Re: [PATCH] lguest32 kallsyms backtrace of guest.
On Thu, 2007-04-05 at 12:54 +1000, Rusty Russell wrote: > > This is a cool idea, but there are two issues with this patch. The > first is that it's 500 lines of code: that's around +10% on lguest's > total code size! The second is that it conflicts with the medium-term > plan to allow any user to run up lguests: this is why lg.ko never > printk()s about problems with the guest. Not much I can do about the size, but it's in the debug section so hopefully it's not considered too bad :) > > While it is useful for cases where a guest dies mysteriously before it > brings up the console, three alternatives come to mind: > > 1) Modify early_printk so Guests can use it. > 2) Have a separate tool(-set?) for this kind of post-mortem. Then you > just have to implement guest suspend! 8) > 3) Put this in a CONFIG_LGUEST_DEBUG. > > Note that options 1 or 2 make you do more work, but are probably better > in the long term. I'm happy for #3 to sit as a patch in the tree for > the duration, tho! OK, I'll make a #3 patch to send, but the #1 looks best. Not to mention that I still need to make it so that the console can read it. -- Steve - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] lguest32 kallsyms backtrace of guest.
On Wed, 2007-04-04 at 14:23 -0400, Steven Rostedt wrote: > This is taken from the work I did on lguest64. > > When killing a guest, we read the guest stack to do a nice back trace of > the guest and send it via printk to the host. > > So instead of just getting an error message from the lguest launcher of: > > lguest: bad read address 537012178 len 1 > > I also get in my dmesg: > > called from [] show_trace_log_lvl+0x1a/0x2f Hi Steven, This is a cool idea, but there are two issues with this patch. The first is that it's 500 lines of code: that's around +10% on lguest's total code size! The second is that it conflicts with the medium-term plan to allow any user to run up lguests: this is why lg.ko never printk()s about problems with the guest. While it is useful for cases where a guest dies mysteriously before it brings up the console, three alternatives come to mind: 1) Modify early_printk so Guests can use it. 2) Have a separate tool(-set?) for this kind of post-mortem. Then you just have to implement guest suspend! 8) 3) Put this in a CONFIG_LGUEST_DEBUG. Note that options 1 or 2 make you do more work, but are probably better in the long term. I'm happy for #3 to sit as a patch in the tree for the duration, tho! Cheers, Rusty. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] lguest32 kallsyms backtrace of guest.
This is taken from the work I did on lguest64. When killing a guest, we read the guest stack to do a nice back trace of the guest and send it via printk to the host. So instead of just getting an error message from the lguest launcher of: lguest: bad read address 537012178 len 1 I also get in my dmesg: called from [] show_trace_log_lvl+0x1a/0x2f [] show_trace+0x12/0x14 [] dump_stack+0x16/0x18 [] lguest_dump_lg_regs+0x22/0x13c [lg] [] lgread+0x59/0x90 [lg] [] run_guest+0x26b/0x406 [lg] [] read+0x73/0x7d [lg] [] vfs_read+0xad/0x161 [] sys_read+0x3d/0x61 [] syscall_call+0x7/0xb === [] lgread+0x59/0x90 [lg] Printing LG 0 regs cr3: 021eb000 EIP: 0061: [] ESP: 0069:c236fe3c EFLAGS: 00010202 EAX: 0004 EBX: e001fb20 ECX: 0008 EDX: 03f2 ESI: e001ee00 EDI: e001fb60 EBP: c236fea0 CR2: 1278000 lguest_data->cr2: 80011380 