Bug #5998
closed
mdb_ctf_vread fails in dcmds run via mdb_pwalk_dcmd
100%
Description
This is essentially the same problem as #3473 but with mdb_pwalk_dcmd, where #3473 fixed mdb_pwalk.
The manifestation was seen with the "smbsrv" mdb module after modifications to use mdb_ctf_vread.
The dcmds implement with mdb_pwalk_dcmd fail like this:
$ mdb -L $ROOT/usr/lib/mdb/proc:/usr/lib/mdb/proc /var/smb/core.3470 Loading modules: [ libumem.so.1 libfksmbsrv.so.1 libcmdutils.so.1 libc.so.1 libavl.so.1 libtopo.so.1 libuutil.so.1 libnvpair.so.1 ld.so.1 ] > ::smblist mdb: couldn't find ctf data for type mdb_smb_server_t in mdb module libcmdutils.so.1 mdb: failed to read smb_server at 82ac000: No type information available for that name
Related issues
Updated by Gordon Ross over 8 years ago
The fix for #3473 added a check for the f_cbactive flag on the "top" (deepest) walker.
That flag is set by mdb_pwalk when it invokes the call-back function.
By comparison, mdb_pwalk_dcmd calls walk_dcmd, which calls
mdb_call_idcmd. That last is essentially our "call-back" function
corresponding to the call back in mdb_pwalk / walk_step.
At that point, we're no longer in walker module code and should
set f_cbactive there like mdb_pwalk does. That fixes it for me.
The fix is small, so here it is:
diff --git a/usr/src/cmd/mdb/common/mdb/mdb_modapi.c b/usr/src/cmd/mdb/common/mdb/mdb_modapi.c
index a95a866..9f6cd92 100644
--- a/usr/src/cmd/mdb/common/mdb/mdb_modapi.c
+++ b/usr/src/cmd/mdb/common/mdb/mdb_modapi.c
@@ -580,8 +580,12 @@ mdb_walk(const char *name, mdb_walk_cb_t func, void *data)
static int
walk_dcmd(uintptr_t addr, const void *ignored, dcmd_walk_arg_t *dwp)
{
- int status = mdb_call_idcmd(dwp->dw_dcmd, addr, 1, dwp->dw_flags,
+ int status;
+
+ mdb.m_frame->f_cbactive = B_TRUE;
+ status = mdb_call_idcmd(dwp->dw_dcmd, addr, 1, dwp->dw_flags,
&dwp->dw_argv, NULL, NULL);
+ mdb.m_frame->f_cbactive = B_FALSE;
if (status == DCMD_USAGE || status == DCMD_ABORT)
return (WALK_ERR);
Updated by Gordon Ross over 8 years ago
BTW, this is doing essentially the same thing as mdb_modapi.c:pwalk_step
http://src.illumos.org/source/xref/illumos-gate/usr/src/cmd/mdb/common/mdb/mdb_modapi.c#537
Updated by Gordon Ross over 8 years ago
- Related to Bug #3473: mdb_get_module() returns wrong module added
Updated by Electric Monk about 8 years ago
- Status changed from In Progress to Closed
- % Done changed from 0 to 100
git commit 315fecc41c08848bacfc1ee331b9693077b057ff
commit 315fecc41c08848bacfc1ee331b9693077b057ff
Author: Gordon Ross <gwr@nexenta.com>
Date: 2015-10-03T22:09:30.000Z
5998 mdb_ctf_vread fails in dcmds run via mdb_pwalk_dcmd
Reviewed by: Josef Sipek <jeffpc@josefsipek.net>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>