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Date:      Tue, 21 Jul 2015 23:03:22 +0000 (UTC)
From:      Mark Johnston <markj@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r285773 - head/sys/amd64/amd64
Message-ID:  <201507212303.t6LN3Msj002079@repo.freebsd.org>
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Author: markj
Date: Tue Jul 21 23:03:21 2015
New Revision: 285773
URL: https://svnweb.freebsd.org/changeset/base/285773

Log:
  Remove some dead code from DDB's amd64 stack unwinder.
  
  The amd64 port copied some code from i386 to fetch function arguments and
  display them in backtraces. However, it was commented out and can't easily
  be implemented since the function arguments are passed in
  registers rather than on the stack in amd64. Remove it in preparation for
  some bug fixes in this area.
  
  Reviewed by:	jhb
  Sponsored by:	EMC / Isilon Storage Division
  Differential Revision:	https://reviews.freebsd.org/D2857

Modified:
  head/sys/amd64/amd64/db_trace.c

Modified: head/sys/amd64/amd64/db_trace.c
==============================================================================
--- head/sys/amd64/amd64/db_trace.c	Tue Jul 21 22:57:27 2015	(r285772)
+++ head/sys/amd64/amd64/db_trace.c	Tue Jul 21 23:03:21 2015	(r285773)
@@ -188,9 +188,7 @@ db_ss(struct db_variable *vp, db_expr_t 
 #define	TRAP_INTERRUPT	5
 
 static void db_nextframe(struct amd64_frame **, db_addr_t *, struct thread *);
-static int db_numargs(struct amd64_frame *);
-static void db_print_stack_entry(const char *, int, char **, long *, db_addr_t,
-    void *);
+static void db_print_stack_entry(const char *, db_addr_t, void *);
 static void decode_syscall(int, struct thread *);
 
 static const char * watchtype_str(int type);
@@ -198,62 +196,11 @@ int  amd64_set_watch(int watchnum, unsig
 		    int access, struct dbreg *d);
 int  amd64_clr_watch(int watchnum, struct dbreg *d);
 
-/*
- * Figure out how many arguments were passed into the frame at "fp".
- */
-static int
-db_numargs(fp)
-	struct amd64_frame *fp;
-{
-#if 1
-	return (0);	/* regparm, needs dwarf2 info */
-#else
-	long	*argp;
-	int	inst;
-	int	args;
-
-	argp = (long *)db_get_value((long)&fp->f_retaddr, 8, FALSE);
-	/*
-	 * XXX etext is wrong for LKMs.  We should attempt to interpret
-	 * the instruction at the return address in all cases.  This
-	 * may require better fault handling.
-	 */
-	if (argp < (long *)btext || argp >= (long *)etext) {
-		args = 5;
-	} else {
-		inst = db_get_value((long)argp, 4, FALSE);
-		if ((inst & 0xff) == 0x59)	/* popl %ecx */
-			args = 1;
-		else if ((inst & 0xffff) == 0xc483)	/* addl $Ibs, %esp */
-			args = ((inst >> 16) & 0xff) / 4;
-		else
-			args = 5;
-	}
-	return (args);
-#endif
-}
-
 static void
-db_print_stack_entry(name, narg, argnp, argp, callpc, frame)
-	const char *name;
-	int narg;
-	char **argnp;
-	long *argp;
-	db_addr_t callpc;
-	void *frame;
+db_print_stack_entry(const char *name, db_addr_t callpc, void *frame)
 {
-	db_printf("%s(", name);
-#if 0
-	while (narg) {
-		if (argnp)
-			db_printf("%s=", *argnp++);
-		db_printf("%lr", (long)db_get_value((long)argp, 8, FALSE));
-		argp++;
-		if (--narg != 0)
-			db_printf(",");
-	}
-#endif
-	db_printf(") at ");
+
+	db_printf("%s() at ", name);
 	db_printsym(callpc, DB_STGY_PROC);
 	if (frame != NULL)
 		db_printf("/frame 0x%lx", (register_t)frame);
@@ -348,7 +295,7 @@ db_nextframe(struct amd64_frame **fp, db
 		return;
 	}
 
-	db_print_stack_entry(name, 0, 0, 0, rip, &(*fp)->f_frame);
+	db_print_stack_entry(name, rip, &(*fp)->f_frame);
 
 	/*
 	 * Point to base of trapframe which is just above the
@@ -388,13 +335,9 @@ db_backtrace(struct thread *td, struct t
     struct amd64_frame *frame, db_addr_t pc, int count)
 {
 	struct amd64_frame *actframe;
-#define MAXNARG	16
-	char *argnames[MAXNARG], **argnp = NULL;
 	const char *name;
-	long *argp;
 	db_expr_t offset;
 	c_db_sym_t sym;
-	int narg;
 	boolean_t first;
 
 	if (count == -1)
@@ -444,22 +387,13 @@ db_backtrace(struct thread *td, struct t
 				 * Don't try to walk back on a stack for a
 				 * process that hasn't actually been run yet.
 				 */
-				db_print_stack_entry(name, 0, 0, 0, pc,
-				    actframe);
+				db_print_stack_entry(name, pc, actframe);
 				break;
 			}
 			first = FALSE;
 		}
 
-		argp = &actframe->f_arg0;
-		narg = MAXNARG;
-		if (sym != NULL && db_sym_numargs(sym, &narg, argnames)) {
-			argnp = argnames;
-		} else {
-			narg = db_numargs(frame);
-		}
-
-		db_print_stack_entry(name, narg, argnp, argp, pc, actframe);
+		db_print_stack_entry(name, pc, actframe);
 
 		if (actframe != frame) {
 			/* `frame' belongs to caller. */
@@ -473,7 +407,7 @@ db_backtrace(struct thread *td, struct t
 		if (INKERNEL((long)pc) && !INKERNEL((long)frame)) {
 			sym = db_search_symbol(pc, DB_STGY_ANY, &offset);
 			db_symbol_values(sym, &name, NULL);
-			db_print_stack_entry(name, 0, 0, 0, pc, frame);
+			db_print_stack_entry(name, pc, frame);
 			break;
 		}
 		if (!INKERNEL((long) frame)) {

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