OS-7034 ctxops should use stack ordering for save/restore

Reviewed by: John Levon <john.levon@joyent.com> Reviewed by: Robert Mustacchi <rm@joyent.com> Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com> Approved by: Jerry Jelinek <jerry.jelinek@joyent.com>
TritonDataCenter · Jun 26, 2018 · 9d61057 · 9d61057
1 parent 8ab68c6
commit 9d61057
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Showing 5 changed files with 202 additions and 77 deletions.
diff --git a/usr/src/cmd/mdb/common/modules/genunix/ctxop.c b/usr/src/cmd/mdb/common/modules/genunix/ctxop.c
@@ -23,56 +23,97 @@
  * Copyright (c) 2000 by Sun Microsystems, Inc.
  * All rights reserved.
  */
+/*
+ * Copyright 2018 Joyent, Inc.
+ */
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
-#include <sys/mdb_modapi.h>
-#include <sys/thread.h>
+#include <mdb/mdb_modapi.h>
+#include <mdb/mdb_ctf.h>
 #include "ctxop.h"
 
+struct ctxop_walk_state {
+	uintptr_t	cws_head;
+	uint_t		cws_next_offset;
+};
+
 int
 ctxop_walk_init(mdb_walk_state_t *wsp)
 {
-	kthread_t thread, *tp = &thread;
+	struct ctxop_walk_state *priv;
+	int offset;
+	uintptr_t addr;
 
 	if (wsp->walk_addr == NULL) {
 		mdb_warn("must specify thread for ctxop walk\n");
 		return (WALK_ERR);
 	}
-	if (mdb_vread(tp, sizeof (*tp), wsp->walk_addr) == -1) {
-		mdb_warn("failed to read thread at %p", wsp->walk_addr);
+
+	offset = mdb_ctf_offsetof_by_name("kthread_t", "t_ctx");
+	if (offset == -1)
 		return (WALK_ERR);
+
+	if (mdb_vread(&addr, sizeof (addr),
+	    wsp->walk_addr + offset) != sizeof (addr)) {
+		mdb_warn("failed to read thread %p", wsp->walk_addr);
+		return (WALK_ERR);
+	}
+
+	/* No further work for threads with a NULL t_ctx */
+	if (addr == 0) {
+		wsp->walk_data = NULL;
+		return (WALK_DONE);
 	}
 
-	wsp->walk_data = mdb_alloc(sizeof (ctxop_t), UM_SLEEP);
-	wsp->walk_addr = (uintptr_t)tp->t_ctx;
+	/* rely on CTF for the offset of the 'next' pointer */
+	offset = mdb_ctf_offsetof_by_name("struct ctxop", "next");
+	if (offset == -1)
+		return (WALK_ERR);
+
+	priv = mdb_alloc(sizeof (*priv), UM_SLEEP);
+	priv->cws_head = addr;
+	priv->cws_next_offset = (uint_t)offset;
 
+	wsp->walk_data = priv;
+	wsp->walk_addr = addr;
 	return (WALK_NEXT);
 }
 
 int
 ctxop_walk_step(mdb_walk_state_t *wsp)
 {
+	struct ctxop_walk_state *priv = wsp->walk_data;
+	uintptr_t next;
 	int status;
 
-	if (wsp->walk_addr == NULL)
-		return (WALK_DONE);
-
-	if (mdb_vread(wsp->walk_data,
-	    sizeof (ctxop_t), wsp->walk_addr) == -1) {
-		mdb_warn("failed to read ctxop at %p", wsp->walk_addr);
+	if (mdb_vread(&next, sizeof (next),
+	    wsp->walk_addr + priv->cws_next_offset) == -1) {
+		mdb_warn("failed to read ctxop`next at %p",
+		    wsp->walk_addr + priv->cws_next_offset);
 		return (WALK_DONE);
 	}
 
-	status = wsp->walk_callback(wsp->walk_addr, wsp->walk_data,
-	    wsp->walk_cbdata);
+	status = wsp->walk_callback(wsp->walk_addr, NULL, wsp->walk_cbdata);
 
-	wsp->walk_addr = (uintptr_t)(((ctxop_t *)wsp->walk_data)->next);
+	if (status == WALK_NEXT) {
+		/*
+		 * If a NULL terminator or a loop back to the head element is
+		 * encountered, the walk is done.
+		 */
+		if (next == 0 || next == priv->cws_head) {
+			status = WALK_DONE;
+		}
+	}
+
+	wsp->walk_addr = next;
 	return (status);
 }
 
 void
 ctxop_walk_fini(mdb_walk_state_t *wsp)
 {
-	mdb_free(wsp->walk_data, sizeof (ctxop_t));
+	struct ctxop_walk_state *priv = wsp->walk_data;
+
+	if (priv != NULL) {
+		mdb_free(priv, sizeof (*priv));
+	}
 }
diff --git a/usr/src/cmd/mdb/common/modules/genunix/ctxop.h b/usr/src/cmd/mdb/common/modules/genunix/ctxop.h
@@ -27,8 +27,6 @@
 #ifndef	_MDB_CTXOP_H
 #define	_MDB_CTXOP_H
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 #include <mdb/mdb_modapi.h>
 
 #ifdef	__cplusplus