On Wednesday 27 July 2005 21:22, Allan Graves wrote:
> Hi guys, from the lists, this looks like it should work. Its not
> though, and so my question. :)
> I'm working on debugging a module, and it panics and takes down uml.
> I'm running uml in a gdb session, but since UML exits after the panic
> code, i don't have a backtrace, context, or really anything to help me
> debug. I've tried putting a breakpoint on panic to catch it, but for
> some reason, it didn't stop it. Any thoughts on how i can get gdb to
> catch and keep the context of the panic and not just let UML exit?
Well, a first thing might be to compile in only SKAS mode, and play with
static / dynamic. GDB has always appreciated more a standard binary than a TT
one.
If it's a segfault put a breakpoint on handle_segv, otherwise you can always
try adding something as dump_stack() at the beginning of panic(); there's
currently one done by
notifier_call_chain(&panic_notifier_list, 0, buf);
in particular by panic_exit, but it doesn't always work.
And I think that the two attached patches might improve this (I can't use GDB
on UML without them).
--
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <[EMAIL PROTECTED]>
---
linux-2.6.git-paolo/arch/um/kernel/uml.lds.S | 25 +++++++++++++++++++++++++
1 files changed, 25 insertions(+)
diff -puN arch/um/kernel/uml.lds.S~uml-add-dwarf-sections-to-static-link-script arch/um/kernel/uml.lds.S
--- linux-2.6.git/arch/um/kernel/uml.lds.S~uml-add-dwarf-sections-to-static-link-script 2005-07-18 18:53:15.000000000 +0200
+++ linux-2.6.git-paolo/arch/um/kernel/uml.lds.S 2005-07-18 18:53:15.000000000 +0200
@@ -103,4 +103,29 @@ SECTIONS
.stab.index 0 : { *(.stab.index) }
.stab.indexstr 0 : { *(.stab.indexstr) }
.comment 0 : { *(.comment) }
+ /* DWARF debug sections.
+ Symbols in the DWARF debugging sections are relative to the beginning
+ of the section so we begin them at 0. */
+ /* DWARF 1 */
+ .debug 0 : { *(.debug) }
+ .line 0 : { *(.line) }
+ /* GNU DWARF 1 extensions */
+ .debug_srcinfo 0 : { *(.debug_srcinfo) }
+ .debug_sfnames 0 : { *(.debug_sfnames) }
+ /* DWARF 1.1 and DWARF 2 */
+ .debug_aranges 0 : { *(.debug_aranges) }
+ .debug_pubnames 0 : { *(.debug_pubnames) }
+ /* DWARF 2 */
+ .debug_info 0 : { *(.debug_info .gnu.linkonce.wi.*) }
+ .debug_abbrev 0 : { *(.debug_abbrev) }
+ .debug_line 0 : { *(.debug_line) }
+ .debug_frame 0 : { *(.debug_frame) }
+ .debug_str 0 : { *(.debug_str) }
+ .debug_loc 0 : { *(.debug_loc) }
+ .debug_macinfo 0 : { *(.debug_macinfo) }
+ /* SGI/MIPS DWARF 2 extensions */
+ .debug_weaknames 0 : { *(.debug_weaknames) }
+ .debug_funcnames 0 : { *(.debug_funcnames) }
+ .debug_typenames 0 : { *(.debug_typenames) }
+ .debug_varnames 0 : { *(.debug_varnames) }
}
_
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <[EMAIL PROTECTED]>
---
linux-2.6.git-paolo/arch/um/Kconfig | 10 ++++++++++
linux-2.6.git-paolo/arch/um/kernel/main.c | 2 +-
linux-2.6.git-paolo/arch/um/kernel/um_arch.c | 6 +++---
3 files changed, 14 insertions(+), 4 deletions(-)
diff -puN arch/um/kernel/main.c~uml-fix-host-debug-on-TT-binaries arch/um/kernel/main.c
--- linux-2.6.git/arch/um/kernel/main.c~uml-fix-host-debug-on-TT-binaries 2005-07-18 18:53:19.000000000 +0200
+++ linux-2.6.git-paolo/arch/um/kernel/main.c 2005-07-18 18:53:19.000000000 +0200
@@ -97,7 +97,7 @@ int main(int argc, char **argv, char **e
exit(1);
}
-#ifdef UML_CONFIG_MODE_TT
+#ifdef UML_CONFIG_CMDLINE_ON_HOST
/* Allocate memory for thread command lines */
if(argc < 2 || strlen(argv[1]) < THREAD_NAME_LEN - 1){
diff -puN arch/um/kernel/um_arch.c~uml-fix-host-debug-on-TT-binaries arch/um/kernel/um_arch.c
--- linux-2.6.git/arch/um/kernel/um_arch.c~uml-fix-host-debug-on-TT-binaries 2005-07-18 18:53:19.000000000 +0200
+++ linux-2.6.git-paolo/arch/um/kernel/um_arch.c 2005-07-18 18:53:19.000000000 +0200
@@ -123,7 +123,7 @@ unsigned long start_vm;
unsigned long end_vm;
int ncpus = 1;
-#ifdef CONFIG_MODE_TT
+#ifdef CONFIG_CMDLINE_ON_HOST
/* Pointer set in linux_main, the array itself is private to each thread,
* and changed at address space creation time so this poses no concurrency
* problems.
@@ -138,7 +138,7 @@ long physmem_size = 32 * 1024 * 1024;
void set_cmdline(char *cmd)
{
-#ifdef CONFIG_MODE_TT
+#ifdef CONFIG_CMDLINE_ON_HOST
char *umid, *ptr;
if(CHOOSE_MODE(honeypot, 0)) return;
@@ -366,7 +366,7 @@ int linux_main(int argc, char **argv)
setup_machinename(system_utsname.machine);
-#ifdef CONFIG_MODE_TT
+#ifdef CONFIG_CMDLINE_ON_HOST
argv1_begin = argv[1];
argv1_end = &argv[1][strlen(argv[1])];
#endif
diff -puN arch/um/Kconfig~uml-fix-host-debug-on-TT-binaries arch/um/Kconfig
--- linux-2.6.git/arch/um/Kconfig~uml-fix-host-debug-on-TT-binaries 2005-07-18 18:53:19.000000000 +0200
+++ linux-2.6.git-paolo/arch/um/Kconfig 2005-07-18 18:53:19.000000000 +0200
@@ -51,6 +51,16 @@ config MODE_TT
use only skas mode (and the host has the skas patch applied to it),
then it is OK to say N here.
+config CMDLINE_ON_HOST
+ bool
+ depends on MODE_TT && !DEBUG_INFO
+ default y
+ help
+ This controls whether arguments in guest processes should be shown at all.
+ I'm disabling this when TT mode is enabled because it creates problems
+ with host debugging, on recent GDB versions (starting from the execvp
+ point).
+
config STATIC_LINK
bool "Force a static link"
default n
_
