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Message-Id: <20250122-riscv_optimize_entry-v1-3-4ee95559cfd0@rivosinc.com>
Date: Wed, 22 Jan 2025 14:56:22 -0800
From: Charlie Jenkins <charlie@...osinc.com>
To: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>, Huacai Chen <chenhuacai@...nel.org>,
WANG Xuerui <kernel@...0n.name>, Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>, Andy Lutomirski <luto@...nel.org>,
Alexandre Ghiti <alexghiti@...osinc.com>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
loongarch@...ts.linux.dev, Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH 3/4] loongarch: entry: Migrate ret_from_fork() to C
Loongarch is the only architecture that calls
syscall_exit_to_user_mode() from asm. Move the call into C so that this
function can be inlined across all architectures.
Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
---
arch/loongarch/include/asm/switch_to.h | 8 ++++++++
arch/loongarch/kernel/entry.S | 22 ++++++++++-----------
arch/loongarch/kernel/process.c | 36 ++++++++++++++++++++++++++++------
3 files changed, 48 insertions(+), 18 deletions(-)
diff --git a/arch/loongarch/include/asm/switch_to.h b/arch/loongarch/include/asm/switch_to.h
index 5b225aff3ba21aa06d0713bc8e73e1b941389630..a1c5576f1fd145670e13038bec6dd390486099ab 100644
--- a/arch/loongarch/include/asm/switch_to.h
+++ b/arch/loongarch/include/asm/switch_to.h
@@ -26,6 +26,14 @@ extern asmlinkage struct task_struct *__switch_to(struct task_struct *prev,
struct task_struct *next, struct thread_info *next_ti,
void *sched_ra, void *sched_cfa);
+void noinstr __no_stack_protector ret_from_kernel_thread(struct task_struct *prev,
+ struct pt_regs *regs,
+ int (*fn)(void *),
+ void *fn_arg);
+
+void noinstr __no_stack_protector ret_from_fork(struct task_struct *prev,
+ struct pt_regs *regs);
+
/*
* For newly created kernel threads switch_to() will return to
* ret_from_kernel_thread, newly created user threads to ret_from_fork.
diff --git a/arch/loongarch/kernel/entry.S b/arch/loongarch/kernel/entry.S
index 48e7e34e355e83eae8165957ba2eac05a8bf17df..2abc29e573810e000f2fef4646ddca0dbb80eabe 100644
--- a/arch/loongarch/kernel/entry.S
+++ b/arch/loongarch/kernel/entry.S
@@ -77,24 +77,22 @@ SYM_CODE_START(handle_syscall)
SYM_CODE_END(handle_syscall)
_ASM_NOKPROBE(handle_syscall)
-SYM_CODE_START(ret_from_fork)
+SYM_CODE_START(ret_from_fork_asm)
UNWIND_HINT_REGS
- bl schedule_tail # a0 = struct task_struct *prev
- move a0, sp
- bl syscall_exit_to_user_mode
+ move a1, sp
+ bl ret_from_fork
RESTORE_STATIC
RESTORE_SOME
RESTORE_SP_AND_RET
-SYM_CODE_END(ret_from_fork)
+SYM_CODE_END(ret_from_fork_asm)
-SYM_CODE_START(ret_from_kernel_thread)
+SYM_CODE_START(ret_from_kernel_thread_asm)
UNWIND_HINT_REGS
- bl schedule_tail # a0 = struct task_struct *prev
- move a0, s1
- jirl ra, s0, 0
- move a0, sp
- bl syscall_exit_to_user_mode
+ move a1, sp
+ move a2, s0
+ move a3, s1
+ bl ret_from_kernel_thread
RESTORE_STATIC
RESTORE_SOME
RESTORE_SP_AND_RET
-SYM_CODE_END(ret_from_kernel_thread)
+SYM_CODE_END(ret_from_kernel_thread_asm)
diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
index 6e58f65455c7ca3eae2e88ed852c8655a6701e5c..9bb069ef363fefed1f2115e6572b31c2b76bb414 100644
--- a/arch/loongarch/kernel/process.c
+++ b/arch/loongarch/kernel/process.c
@@ -14,6 +14,7 @@
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/errno.h>
+#include <linux/entry-common.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task.h>
@@ -47,6 +48,7 @@
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/reg.h>
+#include <asm/switch_to.h>
#include <asm/unwind.h>
#include <asm/vdso.h>
@@ -63,8 +65,12 @@ EXPORT_SYMBOL(__stack_chk_guard);
unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
EXPORT_SYMBOL(boot_option_idle_override);
-asmlinkage void ret_from_fork(void);
-asmlinkage void ret_from_kernel_thread(void);
+asmlinkage void restore_and_ret(void);
+asmlinkage void ret_from_fork_asm(void);
+void noinstr __no_stack_protector ret_from_kernel_thread(struct task_struct *prev,
+ struct pt_regs *regs,
+ int (*fn)(void *),
+ void *fn_arg)
void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
{
@@ -138,6 +144,24 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
return 0;
}
+void noinstr __no_stack_protector ret_from_kernel_thread(struct task_struct *prev,
+ struct pt_regs *regs,
+ int (*fn)(void *),
+ void *fn_arg)
+{
+ schedule_tail(prev);
+
+ fn(fn_arg);
+
+ syscall_exit_to_user_mode(regs);
+}
+
+void noinstr __no_stack_protector ret_from_fork(struct task_struct *prev, struct pt_regs *regs)
+{
+ schedule_tail(prev);
+ syscall_exit_to_user_mode(regs);
+}
+
/*
* Copy architecture-specific thread state
*/
@@ -165,8 +189,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
p->thread.reg03 = childksp;
p->thread.reg23 = (unsigned long)args->fn;
p->thread.reg24 = (unsigned long)args->fn_arg;
- p->thread.reg01 = (unsigned long)ret_from_kernel_thread;
- p->thread.sched_ra = (unsigned long)ret_from_kernel_thread;
+ p->thread.reg01 = (unsigned long)ret_from_kernel_thread_asm;
+ p->thread.sched_ra = (unsigned long)ret_from_kernel_thread_asm;
memset(childregs, 0, sizeof(struct pt_regs));
childregs->csr_euen = p->thread.csr_euen;
childregs->csr_crmd = p->thread.csr_crmd;
@@ -182,8 +206,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
childregs->regs[3] = usp;
p->thread.reg03 = (unsigned long) childregs;
- p->thread.reg01 = (unsigned long) ret_from_fork;
- p->thread.sched_ra = (unsigned long) ret_from_fork;
+ p->thread.reg01 = (unsigned long) ret_from_fork_asm;
+ p->thread.sched_ra = (unsigned long) ret_from_fork_asm;
/*
* New tasks lose permission to use the fpu. This accelerates context
--
2.43.0
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