+ stable ML
On Thu, 25 Feb 2021 at 21:26, Daniel Thompson
<daniel.thompson@xxxxxxxxxx> wrote:
>
> On Wed, Feb 24, 2021 at 01:46:52PM +0530, Sumit Garg wrote:
> > Currently breakpoints in kernel .init.text section are not handled
> > correctly while allowing to remove them even after corresponding pages
> > have been freed.
> >
> > Fix it via killing .init.text section breakpoints just prior to initmem
> > pages being freed.
> >
> > Suggested-by: Doug Anderson <dianders@xxxxxxxxxxxx>
> > Signed-off-by: Sumit Garg <sumit.garg@xxxxxxxxxx>
>
> I saw Andrew has picked this one up. That's ok for me:
> Acked-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
>
> I already enriched kgdbtest to cover this (and they pass) so I guess
> this is also:
> Tested-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
>
Thanks Daniel.
> BTW this is not Cc:ed to stable and I do wonder if it crosses the
> threshold to be considered a fix rather than a feature. Normally I
> consider adding safety rails for kgdb to be a new feature but, in this
> case, the problem would easily ensnare an inexperienced developer who is
> doing nothing more than debugging their own driver (assuming they
> correctly marked their probe function as .init) so I think this weighs
> in favour of being a fix.
>
Makes sense, Cc:ed stable.
-Sumit
>
> Daniel.
>
>
> > ---
> > include/linux/kgdb.h | 2 ++
> > init/main.c | 1 +
> > kernel/debug/debug_core.c | 11 +++++++++++
> > 3 files changed, 14 insertions(+)
> >
> > diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
> > index 57b8885708e5..3aa503ef06fc 100644
> > --- a/include/linux/kgdb.h
> > +++ b/include/linux/kgdb.h
> > @@ -361,9 +361,11 @@ extern atomic_t kgdb_active;
> > extern bool dbg_is_early;
> > extern void __init dbg_late_init(void);
> > extern void kgdb_panic(const char *msg);
> > +extern void kgdb_free_init_mem(void);
> > #else /* ! CONFIG_KGDB */
> > #define in_dbg_master() (0)
> > #define dbg_late_init()
> > static inline void kgdb_panic(const char *msg) {}
> > +static inline void kgdb_free_init_mem(void) { }
> > #endif /* ! CONFIG_KGDB */
> > #endif /* _KGDB_H_ */
> > diff --git a/init/main.c b/init/main.c
> > index c68d784376ca..a446ca3d334e 100644
> > --- a/init/main.c
> > +++ b/init/main.c
> > @@ -1417,6 +1417,7 @@ static int __ref kernel_init(void *unused)
> > async_synchronize_full();
> > kprobe_free_init_mem();
> > ftrace_free_init_mem();
> > + kgdb_free_init_mem();
> > free_initmem();
> > mark_readonly();
> >
> > diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
> > index 229dd119f430..319381e95d1d 100644
> > --- a/kernel/debug/debug_core.c
> > +++ b/kernel/debug/debug_core.c
> > @@ -465,6 +465,17 @@ int dbg_remove_all_break(void)
> > return 0;
> > }
> >
> > +void kgdb_free_init_mem(void)
> > +{
> > + int i;
> > +
> > + /* Clear init memory breakpoints. */
> > + for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
> > + if (init_section_contains((void *)kgdb_break[i].bpt_addr, 0))
> > + kgdb_break[i].state = BP_UNDEFINED;
> > + }
> > +}
> > +
> > #ifdef CONFIG_KGDB_KDB
> > void kdb_dump_stack_on_cpu(int cpu)
> > {
> > --
> > 2.25.1
