Jan Kiszka wrote:
> This patch addresses the recently discovered issue that I-pipe actually
> need to deal with faults over non-root domain in which the current
> domain shows no interest in. Such faults could be triggered inside
> copy_*_user, thus can cleanly be handled by Linux - if we only allow for
> this. Currently, if debugging is on, we warn about a potential bug, and
> corrupt the pipeline states otherwise.
>
> The new approach is to unconditionally drop to root domain in such
> cases, but - for debugging purposes of non-fixable faults - keep track
> of the original domain and report it on oops.
>
> Similar patches are required for other archs. Maybe I can look into
> x86_64 later.
>
> Jan
[Damn it... now with attachment.]
--
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux
---
arch/i386/kernel/ipipe.c | 27 +++++++++++++++------------
arch/i386/kernel/traps.c | 3 ++-
include/linux/ipipe.h | 1 +
include/linux/ipipe_percpu.h | 1 +
kernel/ipipe/core.c | 1 +
5 files changed, 20 insertions(+), 13 deletions(-)
Index: linux-2.6.23.1-xeno/arch/i386/kernel/ipipe.c
===================================================================
--- linux-2.6.23.1-xeno.orig/arch/i386/kernel/ipipe.c
+++ linux-2.6.23.1-xeno/arch/i386/kernel/ipipe.c
@@ -634,7 +634,7 @@ fastcall int __ipipe_handle_exception(st
}
#ifdef CONFIG_KGDB
- /* catch exception KGDB is interested in over non-root domains */
+ /* catch exceptions KGDB is interested in over non-root domains */
if (!ipipe_root_domain_p &&
__ipipe_xlate_signo[vector] >= 0 &&
!kgdb_handle_exception(vector, __ipipe_xlate_signo[vector], error_code, regs)) {
@@ -643,18 +643,21 @@ fastcall int __ipipe_handle_exception(st
}
#endif /* CONFIG_KGDB */
- if (!ipipe_trap_notify(vector, regs)) {
-#ifdef CONFIG_IPIPE_DEBUG
- if (!ipipe_root_domain_p) {
- /* Fix up domain so that Linux can handle this. */
+ if (likely(!ipipe_trap_notify(vector, regs))) {
+ if (unlikely(!ipipe_root_domain_p)) {
+ struct ipipe_domain *prev_orig = ipipe_orig_domain;
+
+ /* Drop to root domain so that Linux can handle the
+ * fault, but save the original domain for reporting
+ * purposes of oopses over non-root contexts. */
+ ipipe_orig_domain = ipipe_current_domain;
ipipe_current_domain = ipipe_root_domain;
- ipipe_trace_panic_freeze();
- printk(KERN_ERR "BUG: Unhandled exception over domain"
- " %s - switching to ROOT\n",
- ipipe_current_domain->name);
- }
-#endif /* CONFIG_IPIPE_DEBUG */
- __ipipe_std_extable[vector](regs, error_code);
+
+ __ipipe_std_extable[vector](regs, error_code);
+
+ ipipe_orig_domain = prev_orig;
+ } else
+ __ipipe_std_extable[vector](regs, error_code);
local_irq_restore(flags);
__fixup_if(regs);
return 0;
Index: linux-2.6.23.1-xeno/arch/i386/kernel/traps.c
===================================================================
--- linux-2.6.23.1-xeno.orig/arch/i386/kernel/traps.c
+++ linux-2.6.23.1-xeno/arch/i386/kernel/traps.c
@@ -321,7 +321,8 @@ void show_registers(struct pt_regs *regs
TASK_COMM_LEN, current->comm, current->pid,
current_thread_info(), current, task_thread_info(current));
#ifdef CONFIG_IPIPE
- printk(KERN_EMERG "\nI-pipe domain %s", ipipe_current_domain->name);
+ printk(KERN_EMERG "\nI-pipe domain %s", ipipe_orig_domain ?
+ ipipe_orig_domain->name : ipipe_current_domain->name);
#endif /* CONFIG_IPIPE */
/*
* When in-kernel, we also print out the stack and code at the
Index: linux-2.6.23.1-xeno/include/linux/ipipe.h
===================================================================
--- linux-2.6.23.1-xeno.orig/include/linux/ipipe.h
+++ linux-2.6.23.1-xeno/include/linux/ipipe.h
@@ -83,6 +83,7 @@
#define IPIPE_NR_CPUS NR_CPUS
#define ipipe_current_domain ipipe_cpu_var(ipipe_percpu_domain)
+#define ipipe_orig_domain ipipe_cpu_var(ipipe_percpu_orig_domain)
#define ipipe_virtual_irq_p(irq) ((irq) >= IPIPE_VIRQ_BASE && \
(irq) < IPIPE_NR_IRQS)
Index: linux-2.6.23.1-xeno/include/linux/ipipe_percpu.h
===================================================================
--- linux-2.6.23.1-xeno.orig/include/linux/ipipe_percpu.h
+++ linux-2.6.23.1-xeno/include/linux/ipipe_percpu.h
@@ -52,6 +52,7 @@ DECLARE_PER_CPU(struct ipipe_percpu_doma
DECLARE_PER_CPU(struct ipipe_percpu_domain_data, ipipe_percpu_darray[CONFIG_IPIPE_DOMAINS]);
DECLARE_PER_CPU(struct ipipe_domain *, ipipe_percpu_domain);
+DECLARE_PER_CPU(struct ipipe_domain *, ipipe_percpu_orig_domain);
#ifdef CONFIG_IPIPE_DEBUG_CONTEXT
DECLARE_PER_CPU(int, ipipe_percpu_context_check);
Index: linux-2.6.23.1-xeno/kernel/ipipe/core.c
===================================================================
--- linux-2.6.23.1-xeno.orig/kernel/ipipe/core.c
+++ linux-2.6.23.1-xeno/kernel/ipipe/core.c
@@ -78,6 +78,7 @@ DEFINE_PER_CPU(struct ipipe_percpu_domai
{ [0] = { .status = IPIPE_STALL_MASK } }; /* Root domain stalled on each CPU at startup. */
DEFINE_PER_CPU(struct ipipe_domain *, ipipe_percpu_domain) = { &ipipe_root };
+DEFINE_PER_CPU(struct ipipe_domain *, ipipe_percpu_orig_domain) = { NULL };
static IPIPE_DEFINE_SPINLOCK(__ipipe_pipelock);
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