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SubjectRe: [PATCH] riscv: Fix the bug in memory access fixup code
From
On Mon, 07 May 2018 19:59:33 PDT (-0700), alankao@andestech.com wrote:
> A piece of fixup code is currently shared by __copy_user and
> __clear_user. It first disables the access to user-space memory
> and then returns the "n" argument, which represents #(bytes not processed).
> However,__copy_user's "n" is in register a2, while __clear_user's in a1,
> and thus it causes errors for programs like setdomainname02 testcase in LTP.
>
> This patch fixes this issue by separating their fixup code and returning
> the right value for the kernel to handle a relative fault properly.
>
> Signed-off-by: Alan Kao <alankao@andestech.com>
> Cc: Greentime Hu <greentime@andestech.com>
> Cc: Zong Li <zong@andestech.com>
> Cc: Vincent Chen <vincentc@andestech.com>
> ---
> arch/riscv/lib/uaccess.S | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
> index 58fb2877c865..0173ea296baa 100644
> --- a/arch/riscv/lib/uaccess.S
> +++ b/arch/riscv/lib/uaccess.S
> @@ -84,7 +84,7 @@ ENTRY(__clear_user)
> bgeu t0, t1, 2f
> bltu a0, t0, 4f
> 1:
> - fixup REG_S, zero, (a0), 10f
> + fixup REG_S, zero, (a0), 11f
> addi a0, a0, SZREG
> bltu a0, t1, 1b
> 2:
> @@ -96,12 +96,12 @@ ENTRY(__clear_user)
> li a0, 0
> ret
> 4: /* Edge case: unalignment */
> - fixup sb, zero, (a0), 10f
> + fixup sb, zero, (a0), 11f
> addi a0, a0, 1
> bltu a0, t0, 4b
> j 1b
> 5: /* Edge case: remainder */
> - fixup sb, zero, (a0), 10f
> + fixup sb, zero, (a0), 11f
> addi a0, a0, 1
> bltu a0, a3, 5b
> j 3b
> @@ -109,9 +109,14 @@ ENDPROC(__clear_user)
>
> .section .fixup,"ax"
> .balign 4
> + /* Fixup code for __copy_user(10) and __clear_user(11) */
> 10:
> /* Disable access to user memory */
> csrs sstatus, t6
> - sub a0, a3, a0
> + mv a0, a2
> + ret
> +11:
> + csrs sstatus, t6
> + mv a0, a1
> ret
> .previous

Thanks!

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