2023-02-26 00:01:50

by Josh Poimboeuf

[permalink] [raw]
Subject: [PATCH] x86/entry: Fix noinstr warning in __enter_from_user_mode()

__enter_from_user_mode() is triggering noinstr warnings with
CONFIG_DEBUG_PREEMPT due to its call of preempt_count_add() via
ct_state().

The preemption disable isn't needed as interrupts are already disabled.
And the context_tracking_enabled() check in ct_state() also isn't needed
as that's already being done by the CT_WARN_ON().

Just use __ct_state() instead.

Fixes the following warnings:

vmlinux.o: warning: objtool: enter_from_user_mode+0xba: call to preempt_count_add() leaves .noinstr.text section
vmlinux.o: warning: objtool: syscall_enter_from_user_mode+0xf9: call to preempt_count_add() leaves .noinstr.text section
vmlinux.o: warning: objtool: syscall_enter_from_user_mode_prepare+0xc7: call to preempt_count_add() leaves .noinstr.text section
vmlinux.o: warning: objtool: irqentry_enter_from_user_mode+0xba: call to preempt_count_add() leaves .noinstr.text section

Fixes: 171476775d32 ("context_tracking: Convert state to atomic_t")
Signed-off-by: Josh Poimboeuf <[email protected]>
---
include/linux/context_tracking.h | 1 +
kernel/entry/common.c | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index d4afa8508a80..3a7909ed5498 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -96,6 +96,7 @@ static inline void user_exit_irqoff(void) { }
static inline int exception_enter(void) { return 0; }
static inline void exception_exit(enum ctx_state prev_ctx) { }
static inline int ct_state(void) { return -1; }
+static inline int __ct_state(void) { return -1; }
static __always_inline bool context_tracking_guest_enter(void) { return false; }
static inline void context_tracking_guest_exit(void) { }
#define CT_WARN_ON(cond) do { } while (0)
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 846add8394c4..1314894d2efa 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -21,7 +21,7 @@ static __always_inline void __enter_from_user_mode(struct pt_regs *regs)
arch_enter_from_user_mode(regs);
lockdep_hardirqs_off(CALLER_ADDR0);

- CT_WARN_ON(ct_state() != CONTEXT_USER);
+ CT_WARN_ON(__ct_state() != CONTEXT_USER);
user_exit_irqoff();

instrumentation_begin();
--
2.39.1



Subject: [tip: core/urgent] entry: Fix noinstr warning in __enter_from_user_mode()

The following commit has been merged into the core/urgent branch of tip:

Commit-ID: 3e2619c4ebba2cab8414c55b131b7a28f628de3b
Gitweb: https://git.kernel.org/tip/3e2619c4ebba2cab8414c55b131b7a28f628de3b
Author: Josh Poimboeuf <[email protected]>
AuthorDate: Sat, 25 Feb 2023 16:01:36 -08:00
Committer: Thomas Gleixner <[email protected]>
CommitterDate: Mon, 20 Mar 2023 11:57:12 +01:00

entry: Fix noinstr warning in __enter_from_user_mode()

__enter_from_user_mode() is triggering noinstr warnings with
CONFIG_DEBUG_PREEMPT due to its call of preempt_count_add() via
ct_state().

The preemption disable isn't needed as interrupts are already disabled.
And the context_tracking_enabled() check in ct_state() also isn't needed
as that's already being done by the CT_WARN_ON().

Just use __ct_state() instead.

Fixes the following warnings:

vmlinux.o: warning: objtool: enter_from_user_mode+0xba: call to preempt_count_add() leaves .noinstr.text section
vmlinux.o: warning: objtool: syscall_enter_from_user_mode+0xf9: call to preempt_count_add() leaves .noinstr.text section
vmlinux.o: warning: objtool: syscall_enter_from_user_mode_prepare+0xc7: call to preempt_count_add() leaves .noinstr.text section
vmlinux.o: warning: objtool: irqentry_enter_from_user_mode+0xba: call to preempt_count_add() leaves .noinstr.text section

Fixes: 171476775d32 ("context_tracking: Convert state to atomic_t")
Signed-off-by: Josh Poimboeuf <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/d8955fa6d68dc955dda19baf13ae014ae27926f5.1677369694.git.jpoimboe@kernel.org
---
include/linux/context_tracking.h | 1 +
kernel/entry/common.c | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index d4afa85..3a7909e 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -96,6 +96,7 @@ static inline void user_exit_irqoff(void) { }
static inline int exception_enter(void) { return 0; }
static inline void exception_exit(enum ctx_state prev_ctx) { }
static inline int ct_state(void) { return -1; }
+static inline int __ct_state(void) { return -1; }
static __always_inline bool context_tracking_guest_enter(void) { return false; }
static inline void context_tracking_guest_exit(void) { }
#define CT_WARN_ON(cond) do { } while (0)
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 846add8..1314894 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -21,7 +21,7 @@ static __always_inline void __enter_from_user_mode(struct pt_regs *regs)
arch_enter_from_user_mode(regs);
lockdep_hardirqs_off(CALLER_ADDR0);

- CT_WARN_ON(ct_state() != CONTEXT_USER);
+ CT_WARN_ON(__ct_state() != CONTEXT_USER);
user_exit_irqoff();

instrumentation_begin();

2023-03-21 09:08:44

by Thomas Gleixner

[permalink] [raw]
Subject: Re: [PATCH] x86/entry: Fix noinstr warning in __enter_from_user_mode()

