musl - [PATCH] riscv64: fenv.S: Fix fesetenv(FE_DFL

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Message-ID: <20191202110648.GA3068@APC301.andestech.com>
Date: Mon, 2 Dec 2019 19:06:52 +0800
From: Ruinland ChuanTzu Tsai <ruinland@...estech.com>
To: <musl@...ts.openwall.com>
CC: <alankao@...estech.com>
Subject: [PATCH] riscv64: fenv.S: Fix fesetenv(FE_DFL_ENV) failure

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.

Sincerely,
Ruinland Chuan-Tzu Tsai

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