Date: Mon, 14 May 2001 00:46:35 +0300 (EEST) From: kostik@kieb.kiev.ua To: FreeBSD-gnats-submit@freebsd.org Cc: kostya@tessart.kiev.ua Subject: i386/27306: hw watchpoints work unreliable under gdb Message-ID: <200105132146.f4DLkZJ12935@kib.kiev.ua>
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>Number: 27306
>Category: i386
>Synopsis: hw watchpoints work unreliable under gdb
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Sun May 13 14:50:01 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator: Kostik I. Belousov
>Release: FreeBSD 4.3-RELEASE i386
>Organization:
@home
>Environment:
System: FreeBSD little.home 4.3-RELEASE FreeBSD 4.3-RELEASE #0: Wed Apr 25 22:39:00 EEST 2001 root@little.home:/usr/src/sys/compile/LITTLE i386
K6-2/266, 64 Mb, ... - not relevant
>Description:
The insert_watchpoint()
in the /usr/src/gnu/usr.bin/binutils/gdb/i386/freebsd-nat.c
contains at least 2 bugs:
1. at line 604, fragment
if (ptrace(PT_SETDBREGS, pid, (caddr_t)&dbr, 0) == -1)
{
perror("ptrace(PT_SETDBREGS) failed");
return 0;
}
}
does not specify return value.
insert_breakpoints() sometimes is misinformed on the result
of the watch insertion. It seems that the "return 0;" statement is missed.
2. At least on my K6-2, reserved bit 10 of dr7 could be eq 1.
In this case, ptrace(PT_SETDBREGS, ...) fails. Might be,
all reserved bits in the dr7 should be explicitly cleared
after ptrace(PT_GETDBREGS,...) at line 535.
The same is true for remove_watchpoint().
>How-To-Repeat:
Some attempts of setting hw watchpoint under gdb fail.
>Fix:
The following is the proposed
diff for
/usr/src/gnu/usr.bin/binutils/gdb/i386/freebsd-nat.c
--- freebsd-nat.c.orig Fri Jan 5 19:51:06 2001
+++ freebsd-nat.c Mon May 14 00:25:36 2001
@@ -534,4 +534,5 @@
return 0;
}
+ dbr.dr7 &= ~0xfc00;
for (i = 0, mask = 0x03; i < 4; i++, mask <<= 2)
@@ -603,4 +604,5 @@
return 0;
}
+ return 0;
}
else
@@ -634,4 +636,5 @@
return 0;
}
+ dbr.dr7 &= ~0xfc00;
for (i = 0, dbregp = &dbr.dr0; i < 4; i++, dbregp++)
@@ -658,4 +661,5 @@
return 0;
}
+ return 0;
}
else
>Release-Note:
>Audit-Trail:
>Unformatted:
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