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

Mark Rutland
2016-09-21T08:57:21Z

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@linaro.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Jason Wessel <jason.wessel@windriver.com>
> Cc: <stable@vger.kernel.org> # 3.18-3.19: 2f896d5: arm64: use fixmap
> Cc: <stable@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.

With that:

Reviewed-by: Mark Rutland <mark.rutland@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
>