Re: vnet: acessing module's virtualized global variables from another module
On Monday 09 May 2011 19:05:28 Mikolaj Golub wrote:
> On Mon, 9 May 2011 16:21:15 +0200 Marko Zec wrote:
>
> MZ> On Monday 09 May 2011 14:48:25 Mikolaj Golub wrote:
> >> Hi,
> >>
> >> Trying ipfw_nat under VIMAGE kernel I got this panic on the module
> >> load:
>
> MZ> Hi,
>
> MZ> I think the problem here is that curvnet context is not set properly
> on entry MZ> to ipfw_nat_modevent(). The canonical way to initialize
> VNET-enabled MZ> subsystems is to trigger them using VNET_SYSINIT() macros
> (instead of using MZ> modevent mechanisms), which in turn ensure that:
>
> MZ> a) that the initializer function gets invoked for each existing vnet
> MZ> b) curvnet context is set properly on entry to initializer functions
> and
>
> hm, sorry, but I don't see how curvnet context might help here.
You're getting a panic in a function, i.e. in ipfw_nat_modevent() which has
ipfw_nat_init() inlined into it, where you attempt to access per-vnet data
without having curvnet context set. By definition that is not supposed to
work on a VIMAGE kernel, so what you observe is not unexpected at all.
Please set the curvnet context using VNET_SYSINIT() macros, or by hand using
CURVNET_SET() / CURVNET_RESTORE(), before accesing any V_ data.
Marko
> For me this
> does not look like curvnet context problem or my understanding how it works
> completely wrong.
>
> Below is kgdb session on live VIMAGE system with ipfw.ko loaded.
>
> Let's look at some kernel virtualized variable:
>
> (kgdb) p vnet_entry_ifnet
> $1 = {tqh_first = 0x0, tqh_last = 0x0}
> (kgdb) p &vnet_entry_ifnet
> $2 = (struct ifnethead *) 0x8102d488
>
> As expected the address is in kernel 'set_vnet':
>
> kopusha:/usr/src/sys% kldstat |grep kernel
> 1 69 0x8040 1092700 kernel
> kopusha:/usr/src/sys% nm /boot/kernel/kernel |grep __start_set_vnet
> 8102d480 A __start_set_vnet
>
> default vnet:
>
> (kgdb) p vnet0
> $3 = (struct vnet *) 0x86d9b000
>
> Calculate ifnet location on vnet0 (a la VNET_VNET(vnet0, ifnet)):
>
> (kgdb) printf "0x%x\n", vnet0->vnet_data_base + (uintptr_t) &
> vnet_entry_ifnet 0x86d9c008
>
> Access it:
>
> (kgdb) p *((struct ifnethead *)0x86d9c008)
> $4 = {tqh_first = 0x86da5c00, tqh_last = 0x89489c0c}
> (kgdb) p (*((struct ifnethead *)0x86d9c008)).tqh_first->if_dname
> $7 = 0x80e8b480 "usbus"
> (kgdb) p (*((struct ifnethead *)0x86d9c008)).tqh_first->if_vnet
> $8 = (struct vnet *) 0x86d9b000
>
> Everything looks good. Now try the same with virtualized variable
> layer3_chain from ipfw module:
>
> (kgdb) p vnet_entry_layer3_chain
> $9 = {rules = 0x0, reap = 0x0, default_rule = 0x0, n_rules = 0, static_len
> = 0, map = 0x0, nat = {lh_first = 0x0}, tables = {0x0 },
> rwmtx = {lock_object = { lo_name = 0x0, lo_flags = 0, lo_data = 0,
> lo_witness = 0x0}, rw_lock = 0}, uh_lock = { lock_object = {lo_name = 0x0,
> lo_flags = 0, lo_data = 0, lo_witness = 0x0}, rw_lock = 0}, id = 0, gencnt
> = 0}
>
> "master" variable looks good (initialized to zeros), what about its
> address?
