arm64: debug: remove debug exception registration infrastructure

Now that debug exceptions are handled individually and without the need
for dynamic registration, remove the unused registration infrastructure.

This removes the external caller for `debug_exception_enter()` and
`debug_exception_exit()`.
Make them static again and remove them from the header.

Remove `early_brk64()` as it has been made redundant by
(arm64: debug: split brk64 exception entry) and is not used anymore.
Note : in `early_brk64()` `bug_brk_handler()` is called unconditionally
as a fall-through, but now `call_break_hook()` only calls it if the
immediate matches.
This does not change the behaviour in early boot, as if
`bug_brk_handler()` was called on a non-BUG immediate it would return
DBG_HOOK_ERROR anyway, which `call_break_hook()` will do if no immediate
matches.

Remove `trap_init()`, as it would be empty and a weak definition already
exists in `init/main.c`.

Signed-off-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Tested-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Reviewed-by: Will Deacon <will@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20250707114109.35672-14-ada.coupriediaz@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

3 files changed, 2 insertions, 32 deletions

diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 43a612eaa7d2..43f342a01fdf 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -316,9 +316,6 @@ bool try_handle_aarch32_break(struct pt_regs *regs)
 }
 NOKPROBE_SYMBOL(try_handle_aarch32_break);
 
-void __init debug_traps_init(void)
-{}
-
 /* Re-enable single step for syscall restarting. */
 void user_rewind_single_step(struct task_struct *task)
 {
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index bbf58fcab142..4b67312a88ad 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -448,7 +448,7 @@ static __always_inline void fpsimd_syscall_exit(void)
  * accidentally schedule in exception context and it will force a warning
  * if we somehow manage to schedule by accident.
  */
-void debug_exception_enter(struct pt_regs *regs)
+static void debug_exception_enter(struct pt_regs *regs)
 {
 	preempt_disable();
 
@@ -457,7 +457,7 @@ void debug_exception_enter(struct pt_regs *regs)
 }
 NOKPROBE_SYMBOL(debug_exception_enter);
 
-void debug_exception_exit(struct pt_regs *regs)
+static void debug_exception_exit(struct pt_regs *regs)
 {
 	preempt_enable_no_resched();
 }
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 654c8ea46ec6..98b11da5a5ad 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -1100,30 +1100,3 @@ int ubsan_brk_handler(struct pt_regs *regs, unsigned long esr)
 	return DBG_HOOK_HANDLED;
 }
 #endif
-
-/*
- * Initial handler for AArch64 BRK exceptions
- * This handler only used until debug_traps_init().
- */
-int __init early_brk64(unsigned long addr, unsigned long esr,
-		struct pt_regs *regs)
-{
-#ifdef CONFIG_CFI_CLANG
-	if (esr_is_cfi_brk(esr))
-		return cfi_brk_handler(regs, esr) != DBG_HOOK_HANDLED;
-#endif
-#ifdef CONFIG_KASAN_SW_TAGS
-	if ((esr_brk_comment(esr) & ~KASAN_BRK_MASK) == KASAN_BRK_IMM)
-		return kasan_brk_handler(regs, esr) != DBG_HOOK_HANDLED;
-#endif
-#ifdef CONFIG_UBSAN_TRAP
-	if (esr_is_ubsan_brk(esr))
-		return ubsan_brk_handler(regs, esr) != DBG_HOOK_HANDLED;
-#endif
-	return bug_brk_handler(regs, esr) != DBG_HOOK_HANDLED;
-}
-
-void __init trap_init(void)
-{
-	debug_traps_init();
-}