public inbox for cygwin-cvs@sourceware.org help / color / mirror / Atom feed
From: Corinna Vinschen <corinna@sourceware.org> To: cygwin-cvs@sourceware.org Subject: [newlib-cygwin] Cygwin: cygtls: fix context alignment Date: Mon, 29 Aug 2022 13:21:23 +0000 (GMT) [thread overview] Message-ID: <20220829132123.83F353858D32@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=dcab768cb93e59712af5818736c4de783ae2c612 commit dcab768cb93e59712af5818736c4de783ae2c612 Author: Corinna Vinschen <corinna@vinschen.de> Date: Mon Aug 29 15:18:53 2022 +0200 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> Diff: --- winsup/cygwin/local_includes/cygtls.h | 7 +++++-- 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 018a59946..61c4cbeef 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 0adb702a3..040b5de6b 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
reply other threads:[~2022-08-29 13:21 UTC|newest] Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20220829132123.83F353858D32@sourceware.org \ --to=corinna@sourceware.org \ --cc=cygwin-cvs@sourceware.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).