>
> (kgdb) p &vnet_entry_layer3_chain
> $10 = (struct ip_fw_chain *) 0x894a5c00
>
> It points to 'set_vnet' of the ipfw.ko:
>
> kopusha# kldstat |grep ipfw.ko
> 132 0x89495000 11000ipfw.ko
> kopusha:/usr/src/sys% nm /boot/kernel/ipfw.ko |grep __start_set_vnet
> 00010be0 A __start_set_vnet
> kopusha:/usr/src/sys% printf "0x%x\n" $((0x89495000 + 0x00010be0))
> 0x894a5be0
>
> Calculate layer3_chain location on vnet0 (a la VNET_VNET(vnet0,
> layer3_chain)):
>
> (kgdb) printf "0x%x\n", vnet0->vnet_data_base + (uintptr_t) &
> vnet_entry_layer3_chain 0x8f214780
>
> Try to read it:
>
> (kgdb) p ((struct ip_fw_chain *)0x8f214780)->rwmtx
> $13 = {lock_object = {lo_name = 0x0, lo_flags = 0, lo_data = 0, lo_witness
> = 0x0}, rw_lock = 0} (kgdb) p ((struct ip_fw_chain *)0x8f214780)->rules
> $14 = (struct ip_fw *) 0x6
>
> Data looks wrong. But this is the way how this variable is acessed by
> ipfw_nat. I see the same in the crash image:
>
> (kgdb) where
> ...
> #11 0xc09a4882 in _rw_wlock (rw=0xc6d5e91c,
> file=0xca0ac2e3
> "/usr/src/sys/modules/ipfw_nat/../../netinet/ipfw/ip_fw_nat.c", line=547)
> at /usr/src/sys/kern/kern_rwlock.c:238
> #12 0xca0ab841 in ipfw_nat_modevent (mod=0xc98a48c0, type=0, unused=0x0)
> at /usr/src/sys/modules/ipfw_nat/../../netinet/ipfw/ip_fw_nat.c:547
>
> note, rw=0xc6d5e91c (it crashed on it). And I get the same address doing
> like I did above:
>
> (kgdb) VNET_VNET vnet0 vnet_entry_layer3_chain
> at 0xc6d5e700 of type = struct ip_fw_chain
> (kgdb) p &((struct ip_fw_chain *)0xc6d5e700)->rwmtx
> $8 = (struct rwlock *) 0xc6d5e91c
>
> Thus ipfw_nat was in vnet0 context then. I saw crashes (in other modules)
> when the context was not initialised and they looked differently.
>
> Right location was 0x86d9c160 (found adding print to ipfw module, I don't
> know easier way):
>
> (kgdb) p ((struct ip_fw_chain *)0x86d9c160)->rwmtx
> $1 = {lock_object = {lo_name = 0x932ba4b3 "IPFW static rules", lo_flags =
> 69402624, lo_data = 0, lo_w
Re: vnet: acessing module's virtualized global variables from another module
On Mon, 9 May 2011 16:21:15 +0200 Marko Zec wrote:
MZ> On Monday 09 May 2011 14:48:25 Mikolaj Golub wrote:
>> Hi,
>>
>> Trying ipfw_nat under VIMAGE kernel I got this panic on the module load:
MZ> Hi,
MZ> I think the problem here is that curvnet context is not set properly on
entry
MZ> to ipfw_nat_modevent(). The canonical way to initialize VNET-enabled
MZ> subsystems is to trigger them using VNET_SYSINIT() macros (instead of
using
MZ> modevent mechanisms), which in turn ensure that:
MZ> a) that the initializer function gets invoked for each existing vnet
MZ> b) curvnet context is set properly on entry to initializer functions and
hm, sorry, but I don't see how curvnet context might help here. For me this
does not look like curvnet context problem or my understanding how it works
completely wrong.
Below is kgdb session on live VIMAGE system with ipfw.ko loaded.
