[PATCH v2] arm64: kgdb: handle read-only text / modules

[AKASHI Takahiro]

On Wed, Sep 21, 2016 at 09:57:21AM +0100, Mark Rutland wrote:
> On Wed, Sep 21, 2016 at 04:19:55PM +0900, AKASHI Takahiro wrote:
> > Handle read-only cases (CONFIG_DEBUG_RODATA/CONFIG_DEBUG_SET_MODULE_RONX)
> > by using aarch64_insn_write() instead of probe_kernel_write().
> > See how this works:
> >     commit 2f896d586610 ("arm64: use fixmap for text patching")
> > 
> > Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> > Cc: Catalin Marinas <catalin.marinas at arm.com>
> > Cc: Will Deacon <will.deacon at arm.com>
> > Cc: Jason Wessel <jason.wessel at windriver.com>
> > Cc: <stable at vger.kernel.org> # 3.18-3.19: 2f896d5: arm64: use fixmap
> > Cc: <stable at vger.kernel.org> # 4.0-
> 
> For v3.18-v3.19, we also need commit f6242cac10427c54 ("arm64: Fix text
> patching logic when using fixmap"), so as to not break the
> !CONFIG_DEBUG_SET_MODULE_RONX case.

Ah, thank you.
I will post the patch as v2.1.

-Takahiro AKASHI

> With that:
> 
> Reviewed-by: Mark Rutland <mark.rutland at arm.com>
> 
> Thanks,
> Mark.
> 
> > ---
> >  arch/arm64/include/asm/debug-monitors.h |  2 --
> >  arch/arm64/kernel/kgdb.c                | 36 ++++++++++++++++++++++-----------
> >  2 files changed, 24 insertions(+), 14 deletions(-)
> > 
> > diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h
> > index 4b6b3f7..b71420a 100644
> > --- a/arch/arm64/include/asm/debug-monitors.h
> > +++ b/arch/arm64/include/asm/debug-monitors.h
> > @@ -61,8 +61,6 @@
> >  
> >  #define AARCH64_BREAK_KGDB_DYN_DBG	\
> >  	(AARCH64_BREAK_MON | (KGDB_DYN_DBG_BRK_IMM << 5))
> > -#define KGDB_DYN_BRK_INS_BYTE(x)	\
> > -	((AARCH64_BREAK_KGDB_DYN_DBG >> (8 * (x))) & 0xff)
> >  
> >  #define CACHE_FLUSH_IS_SAFE		1
> >  
> > diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c
> > index 6732a27..b06a7a2 100644
> > --- a/arch/arm64/kernel/kgdb.c
> > +++ b/arch/arm64/kernel/kgdb.c
> > @@ -19,6 +19,7 @@
> >   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> >   */
> >  
> > +#include <linux/bug.h>
> >  #include <linux/cpumask.h>
> >  #include <linux/irq.h>
> >  #include <linux/irq_work.h>
> > @@ -26,6 +27,8 @@
> >  #include <linux/kgdb.h>
> >  #include <linux/kprobes.h>
> >  #include <linux/percpu.h>
> > +#include <asm/debug-monitors.h>
> > +#include <asm/insn.h>
> >  #include <asm/ptrace.h>
> >  #include <asm/traps.h>
> >  
> > @@ -370,15 +373,24 @@ void kgdb_arch_exit(void)
> >  	unregister_die_notifier(&kgdb_notifier);
> >  }
> >  
> > -/*
> > - * ARM instructions are always in LE.
> > - * Break instruction is encoded in LE format
> > - */
> > -struct kgdb_arch arch_kgdb_ops = {
> > -	.gdb_bpt_instr = {
> > -		KGDB_DYN_BRK_INS_BYTE(0),
> > -		KGDB_DYN_BRK_INS_BYTE(1),
> > -		KGDB_DYN_BRK_INS_BYTE(2),
> > -		KGDB_DYN_BRK_INS_BYTE(3),
> > -	}
> > -};
> > +struct kgdb_arch arch_kgdb_ops;
> > +
> > +int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
> > +{
> > +	int err;
> > +
> > +	BUILD_BUG_ON(AARCH64_INSN_SIZE != BREAK_INSTR_SIZE);
> > +
> > +	err = aarch64_insn_read((void *)bpt->bpt_addr, (u32 *)bpt->saved_instr);
> > +	if (err)
> > +		return err;
> > +
> > +	return aarch64_insn_write((void *)bpt->bpt_addr,
> > +			(u32)AARCH64_BREAK_KGDB_DYN_DBG);
> > +}
> > +
> > +int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
> > +{
> > +	return aarch64_insn_write((void *)bpt->bpt_addr,
> > +			*(u32 *)bpt->saved_instr);
> > +}
> > -- 
> > 2.10.0
> >