Use kgdb_parse() instead of libkvm(3) to read the first instruction from

"calltrap" to see which method is used to pass trap frames.  This seg
faulted on remote gdb connections (where libkvm isn't used).

MFC after:	3 days

1 files changed, 9 insertions, 16 deletions

diff --git a/gnu/usr.bin/gdb/kgdb/trgt_i386.c b/gnu/usr.bin/gdb/kgdb/trgt_i386.c
index de15a63..995f1a6 100644
--- a/gnu/usr.bin/gdb/kgdb/trgt_i386.c
+++ b/gnu/usr.bin/gdb/kgdb/trgt_i386.c
@@ -299,22 +299,15 @@ kgdb_trgt_trapframe_prev_register(struct frame_info *next_frame,
 	*realnump = -1;
 
 	if (!ofs_fixed) {
-		uintptr_t calltrap_addr;
-		char calltrap[1];
-
-		calltrap_addr = kgdb_lookup("calltrap");
-		if (calltrap_addr != 0) {
-			if (kvm_read(kvm, calltrap_addr, calltrap,
-				     sizeof(calltrap)) != sizeof(calltrap)) {
-				warnx("kvm_read: %s", kvm_geterr(kvm));
-			} else if (calltrap[0] == 0x54) /* push %esp */ {
-				/*
-				 * To accomodate for rev. 1.117 of
-				 * i386/i386/exception.s
-				 */
-				ofs_fix = 4;
-			}
-		}
+		/*
+		 * In revision 1.117 of i386/i386/exception.S trap handlers
+		 * were changed to pass trapframes by reference rather than
+		 * by value.  Detect this by seeing if the first instruction
+		 * at the 'calltrap' label is a "push %esp" which has the
+		 * opcode 0x54.
+		 */
+		if (kgdb_parse("((char *)calltrap)[0]") == 0x54)
+			ofs_fix = 4;
 		ofs_fixed = 1;
 	}
 	ofs = (regnum >= I386_EAX_REGNUM && regnum <= I386_FS_REGNUM)