Let's look at some kernel virtualized variable:
(kgdb) p vnet_entry_ifnet
$1 = {tqh_first = 0x0, tqh_last = 0x0}
(kgdb) p &vnet_entry_ifnet
$2 = (struct ifnethead *) 0x8102d488
As expected the address is in kernel 'set_vnet':
kopusha:/usr/src/sys% kldstat |grep kernel
1 69 0x8040 1092700 kernel
kopusha:/usr/src/sys% nm /boot/kernel/kernel |grep __start_set_vnet
8102d480 A __start_set_vnet
default vnet:
(kgdb) p vnet0
$3 = (struct vnet *) 0x86d9b000
Calculate ifnet location on vnet0 (a la VNET_VNET(vnet0, ifnet)):
(kgdb) printf "0x%x\n", vnet0->vnet_data_base + (uintptr_t) & vnet_entry_ifnet
0x86d9c008
Access it:
(kgdb) p *((struct ifnethead *)0x86d9c008)
$4 = {tqh_first = 0x86da5c00, tqh_last = 0x89489c0c}
(kgdb) p (*((struct ifnethead *)0x86d9c008)).tqh_first->if_dname
$7 = 0x80e8b480 "usbus"
(kgdb) p (*((struct ifnethead *)0x86d9c008)).tqh_first->if_vnet
$8 = (struct vnet *) 0x86d9b000
Everything looks good. Now try the same with virtualized variable layer3_chain
from ipfw module:
(kgdb) p vnet_entry_layer3_chain
$9 = {rules = 0x0, reap = 0x0, default_rule = 0x0, n_rules = 0, static_len = 0,
map = 0x0,
nat = {lh_first = 0x0}, tables = {0x0 }, rwmtx =
{lock_object = {
lo_name = 0x0, lo_flags = 0, lo_data = 0, lo_witness = 0x0}, rw_lock =
0}, uh_lock = {
lock_object = {lo_name = 0x0, lo_flags = 0, lo_data = 0, lo_witness = 0x0},
rw_lock = 0},
id = 0, gencnt = 0}
"master" variable looks good (initialized to zeros), what about its address?
(kgdb) p &vnet_entry_layer3_chain
$10 = (struct ip_fw_chain *) 0x894a5c00
It points to 'set_vnet' of the ipfw.ko:
kopusha# kldstat |grep ipfw.ko
132 0x89495000 11000ipfw.ko
kopusha:/usr/src/sys% nm /boot/kernel/ipfw.ko |grep __start_set_vnet
00010be0 A __start_set_vnet
kopusha:/usr/src/sys% printf "0x%x\n" $((0x89495000 + 0x00010be0))
0x894a5be0
Calculate layer3_chain location on vnet0 (a la VNET_VNET(vnet0, layer3_chain)):
(kgdb) printf "0x%x\n", vnet0->vnet_data_base + (uintptr_t) &
vnet_entry_layer3_chain
0x8f214780
Try to read it:
(kgdb) p ((struct ip_fw_chain *)0x8f214780)->rwmtx
$13 = {lock_object = {lo_name = 0x0, lo_flags = 0, lo_data = 0, lo_witness =
0x0}, rw_lock = 0}
(kgdb) p ((struct ip_fw_chain *)0x8f214780)->rules
$14 = (struct ip_fw *) 0x6
Data looks wrong. But this is the way how this variable is acessed by
ipfw_nat. I see the same in the crash image:
(kgdb) where
...
#11 0xc09a4882 in _rw_wlock (rw=0xc6d5e91c,
file=0xca0ac2e3
"/usr/src/sys/modules/ipfw_nat/../../netinet/ipfw/ip_fw_nat.c", line=547)
at /usr/src/sys/kern/kern_rwlock.c:238
#12 0xca0ab841 in ipfw_nat_modevent (mod=0xc98a48c0, type=0, unused=0x0)
at /usr/src/sys/modules/ipfw_nat/../../netinet/ipfw/ip_fw_nat.c:547
note, rw=0xc6d5e91c (it crashed on it). And I get the same address doing like I
did above:
(kgdb) VNET_VNET vnet0 vnet_entry_layer3_chain
at 0xc6d5e700 of type = struct ip_fw_chain
(kgdb) p &((struct ip_fw_chain *)0xc6d5e700)->rwmtx
$8 = (struct rwlock *) 0xc6d5e91c
Thus ipfw_nat was in vnet0 context then. I saw crashes (in other modules) when
the context was not initialised and they looked differently.
