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author | Corinna Vinschen <corinna@vinschen.de> | 2022-08-29 15:18:53 +0200 |
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committer | Corinna Vinschen <corinna@vinschen.de> | 2022-08-29 15:18:53 +0200 |
commit | dcab768cb93e59712af5818736c4de783ae2c612 (patch) | |
tree | 148ba764d72ccf276a1c752798400fdf48d517c1 | |
parent | 717c36c0a4e387a73146c1181b7b89f091176e85 (diff) | |
download | newlib-dcab768cb93e59712af5818736c4de783ae2c612.zip newlib-dcab768cb93e59712af5818736c4de783ae2c612.tar.gz newlib-dcab768cb93e59712af5818736c4de783ae2c612.tar.bz2 |
Cygwin: cygtls: fix context alignment
A hang was encountered, apparently triggered by commit 63b503916d42,
changing tls_pathbufs from malloc'ed to HeapAlloc'ed memory. After
lengthy debugging it transpired that adding the heap handle to the
tls_pathbuf struct added 8 bytes to the cygtls area, thus moving
the "context" member by 8 bytes, too, so it was suddently unaligned.
Fix this for now by changing the alignment.
Fix this once and for all, by adding code to the gentls_offsets script
to check if the alignment of the "context" member is 16 bytes. If not,
print a matching error message, remove the just generated file, and exit
with error.
FIXME: It would be really nice to find a way to auomate the correct
alignment of the "context" member, but I don't see any way to use
alignment attributes to get what we need here.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
-rw-r--r-- | winsup/cygwin/local_includes/cygtls.h | 7 | ||||
-rwxr-xr-x | winsup/cygwin/scripts/gentls_offsets | 9 |
2 files changed, 14 insertions, 2 deletions
diff --git a/winsup/cygwin/local_includes/cygtls.h b/winsup/cygwin/local_includes/cygtls.h index 018a599..61c4cbe 100644 --- a/winsup/cygwin/local_includes/cygtls.h +++ b/winsup/cygwin/local_includes/cygtls.h @@ -178,11 +178,14 @@ public: /* Do NOT remove this public: line, it's a marker for gentls_offsets. */ siginfo_t *sigwait_info; HANDLE signal_arrived; bool will_wait_for_signal; +#if 0 long __align; /* Needed to align context to 16 byte. */ +#endif /* context MUST be aligned to 16 byte, otherwise RtlCaptureContext fails. If you prepend cygtls members here, make sure context stays 16 byte - aligned. */ - ucontext_t context; + aligned. The gentls_offsets script checks for that now and fails + if the alignment is wrong. */ + ucontext_t __attribute__((__aligned__(__alignof__(long double)))) context; DWORD thread_id; siginfo_t infodata; struct pthread *tid; diff --git a/winsup/cygwin/scripts/gentls_offsets b/winsup/cygwin/scripts/gentls_offsets index 0adb702..040b5de 100755 --- a/winsup/cygwin/scripts/gentls_offsets +++ b/winsup/cygwin/scripts/gentls_offsets @@ -98,3 +98,12 @@ gawk -v start_offset="$start_offset" '\ } } ' ${tmp_file} > "${output_file}" +# Check if the `context' member is 16 bytes aligned. Delete output_file +# and bail out with error if not. +MOD=$(awk '/_cygtls.context_p/{ print $3 % 16; }' "${output_file}") +if [ $MOD -ne 0 ] +then + echo "Error: _cygtls.context member is not 16 bytes aligned!" + rm "${output_file}" + exit 1 +fi |