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Subject[RFC][PATCH] modular kgdb-light (was: Re: [git pull] kgdb-light -v10)
Andi Kleen wrote:
>> This includes things like having "breakpoint reservations" (discussed
>> earlier) and just generally trying to add lots of infrastructure to make
>> kgdb "fit in" to the kernel.
>
> I think that part is actually mostly ok now (old kgdb stubs were
> much worse in this regard)
>
> I still think the ultimative proof for this would be working
> "modprobe kgdb" though.

To pick up this idea again I did the experimental patch below. It
applies against Jason's latest kgdb-light patch queue:

http://git.kernel.org/?p=linux/kernel/git/jwessel/linux-2.6-kgdb.git;a=shortlog;h=for_ingo

The patch nicely demonstrates what deeper dependencies on kernel
services currently exist in kgdb-light. The following symbols were
unresolvable:

o genapic - for send_IPI_allbutself, ie. CPU roundup
o machine_emergency_restart - for implementing "R0" gdb packet
o idle_task - kgdb tells the per-cpu idle tasks apart
o clocksource_touch_watchdog - obvious

For simplicity reasons I just gpl-exported all of them. The result is
a fully modular kgdb that may help to reduce concerns regarding its
intrusiveness.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

---
arch/x86/kernel/Makefile | 4 +++-
arch/x86/kernel/genapic_64.c | 1 +
arch/x86/kernel/{kgdb.c => kgdb-x86.c} | 0
arch/x86/kernel/reboot.c | 1 +
arch/x86/mach-generic/probe.c | 1 +
kernel/Makefile | 1 -
kernel/sched.c | 1 +
kernel/time/clocksource.c | 1 +
lib/Kconfig.kgdb | 2 +-
{kernel => lib}/kgdb.c | 8 ++++++--
10 files changed, 15 insertions(+), 5 deletions(-)
rename arch/x86/kernel/{kgdb.c => kgdb-x86.c} (100%)
rename {kernel => lib}/kgdb.c (100%)
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 4cd39cd..2e733b1 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -58,7 +58,6 @@ obj-$(CONFIG_MODULES) += module_$(BITS).o
obj-$(CONFIG_ACPI_SRAT) += srat_32.o
obj-$(CONFIG_EFI) += efi.o efi_$(BITS).o efi_stub_$(BITS).o
obj-$(CONFIG_DOUBLEFAULT) += doublefault_32.o
-obj-$(CONFIG_KGDB) += kgdb.o
obj-$(CONFIG_VM86) += vm86_32.o
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o

@@ -79,6 +78,9 @@ endif
obj-$(CONFIG_SCx200) += scx200.o
scx200-y += scx200_32.o

+kgdb-objs := ../../../lib/kgdb.o kgdb-x86.o
+obj-$(CONFIG_KGDB) += kgdb.o
+
###
# 64 bit specific files
ifeq ($(CONFIG_X86_64),y)
diff --git a/arch/x86/kernel/genapic_64.c b/arch/x86/kernel/genapic_64.c
index 4ae7b64..d0518a7 100644
--- a/arch/x86/kernel/genapic_64.c
+++ b/arch/x86/kernel/genapic_64.c
@@ -32,6 +32,7 @@ DEFINE_PER_CPU(u16, x86_cpu_to_apicid) = BAD_APICID;
EXPORT_PER_CPU_SYMBOL(x86_cpu_to_apicid);

struct genapic __read_mostly *genapic = &apic_flat;
+EXPORT_SYMBOL_GPL(genapic);

/*
* Check the APIC IDs in bios_cpu_apicid and choose the APIC mode.
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb-x86.c
similarity index 100%
rename from arch/x86/kernel/kgdb.c
rename to arch/x86/kernel/kgdb-x86.c
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 5818dc2..66d7c27 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -375,6 +375,7 @@ void machine_emergency_restart(void)
}
}
}
+EXPORT_SYMBOL_GPL(machine_emergency_restart);

void machine_shutdown(void)
{
diff --git a/arch/x86/mach-generic/probe.c b/arch/x86/mach-generic/probe.c
index f410d3c..4156d64 100644
--- a/arch/x86/mach-generic/probe.c
+++ b/arch/x86/mach-generic/probe.c
@@ -21,6 +21,7 @@ extern struct genapic apic_es7000;
extern struct genapic apic_default;

struct genapic *genapic = &apic_default;
+EXPORT_SYMBOL_GPL(genapic);

static struct genapic *apic_probe[] __initdata = {
&apic_summit,
diff --git a/kernel/Makefile b/kernel/Makefile
index 05c8003..6c584c5 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -53,7 +53,6 @@ obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
obj-$(CONFIG_AUDIT_TREE) += audit_tree.o
obj-$(CONFIG_KPROBES) += kprobes.o
-obj-$(CONFIG_KGDB) += kgdb.o
obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
obj-$(CONFIG_SECCOMP) += seccomp.o
diff --git a/kernel/sched.c b/kernel/sched.c
index 3eedd52..e2ffff4 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4463,6 +4463,7 @@ struct task_struct *idle_task(int cpu)
{
return cpu_rq(cpu)->idle;
}
+EXPORT_SYMBOL_GPL(idle_task);

/**
* find_process_by_pid - find a process with a matching PID value.
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index ace23d3..e83dc5d 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -238,6 +238,7 @@ void clocksource_touch_watchdog(void)
{
clocksource_resume_watchdog();
}
+EXPORT_SYMBOL_GPL(clocksource_touch_watchdog);

/**
* clocksource_get_next - Returns the selected clocksource
diff --git a/lib/Kconfig.kgdb b/lib/Kconfig.kgdb
index 9631ba3..413e3b8 100644
--- a/lib/Kconfig.kgdb
+++ b/lib/Kconfig.kgdb
@@ -1,6 +1,6 @@

menuconfig KGDB
- bool "KGDB: kernel debugging with remote gdb"
+ tristate "KGDB: kernel debugging with remote gdb"
select FRAME_POINTER
depends on HAVE_ARCH_KGDB
depends on DEBUG_KERNEL && EXPERIMENTAL
diff --git a/kernel/kgdb.c b/lib/kgdb.c
similarity index 100%
rename from kernel/kgdb.c
rename to lib/kgdb.c
index b516de0..2ef8e9d 100644
--- a/kernel/kgdb.c
+++ b/lib/kgdb.c
@@ -91,13 +91,14 @@ static int kgdb_con_registered;
/* determine if kgdb console output should be used */
static int kgdb_use_con;

+#ifdef CONFIG_KGDB
static int __init opt_kgdb_con(char *str)
{
kgdb_use_con = 1;
return 0;
}
-
early_param("kgdbcon", opt_kgdb_con);
+#endif

module_param(kgdb_use_con, int, 0644);

@@ -1667,6 +1668,7 @@ void kgdb_breakpoint(void)
}
EXPORT_SYMBOL_GPL(kgdb_breakpoint);

+#ifdef CONFIG_KGDB
static int __init opt_kgdb_wait(char *str)
{
kgdb_break_asap = 1;
@@ -1676,5 +1678,7 @@ static int __init opt_kgdb_wait(char *str)

return 0;
}
-
early_param("kgdbwait", opt_kgdb_wait);
+#endif
+
+MODULE_LICENSE("GPL");


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