Right location was 0x86d9c160 (found adding print to ipfw module, I don't know
easier way):
(kgdb) p ((struct ip_fw_chain *)0x86d9c160)->rwmtx
$1 = {lock_object = {lo_name = 0x932ba4b3 "IPFW static rules", lo_flags =
69402624,
lo_data = 0, lo_witness = 0x86d6ab30}, rw_lock = 1}
(kgdb) p ((struct ip_fw_chain *)0x86d9c160)->rules
$2 = (struct ip_fw *) 0x8f2d1c80
So I don't see a way how to reach module's virtualized variable from outside
the module even if you are in the right vnet context. The linker, when loading
the module and allocating the variable on vnet stacks in 'modspace' possesses
this information and it reallocates addresses in the module and they are
accessible from inside the module, but not from outside.
MZ> Cheers,
MZ> Marko
>> Fatal trap 12: page fault while in kernel mode
>> cpuid = 1; apic id = 01
>> fault virtual address = 0x4
>> fault code = supervisor read, page not p
Re: vnet: acessing module's virtualized global variables from another module
On Monday 09 May 2011 14:48:25 Mikolaj Golub wrote: > Hi, > > Trying ipfw_nat under VIMAGE kernel I got this panic on the module load: Hi, I think the problem here is that curvnet context is not set properly on entry to ipfw_nat_modevent(). The canonical way to initialize VNET-enabled subsystems is to trigger them using VNET_SYSINIT() macros (instead of using modevent mechanisms), which in turn ensure that: a) that the initializer function gets invoked for each existing vnet b) curvnet context is set properly on entry to initializer functions and Cheers, Marko > Fatal trap 12: page fault while in kernel mode > cpuid = 1; apic id = 01 > fault virtual address = 0x4 > fault code = supervisor read, page not present > instruction pointer = 0x20:0xc09f098e > stack pointer = 0x28:0xf563b944 > frame pointer = 0x28:0xf563b998 > code segment= base 0x0, limit 0xf, type 0x1b > = DPL 0, pres 1, def32 1, gran 1 > processor eflags= interrupt enabled, resume, IOPL = 0 > current process = 4264 (kldload) > > witness_checkorder(c6d5e91c,9,ca0ac2e3,223,0,...) at > witness_checkorder+0x6e _rw_wlock(c6d5e91c,ca0ac2e3,223,0,c0e8f795,...) at > _rw_wlock+0x82 > ipfw_nat_modevent(c98a48c0,0,0,75,0,...) at ipfw_nat_modevent+0x41 > module_register_init(ca0ad508,0,c0e8d834,e6,0,...) at > module_register_init+0xa7 > linker_load_module(0,f563bc18,c0e8d834,3fc,f563bc28,...) at > linker_load_module+0xa05 > kern_kldload(c86835c0,c72d3400,f563bc40,0,c8d0d000,...) at > kern_kldload+0x133 kldload(c86835c0,f563bcec,c09e8940,c86835c0,0,...) at > kldload+0x74 syscallenter(c86835c0,f563bce4,c0ce05dd,c1022150,0,...) at > syscallenter+0x263 syscall(f563bd28) at syscall+0x34 > Xint0x80_syscall() at Xint0x80_syscall+0x21 > --- syscall (304, FreeBSD ELF32, kldload), eip = 0x280da00b, esp = > 0xbfbfe79c, ebp = 0xbfbfec88 - > > It crashed on acessing data from virtualized global variable V_layer3_chain > in ipfw_nat_modevent(). V_layer3_chain is defined in ipfw module and it > turns out that &V_layer3_chain returns wrong location from anywhere but > ipfw.ko. > > May be this is a known issue, but I have not found info about this, so > below are details of investigation why this happens. > > Virtualized global variables are defined using the VNET_DEFINE() macro, > which places them in the 'set_vnet' linker set (in the base kernel or in > module). This is used to > > 1) copy these "default" values to each virtual network stack instance when > created; > > 2) act as unique global names by which the variable can be referred to. The > location of a per-virtual instance variable is calculated at run-time like > in the example below for layer3_chain variable in the default vnet (vnet0): > > vnet0->vnet_data_base + (uintptr_t) & vnet_entry_layer3_chain (1) > > For modules the thing is more complicated. When a module is loaded its > global variables from 'set_vnet' linker set are copied to the kernel > 'set_vnet', and for