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[commit] OpenBSD/i386 kernel debugging improvements
- From: Mark Kettenis <mark dot kettenis at xs4all dot nl>
- To: gdb-patches at sourceware dot org
- Date: Mon, 19 Dec 2005 23:23:03 +0100 (CET)
- Subject: [commit] OpenBSD/i386 kernel debugging improvements
This teaches GDB how to unwind OpenBSD/i386 kernel trap frames,
terminating backtraces at system calls. This is a huge improvement
post-mortem debugging using kernel core dumps.
Committed,
Mark
Index: ChangeLog
from Mark Kettenis <kettenis@gnu.org>
* i386-tdep.h (I386_SEL_RPL, I386_SEL_UPL, I386_SEL_KPL): New
defines.
* i386obsd-tdep.c: Include "frame-unwind.h" and "trad-frame.h".
(i386obsd_tf_reg_offset, i386obsd_trapframe_unwind): New
variables.
(i386obsd_trapframe_cache, i386obsd_trapframe_this_id)
(i386obsd_trapframe_prev_register, i386obsd_trapframe_sniffer):
New functions.
(i386obsd_init_abi): Append i386obsd_trapframe_sniffer.
* Makefile.in (i386obsd-tdep.o): Update dependencies.
Index: Makefile.in
===================================================================
RCS file: /cvs/src/src/gdb/Makefile.in,v
retrieving revision 1.763
diff -u -p -r1.763 Makefile.in
--- Makefile.in 17 Dec 2005 22:33:59 -0000 1.763
+++ Makefile.in 19 Dec 2005 22:18:41 -0000
@@ -2072,9 +2072,10 @@ i386-nto-tdep.o: i386-nto-tdep.c $(defs_
$(i386_tdep_h) $(i387_tdep_h) $(nto_tdep_h) $(solib_svr4_h)
i386obsd-nat.o: i386obsd-nat.c $(defs_h) $(i386_tdep_h)
i386obsd-tdep.o: i386obsd-tdep.c $(defs_h) $(arch_utils_h) $(frame_h) \
- $(gdbcore_h) $(regcache_h) $(regset_h) $(symtab_h) $(objfiles_h) \
- $(osabi_h) $(target_h) $(gdb_assert_h) $(gdb_string_h) \
- $(i386_tdep_h) $(i387_tdep_h) $(solib_svr4_h) $(bsd_uthread_h)
+ $(frame_unwind_h) $(gdbcore_h) $(regcache_h) $(regset_h) $(symtab_h) \
+ $(objfiles_h) $(osabi_h) $(target_h) $(trad_frame_h) $(gdb_assert_h) \
+ $(gdb_string_h) $(i386_tdep_h) $(i387_tdep_h) $(solib_svr4_h) \
+ $(bsd_uthread_h)
i386-sol2-nat.o: i386-sol2-nat.c $(defs_h) $(regcache_h) $(gregset_h) \
$(amd64_nat_h) $(amd64_tdep_h)
i386-sol2-tdep.o: i386-sol2-tdep.c $(defs_h) $(value_h) $(osabi_h) \
Index: i386-tdep.h
===================================================================
RCS file: /cvs/src/src/gdb/i386-tdep.h,v
retrieving revision 1.43
diff -u -p -r1.43 i386-tdep.h
--- i386-tdep.h 17 Dec 2005 22:34:01 -0000 1.43
+++ i386-tdep.h 19 Dec 2005 22:18:41 -0000
@@ -149,6 +149,11 @@ enum i386_regnum
/* Size of the largest register. */
#define I386_MAX_REGISTER_SIZE 16
+/* Segment selectors. */
+#define I386_SEL_RPL 0x0003 /* Requester's Privilege Level mask. */
+#define I386_SEL_UPL 0x0003 /* User Privilige Level. */
+#define I386_SEL_KPL 0x0000 /* Kernel Privilige Level. */
+
/* Functions exported from i386-tdep.c. */
extern CORE_ADDR i386_pe_skip_trampoline_code (CORE_ADDR pc, char *name);
Index: i386obsd-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/i386obsd-tdep.c,v
retrieving revision 1.25
diff -u -p -r1.25 i386obsd-tdep.c
--- i386obsd-tdep.c 17 Dec 2005 22:34:01 -0000 1.25
+++ i386obsd-tdep.c 19 Dec 2005 22:18:41 -0000
@@ -24,6 +24,7 @@
#include "defs.h"
#include "arch-utils.h"
#include "frame.h"
+#include "frame-unwind.h"
#include "gdbcore.h"
#include "regcache.h"
#include "regset.h"
@@ -31,6 +32,7 @@
#include "objfiles.h"
#include "osabi.h"
#include "target.h"
+#include "trad-frame.h"
#include "gdb_assert.h"
#include "gdb_string.h"
@@ -265,7 +267,6 @@ i386obsd_supply_uthread (struct regcache
regcache_raw_supply (regcache, i, buf);
}
}
-
}
static void
@@ -313,6 +314,119 @@ i386obsd_collect_uthread (const struct r