errcode: 0 trapnum: d Stack Dump: [ ] trace_hardirqs_on+0x125/0x149 [ ] wait_for_completion+0x90/0x98 [ ] __mutex_unlock_slowpath+0x129/0x13e [ ] unlock_cpu_hotplug+0x62/0x64 [ ] sys_init_module+0x14e3/0x162c [ ] do_sync_read+0xc2/0xff [ ] restore_nocheck+0x12/0x15 [ ] syscall_call+0x7/0xb TODO: - Clean up a little (still has stuff from lguest64 in it). - Perhaps make a config option or runtime switch to turn it off. - Send to the launcher the dump instead of printk. - make modules work too. Also I need to change the %u of the bad read print to a %x, because seeing 0x200227d2 is better than seeing 537012178 for addresses. Signed-off-by: Steven Rostedt <[EMAIL PROTECTED]> Index: linux-2.6.21-rc5-mm2/drivers/lguest/Makefile === --- linux-2.6.21-rc5-mm2.orig/drivers/lguest/Makefile +++ linux-2.6.21-rc5-mm2/drivers/lguest/Makefile @@ -4,4 +4,4 @@ obj-$(CONFIG_LGUEST_GUEST) += lguest.o l # Host requires the other files, which can be a module. obj-$(CONFIG_LGUEST) += lg.o lg-objs := core.o hypercalls.o page_tables.o interrupts_and_traps.o \ - segments.o io.o lguest_user.o hypervisor.o + segments.o io.o lguest_user.o hypervisor.o lguest_debug.o Index: linux-2.6.21-rc5-mm2/drivers/lguest/core.c === --- linux-2.6.21-rc5-mm2.orig/drivers/lguest/core.c +++ linux-2.6.21-rc5-mm2/drivers/lguest/core.c @@ -210,6 +210,28 @@ int lguest_address_ok(const struct lgues } /* Just like get_user, but don't let guest access lguest binary. */ +u8 lgread_u8(struct lguest *lg, u32 addr) +{ + u8 val = 0; + + /* Don't let them access lguest binary */ + if (!lguest_address_ok(lg, addr) + || get_user(val, (u32 __user *)addr) != 0) + kill_guest(lg, "bad read address %u", addr); + return val; +} + +u16 lgread_u16(struct lguest *lg, u32 addr) +{ + u16 val = 0; + + /* Don't let them access lguest binary */ + if (!lguest_address_ok(lg, addr) + || get_user(val, (u32 __user *)addr) != 0) + kill_guest(lg, "bad read address %u", addr); + return val; +} + u32 lgread_u32(struct lguest *lg, u32 addr) { u32 val = 0; Index: linux-2.6.21-rc5-mm2/drivers/lguest/lg.h === --- linux-2.6.21-rc5-mm2.orig/drivers/lguest/lg.h +++ linux-2.6.21-rc5-mm2/drivers/lguest/lg.h @@ -176,6 +176,8 @@ extern struct mutex lguest_lock; /* core.c: */ /* Entry points in hypervisor */ const unsigned long *__lguest_default_idt_entries(void); +u8 lgread_u8(struct lguest *lg, u32 addr); +u16 lgread_u16(struct lguest *lg, u32 addr); u32 lgread_u32(struct lguest *lg, u32 addr); void lgwrite_u32(struct lguest *lg, u32 val, u32 addr); void lgread(struct lguest *lg, void *buf, u32 addr, unsigned bytes); @@ -238,6 +240,7 @@ int hypercall(struct lguest *info, struc #define kill_guest(lg, fmt...) \ do { \ if (!(lg)->dead) { \ + lguest_dump_lg_regs(lg);\ (lg)->dead = kasprintf(GFP_ATOMIC, fmt);\ if (!(lg)->dead)\ (lg)->dead = (void *)1; \ @@ -248,5 +251,11 @@ static inline unsigned long guest_pa(str { return vaddr - lg->page_offset; } + +/* lguest_debug.c */ +void lguest_print_address(struct lguest *lg, unsigned long address); +void lguest_dump_trace(struct lguest *lg, struct lguest_regs *regs); +void lguest_dump_lg_regs(struct lguest *lg); + #endif /* __ASSEMBLY__ */ #endif /* _LGUEST_H */ Index: linux-2.6.21-rc5-mm2/drivers/lguest/lguest.c === ---
[PATCH] lguest32 kallsyms backtrace of guest.
This is taken from the work I did on lguest64.
When killing a guest, we read the guest stack to do a nice back trace of
the guest and send it via printk to the host.
