[PATCH] arm64: ftrace: fix building without CONFIG_MODULES

When CONFIG_MODULES is disabled, we cannot dereference a module pointer:

arch/arm64/kernel/ftrace.c: In function 'ftrace_make_call':
arch/arm64/kernel/ftrace.c:107:36: error: dereferencing pointer to incomplete type 'struct module'
   trampoline = (unsigned long *)mod->arch.ftrace_trampoline;

Also, the within_module() function is not defined:

arch/arm64/kernel/ftrace.c: In function 'ftrace_make_nop':
arch/arm64/kernel/ftrace.c:171:8: error: implicit declaration of function 'within_module'; did you mean 'init_module'? [-Werror=implicit-function-declaration]

This addresses both by adding the appropriate stubs.

Fixes: e71a4e1bebaf ("arm64: ftrace: add support for far branches to dynamic ftrace")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/arm64/include/asm/module.h | 6 ++++++
 arch/arm64/kernel/ftrace.c      | 2 +-
 include/linux/module.h          | 5 +++++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/module.h b/arch/arm64/include/asm/module.h
index 19bd97671bb8..ca5d024f4247 100644
--- a/arch/arm64/include/asm/module.h
+++ b/arch/arm64/include/asm/module.h

@@ -36,6 +36,12 @@ struct mod_arch_specific {
 };
 #endif
 
+#if defined(CONFIG_MODULES) && defined(CONFIG_ARM64_MODULE_PLTS)
+#define module_ftrace_trampoline(mod) ((mod)->arch.ftrace_trampoline)
+#else
+#define module_ftrace_trampoline(mod) NULL
+#endif
+
 u64 module_emit_plt_entry(struct module *mod, void *loc, const Elf64_Rela *rela,
 			  Elf64_Sym *sym);
 

diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index 8a42be0693c9..7f5eb9939a55 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c

@@ -104,7 +104,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 		 * is added in the future, but for now, the pr_err() below
 		 * deals with a theoretical issue only.
 		 */
-		trampoline = (unsigned long *)mod->arch.ftrace_trampoline;
+		trampoline = module_ftrace_trampoline(mod);
 		if (trampoline[0] != addr) {
 			if (trampoline[0] != 0) {
 				pr_err("ftrace: far branches to multiple entry points unsupported inside a single module\n");

diff --git a/include/linux/module.h b/include/linux/module.h
index 21f56393602f..9196f532f158 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h

@@ -671,6 +671,11 @@ static inline bool is_module_text_address(unsigned long addr)
 	return false;
 }
 
+static inline bool within_module(unsigned long addr, const struct module *mod)
+{
+	return false;
+}
+
 /* Get/put a kernel symbol (calls should be symmetric) */
 #define symbol_get(x) ({ extern typeof(x) x __attribute__((weak)); &(x); })
 #define symbol_put(x) do { } while (0)

-- 
2.9.0

Hi Arnd,

On Fri, Jun 09, 2017 at 12:27:06PM +0200, Arnd Bergmann wrote:

When CONFIG_MODULES is disabled, we cannot dereference a module pointer:

arch/arm64/kernel/ftrace.c: In function 'ftrace_make_call':
arch/arm64/kernel/ftrace.c:107:36: error: dereferencing pointer to incomplete type 'struct module'
   trampoline = (unsigned long *)mod->arch.ftrace_trampoline;

Also, the within_module() function is not defined:

arch/arm64/kernel/ftrace.c: In function 'ftrace_make_nop':
arch/arm64/kernel/ftrace.c:171:8: error: implicit declaration of function 'within_module'; did you mean 'init_module'? [-Werror=implicit-function-declaration]

This addresses both by adding the appropriate stubs.

