[PATCH v4 1/6] arm64: hw_breakpoint: Disallow breakpoints in no kprobe code

[Rob Herring (Arm)]

Taking debug exceptions while manipulating the breakpoints is likely to
be unsafe. The setting kprobes in the breakpoint code is already
forbidden, but the setting of h/w breakpoints is not. Copy what x86 does
and exclude breakpoints that fall within the kprobe section.

Signed-off-by: Rob Herring (Arm) <robh@xxxxxxxxxx>
---
 arch/arm64/kernel/hw_breakpoint.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index ab76b36dce82..38fbd67b2a6e 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -418,6 +418,16 @@ static int arch_build_bp_info(struct perf_event *bp,
 	/* Type */
 	switch (attr->bp_type) {
 	case HW_BREAKPOINT_X:
+		/*
+		 * We don't allow kernel breakpoints in places that are not
+		 * acceptable for kprobes.  On non-kprobes kernels, we don't
+		 * allow kernel breakpoints at all.
+		 */
+		if (attr->bp_addr >= TASK_SIZE_MAX) {
+			if (within_kprobe_blacklist(attr->bp_addr))
+				return -EINVAL;
+		}
+
 		hw->ctrl.type = ARM_BREAKPOINT_EXECUTE;
 		break;
 	case HW_BREAKPOINT_R:

-- 
2.53.0