2022-01-24 07:14:55

by Jisheng Zhang

Subject: [PATCH] riscv: extable: fix err reg writing in dedicated uaccess handler

Mayuresh reported commit 20802d8d477d ("riscv: extable: add a dedicated
uaccess handler") breaks the writev02 test case in LTP. This is due to
the err reg isn't correctly set with the errno(-EFAULT in writev02
case). First of all, the err and zero regs are reg numbers rather than
reg offsets in struct pt_regs; Secondly, regs_set_gpr() should write
the regs when offset isn't zero(zero means epc)

Fix it by correcting regs_set_gpr() logic and passing the correct reg
offset to it.

Reported-by: Mayuresh Chitale <[email protected]>
Fixes: 20802d8d477d ("riscv: extable: add a dedicated uaccess handler")
Signed-off-by: Jisheng Zhang <[email protected]>
---
arch/riscv/mm/extable.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/mm/extable.c b/arch/riscv/mm/extable.c
index 05978f78579f..35484d830fd6 100644
--- a/arch/riscv/mm/extable.c
+++ b/arch/riscv/mm/extable.c
@@ -33,7 +33,7 @@ static inline void regs_set_gpr(struct pt_regs *regs, unsigned int offset,
if (unlikely(offset > MAX_REG_OFFSET))
return;

- if (!offset)
+ if (offset)
*(unsigned long *)((unsigned long)regs + offset) = val;
}

@@ -43,8 +43,8 @@ static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);

- regs_set_gpr(regs, reg_err, -EFAULT);
- regs_set_gpr(regs, reg_zero, 0);
+ regs_set_gpr(regs, reg_err * sizeof(unsigned long), -EFAULT);
+ regs_set_gpr(regs, reg_zero * sizeof(unsigned long), 0);

regs->epc = get_ex_fixup(ex);
return true;
--
2.34.1

2022-02-09 06:05:15

by Palmer Dabbelt

Subject: Re: [PATCH] riscv: extable: fix err reg writing in dedicated uaccess handler

On Sun, 23 Jan 2022 01:04:17 PST (-0800), [email protected] wrote:
> Mayuresh reported commit 20802d8d477d ("riscv: extable: add a dedicated
> uaccess handler") breaks the writev02 test case in LTP. This is due to
> the err reg isn't correctly set with the errno(-EFAULT in writev02
> case). First of all, the err and zero regs are reg numbers rather than
> reg offsets in struct pt_regs; Secondly, regs_set_gpr() should write
> the regs when offset isn't zero(zero means epc)
>
> Fix it by correcting regs_set_gpr() logic and passing the correct reg
> offset to it.
>
> Reported-by: Mayuresh Chitale <[email protected]>
> Fixes: 20802d8d477d ("riscv: extable: add a dedicated uaccess handler")
> Signed-off-by: Jisheng Zhang <[email protected]>
> ---
> arch/riscv/mm/extable.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/mm/extable.c b/arch/riscv/mm/extable.c
> index 05978f78579f..35484d830fd6 100644
> --- a/arch/riscv/mm/extable.c
> +++ b/arch/riscv/mm/extable.c
> @@ -33,7 +33,7 @@ static inline void regs_set_gpr(struct pt_regs *regs, unsigned int offset,
> if (unlikely(offset > MAX_REG_OFFSET))
> return;
>
> - if (!offset)
> + if (offset)
> *(unsigned long *)((unsigned long)regs + offset) = val;
> }
>
> @@ -43,8 +43,8 @@ static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
> int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
> int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);
>
> - regs_set_gpr(regs, reg_err, -EFAULT);
> - regs_set_gpr(regs, reg_zero, 0);
> + regs_set_gpr(regs, reg_err * sizeof(unsigned long), -EFAULT);
> + regs_set_gpr(regs, reg_zero * sizeof(unsigned long), 0);
>
> regs->epc = get_ex_fixup(ex);
> return true;

Thanks, this is on fixes. I'm not sure if it's saner to have these be
register numbers rather than offsets, but regs_get_register is this way
so it's probably better to have them match.