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SubjectRe: [PATCH 8/8] riscv: remove address space overrides using set_fs()
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On Sun, 06 Sep 2020 22:58:25 PDT (-0700), Christoph Hellwig wrote:
> Stop providing the possibility to override the address space using
> set_fs() now that there is no need for that any more.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> arch/riscv/Kconfig | 1 -
> arch/riscv/include/asm/thread_info.h | 6 ------
> arch/riscv/include/asm/uaccess.h | 27 +--------------------------
> arch/riscv/kernel/process.c | 1 -
> 4 files changed, 1 insertion(+), 34 deletions(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 460e3971a80fde..33dde87218ddab 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -86,7 +86,6 @@ config RISCV
> select SPARSE_IRQ
> select SYSCTL_EXCEPTION_TRACE
> select THREAD_INFO_IN_TASK
> - select SET_FS
> select UACCESS_MEMCPY if !MMU
>
> config ARCH_MMAP_RND_BITS_MIN
> diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
> index 464a2bbc97ea33..a390711129de64 100644
> --- a/arch/riscv/include/asm/thread_info.h
> +++ b/arch/riscv/include/asm/thread_info.h
> @@ -24,10 +24,6 @@
> #include <asm/processor.h>
> #include <asm/csr.h>
>
> -typedef struct {
> - unsigned long seg;
> -} mm_segment_t;
> -
> /*
> * low level task data that entry.S needs immediate access to
> * - this struct should fit entirely inside of one cache line
> @@ -39,7 +35,6 @@ typedef struct {
> struct thread_info {
> unsigned long flags; /* low level flags */
> int preempt_count; /* 0=>preemptible, <0=>BUG */
> - mm_segment_t addr_limit;
> /*
> * These stack pointers are overwritten on every system call or
> * exception. SP is also saved to the stack it can be recovered when
> @@ -59,7 +54,6 @@ struct thread_info {
> { \
> .flags = 0, \
> .preempt_count = INIT_PREEMPT_COUNT, \
> - .addr_limit = KERNEL_DS, \
> }
>
> #endif /* !__ASSEMBLY__ */
> diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
> index 264e52fb62b143..c47e6b35c551f4 100644
> --- a/arch/riscv/include/asm/uaccess.h
> +++ b/arch/riscv/include/asm/uaccess.h
> @@ -26,29 +26,6 @@
> #define __disable_user_access() \
> __asm__ __volatile__ ("csrc sstatus, %0" : : "r" (SR_SUM) : "memory")
>
> -/*
> - * The fs value determines whether argument validity checking should be
> - * performed or not. If get_fs() == USER_DS, checking is performed, with
> - * get_fs() == KERNEL_DS, checking is bypassed.
> - *
> - * For historical reasons, these macros are grossly misnamed.
> - */
> -
> -#define MAKE_MM_SEG(s) ((mm_segment_t) { (s) })
> -
> -#define KERNEL_DS MAKE_MM_SEG(~0UL)
> -#define USER_DS MAKE_MM_SEG(TASK_SIZE)
> -
> -#define get_fs() (current_thread_info()->addr_limit)
> -
> -static inline void set_fs(mm_segment_t fs)
> -{
> - current_thread_info()->addr_limit = fs;
> -}
> -
> -#define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg)
> -#define user_addr_max() (get_fs().seg)
> -
> /**
> * access_ok: - Checks if a user space pointer is valid
> * @addr: User space pointer to start of block to check
> @@ -76,9 +53,7 @@ static inline void set_fs(mm_segment_t fs)
> */
> static inline int __access_ok(unsigned long addr, unsigned long size)
> {
> - const mm_segment_t fs = get_fs();
> -
> - return size <= fs.seg && addr <= fs.seg - size;
> + return size <= TASK_SIZE && addr <= TASK_SIZE - size;
> }
>
> /*
> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
> index 2b97c493427c9e..19225ec65db62f 100644
> --- a/arch/riscv/kernel/process.c
> +++ b/arch/riscv/kernel/process.c
> @@ -84,7 +84,6 @@ void start_thread(struct pt_regs *regs, unsigned long pc,
> }
> regs->epc = pc;
> regs->sp = sp;
> - set_fs(USER_DS);
> }
>
> void flush_thread(void)

Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>

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