So instead of just getting an error message from the lguest launcher of:
lguest: bad read address 537012178 len 1
I also get in my dmesg:
called from [c0405f30] show_trace_log_lvl+0x1a/0x2f
[c04069aa] show_trace+0x12/0x14
[c0406a03] dump_stack+0x16/0x18
[f8c746de] lguest_dump_lg_regs+0x22/0x13c [lg]
[f8c7131b] lgread+0x59/0x90 [lg]
[f8c715bd] run_guest+0x26b/0x406 [lg]
[f8c739be] read+0x73/0x7d [lg]
[c04825e9] vfs_read+0xad/0x161
[c0482a75] sys_read+0x3d/0x61
[c0404f34] syscall_call+0x7/0xb
===
[f8c7131b] lgread+0x59/0x90 [lg]
Printing LG 0 regs cr3: 021eb000
EIP: 0061: [e00227d2]
ESP: 0069:c236fe3c EFLAGS: 00010202
EAX: 0004 EBX: e001fb20 ECX: 0008 EDX: 03f2
ESI: e001ee00 EDI: e001fb60 EBP: c236fea0
CR2: 1278000 lguest_data-cr2: 80011380
errcode: 0 trapnum: d
Stack Dump:
[c1042b7a] trace_hardirqs_on+0x125/0x149
[c123b0ea] wait_for_completion+0x90/0x98
[c123bddc] __mutex_unlock_slowpath+0x129/0x13e
[c1048769] unlock_cpu_hotplug+0x62/0x64
[c104b5b6] sys_init_module+0x14e3/0x162c
[c1081d44] do_sync_read+0xc2/0xff
[c1004f85] restore_nocheck+0x12/0x15
[c1004f34] syscall_call+0x7/0xb
TODO:
- Clean up a little (still has stuff from lguest64 in it).
- Perhaps make a config option or runtime switch to turn it off.
- Send to the launcher the dump instead of printk.
- make modules work too.
Also I need to change the %u of the bad read print to a %x, because
seeing 0x200227d2 is better than seeing 537012178 for addresses.
Signed-off-by: Steven Rostedt [EMAIL PROTECTED]
Index: linux-2.6.21-rc5-mm2/drivers/lguest/Makefile
===
--- linux-2.6.21-rc5-mm2.orig/drivers/lguest/Makefile
+++ linux-2.6.21-rc5-mm2/drivers/lguest/Makefile
@@ -4,4 +4,4 @@ obj-$(CONFIG_LGUEST_GUEST) += lguest.o l
# Host requires the other files, which can be a module.
obj-$(CONFIG_LGUEST) += lg.o
lg-objs := core.o hypercalls.o page_tables.o interrupts_and_traps.o \
- segments.o io.o lguest_user.o hypervisor.o
+ segments.o io.o lguest_user.o hypervisor.o lguest_debug.o
Index: linux-2.6.21-rc5-mm2/drivers/lguest/core.c
===
--- linux-2.6.21-rc5-mm2.orig/drivers/lguest/core.c
+++ linux-2.6.21-rc5-mm2/drivers/lguest/core.c
@@ -210,6 +210,28 @@ int lguest_address_ok(const struct lgues
}
/* Just like get_user, but don't let guest access lguest binary. */
+u8 lgread_u8(struct lguest *lg, u32 addr)
+{
+ u8 val = 0;
+
+ /* Don't let them access lguest binary */
+ if (!lguest_address_ok(lg, addr)
+ || get_user(val, (u32 __user *)addr) != 0)
+ kill_guest(lg, bad read address %u, addr);
+ return val;
+}
+
+u16 lgread_u16(struct lguest *lg, u32 addr)
+{
+ u16 val = 0;
+
+ /* Don't let them access lguest binary */
+ if (!lguest_address_ok(lg, addr)
+ || get_user(val, (u32 __user *)addr) != 0)
+ kill_guest(lg, bad read address %u, addr);
+ return val;
+}
+
u32 lgread_u32(struct lguest *lg, u32 addr)
{
u32 val = 0;
Index: linux-2.6.21-rc5-mm2/drivers/lguest/lg.h
===
--- linux-2.6.21-rc5-mm2.orig/drivers/lguest/lg.h
+++ linux-2.6.21-rc5-mm2/drivers/lguest/lg.h
@@ -176,6 +176,8 @@ extern struct mutex lguest_lock;
/* core.c: */
/* Entry points in hypervisor */
const unsigned long *__lguest_default_idt_entries(void);
+u8 lgread_u8(struct lguest *lg, u32 addr);
+u16 lgread_u16(struct lguest *lg, u32 addr);
u32 lgread_u32(struct lguest *lg, u32 addr);
