Date: Thu, 27 May 2010 18:33:00 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r208604 - head/sys/i386/i386 Message-ID: <201005271833.o4RIX0bE052335@svn.freebsd.org>
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Author: kib Date: Thu May 27 18:33:00 2010 New Revision: 208604 URL: http://svn.freebsd.org/changeset/base/208604 Log: Clarify a potential issue in get_fpcontext() use. MFC after: 1 week Modified: head/sys/i386/i386/machdep.c Modified: head/sys/i386/i386/machdep.c ============================================================================== --- head/sys/i386/i386/machdep.c Thu May 27 18:07:20 2010 (r208603) +++ head/sys/i386/i386/machdep.c Thu May 27 18:33:00 2010 (r208604) @@ -633,6 +633,13 @@ sendsig(sig_t catcher, ksiginfo_t *ksi, sf.sf_uc.uc_mcontext.mc_gs = rgs(); bcopy(regs, &sf.sf_uc.uc_mcontext.mc_fs, sizeof(*regs)); sf.sf_uc.uc_mcontext.mc_len = sizeof(sf.sf_uc.uc_mcontext); /* magic */ + + /* + * The get_fpcontext() call must be placed before assignments + * to mc_fsbase and mc_gsbase due to the alignment-override + * code in get_fpcontext() that possibly clobbers 12 bytes of + * mcontext after mc_fpstate. + */ get_fpcontext(td, &sf.sf_uc.uc_mcontext); fpstate_drop(td); /* @@ -3240,6 +3247,13 @@ get_mcontext(struct thread *td, mcontext mcp->mc_esp = tp->tf_esp; mcp->mc_ss = tp->tf_ss; mcp->mc_len = sizeof(*mcp); + + /* + * The get_fpcontext() call must be placed before assignments + * to mc_fsbase and mc_gsbase due to the alignment-override + * code in get_fpcontext() that possibly clobbers 12 bytes of + * mcontext after mc_fpstate. + */ get_fpcontext(td, mcp); sdp = &td->td_pcb->pcb_gsd; mcp->mc_fsbase = sdp->sd_hibase << 24 | sdp->sd_lobase;
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