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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