From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Ard Biesheuvel <ardb@kernel.org>,
Keith Packard <keithpac@amazon.com>,
Russell King <linux@armlinux.org.uk>,
Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
Linus Walleij <linus.walleij@linaro.org>
Subject: [PATCH v4 5/5] ARM: smp: Enable THREAD_INFO_IN_TASK
Date: Mon, 13 Sep 2021 12:40:01 +0200 [thread overview]
Message-ID: <20210913104001.3043132-6-ardb@kernel.org> (raw)
In-Reply-To: <20210913104001.3043132-1-ardb@kernel.org>
Now that we no longer rely on thread_info living at the base of the task
stack to be able to access the 'current' pointer, we can wire up the
generic support for moving thread_info into the task struct itself.
Note that this requires us to update the cpu field in thread_info
explicitly, now that the core code no longer does so. Ideally, we would
switch the percpu code to access the cpu field in task_struct instead,
but this unleashes #include circular dependency hell.
Co-developed-by: Keith Packard <keithpac@amazon.com>
Signed-off-by: Keith Packard <keithpac@amazon.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/arm/Kconfig | 1 +
arch/arm/include/asm/assembler.h | 5 +++++
arch/arm/include/asm/switch_to.h | 14 ++++++++++++++
arch/arm/include/asm/thread_info.h | 10 +++++++++-
arch/arm/kernel/asm-offsets.c | 2 ++
arch/arm/kernel/entry-armv.S | 3 +--
arch/arm/kernel/smp.c | 3 +++
7 files changed, 35 insertions(+), 3 deletions(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 24c756299d48..0aa7192b08ea 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -125,6 +125,7 @@ config ARM
select PERF_USE_VMALLOC
select RTC_LIB
select SYS_SUPPORTS_APM_EMULATION
+ select THREAD_INFO_IN_TASK if CURRENT_POINTER_IN_TPIDRURO
select TRACE_IRQFLAGS_SUPPORT if !CPU_V7M
# Above selects are sorted alphabetically; please add new ones
# according to that. Thanks.
diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index c1551dee28be..7d23d4bb2168 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -227,10 +227,15 @@
* Get current thread_info.
*/
.macro get_thread_info, rd
+#ifdef CONFIG_THREAD_INFO_IN_TASK
+ /* thread_info is the first member of struct task_struct */
+ get_current \rd
+#else
ARM( mov \rd, sp, lsr #THREAD_SIZE_ORDER + PAGE_SHIFT )
THUMB( mov \rd, sp )
THUMB( lsr \rd, \rd, #THREAD_SIZE_ORDER + PAGE_SHIFT )
mov \rd, \rd, lsl #THREAD_SIZE_ORDER + PAGE_SHIFT
+#endif
.endm
/*
diff --git a/arch/arm/include/asm/switch_to.h b/arch/arm/include/asm/switch_to.h
index 61e4a3c4ca6e..db2be1f6550d 100644
--- a/arch/arm/include/asm/switch_to.h
+++ b/arch/arm/include/asm/switch_to.h
@@ -23,9 +23,23 @@
*/
extern struct task_struct *__switch_to(struct task_struct *, struct thread_info *, struct thread_info *);
+static inline void set_ti_cpu(struct task_struct *p)
+{
+#ifdef CONFIG_THREAD_INFO_IN_TASK
+ /*
+ * The core code no longer maintains the thread_info::cpu field once
+ * CONFIG_THREAD_INFO_IN_TASK is in effect, but we rely on it for
+ * raw_smp_processor_id(), which cannot access struct task_struct*
+ * directly for reasons of circular #inclusion hell.