}
}
}
+
+/* Kernel debugging support. */
+
+/* From <machine/frame.h>. Note that %esp and %ess are only saved in
+ a trap frame when entering the kernel from user space. */
+static int i386obsd_tf_reg_offset[] =
+{
+ 10 * 4, /* %eax */
+ 9 * 4, /* %ecx */
+ 8 * 4, /* %edx */
+ 7 * 4, /* %ebx */
+ -1, /* %esp */
+ 6 * 4, /* %ebp */
+ 5 * 4, /* %esi */
+ 4 * 4, /* %edi */
+ 13 * 4, /* %eip */
+ 15 * 4, /* %eflags */
+ 14 * 4, /* %cs */
+ -1, /* %ss */
+ 3 * 4, /* %ds */
+ 2 * 4, /* %es */
+ 0 * 4, /* %fs */
+ 1 * 4 /* %gs */
+};
+
+static struct trad_frame_cache *
+i386obsd_trapframe_cache(struct frame_info *next_frame, void **this_cache)
+{
+ struct trad_frame_cache *cache;
+ CORE_ADDR func, sp, addr;
+ ULONGEST cs;
+ int i;
+
+ if (*this_cache)
+ return *this_cache;
+
+ cache = trad_frame_cache_zalloc (next_frame);
+ *this_cache = cache;
+
+ func = frame_func_unwind (next_frame);
+ sp = frame_unwind_register_unsigned (next_frame, I386_ESP_REGNUM);
+ for (i = 0; i < ARRAY_SIZE (i386obsd_tf_reg_offset); i++)
+ if (i386obsd_tf_reg_offset[i] != -1)
+ trad_frame_set_reg_addr (cache, i, sp + i386obsd_tf_reg_offset[i]);
+
+ /* Read %cs from trap frame. */
+ addr = sp + i386obsd_tf_reg_offset[I386_CS_REGNUM];
+ cs = read_memory_unsigned_integer (addr, 4);
+ if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
+ {
+ /* Trap from use space; terminate backtrace. */
+ trad_frame_set_id (cache, null_frame_id);
+ }
+ else
+ {
+ /* Construct the frame ID using the function start. */
+ trad_frame_set_id (cache, frame_id_build (sp + 8, func));
+ }
+
+ return cache;
+}
+
+static void
+i386obsd_trapframe_this_id (struct frame_info *next_frame,
+ void **this_cache, struct frame_id *this_id)
+{
+ struct trad_frame_cache *cache =
+ i386obsd_trapframe_cache (next_frame, this_cache);
+
+ trad_frame_get_id (cache, this_id);
+}
+
+static void
+i386obsd_trapframe_prev_register (struct frame_info *next_frame,
+ void **this_cache, int regnum,
+ int *optimizedp, enum lval_type *lvalp,
+ CORE_ADDR *addrp, int *realnump,
+ gdb_byte *valuep)
+{
+ struct trad_frame_cache *cache =
+ i386obsd_trapframe_cache (next_frame, this_cache);
+
+ trad_frame_get_register (cache, next_frame, regnum,
+ optimizedp, lvalp, addrp, realnump, valuep);
+}
+
+static const struct frame_unwind i386obsd_trapframe_unwind = {
+ /* FIXME: kettenis/20051219: This really is more like an interrupt
+ frame, but SIGTRAMP_FRAME would print <signal handler called>,
+ which really is not what we want here. */
+ NORMAL_FRAME,
+ i386obsd_trapframe_this_id,
+ i386obsd_trapframe_prev_register
+};
+
+static const struct frame_unwind *
+i386obsd_trapframe_sniffer (struct frame_info *next_frame)
+{
+ ULONGEST cs;
+ char *name;
+
+ cs = frame_unwind_register_unsigned (next_frame, I386_CS_REGNUM);
+ if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
+ return NULL;
+
+ find_pc_partial_function (frame_pc_unwind (next_frame), &name, NULL, NULL);
+ if (name && ((strcmp ("calltrap", name) == 0)
+ || (strcmp ("syscall1", name) == 0)))
+ return &i386obsd_trapframe_unwind;
+
+ return NULL;
+}
+
static void
i386obsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
@@ -343,6 +457,9 @@ i386obsd_init_abi (struct gdbarch_info i
/* OpenBSD provides a user-level threads implementation. */
bsd_uthread_set_supply_uthread (gdbarch, i386obsd_supply_uthread);
bsd_uthread_set_collect_uthread (gdbarch, i386obsd_collect_uthread);
+
+ /* Unwind kernel trap frames correctly. */
+ frame_unwind_append_sniffer (gdbarch, i386obsd_trapframe_sniffer);
}
/* OpenBSD a.out. */