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Subject[PATCH v2 5/9] arm64: Add call_break_hook() to early_brk64() for early kgdb
Date
In order to make early kgdb work properly we need early_brk64() to be
able to call into it. This is as easy as adding a call into
call_break_hook() just like we do later in the normal brk_handler().

Once we do this we can let kgdb know that it can break into the
debugger a little earlier (specifically when parsing early_param's).

NOTE: without this patch it turns out that arm64 can't do breakpoints
even at dbg_late_init(), so if we decide something about this patch is
wrong we might need to move dbg_late_init() a little later.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
---

Changes in v2: None

arch/arm64/include/asm/debug-monitors.h | 2 ++
arch/arm64/kernel/debug-monitors.c | 2 +-
arch/arm64/kernel/kgdb.c | 5 +++++
arch/arm64/kernel/traps.c | 3 +++
4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h
index 7619f473155f..2d82a0314d29 100644
--- a/arch/arm64/include/asm/debug-monitors.h
+++ b/arch/arm64/include/asm/debug-monitors.h
@@ -97,6 +97,8 @@ void unregister_user_break_hook(struct break_hook *hook);
void register_kernel_break_hook(struct break_hook *hook);
void unregister_kernel_break_hook(struct break_hook *hook);

+int call_break_hook(struct pt_regs *regs, unsigned int esr);
+
u8 debug_monitors_arch(void);

enum dbg_active_el {
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 48222a4760c2..59c353dfc8e9 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -297,7 +297,7 @@ void unregister_kernel_break_hook(struct break_hook *hook)
unregister_debug_hook(&hook->node);
}

-static int call_break_hook(struct pt_regs *regs, unsigned int esr)
+int call_break_hook(struct pt_regs *regs, unsigned int esr)
{
struct break_hook *hook;
struct list_head *list;
diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c
index 43119922341f..96a47af870bc 100644
--- a/arch/arm64/kernel/kgdb.c
+++ b/arch/arm64/kernel/kgdb.c
@@ -301,6 +301,11 @@ static struct notifier_block kgdb_notifier = {
.priority = -INT_MAX,
};

+extern bool kgdb_arch_can_debug_early(void)
+{
+ return true;
+}
+
/*
* kgdb_arch_init - Perform any architecture specific initialization.
* This function will handle the initialization of any architecture
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index cf402be5c573..a8173f0c1774 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -1044,6 +1044,9 @@ int __init early_brk64(unsigned long addr, unsigned int esr,
if ((comment & ~KASAN_BRK_MASK) == KASAN_BRK_IMM)
return kasan_handler(regs, esr) != DBG_HOOK_HANDLED;
#endif
+ if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
+ return 0;
+
return bug_handler(regs, esr) != DBG_HOOK_HANDLED;
}

--
2.26.1.301.g55bc3eb7cb9-goog
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