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| author | Stefan Liebler <stli@linux.ibm.com> | 2023-10-18 15:08:40 +0200 |
|---|---|---|
| committer | Stefan Liebler <stli@linux.ibm.com> | 2023-10-19 14:28:22 +0200 |
| commit | 97a58d885b01ecf432e0d96248556245a232597e (patch) | |
| tree | 84eed7270c358bce0cfc0a89751fd1de0289f58c | |
| parent | c06e10c8130358c409c1d2837f8171ef70169d03 (diff) | |
| download | glibc-97a58d885b01ecf432e0d96248556245a232597e.tar.gz glibc-97a58d885b01ecf432e0d96248556245a232597e.tar.xz glibc-97a58d885b01ecf432e0d96248556245a232597e.zip | |
s390: Fix undefined behaviour in feenableexcept, fedisableexcept [BZ #30960]
If feenableexcept or fedisableexcept gets excepts=FE_INVALID=0x80 as input, we have a signed left shift: 0x80 << 24 which is not representable as int and thus is undefined behaviour according to C standard. This patch casts excepts as unsigned int before shifting, which is defined. For me, the observed undefined behaviour is that the shift is done with "unsigned"-instructions, which is exactly what we want. Furthermore, I don't get any exception-flags. After the fix, the code is using the same instruction sequence as before.
| -rw-r--r-- | sysdeps/s390/fpu/fedisblxcpt.c | 3 | ||||
| -rw-r--r-- | sysdeps/s390/fpu/feenablxcpt.c | 3 |
2 files changed, 4 insertions, 2 deletions
diff --git a/sysdeps/s390/fpu/fedisblxcpt.c b/sysdeps/s390/fpu/fedisblxcpt.c index 728f103f43..55634c299f 100644 --- a/sysdeps/s390/fpu/fedisblxcpt.c +++ b/sysdeps/s390/fpu/fedisblxcpt.c @@ -26,7 +26,8 @@ fedisableexcept (int excepts) _FPU_GETCW (temp); old_exc = (temp & FPC_EXCEPTION_MASK) >> FPC_EXCEPTION_MASK_SHIFT; - new_flags = (temp & (~((excepts & FE_ALL_EXCEPT) << FPC_EXCEPTION_MASK_SHIFT))); + new_flags = (temp & ~(((unsigned int) excepts & FE_ALL_EXCEPT) + << FPC_EXCEPTION_MASK_SHIFT)); _FPU_SETCW (new_flags); return old_exc; diff --git a/sysdeps/s390/fpu/feenablxcpt.c b/sysdeps/s390/fpu/feenablxcpt.c index 0807e610a2..d73659f078 100644 --- a/sysdeps/s390/fpu/feenablxcpt.c +++ b/sysdeps/s390/fpu/feenablxcpt.c @@ -26,7 +26,8 @@ feenableexcept (int excepts) _FPU_GETCW (temp); old_exc = (temp & FPC_EXCEPTION_MASK) >> FPC_EXCEPTION_MASK_SHIFT; - new_flags = (temp | ((excepts & FE_ALL_EXCEPT) << FPC_EXCEPTION_MASK_SHIFT)); + new_flags = (temp | (((unsigned int) excepts & FE_ALL_EXCEPT) + << FPC_EXCEPTION_MASK_SHIFT)); _FPU_SETCW (new_flags); return old_exc; |