riscv: __asm_copy_to-from_user: Fix: overrun copy

There were two causes for the overrun memory access.

The threshold size was too small.
The aligning dst require one SZREG and unrolling word copy requires
8*SZREG, total have to be at least 9*SZREG.

Inside the unrolling copy, the subtracting -(8*SZREG-1) would make
iteration happening one extra loop. Proper value is -(8*SZREG).

Signed-off-by: Akira Tsukamoto <akira.tsukamoto@gmail.com>
Fixes: ca6eaaa210de ("riscv: __asm_copy_to-from_user: Optimize unaligned memory access and pipeline stall")
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
index bceb062..8bbeca8 100644 (file)
--- a/arch/riscv/lib/uaccess.S
+++ b/arch/riscv/lib/uaccess.S
@@ -35,7 +35,7 @@ ENTRY(__asm_copy_from_user)
        /*
         * Use byte copy only if too small.
         */
-       li      a3, 8*SZREG /* size must be larger than size in word_copy */
+       li      a3, 9*SZREG /* size must be larger than size in word_copy */
        bltu    a2, a3, .Lbyte_copy_tail
 
        /*
@@ -75,7 +75,7 @@ ENTRY(__asm_copy_from_user)
         * a3 - a1 & mask:(SZREG-1)
         * t0 - end of aligned dst
         */
-       addi    t0, t0, -(8*SZREG-1) /* not to over run */
+       addi    t0, t0, -(8*SZREG) /* not to over run */
 2:
        fixup REG_L   a4,        0(a1), 10f
        fixup REG_L   a5,    SZREG(a1), 10f
@@ -97,7 +97,7 @@ ENTRY(__asm_copy_from_user)
        addi    a1, a1, 8*SZREG
        bltu    a0, t0, 2b
 
-       addi    t0, t0, 8*SZREG-1 /* revert to original value */
+       addi    t0, t0, 8*SZREG /* revert to original value */
        j       .Lbyte_copy_tail
 
 .Lshift_copy: