Create NT_PRSTATUS and NT_FPREGSET notes for each and every thread

in the process. This is required for proper debugging of corefiles
created by 1:1 or M:N threaded processes. Add an XXX comment where
we should actually call a function that dumps MD specific notes.
An example of a MD specific note is the NT_PRXFPREG note for SSE
registers.

Since BFD creates non-annotated pseudo-sections for the first PRSTATUS
and FPREGSET notes (non-annotated in the sense that the name of the
section does not contain the pid/tid), make sure those sections describe
the initial thread of the process (i.e. the thread which tid equals the
pid). This is not strictly necessary, but makes sure that tools that use
the non-annotated section names will not change behaviour due to this
change.

The practical upshot of this all is that one can see the threads in
the debugger when looking at a corefile. For 1:1 threading this means
that *all* threads are visible.

1 files changed, 81 insertions, 50 deletions

diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c
index 73c8729..7728469 100644
--- a/sys/kern/imgact_elf.c
+++ b/sys/kern/imgact_elf.c
@@ -922,8 +922,7 @@ static void cb_size_segment(vm_map_entry_t, void *);
 static void each_writable_segment(struct proc *, segment_callback, void *);
 static int __elfN(corehdr)(struct thread *, struct vnode *, struct ucred *,
     int, void *, size_t);
-static void __elfN(puthdr)(struct proc *, void *, size_t *,
-    const prstatus_t *, const prfpregset_t *, const prpsinfo_t *, int);
+static void __elfN(puthdr)(struct proc *, void *, size_t *, int);
 static void __elfN(putnote)(void *, size_t *, const char *, int,
     const void *, size_t);
 
@@ -953,9 +952,7 @@ __elfN(coredump)(td, vp, limit)
 	 * size is calculated.
 	 */
 	hdrsize = 0;
-	__elfN(puthdr)((struct proc *)NULL, (void *)NULL, &hdrsize,
-	    (const prstatus_t *)NULL, (const prfpregset_t *)NULL,
-	    (const prpsinfo_t *)NULL, seginfo.count);
+	__elfN(puthdr)(p, (void *)NULL, &hdrsize, seginfo.count);
 
 	if (hdrsize + seginfo.size >= limit)
 		return (EFAULT);
@@ -1115,47 +1112,13 @@ __elfN(corehdr)(td, vp, cred, numsegs, hdr, hdrsize)
 	size_t hdrsize;
 	void *hdr;
 {
-	struct {
-		prstatus_t status;
-		prfpregset_t fpregset;
-		prpsinfo_t psinfo;
-	} *tempdata;
 	struct proc *p = td->td_proc;
 	size_t off;
-	prstatus_t *status;
-	prfpregset_t *fpregset;
-	prpsinfo_t *psinfo;
-
-	tempdata = malloc(sizeof(*tempdata), M_TEMP, M_ZERO | M_WAITOK);
-	status = &tempdata->status;
-	fpregset = &tempdata->fpregset;
-	psinfo = &tempdata->psinfo;
-
-	/* Gather the information for the header. */
-	status->pr_version = PRSTATUS_VERSION;
-	status->pr_statussz = sizeof(prstatus_t);
-	status->pr_gregsetsz = sizeof(gregset_t);
-	status->pr_fpregsetsz = sizeof(fpregset_t);
-	status->pr_osreldate = osreldate;
-	status->pr_cursig = p->p_sig;
-	status->pr_pid = p->p_pid;
-	fill_regs(td, &status->pr_reg);
-
-	fill_fpregs(td, fpregset);
-
-	psinfo->pr_version = PRPSINFO_VERSION;
-	psinfo->pr_psinfosz = sizeof(prpsinfo_t);
-	strlcpy(psinfo->pr_fname, p->p_comm, sizeof(psinfo->pr_fname));
-
-	/* XXX - We don't fill in the command line arguments properly yet. */
-	strlcpy(psinfo->pr_psargs, p->p_comm, sizeof(psinfo->pr_psargs));
 
 	/* Fill in the header. */
 	bzero(hdr, hdrsize);
 	off = 0;
-	__elfN(puthdr)(p, hdr, &off, status, fpregset, psinfo, numsegs);
-
-	free(tempdata, M_TEMP);
+	__elfN(puthdr)(p, hdr, &off, numsegs);
 
 	/* Write it to the core file. */
 	return (vn_rdwr_inchunks(UIO_WRITE, vp, hdr, hdrsize, (off_t)0,
@@ -1164,13 +1127,18 @@ __elfN(corehdr)(td, vp, cred, numsegs, hdr, hdrsize)
 }
 
 static void
-__elfN(puthdr)(struct proc *p, void *dst, size_t *off, const prstatus_t *status,
-    const prfpregset_t *fpregset, const prpsinfo_t *psinfo, int numsegs)
+__elfN(puthdr)(struct proc *p, void *dst, size_t *off, int numsegs)
 {
-	size_t ehoff;
-	size_t phoff;
-	size_t noteoff;
-	size_t notesz;
+	struct {
+		prstatus_t status;
+		prfpregset_t fpregset;
+		prpsinfo_t psinfo;
+	} *tempdata;
+	prstatus_t *status;
+	prfpregset_t *fpregset;
+	prpsinfo_t *psinfo;
+	struct thread *first, *thr;
+	size_t ehoff, noteoff, notesz, phoff;
 
 	ehoff = *off;
 	*off += sizeof(Elf_Ehdr);
@@ -1179,14 +1147,77 @@ __elfN(puthdr)(struct proc *p, void *dst, size_t *off, const prstatus_t *status,
 	*off += (numsegs + 1) * sizeof(Elf_Phdr);
 
 	noteoff = *off;
-	__elfN(putnote)(dst, off, "FreeBSD", NT_PRSTATUS, status,
-	    sizeof *status);
-	__elfN(putnote)(dst, off, "FreeBSD", NT_FPREGSET, fpregset,
-	    sizeof *fpregset);
+	/*
+	 * Don't allocate space for the notes if we're just calculating
+	 * the size of the header. We also don't collect the data.
+	 */
+	if (dst != NULL) {
+		tempdata = malloc(sizeof(*tempdata), M_TEMP, M_ZERO|M_WAITOK);
+		status = &tempdata->status;
+		fpregset = &tempdata->fpregset;
+		psinfo = &tempdata->psinfo;
+	} else {
+		tempdata = NULL;
+		status = NULL;
+		fpregset = NULL;
+		psinfo = NULL;
+	}
+
+	if (dst != NULL) {
+		psinfo->pr_version = PRPSINFO_VERSION;
+		psinfo->pr_psinfosz = sizeof(prpsinfo_t);
+		strlcpy(psinfo->pr_fname, p->p_comm, sizeof(psinfo->pr_fname));
+		/*
+		 * XXX - We don't fill in the command line arguments properly
+		 * yet.
+		 */
+		strlcpy(psinfo->pr_psargs, p->p_comm,
+		    sizeof(psinfo->pr_psargs));
+	}
 	__elfN(putnote)(dst, off, "FreeBSD", NT_PRPSINFO, psinfo,
 	    sizeof *psinfo);
+
+	/*
+	 * We want to start with the registers of the first thread in the
+	 * process so that the .reg and .reg2 pseudo-sections created by bfd
+	 * will be identical to the .reg/$PID and .reg2/$PID pseudo-sections.
+	 * This makes sure that any tool that only looks for .reg and .reg2
+	 * and not for .reg/$PID and .reg2/$PID will behave the same as
+	 * before. The first thread is the thread with an ID equal to the 
+	 * process' ID.
+	 */
+	first = TAILQ_FIRST(&p->p_threads);
+	while (first->td_tid > PID_MAX)
+		first = TAILQ_NEXT(first, td_plist);
+	thr = first;
+	do {
+		if (dst != NULL) {
+			status->pr_version = PRSTATUS_VERSION;
+			status->pr_statussz = sizeof(prstatus_t);
+			status->pr_gregsetsz = sizeof(gregset_t);
+			status->pr_fpregsetsz = sizeof(fpregset_t);
+			status->pr_osreldate = osreldate;
+			status->pr_cursig = p->p_sig;
+			status->pr_pid = thr->td_tid;
+			fill_regs(thr, &status->pr_reg);
+			fill_fpregs(thr, fpregset);
+		}
+		__elfN(putnote)(dst, off, "FreeBSD", NT_PRSTATUS, status,
+		    sizeof *status);
+		__elfN(putnote)(dst, off, "FreeBSD", NT_FPREGSET, fpregset,
+		    sizeof *fpregset);
+		/* XXX allow for MD specific notes. */
+		thr = (thr == first) ? TAILQ_FIRST(&p->p_threads) :
+		    TAILQ_NEXT(thr, td_plist);
+		if (thr == first)
+			thr = TAILQ_NEXT(thr, td_plist);
+	} while (thr != NULL);
+
 	notesz = *off - noteoff;
 
+	if (dst != NULL)
+		free(tempdata, M_TEMP);
+
 	/* Align up to a page boundary for the program segments. */
 	*off = round_page(*off);