mirror of
https://github.com/Fishwaldo/linux-bl808.git
synced 2025-06-17 20:25:19 +00:00
8ac71d7e46
The following two reasons cause FP registers are sometimes not
initialized before starting the user program.
1. Currently, the FP context is initialized in flush_thread() function
and we expect these initial values to be restored to FP register when
doing FP context switch. However, the FP context switch only occurs in
switch_to function. Hence, if this process does not be scheduled out
and scheduled in before entering the user space, the FP registers
have no chance to initialize.
2. In flush_thread(), the state of reg->sstatus.FS inherits from the
parent. Hence, the state of reg->sstatus.FS may be dirty. If this
process is scheduled out during flush_thread() and initializing the
FP register, the fstate_save() in switch_to will corrupt the FP context
which has been initialized until flush_thread().
To solve the 1st case, the initialization of the FP register will be
completed in start_thread(). It makes sure all FP registers are initialized
before starting the user program. For the 2nd case, the state of
reg->sstatus.FS in start_thread will be set to SR_FS_OFF to prevent this
process from corrupting FP context in doing context save. The FP state is
set to SR_FS_INITIAL in start_trhead().
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Fixes: 7db91e57a0 ("RISC-V: Task implementation")
Cc: stable@vger.kernel.org
[paul.walmsley@sifive.com: fixed brace alignment issue reported by
checkpatch]
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
77 lines
1.8 KiB
C
77 lines
1.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
|
|
/*
|
|
* Copyright (C) 2012 Regents of the University of California
|
|
*/
|
|
|
|
#ifndef _ASM_RISCV_SWITCH_TO_H
|
|
#define _ASM_RISCV_SWITCH_TO_H
|
|
|
|
#include <asm/processor.h>
|
|
#include <asm/ptrace.h>
|
|
#include <asm/csr.h>
|
|
|
|
#ifdef CONFIG_FPU
|
|
extern void __fstate_save(struct task_struct *save_to);
|
|
extern void __fstate_restore(struct task_struct *restore_from);
|
|
|
|
static inline void __fstate_clean(struct pt_regs *regs)
|
|
{
|
|
regs->sstatus |= (regs->sstatus & ~(SR_FS)) | SR_FS_CLEAN;
|
|
}
|
|
|
|
static inline void fstate_off(struct task_struct *task,
|
|
struct pt_regs *regs)
|
|
{
|
|
regs->sstatus = (regs->sstatus & ~SR_FS) | SR_FS_OFF;
|
|
}
|
|
|
|
static inline void fstate_save(struct task_struct *task,
|
|
struct pt_regs *regs)
|
|
{
|
|
if ((regs->sstatus & SR_FS) == SR_FS_DIRTY) {
|
|
__fstate_save(task);
|
|
__fstate_clean(regs);
|
|
}
|
|
}
|
|
|
|
static inline void fstate_restore(struct task_struct *task,
|
|
struct pt_regs *regs)
|
|
{
|
|
if ((regs->sstatus & SR_FS) != SR_FS_OFF) {
|
|
__fstate_restore(task);
|
|
__fstate_clean(regs);
|
|
}
|
|
}
|
|
|
|
static inline void __switch_to_aux(struct task_struct *prev,
|
|
struct task_struct *next)
|
|
{
|
|
struct pt_regs *regs;
|
|
|
|
regs = task_pt_regs(prev);
|
|
if (unlikely(regs->sstatus & SR_SD))
|
|
fstate_save(prev, regs);
|
|
fstate_restore(next, task_pt_regs(next));
|
|
}
|
|
|
|
extern bool has_fpu;
|
|
#else
|
|
#define has_fpu false
|
|
#define fstate_save(task, regs) do { } while (0)
|
|
#define fstate_restore(task, regs) do { } while (0)
|
|
#define __switch_to_aux(__prev, __next) do { } while (0)
|
|
#endif
|
|
|
|
extern struct task_struct *__switch_to(struct task_struct *,
|
|
struct task_struct *);
|
|
|
|
#define switch_to(prev, next, last) \
|
|
do { \
|
|
struct task_struct *__prev = (prev); \
|
|
struct task_struct *__next = (next); \
|
|
if (has_fpu) \
|
|
__switch_to_aux(__prev, __next); \
|
|
((last) = __switch_to(__prev, __next)); \
|
|
} while (0)
|
|
|
|
#endif /* _ASM_RISCV_SWITCH_TO_H */
|