Re: [PATCH v2 1/2] riscv: consolidate __ex_table construction

Kefeng Wang
2021-10-21T11:38:46Z

On 2021/10/20 22:06, Jisheng Zhang wrote:
> From: Jisheng Zhang <jszhang@kernel.org>
>
> Consolidate all the __ex_table constuction code with a _ASM_EXTABLE
> helper.
>
> There should be no functional change as a result of this patch.
>
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
> arch/riscv/include/asm/futex.h | 12 +++-------
> arch/riscv/include/asm/uaccess.h | 40 +++++++++++---------------------
> 2 files changed, 17 insertions(+), 35 deletions(-)
>
> diff --git a/arch/riscv/include/asm/futex.h b/arch/riscv/include/asm/futex.h
> index 1b00badb9f87..3191574e135c 100644
> --- a/arch/riscv/include/asm/futex.h
> +++ b/arch/riscv/include/asm/futex.h
> @@ -30,10 +30,7 @@
> "3: li %[r],%[e] \n" \
> " jump 2b,%[t] \n" \
> " .previous \n" \
> - " .section __ex_table,\"a\" \n" \
> - " .balign " RISCV_SZPTR " \n" \
> - " " RISCV_PTR " 1b, 3b \n" \
> - " .previous \n" \
> + _ASM_EXTABLE(1b, 3b) \
> : [r] "+r" (ret), [ov] "=&r" (oldval), \
> [u] "+m" (*uaddr), [t] "=&r" (tmp) \
> : [op] "Jr" (oparg), [e] "i" (-EFAULT) \
> @@ -103,11 +100,8 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
> "4: li %[r],%[e] \n"
> " jump 3b,%[t] \n"
> " .previous \n"
> - " .section __ex_table,\"a\" \n"
> - " .balign " RISCV_SZPTR " \n"
> - " " RISCV_PTR " 1b, 4b \n"
> - " " RISCV_PTR " 2b, 4b \n"
> - " .previous \n"
> + _ASM_EXTABLE(1b, 4b) \
> + _ASM_EXTABLE(2b, 4b) \
> : [r] "+r" (ret), [v] "=&r" (val), [u] "+m" (*uaddr), [t] "=&r" (tmp)
> : [ov] "Jr" (oldval), [nv] "Jr" (newval), [e] "i" (-EFAULT)
> : "memory");
> diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
> index f314ff44c48d..35802e72ace8 100644
> --- a/arch/riscv/include/asm/uaccess.h
> +++ b/arch/riscv/include/asm/uaccess.h
> @@ -10,6 +10,12 @@
>
> #include <asm/pgtable.h> /* for TASK_SIZE */
>
> +#define _ASM_EXTABLE(from, to) \
> + " .pushsection __ex_table, \"a\"\n" \
> + " .balign " RISCV_SZPTR " \n" \
> + " " RISCV_PTR "(" #from "), (" #to ")\n" \
> + " .popsection\n"
> +

The jump_label mechanism could use this macro too,
see arch/riscv/include/asm/jump_label.h, maybe move the above into asm.h
and also do some replace in next patch ?

Question: the jump label use relative address, but why not trigger the
Section mismatch issue?