A recent enhancement intentionally fails the kernel build if the
compiler does not support retpolines and CONFIG_RETPOLINE is set.
However, the patch that introduced it did not change RETPOLINE macro
references into CONFIG_RETPOLINE ones. As a result, indirect branches
that are used by init functions are not kept (i.e., they use
retpolines), and modules that do not use retpolines are marked as
retpoline-safe.
Fix it be changing RETPOLINE into CONFIG_RETPOLINE.
Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler support")
Cc: Peter Zijlstra <[email protected]>
Cc: Zhenzhong Duan <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: [email protected]
Signed-off-by: Nadav Amit <[email protected]>
---
arch/x86/kernel/cpu/bugs.c | 2 +-
include/linux/compiler-gcc.h | 2 +-
include/linux/module.h | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 8654b8b0c848..1de0f4170178 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -215,7 +215,7 @@ static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
static enum spectre_v2_user_mitigation spectre_v2_user __ro_after_init =
SPECTRE_V2_USER_NONE;
-#ifdef RETPOLINE
+#ifdef CONFIG_RETPOLINE
static bool spectre_v2_bad_module;
bool retpoline_module_ok(bool has_retpoline)
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 2010493e1040..977ddf2774f9 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -68,7 +68,7 @@
*/
#define uninitialized_var(x) x = x
-#ifdef RETPOLINE
+#ifdef CONFIG_RETPOLINE
#define __noretpoline __attribute__((__indirect_branch__("keep")))
#endif
diff --git a/include/linux/module.h b/include/linux/module.h
index fce6b4335e36..0c575f51fe57 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -817,7 +817,7 @@ static inline void module_bug_finalize(const Elf_Ehdr *hdr,
static inline void module_bug_cleanup(struct module *mod) {}
#endif /* CONFIG_GENERIC_BUG */
-#ifdef RETPOLINE
+#ifdef CONFIG_RETPOLINE
extern bool retpoline_module_ok(bool has_retpoline);
#else
static inline bool retpoline_module_ok(bool has_retpoline)
--
2.17.1
On 2019/1/1 7:42, Nadav Amit wrote:
> A recent enhancement intentionally fails the kernel build if the
> compiler does not support retpolines and CONFIG_RETPOLINE is set.
>
> However, the patch that introduced it did not change RETPOLINE macro
> references into CONFIG_RETPOLINE ones. As a result, indirect branches
> that are used by init functions are not kept (i.e., they use
> retpolines), and modules that do not use retpolines are marked as
> retpoline-safe.
>
> Fix it be changing RETPOLINE into CONFIG_RETPOLINE.
>
> Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler support")
> Cc: Peter Zijlstra <[email protected]>
> Cc: Zhenzhong Duan <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: David Woodhouse <[email protected]>
> Cc: Andy Lutomirski <[email protected]>
> Cc: Masahiro Yamada <[email protected]>
> Cc: [email protected]
> Signed-off-by: Nadav Amit <[email protected]>
> ---
> arch/x86/kernel/cpu/bugs.c | 2 +-
> include/linux/compiler-gcc.h | 2 +-
> include/linux/module.h | 2 +-
> 3 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index 8654b8b0c848..1de0f4170178 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -215,7 +215,7 @@ static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
> static enum spectre_v2_user_mitigation spectre_v2_user __ro_after_init =
> SPECTRE_V2_USER_NONE;
>
> -#ifdef RETPOLINE
> +#ifdef CONFIG_RETPOLINE
> static bool spectre_v2_bad_module;
>
> bool retpoline_module_ok(bool has_retpoline)
> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> index 2010493e1040..977ddf2774f9 100644
> --- a/include/linux/compiler-gcc.h
> +++ b/include/linux/compiler-gcc.h
> @@ -68,7 +68,7 @@
> */
> #define uninitialized_var(x) x = x
>
> -#ifdef RETPOLINE
> +#ifdef CONFIG_RETPOLINE
> #define __noretpoline __attribute__((__indirect_branch__("keep")))
> #endif
>
> diff --git a/include/linux/module.h b/include/linux/module.h
> index fce6b4335e36..0c575f51fe57 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -817,7 +817,7 @@ static inline void module_bug_finalize(const Elf_Ehdr *hdr,
> static inline void module_bug_cleanup(struct module *mod) {}
> #endif /* CONFIG_GENERIC_BUG */
>
> -#ifdef RETPOLINE
> +#ifdef CONFIG_RETPOLINE
> extern bool retpoline_module_ok(bool has_retpoline);
> #else
> static inline bool retpoline_module_ok(bool has_retpoline)
Someone sent a similar patch last month, see below link, you missed the
change in scripts/mod/modpost.c
https://lkml.org/lkml/2018/12/10/540
But you patch description is more clear.