module to be able to access them the linker reallocates > all references accordingly (kern/link_elf.c:elf_relocaddr()): > > if (x >= ef->vnet_start && x < ef->vnet_stop) > return ((x - ef->vnet_start) + ef->vnet_base); > > So from inside the module the access to its virtualized variables works, > but from the outside we get wrong location using calculation like above > (1), because &vnet_entry_layer3_chain returns address of the variable in > the module's 'set_vnet'. > > The workaround is to compile such modules into the kernel or use a hack I > have done for ipfw_nat -- add the function to ipfw module which returns the > location of virtualized layer3_chain variable and use this location instead > of V_layer3_chain macro (see the attached patch). > > But I suppose the problem is not a new and there might be better approach > already invented to deal with this? ___ freebsd-virtualization@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-virtualization To unsubscribe, send any mail to "freebsd-virtualization-unsubscr...@freebsd.org"
vnet: acessing module's virtualized global variables from another module
Hi,
Trying ipfw_nat under VIMAGE kernel I got this panic on the module load:
Fatal trap 12: page fault while in kernel mode
cpuid = 1; apic id = 01
fault virtual address = 0x4
fault code = supervisor read, page not present
instruction pointer = 0x20:0xc09f098e
stack pointer = 0x28:0xf563b944
frame pointer = 0x28:0xf563b998
code segment= base 0x0, limit 0xf, type 0x1b
= DPL 0, pres 1, def32 1, gran 1
processor eflags= interrupt enabled, resume, IOPL = 0
current process = 4264 (kldload)
witness_checkorder(c6d5e91c,9,ca0ac2e3,223,0,...) at witness_checkorder+0x6e
_rw_wlock(c6d5e91c,ca0ac2e3,223,0,c0e8f795,...) at _rw_wlock+0x82
ipfw_nat_modevent(c98a48c0,0,0,75,0,...) at ipfw_nat_modevent+0x41
module_register_init(ca0ad508,0,c0e8d834,e6,0,...) at module_register_init+0xa7
linker_load_module(0,f563bc18,c0e8d834,3fc,f563bc28,...) at
linker_load_module+0xa05
kern_kldload(c86835c0,c72d3400,f563bc40,0,c8d0d000,...) at kern_kldload+0x133
kldload(c86835c0,f563bcec,c09e8940,c86835c0,0,...) at kldload+0x74
syscallenter(c86835c0,f563bce4,c0ce05dd,c1022150,0,...) at syscallenter+0x263
syscall(f563bd28) at syscall+0x34
Xint0x80_syscall() at Xint0x80_syscall+0x21
--- syscall (304, FreeBSD ELF32, kldload), eip = 0x280da00b, esp = 0xbfbfe79c,
ebp = 0xbfbfec88 -
It crashed on acessing data from virtualized global variable V_layer3_chain in
ipfw_nat_modevent(). V_layer3_chain is defined in ipfw module and it turns out
that &V_layer3_chain returns wrong location from anywhere but ipfw.ko.
May be this is a known issue, but I have not found info about this, so below
are details of investigation why this happens.
Virtualized global variables are defined using the VNET_DEFINE() macro, which
places them in the 'set_vnet' linker set (in the base kernel or in
module). This is used to
1) copy these "default" values to each virtual network stack instance when
created;
2) act as unique global names by which the variable can be referred to. The
location of a per-virtual instance variable is calculated at run-time like in
the example below for layer3_chain variable in the default vnet (vnet0):
vnet0->vnet_data_base + (uintptr_t) & vnet_entry_layer3_chain (1)
For modules the thing is more complicated. When a module is loaded its global
variables from 'set_vnet' linker set are copied to the kernel 'set_vnet', and
for module to be able to access them the linker reallocates all references
accordingly (kern/link_elf.c:elf_relocaddr()):
if (x >= ef->vnet_start && x < ef->vnet_stop)
return ((x - ef->vnet_start) + ef->vnet_base);
So from inside the module the access to its virtualized variables works, but
from the outside we get wrong location using calculation like above (1),
because &vnet_entry_layer3_chain returns address of the variable in the
module's 'set_vnet'.
