arm64: kgdb: handle read-only text / modules

Handle read-only cases when CONFIG_DEBUG_RODATA (4.0) or
CONFIG_DEBUG_SET_MODULE_RONX (3.18) are enabled by using
aarch64_insn_write() instead of probe_kernel_write() as introduced by
commit 2f896d586610 ("arm64: use fixmap for text patching") in 4.0.

Fixes: 11d91a770f1f ("arm64: Add CONFIG_DEBUG_SET_MODULE_RONX support")
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

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 4b6b3f72a215..b71420a12f26 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 8c57f6496e56..e017a9493b92 100644
--- a/arch/arm64/kernel/kgdb.c
+++ b/arch/arm64/kernel/kgdb.c
@@ -19,10 +19,13 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/bug.h>
 #include <linux/irq.h>
 #include <linux/kdebug.h>
 #include <linux/kgdb.h>
 #include <linux/kprobes.h>
+#include <asm/debug-monitors.h>
+#include <asm/insn.h>
 #include <asm/traps.h>
 
 struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
@@ -338,15 +341,24 @@ 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);
+}