool __is_module_percpu_address(unsigned long addr, unsigned long *can_addr);
 bool is_module_percpu_address(unsigned long addr);
 bool is_module_text_address(unsigned long addr);
+bool is_module_noinstr_text_address(unsigned long addr);
 
 static inline bool within_module_mem_type(unsigned long addr,
 					  const struct module *mod,
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index ffe0c3d523063..9a799faee68a1 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2547,9 +2547,9 @@ static void add_module_kprobe_blacklist(struct module *mod)
 		kprobe_add_area_blacklist(start, end);
 	}
 
-	start = (unsigned long)mod->noinstr_text_start;
+	start = (unsigned long)mod->mem[MOD_NOINSTR_TEXT].base;
 	if (start) {
-		end = start + mod->noinstr_text_size;
+		end = start + mod->mem[MOD_NOINSTR_TEXT].size;
 		kprobe_add_area_blacklist(start, end);
 	}
 }
@@ -2570,9 +2570,9 @@ static void remove_module_kprobe_blacklist(struct module *mod)
 		kprobe_remove_area_blacklist(start, end);
 	}
 
-	start = (unsigned long)mod->noinstr_text_start;
+	start = (unsigned long)mod->mem[MOD_NOINSTR_TEXT].base;
 	if (start) {
-		end = start + mod->noinstr_text_size;
+		end = start + mod->mem[MOD_NOINSTR_TEXT].size;
 		kprobe_remove_area_blacklist(start, end);
 	}
 }
diff --git a/kernel/module/main.c b/kernel/module/main.c
index b9f010daaa4c7..0126bae64b698 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1558,7 +1558,17 @@ bool module_init_layout_section(const char *sname)
 	return module_init_section(sname);
 }
 
-static void __layout_sections(struct module *mod, struct load_info *info, bool is_init)
+static bool module_noinstr_layout_section(const char *sname)
+{
+	return strstarts(sname, ".noinstr");
+}
+
+static bool module_default_layout_section(const char *sname)
+{
+	return !module_init_layout_section(sname) && !module_noinstr_layout_section(sname);
+}
+
+static void __layout_sections(struct module *mod, struct load_info *info)
 {
 	unsigned int m, i;
 
@@ -1567,20 +1577,44 @@ static void __layout_sections(struct module *mod, struct load_info *info, bool i
 	 *   Mask of excluded section header flags }
 	 */
 	static const unsigned long masks[][2] = {
+		/* Core */
+		{ SHF_EXECINSTR | SHF_ALLOC, ARCH_SHF_SMALL },
+		{ SHF_EXECINSTR | SHF_ALLOC, ARCH_SHF_SMALL },
+		{ SHF_ALLOC, SHF_WRITE | ARCH_SHF_SMALL },
+		{ SHF_RO_AFTER_INIT | SHF_ALLOC, ARCH_SHF_SMALL },
+		{ SHF_WRITE | SHF_ALLOC, ARCH_SHF_SMALL },
+		{ ARCH_SHF_SMALL | SHF_ALLOC, 0 },
+		/* Init */
 		{ SHF_EXECINSTR | SHF_ALLOC, ARCH_SHF_SMALL },
 		{ SHF_ALLOC, SHF_WRITE | ARCH_SHF_SMALL },
 		{ SHF_RO_AFTER_INIT | SHF_ALLOC, ARCH_SHF_SMALL },
 		{ SHF_WRITE | SHF_ALLOC, ARCH_SHF_SMALL },
-		{ ARCH_SHF_SMALL | SHF_ALLOC, 0 }
+		{ ARCH_SHF_SMALL | SHF_ALLOC, 0 },
 	};
-	static const int core_m_to_mem_type[] = {
+	static bool (*const section_filter[])(const char *) = {
+		/* Core */
+		module_default_layout_section,
+		module_noinstr_layout_section,
+		module_default_layout_section,
+		module_default_layout_section,
+		module_default_layout_section,
+		module_default_layout_section,
+		/* Init */
+		module_init_layout_section,
+		module_init_layout_section,
+		module_init_layout_section,
+		module_init_layout_section,
+		module_init_layout_section,
+	};
+	static const int mem_type_map[] = {
+		/* Core */
 		MOD_TEXT,
+		MOD_NOINSTR_TEXT,
 		MOD_RODATA,
 		MOD_RO_AFTER_INIT,
 		MOD_DATA,
 		MOD_DATA,
-	};
-	static const int init_m_to_mem_type[] = {
+		/* Init */
 		MOD_INIT_TEXT,
 		MOD_INIT_RODATA,
 		MOD_INVALID,
@@ -1589,16 +1623,16 @@ static void __layout_sections(struct module *mod, struct load_info *info, bool i
 	};
 
 	for (m = 0; m < ARRAY_SIZE(masks); ++m) {
-		enum mod_mem_type type = is_init ? init_m_to_mem_type[m] : core_m_to_mem_type[m];
+		enum mod_mem_type type = mem_type_map[m];
 
 		for (i = 0; i < info->hdr->e_shnum; ++i) {
 			Elf_Shdr *s = &info->sechdrs[i];
 			const char *sname = info->secstrings + s->sh_name;
 
-			if ((s->sh_flags & masks[m][0]) != masks[m][0]
-			    || (s->sh_flags & masks[m][1])
-			    || s->sh_entsize != ~0UL
-			    || is_init != module_init_layout_section(sname))
+			if ((s->sh_flags & masks[m][0]) != masks[m][0] ||
+			    (s->sh_flags & masks[m][1])                ||
+			    s->sh_entsize != ~0UL                      ||
+			    !section_filter[m](sname))
 				continue;
 
 			if (WARN_ON_ONCE(type == MOD_INVALID))
@@ -1638,10 +1672,7 @@ static void layout_sections(struct module *mod, struct load_info *info)
 		info->sechdrs[i].sh_entsize = ~0UL;
 
 	pr_debug("Core section allocation order for %s:\n", mod->name);
-	__layout_sections(mod, info, false);
-
-	pr_debug("Init section allocation order for %s:\n", mod->name);
-	__layout_sections(mod, info, true);
+	__layout_sections(mod, info);
 }
 
 static void module_license_taint_check(struct module *mod, const char *license)
@@ -2515,9 +2546,6 @@ static int find_module_sections(struct module *mod, struct load_info *info)
 	}
 #endif
 
-	mod->noinstr_text_start = section_objs(info, ".noinstr.text", 1,
-						&mod->noinstr_text_size);
-
 #ifdef CONFIG_TRACEPOINTS
 	mod->tracepoints_ptrs = section_objs(info, "__tracepoints_ptrs",
 					     sizeof(*mod->tracepoints_ptrs),
@@ -3769,12 +3797,26 @@ struct module *__module_text_address(unsigned long addr)
 	if (mod) {
 		/* Make sure it's within the text section. */
 		if (!within_module_mem_type(addr, mod, MOD_TEXT) &&
+		    !within_module_mem_type(addr, mod, MOD_NOINSTR_TEXT) &&
 		    !within_module_mem_type(addr, mod, MOD_INIT_TEXT))
 			mod = NULL;
 	}
 	return mod;
 }
 
+bool is_module_noinstr_text_address(unsigned long addr)
+{
+	scoped_guard(preempt) {
+		struct module *mod = __module_address(addr);
+
+		/* Make sure it's within the .noinstr.text section. */
+		if (mod)
+			return within_module_mem_type(addr, mod, MOD_NOINSTR_TEXT);
+	}
+
+	return false;
+}
+
 /* Don't grab lock, we're oopsing. */
 void print_modules(void)
 {
-- 
2.49.0

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