Fixes: e71a4e1bebaf ("arm64: ftrace: add support for far branches to dynamic ftrace")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/arm64/include/asm/module.h | 6 ++++++
 arch/arm64/kernel/ftrace.c      | 2 +-
 include/linux/module.h          | 5 +++++
 3 files changed, 12 insertions(+), 1 deletion(-)

I can't seem to reproduce this simply by disabling MODULES in defconfig.
Could you share your .config, please?

Will

On Fri, Jun 9, 2017 at 1:38 PM, Will Deacon [off-list ref] wrote:

Hi Arnd,

On Fri, Jun 09, 2017 at 12:27:06PM +0200, Arnd Bergmann wrote:

quoted

When CONFIG_MODULES is disabled, we cannot dereference a module pointer:

arch/arm64/kernel/ftrace.c: In function 'ftrace_make_call':
arch/arm64/kernel/ftrace.c:107:36: error: dereferencing pointer to incomplete type 'struct module'
   trampoline = (unsigned long *)mod->arch.ftrace_trampoline;

Also, the within_module() function is not defined:

arch/arm64/kernel/ftrace.c: In function 'ftrace_make_nop':
arch/arm64/kernel/ftrace.c:171:8: error: implicit declaration of function 'within_module'; did you mean 'init_module'? [-Werror=implicit-function-declaration]

This addresses both by adding the appropriate stubs.

Fixes: e71a4e1bebaf ("arm64: ftrace: add support for far branches to dynamic ftrace")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/arm64/include/asm/module.h | 6 ++++++
 arch/arm64/kernel/ftrace.c      | 2 +-
 include/linux/module.h          | 5 +++++
 3 files changed, 12 insertions(+), 1 deletion(-)

I can't seem to reproduce this simply by disabling MODULES in defconfig.
Could you share your .config, please?

This is the randconfig I used: https://pastebin.com/SfKBY7f8

      Arnd

On Fri, Jun 09, 2017 at 08:57:31PM +0200, Arnd Bergmann wrote:

On Fri, Jun 9, 2017 at 1:38 PM, Will Deacon [off-list ref] wrote:

quoted

On Fri, Jun 09, 2017 at 12:27:06PM +0200, Arnd Bergmann wrote:

quoted

When CONFIG_MODULES is disabled, we cannot dereference a module pointer:

arch/arm64/kernel/ftrace.c: In function 'ftrace_make_call':
arch/arm64/kernel/ftrace.c:107:36: error: dereferencing pointer to incomplete type 'struct module'
   trampoline = (unsigned long *)mod->arch.ftrace_trampoline;

Also, the within_module() function is not defined:

arch/arm64/kernel/ftrace.c: In function 'ftrace_make_nop':
arch/arm64/kernel/ftrace.c:171:8: error: implicit declaration of function 'within_module'; did you mean 'init_module'? [-Werror=implicit-function-declaration]

This addresses both by adding the appropriate stubs.

Fixes: e71a4e1bebaf ("arm64: ftrace: add support for far branches to dynamic ftrace")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/arm64/include/asm/module.h | 6 ++++++
 arch/arm64/kernel/ftrace.c      | 2 +-
 include/linux/module.h          | 5 +++++
 3 files changed, 12 insertions(+), 1 deletion(-)

I can't seem to reproduce this simply by disabling MODULES in defconfig.
Could you share your .config, please?

This is the randconfig I used: https://pastebin.com/SfKBY7f8

Thanks, I was forgetting to enable ftrace. I think a simpler patch (and one
that I can just apply via arm64) is switching the IS_ENABLEDs out for
#ifdefs. See below.

