From patchwork Tue May 16 19:11:01 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adhemerval Zanella Netto X-Patchwork-Id: 20469 Received: (qmail 29853 invoked by alias); 16 May 2017 19:11:10 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 29841 invoked by uid 89); 16 May 2017 19:11:09 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-24.9 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_NONE, RCVD_IN_SORBS_SPAM, SPF_PASS autolearn=ham version=3.3.2 spammy=states X-HELO: mail-qt0-f169.google.com X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id; bh=a4fF4lFabKwbYIg7NKZMnUHKAt+ODAEaBBgsM1Divrk=; b=QryslJ8XfF2dvKKSZNv5kj6IMHkR1N7vQZz9JqSxV2n1w5WHl83LyWVdr6quXrpQ0u KIUSaOUuYMK1vDj+fJ95CGU+gG1RYduSO1KG1hl9M7IWzEMn9rQelb21EqDOWpQc5oND EiVOzkNulyFsDOm0/PSp/ng7EU13WiFPDonbN+kG2xefhhTh8b54UReuYR4Cfy+5NKJE ByGWrQ3dDaaAV/wnApL8Yu8GLW4duoHx+TmL5J+ayWqPSSVB5GIzVYB0k1u1jzGnC8a8 vKFrlnX5zKwvV1//XR2BXbdUxpdp7Oknov8W4WCXGl8MtQ0GURLwGELbsYxG1l1AvPvG kmTQ== X-Gm-Message-State: AODbwcBL0Kw9ybfIWnRl4o7E7sndITyKD2VZEMy2bKd3tKAG5tZAZqKQ rdDQVi6i3yobSk/dW9dM4A== X-Received: by 10.200.47.161 with SMTP id l30mr12711181qta.153.1494961867681; Tue, 16 May 2017 12:11:07 -0700 (PDT) From: Adhemerval Zanella To: libc-alpha@sourceware.org Subject: [PATCH] manual: Document getcontext uc_stack value on Linux [BZ #759] Date: Tue, 16 May 2017 16:11:01 -0300 Message-Id: <1494961861-30734-1-git-send-email-adhemerval.zanella@linaro.org> As decribed in BZ#759, Linux getcontext implementation on Linux does differs from other SysV system about the returned uc_stack. This is true not only for i386, but for all the architecture I could actually check (aarch64, arm, alpha, hppa, m68k, mips, mips64, mips64n32, powerpc, powerpc64, powerpc64le, s390x, sh, sparc, sparc64, and x86). And I think we should not change current behavior for some reasons: 1. POSIX 2008 removed this SySV interface for a good reason and changing this behavior adds nothing for current portable code. POSIX 2001 specification does states that stack should be saved [1] and current GLIBC code does in a arch-specific manner (inside the mcontext_t) which allows the setcontext to work correctly. 2. Changing this behavior would potentially require compat symbols and I see no gain in adding compat symbols for deprecated interfaces. 3. Also, for comment #2 in BZ#759, it is up to kernel do setup the contents for ucontext_t and currently it does not provide the stack information as well. Trying to change it is also another fix that does not worth the possible gains. Instead my proposal is to make it clear the current interface behavior in glibc documentation and close this bug as invalid. [BZ #759] * manual/setjmp.texi (getcontex): Document uc_stack value on Linux. [1] http://pubs.opengroup.org/onlinepubs/009695399/functions/getcontext.html --- ChangeLog | 5 +++++ manual/setjmp.texi | 5 +++++ 2 files changed, 10 insertions(+) diff --git a/manual/setjmp.texi b/manual/setjmp.texi index 94d16be..07cc7bf 100644 --- a/manual/setjmp.texi +++ b/manual/setjmp.texi @@ -302,6 +302,11 @@ the content of the registers, the signal mask, and the current stack. Executing the contents would start at the point where the @code{getcontext} call just returned. +On Linux the stack information return on @code{uc_stack} is empty by +default. It also the case for signal handling information through +@code{sigaction} with @code{SA_SIGINFO}. It could be obtained using +architecture specific field from @code{uc_mcontext} member. + The function returns @code{0} if successful. Otherwise it returns @code{-1} and sets @var{errno} accordingly. @end deftypefun