The workaround is to compile such modules into the kernel or use a hack I have
done for ipfw_nat -- add the function to ipfw module which returns the
location of virtualized layer3_chain variable and use this location instead of
V_layer3_chain macro (see the attached patch).
But I suppose the problem is not a new and there might be better approach
already invented to deal with this?
--
Mikolaj Golub
Index: sys/netinet/ipfw/ip_fw_private.h
===
--- sys/netinet/ipfw/ip_fw_private.h (revision 221673)
+++ sys/netinet/ipfw/ip_fw_private.h (working copy)
@@ -201,6 +201,8 @@ VNET_DECLARE(int, fw_verbose);
VNET_DECLARE(struct ip_fw_chain, layer3_chain);
#define V_layer3_chain VNET(layer3_chain)
+void* vnet_entry_addr_layer3_chain(void);
+#define V_addr_layer3_chain (vnet_entry_addr_layer3_chain())
VNET_DECLARE(u_int32_t, set_disable);
#define V_set_disable VNET(set_disable)
Index: sys/netinet/ipfw/ip_fw_nat.c
===
--- sys/netinet/ipfw/ip_fw_nat.c (revision 221673)
+++ sys/netinet/ipfw/ip_fw_nat.c (working copy)
@@ -62,7 +62,7 @@ ifaddr_change(void *arg __unused, struct ifnet *if
struct ifaddr *ifa;
struct ip_fw_chain *chain;
- chain = &V_layer3_chain;
+ chain = V_addr_layer3_chain;
IPFW_WLOCK(chain);
/* Check every nat entry... */
LIST_FOREACH(ptr, &chain->nat, _next) {
@@ -345,7 +345,7 @@ ipfw_nat_cfg(struct sockopt *sopt)
{
struct cfg_nat *cfg, *ptr;
char *buf;
- struct ip_fw_chain *chain = &V_layer3_chain;
+ struct ip_fw_chain *chain = V_addr_layer3_chain;
size_t len;
int gencnt, error = 0;
@@ -421,7 +421,7 @@ static int
ipfw_nat_del(struct sockopt *sopt)
{
struct cfg_nat *ptr;
- struct ip_fw_chain *chain = &V_layer3_chain;
+ struct ip_fw_chain *chain = V_addr_layer3_chain;
int i;
sooptcopyin(sopt, &i, sizeof i, sizeof i);
@@ -444,7 +444,7 @@ ipfw_nat_del(struct sockopt *sopt)
static int
ipfw_nat_get_cfg(struct sockopt *sopt)
{
- struct ip_fw_chain *chain = &V_layer3_chain;
Current problem reports assigned to freebsd-virtualization@FreeBSD.org
Note: to view an individual PR, use: http://www.freebsd.org/cgi/query-pr.cgi?pr=(number). The following is a listing of current problems submitted by FreeBSD users. These represent problem reports covering all versions including experimental development code and obsolete releases. S Tracker Resp. Description a kern/152047 virtualization[vimage] [panic] TUN\TAP under jail with vimage crashe o kern/148155 virtualization[vimage] Kernel panic with PF/IPFilter + VIMAGE kernel a kern/147950 virtualization[vimage] [carp] VIMAGE + CARP = kernel crash s kern/143808 virtualization[pf] pf does not work inside jail a kern/141696 virtualization[rum] [panic] rum(4)+ vimage = kernel panic 5 problems total. ___ freebsd-virtualization@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-virtualization To unsubscribe, send any mail to "freebsd-virtualization-unsubscr...@freebsd.org"