--
Thanks
Zhenzhong
> On Jan 1, 2019, at 5:17 PM, Zhenzhong Duan <[email protected]> wrote:
>
>
> On 2019/1/1 7:42, Nadav Amit wrote:
>> A recent enhancement intentionally fails the kernel build if the
>> compiler does not support retpolines and CONFIG_RETPOLINE is set.
>>
>> However, the patch that introduced it did not change RETPOLINE macro
>> references into CONFIG_RETPOLINE ones. As a result, indirect branches
>> that are used by init functions are not kept (i.e., they use
>> retpolines), and modules that do not use retpolines are marked as
>> retpoline-safe.
>>
>> Fix it be changing RETPOLINE into CONFIG_RETPOLINE.
>>
>> Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler support")
>> Cc: Peter Zijlstra <[email protected]>
>> Cc: Zhenzhong Duan <[email protected]>
>> Cc: Thomas Gleixner <[email protected]>
>> Cc: David Woodhouse <[email protected]>
>> Cc: Andy Lutomirski <[email protected]>
>> Cc: Masahiro Yamada <[email protected]>
>> Cc: [email protected]
>> Signed-off-by: Nadav Amit <[email protected]>
>> ---
>> arch/x86/kernel/cpu/bugs.c | 2 +-
>> include/linux/compiler-gcc.h | 2 +-
>> include/linux/module.h | 2 +-
>> 3 files changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
>> index 8654b8b0c848..1de0f4170178 100644
>> --- a/arch/x86/kernel/cpu/bugs.c
>> +++ b/arch/x86/kernel/cpu/bugs.c
>> @@ -215,7 +215,7 @@ static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
>> static enum spectre_v2_user_mitigation spectre_v2_user __ro_after_init =
>> SPECTRE_V2_USER_NONE;
>> -#ifdef RETPOLINE
>> +#ifdef CONFIG_RETPOLINE
>> static bool spectre_v2_bad_module;
>> bool retpoline_module_ok(bool has_retpoline)
>> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
>> index 2010493e1040..977ddf2774f9 100644
>> --- a/include/linux/compiler-gcc.h
>> +++ b/include/linux/compiler-gcc.h
>> @@ -68,7 +68,7 @@
>> */
>> #define uninitialized_var(x) x = x
>> -#ifdef RETPOLINE
>> +#ifdef CONFIG_RETPOLINE
>> #define __noretpoline __attribute__((__indirect_branch__("keep")))
>> #endif
>> diff --git a/include/linux/module.h b/include/linux/module.h
>> index fce6b4335e36..0c575f51fe57 100644
>> --- a/include/linux/module.h
>> +++ b/include/linux/module.h
>> @@ -817,7 +817,7 @@ static inline void module_bug_finalize(const Elf_Ehdr *hdr,
>> static inline void module_bug_cleanup(struct module *mod) {}
>> #endif /* CONFIG_GENERIC_BUG */
>> -#ifdef RETPOLINE
>> +#ifdef CONFIG_RETPOLINE
>> extern bool retpoline_module_ok(bool has_retpoline);
>> #else
>> static inline bool retpoline_module_ok(bool has_retpoline)
>
> Someone sent a similar patch last month, see below link, you missed the change in scripts/mod/modpost.c
Indeed. I missed this patch since it wasn’t on tip (and Google wasn’t
helpful either).
