Vincent Chen 8ac71d7e46 riscv: Correct the initialized flow of FP register ... 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>		2019-08-14 13:11:11 -07:00
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asm	riscv: Correct the initialized flow of FP register	2019-08-14 13:11:11 -07:00
uapi/asm	SPDX fixes for 5.3-rc2	2019-07-28 10:00:06 -07:00