void lgwrite_u32(struct lguest *lg, u32 val, u32 addr);
void lgread(struct lguest *lg, void *buf, u32 addr, unsigned bytes);
@@ -238,6 +240,7 @@ int hypercall(struct lguest *info, struc
#define kill_guest(lg, fmt...) \
do { \
if (!(lg)-dead) { \
+ lguest_dump_lg_regs(lg);\
(lg)-dead = kasprintf(GFP_ATOMIC, fmt);\
if (!(lg)-dead)\
(lg)-dead = (void *)1; \
@@ -248,5 +251,11 @@ static inline unsigned long guest_pa(str
{
return vaddr - lg-page_offset;
}
+
+/* lguest_debug.c */
+void lguest_print_address(struct lguest *lg, unsigned long address);
+void lguest_dump_trace(struct lguest *lg, struct lguest_regs *regs);
+void lguest_dump_lg_regs(struct lguest *lg);
+
#endif /* __ASSEMBLY__ */
#endif /* _LGUEST_H */
Index: linux-2.6.21-rc5-mm2/drivers/lguest/lguest.c
Re: [PATCH] lguest32 kallsyms backtrace of guest.
On Wed, 2007-04-04 at 14:23 -0400, Steven Rostedt wrote: This is taken from the work I did on lguest64. When killing a guest, we read the guest stack to do a nice back trace of the guest and send it via printk to the host. So instead of just getting an error message from the lguest launcher of: lguest: bad read address 537012178 len 1 I also get in my dmesg: called from [c0405f30] show_trace_log_lvl+0x1a/0x2f Hi Steven, This is a cool idea, but there are two issues with this patch. The first is that it's 500 lines of code: that's around +10% on lguest's total code size! The second is that it conflicts with the medium-term plan to allow any user to run up lguests: this is why lg.ko never printk()s about problems with the guest. While it is useful for cases where a guest dies mysteriously before it brings up the console, three alternatives come to mind: 1) Modify early_printk so Guests can use it. 2) Have a separate tool(-set?) for this kind of post-mortem. Then you just have to implement guest suspend! 8) 3) Put this in a CONFIG_LGUEST_DEBUG. Note that options 1 or 2 make you do more work, but are probably better in the long term. I'm happy for #3 to sit as a patch in the tree for the duration, tho! Cheers, Rusty. - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] lguest32 kallsyms backtrace of guest.
On Thu, 2007-04-05 at 12:54 +1000, Rusty Russell wrote: This is a cool idea, but there are two issues with this patch. The first is that it's 500 lines of code: that's around +10% on lguest's total code size! The second is that it conflicts with the medium-term plan to allow any user to run up lguests: this is why lg.ko never printk()s about problems with the guest. Not much I can do about the size, but it's in the debug section so hopefully it's not considered too bad :) While it is useful for cases where a guest dies mysteriously before it brings up the console, three alternatives come to mind: 1) Modify early_printk so Guests can use it. 2) Have a separate tool(-set?) for this kind of post-mortem. Then you just have to implement guest suspend! 8) 3) Put this in a CONFIG_LGUEST_DEBUG. Note that options 1 or 2 make you do more work, but are probably better in the long term. I'm happy for #3 to sit as a patch in the tree for the duration, tho! OK, I'll make a #3 patch to send, but the #1 looks best. Not to mention that I still need to make it so that the console can read it. -- Steve - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