I wonder why it has still not been applied.
On 2019/1/3 1:23, Nadav Amit wrote:
>> On Jan 1, 2019, at 5:17 PM, Zhenzhong Duan <[email protected]> wrote:
>>
>>
>> On 2019/1/1 7:42, Nadav Amit wrote:
>>> A recent enhancement intentionally fails the kernel build if the
>>> compiler does not support retpolines and CONFIG_RETPOLINE is set.
>>>
>>> However, the patch that introduced it did not change RETPOLINE macro
>>> references into CONFIG_RETPOLINE ones. As a result, indirect branches
>>> that are used by init functions are not kept (i.e., they use
>>> retpolines), and modules that do not use retpolines are marked as
>>> retpoline-safe.
>>>
>>> Fix it be changing RETPOLINE into CONFIG_RETPOLINE.
>>>
>>> Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler support")
>>> Cc: Peter Zijlstra <[email protected]>
>>> Cc: Zhenzhong Duan <[email protected]>
>>> Cc: Thomas Gleixner <[email protected]>
>>> Cc: David Woodhouse <[email protected]>
>>> Cc: Andy Lutomirski <[email protected]>
>>> Cc: Masahiro Yamada <[email protected]>
>>> Cc: [email protected]
>>> Signed-off-by: Nadav Amit <[email protected]>
>>> ---
>>> arch/x86/kernel/cpu/bugs.c | 2 +-
>>> include/linux/compiler-gcc.h | 2 +-
>>> include/linux/module.h | 2 +-
>>> 3 files changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
>>> index 8654b8b0c848..1de0f4170178 100644
>>> --- a/arch/x86/kernel/cpu/bugs.c
>>> +++ b/arch/x86/kernel/cpu/bugs.c
>>> @@ -215,7 +215,7 @@ static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
>>> static enum spectre_v2_user_mitigation spectre_v2_user __ro_after_init =
>>> SPECTRE_V2_USER_NONE;
>>> -#ifdef RETPOLINE
>>> +#ifdef CONFIG_RETPOLINE
>>> static bool spectre_v2_bad_module;
>>> bool retpoline_module_ok(bool has_retpoline)
>>> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
>>> index 2010493e1040..977ddf2774f9 100644
>>> --- a/include/linux/compiler-gcc.h
>>> +++ b/include/linux/compiler-gcc.h
>>> @@ -68,7 +68,7 @@
>>> */
>>> #define uninitialized_var(x) x = x
>>> -#ifdef RETPOLINE
>>> +#ifdef CONFIG_RETPOLINE
>>> #define __noretpoline __attribute__((__indirect_branch__("keep")))
>>> #endif
>>> diff --git a/include/linux/module.h b/include/linux/module.h
>>> index fce6b4335e36..0c575f51fe57 100644
>>> --- a/include/linux/module.h
>>> +++ b/include/linux/module.h
>>> @@ -817,7 +817,7 @@ static inline void module_bug_finalize(const Elf_Ehdr *hdr,
>>> static inline void module_bug_cleanup(struct module *mod) {}
>>> #endif /* CONFIG_GENERIC_BUG */
>>> -#ifdef RETPOLINE
>>> +#ifdef CONFIG_RETPOLINE
>>> extern bool retpoline_module_ok(bool has_retpoline);
>>> #else
>>> static inline bool retpoline_module_ok(bool has_retpoline)
>> Someone sent a similar patch last month, see below link, you missed the change in scripts/mod/modpost.c
> Indeed. I missed this patch since it wasn’t on tip (and Google wasn’t
> helpful either).
>
> I wonder why it has still not been applied.
See https://lkml.org/lkml/2018/12/21/244
--
Thanks
Zhenzhong