+ */
+ task_thread_info(p)->cpu = p->cpu;
+#endif
+}
+
#define switch_to(prev,next,last) \
do { \
__complete_pending_tlbi(); \
+ set_ti_cpu(next); \
if (IS_ENABLED(CONFIG_CURRENT_POINTER_IN_TPIDRURO)) \
__this_cpu_write(__entry_task, next); \
last = __switch_to(prev,task_thread_info(prev), task_thread_info(next)); \
diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 76b6fbd5540c..787511396f3f 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -54,7 +54,9 @@ struct cpu_context_save {
struct thread_info {
unsigned long flags; /* low level flags */
int preempt_count; /* 0 => preemptable, <0 => bug */
+#ifndef CONFIG_THREAD_INFO_IN_TASK
struct task_struct *task; /* main task structure */
+#endif
__u32 cpu; /* cpu */
__u32 cpu_domain; /* cpu domain */
struct cpu_context_save cpu_context; /* cpu context */
@@ -70,11 +72,16 @@ struct thread_info {
#define INIT_THREAD_INFO(tsk) \
{ \
- .task = &tsk, \
+ INIT_THREAD_INFO_TASK(tsk) \
.flags = 0, \
.preempt_count = INIT_PREEMPT_COUNT, \
}
+#ifdef CONFIG_THREAD_INFO_IN_TASK
+#define INIT_THREAD_INFO_TASK(tsk)
+#else
+#define INIT_THREAD_INFO_TASK(tsk) .task = &(tsk),
+
/*
* how to get the thread information struct from C
*/
@@ -85,6 +92,7 @@ static inline struct thread_info *current_thread_info(void)
return (struct thread_info *)
(current_stack_pointer & ~(THREAD_SIZE - 1));
}
+#endif
#define thread_saved_pc(tsk) \
((unsigned long)(task_thread_info(tsk)->cpu_context.pc))
diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
index 9c864ee76107..645845e4982a 100644
--- a/arch/arm/kernel/asm-offsets.c
+++ b/arch/arm/kernel/asm-offsets.c
@@ -43,7 +43,9 @@ int main(void)
BLANK();
DEFINE(TI_FLAGS, offsetof(struct thread_info, flags));
DEFINE(TI_PREEMPT, offsetof(struct thread_info, preempt_count));
+#ifndef CONFIG_THREAD_INFO_IN_TASK
DEFINE(TI_TASK, offsetof(struct thread_info, task));
+#endif
DEFINE(TI_CPU, offsetof(struct thread_info, cpu));
DEFINE(TI_CPU_DOMAIN, offsetof(struct thread_info, cpu_domain));
DEFINE(TI_CPU_SAVE, offsetof(struct thread_info, cpu_context));
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index aedcaa329fc9..75580528f267 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -777,8 +777,7 @@ ENTRY(__switch_to)
str r7, [r8]
#endif
#ifdef CONFIG_CURRENT_POINTER_IN_TPIDRURO
- ldr ip, [r4, #TI_TASK]
- set_current ip
+ set_current r4
#endif
add r4, r4, #TI_CPU_SAVE
THUMB( mov ip, r4 )
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 97ee6b1567e9..cde5b6d8bac5 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -154,6 +154,9 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
secondary_data.swapper_pg_dir = get_arch_pgd(swapper_pg_dir);
#endif
secondary_data.task = idle;
+ if (IS_ENABLED(CONFIG_THREAD_INFO_IN_TASK))
+ task_thread_info(idle)->cpu = cpu;
+
sync_cache_w(&secondary_data);
/*
--
2.30.2
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next prev parent reply other threads:[~2021-09-13 10:44 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-13 10:39 [PATCH v4 0/5] ARM: support THREAD_INFO_IN_TASK Ard Biesheuvel
2021-09-13 10:39 ` [PATCH v4 1/5] gcc-plugins: arm-ssp: Prepare for THREAD_INFO_IN_TASK support Ard Biesheuvel
2021-09-13 15:40 ` Kees Cook
2021-09-14 22:04 ` Linus Walleij
2021-09-15 6:37 ` Ard Biesheuvel
2021-09-15 16:26 ` Kees Cook
2021-09-13 10:39 ` [PATCH v4 2/5] ARM: smp: Pass task to secondary_start_kernel Ard Biesheuvel
2021-09-13 23:25 ` Linus Walleij
2021-09-13 10:39 ` [PATCH v4 3/5] ARM: smp: Free up the TLS register while running in the kernel Ard Biesheuvel
2021-09-13 10:40 ` [PATCH v4 4/5] ARM: smp: Store current pointer in TPIDRURO register if available Ard Biesheuvel
2021-09-13 11:22 ` Russell King (Oracle)
2021-09-13 12:52 ` Ard Biesheuvel
2021-09-13 13:52 ` Russell King (Oracle)
2021-09-13 10:40 ` Ard Biesheuvel [this message]
2021-09-13 11:23 ` [PATCH v4 0/5] ARM: support THREAD_INFO_IN_TASK Russell King (Oracle)
2021-09-13 15:40 ` Kees Cook
2021-09-14 9:44 ` Arnd Bergmann
2021-09-14 9:50 ` Ard Biesheuvel
2021-09-14 13:07 ` Arnd Bergmann
2021-09-14 17:10 ` Ard Biesheuvel
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