riscv64: fenv.S: Fix fesetenv(FE_DFL_ENV) failure

Submitted by Ruinland ChuanTzu Tsai on Dec. 2, 2019, 11:06 a.m.

Details

Message ID 20191202110648.GA3068@APC301.andestech.com
State New
Series "riscv64: fenv.S: Fix fesetenv(FE_DFL_ENV) failure"
Headers show

Commit Message

Ruinland ChuanTzu Tsai Dec. 2, 2019, 11:06 a.m.
Hi all, 
during testing libc-test on RV64,
I happended to encounter a segfault on math/fenv.exe .

When FE_DFL_ENV is passed to fesetenv(),
the very first instruction : lw t1, 0(a0) 
will fail since a0 is -1 .

Here's quick hack - -

git diff -- src/fenv/riscv64/fenv.S
And the test case will pass.

Sincerely,
Ruinland Chuan-Tzu Tsai

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diff --git a/src/fenv/riscv64/fenv.S b/src/fenv/riscv64/fenv.S
index 97f74dd6..06215954 100644
--- a/src/fenv/riscv64/fenv.S
+++ b/src/fenv/riscv64/fenv.S
@@ -45,8 +45,12 @@  fegetenv:
 .global fesetenv
 .type fesetenv, %function
 fesetenv:
+        li t2, -1
+        li t1, 0
+        beq a0, t2, setfpcsr
         lw t1, 0(a0)
-        fscsr t0, t1
+setfpcsr:
+        fscsr t1
         li a0, 0
         ret


Comments

Szabolcs Nagy Dec. 2, 2019, 4:46 p.m.
* Ruinland ChuanTzu Tsai <ruinland@andestech.com> [2019-12-02 19:06:52 +0800]:
> Hi all, 
> during testing libc-test on RV64,
> I happended to encounter a segfault on math/fenv.exe .
> 
> When FE_DFL_ENV is passed to fesetenv(),
> the very first instruction : lw t1, 0(a0) 
> will fail since a0 is -1 .
> 
> Here's quick hack - -
> 
> git diff -- src/fenv/riscv64/fenv.S
> diff --git a/src/fenv/riscv64/fenv.S b/src/fenv/riscv64/fenv.S
> index 97f74dd6..06215954 100644
> --- a/src/fenv/riscv64/fenv.S
> +++ b/src/fenv/riscv64/fenv.S
> @@ -45,8 +45,12 @@ fegetenv:
>  .global fesetenv
>  .type fesetenv, %function
>  fesetenv:
> +        li t2, -1
> +        li t1, 0
> +        beq a0, t2, setfpcsr
>          lw t1, 0(a0)
> -        fscsr t0, t1
> +setfpcsr:
> +        fscsr t1
>          li a0, 0
>          ret
> 
> And the test case will pass.

thanks, this looks good
Rich Felker Dec. 7, 2019, 6 p.m.
On Mon, Dec 02, 2019 at 07:06:52PM +0800, Ruinland ChuanTzu Tsai wrote:
> Hi all, 
> during testing libc-test on RV64,
> I happended to encounter a segfault on math/fenv.exe .
> 
> When FE_DFL_ENV is passed to fesetenv(),
> the very first instruction : lw t1, 0(a0) 
> will fail since a0 is -1 .
> 
> Here's quick hack - -
> 
> git diff -- src/fenv/riscv64/fenv.S
> diff --git a/src/fenv/riscv64/fenv.S b/src/fenv/riscv64/fenv.S
> index 97f74dd6..06215954 100644
> --- a/src/fenv/riscv64/fenv.S
> +++ b/src/fenv/riscv64/fenv.S
> @@ -45,8 +45,12 @@ fegetenv:
>  .global fesetenv
>  .type fesetenv, %function
>  fesetenv:
> +        li t2, -1
> +        li t1, 0
> +        beq a0, t2, setfpcsr
>          lw t1, 0(a0)
> -        fscsr t0, t1
> +setfpcsr:
> +        fscsr t1
>          li a0, 0
>          ret
> 
> And the test case will pass.

Looks mostly ok. Applying without the label name, 1f/1: instead. I was
a bit confused by the removal of the t0 operand from fscsr but
apparently the one-operand form implicitly uses the zero register as
rd.

Rich