Will

--->8

diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index 8a42be0693c9..401aa27808a4 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c

@@ -71,11 +71,12 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	unsigned long pc = rec->ip;
-	long offset = (long)pc - (long)addr;
 	u32 old, new;
 
-	if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
-	    (offset < -SZ_128M || offset >= SZ_128M)) {
+#ifdef CONFIG_ARM64_MODULE_PLTS
+	long offset = (long)pc - (long)addr;
+
+	if (offset < -SZ_128M || offset >= SZ_128M) {
 		unsigned long *trampoline;
 		struct module *mod;
 

@@ -121,6 +122,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 		}
 		addr = (unsigned long)&trampoline[1];
 	}
+#endif /* CONFIG_ARM64_MODULE_PLTS */
 
 	old = aarch64_insn_gen_nop();
 	new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);

@@ -135,12 +137,13 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 		    unsigned long addr)
 {
 	unsigned long pc = rec->ip;
-	long offset = (long)pc - (long)addr;
 	bool validate = true;
 	u32 old = 0, new;
 
-	if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
-	    (offset < -SZ_128M || offset >= SZ_128M)) {
+#ifdef CONFIG_ARM64_MODULE_PLTS
+	long offset = (long)pc - (long)addr;
+
+	if (offset < -SZ_128M || offset >= SZ_128M) {
 		u32 replaced;
 
 		/*

@@ -177,6 +180,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 		old = aarch64_insn_gen_branch_imm(pc, addr,
 						  AARCH64_INSN_BRANCH_LINK);
 	}
+#endif /* CONFIG_ARM64_MODULE_PLTS */
 
 	new = aarch64_insn_gen_nop();
 

On 12 June 2017 at 14:48, Will Deacon [off-list ref] wrote:

On Fri, Jun 09, 2017 at 08:57:31PM +0200, Arnd Bergmann wrote:

quoted

On Fri, Jun 9, 2017 at 1:38 PM, Will Deacon [off-list ref] wrote:

quoted

On Fri, Jun 09, 2017 at 12:27:06PM +0200, Arnd Bergmann wrote:

quoted

When CONFIG_MODULES is disabled, we cannot dereference a module pointer:

arch/arm64/kernel/ftrace.c: In function 'ftrace_make_call':
arch/arm64/kernel/ftrace.c:107:36: error: dereferencing pointer to incomplete type 'struct module'
   trampoline = (unsigned long *)mod->arch.ftrace_trampoline;

Also, the within_module() function is not defined:

arch/arm64/kernel/ftrace.c: In function 'ftrace_make_nop':
arch/arm64/kernel/ftrace.c:171:8: error: implicit declaration of function 'within_module'; did you mean 'init_module'? [-Werror=implicit-function-declaration]

This addresses both by adding the appropriate stubs.

Fixes: e71a4e1bebaf ("arm64: ftrace: add support for far branches to dynamic ftrace")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/arm64/include/asm/module.h | 6 ++++++
 arch/arm64/kernel/ftrace.c      | 2 +-
 include/linux/module.h          | 5 +++++
 3 files changed, 12 insertions(+), 1 deletion(-)

I can't seem to reproduce this simply by disabling MODULES in defconfig.
Could you share your .config, please?

This is the randconfig I used: https://pastebin.com/SfKBY7f8

Thanks, I was forgetting to enable ftrace. I think a simpler patch (and one
that I can just apply via arm64) is switching the IS_ENABLEDs out for
#ifdefs.

I agree that this makes more sense in this particular case.

Acked-by: Ard Biesheuvel <redacted>

Interestingly, ARM64_MODULE_PLTS does not depend on CONFIG_MODULES,
but I can't remember whether that was deliberate or an oversight.

On Mon, Jun 12, 2017 at 2:48 PM, Will Deacon [off-list ref] wrote:

On Fri, Jun 09, 2017 at 08:57:31PM +0200, Arnd Bergmann wrote:

quoted

On Fri, Jun 9, 2017 at 1:38 PM, Will Deacon [off-list ref] wrote:

quoted

I can't seem to reproduce this simply by disabling MODULES in defconfig.
Could you share your .config, please?

This is the randconfig I used: https://pastebin.com/SfKBY7f8

Thanks, I was forgetting to enable ftrace. I think a simpler patch (and one
that I can just apply via arm64) is switching the IS_ENABLEDs out for
#ifdefs. See below.

Yes, good idea.

        Arnd