On Sat, Feb 25 2023 at 16:01, Josh Poimboeuf wrote:
> __enter_from_user_mode() is triggering noinstr warnings with
> CONFIG_DEBUG_PREEMPT due to its call of preempt_count_add() via
> ct_state().
>
> The preemption disable isn't needed as interrupts are already disabled.
> And the context_tracking_enabled() check in ct_state() also isn't needed
> as that's already being done by the CT_WARN_ON().
>
> Just use __ct_state() instead.
>
> Fixes the following warnings:
>
> vmlinux.o: warning: objtool: enter_from_user_mode+0xba: call to preempt_count_add() leaves .noinstr.text section
> vmlinux.o: warning: objtool: syscall_enter_from_user_mode+0xf9: call to preempt_count_add() leaves .noinstr.text section
> vmlinux.o: warning: objtool: syscall_enter_from_user_mode_prepare+0xc7: call to preempt_count_add() leaves .noinstr.text section
> vmlinux.o: warning: objtool: irqentry_enter_from_user_mode+0xba: call to preempt_count_add() leaves .noinstr.text section
>
> Fixes: 171476775d32 ("context_tracking: Convert state to atomic_t")
> Signed-off-by: Josh Poimboeuf <[email protected]>
> ---
> include/linux/context_tracking.h | 1 +
> kernel/entry/common.c | 2 +-
> 2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
> index d4afa8508a80..3a7909ed5498 100644
> --- a/include/linux/context_tracking.h
> +++ b/include/linux/context_tracking.h
> @@ -96,6 +96,7 @@ static inline void user_exit_irqoff(void) { }
> static inline int exception_enter(void) { return 0; }
> static inline void exception_exit(enum ctx_state prev_ctx) { }
> static inline int ct_state(void) { return -1; }
> +static inline int __ct_state(void) { return -1; }

This results in a redefinition warning due to CONFIG_CONTEXT_TRACKING=y
and CONFIG_CONFIG_TRACKING_USER=n.

Those headers are a fricking mess.

Thanks,

tglx

Subject: [tip: core/urgent] entry: Fix noinstr warning in __enter_from_user_mode()

The following commit has been merged into the core/urgent branch of tip:

Commit-ID: f87d28673b71b35b248231a2086f9404afbb7f28
Gitweb: https://git.kernel.org/tip/f87d28673b71b35b248231a2086f9404afbb7f28
Author: Josh Poimboeuf <[email protected]>
AuthorDate: Sat, 25 Feb 2023 16:01:36 -08:00
Committer: Thomas Gleixner <[email protected]>
CommitterDate: Tue, 21 Mar 2023 11:53:16 +01:00

entry: Fix noinstr warning in __enter_from_user_mode()

__enter_from_user_mode() is triggering noinstr warnings with
CONFIG_DEBUG_PREEMPT due to its call of preempt_count_add() via
ct_state().

The preemption disable isn't needed as interrupts are already disabled.
And the context_tracking_enabled() check in ct_state() also isn't needed
as that's already being done by the CT_WARN_ON().

Just use __ct_state() instead.

Fixes the following warnings:

vmlinux.o: warning: objtool: enter_from_user_mode+0xba: call to preempt_count_add() leaves .noinstr.text section
vmlinux.o: warning: objtool: syscall_enter_from_user_mode+0xf9: call to preempt_count_add() leaves .noinstr.text section
vmlinux.o: warning: objtool: syscall_enter_from_user_mode_prepare+0xc7: call to preempt_count_add() leaves .noinstr.text section
vmlinux.o: warning: objtool: irqentry_enter_from_user_mode+0xba: call to preempt_count_add() leaves .noinstr.text section

Fixes: 171476775d32 ("context_tracking: Convert state to atomic_t")
Signed-off-by: Josh Poimboeuf <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/r/d8955fa6d68dc955dda19baf13ae014ae27926f5.1677369694.git.jpoimboe@kernel.org

---
include/linux/context_tracking.h | 1 +
include/linux/context_tracking_state.h | 2 ++
kernel/entry/common.c | 2 +-
3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index d4afa85..3a7909e 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -96,6 +96,7 @@ static inline void user_exit_irqoff(void) { }
static inline int exception_enter(void) { return 0; }
static inline void exception_exit(enum ctx_state prev_ctx) { }
static inline int ct_state(void) { return -1; }
+static inline int __ct_state(void) { return -1; }
static __always_inline bool context_tracking_guest_enter(void) { return false; }
static inline void context_tracking_guest_exit(void) { }
#define CT_WARN_ON(cond) do { } while (0)
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 4a4d56f..fdd537e 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -46,7 +46,9 @@ struct context_tracking {

#ifdef CONFIG_CONTEXT_TRACKING
DECLARE_PER_CPU(struct context_tracking, context_tracking);
+#endif

+#ifdef CONFIG_CONTEXT_TRACKING_USER
static __always_inline int __ct_state(void)
{
return arch_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 846add8..1314894 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -21,7 +21,7 @@ static __always_inline void __enter_from_user_mode(struct pt_regs *regs)
arch_enter_from_user_mode(regs);
lockdep_hardirqs_off(CALLER_ADDR0);

- CT_WARN_ON(ct_state() != CONTEXT_USER);
+ CT_WARN_ON(__ct_state() != CONTEXT_USER);
user_exit_irqoff();

instrumentation_begin();