Some tools (e.g. perf) incorrectly assume that breakpoints should be
sizeof(long), but this is wrong for AArch64 where breakpoints must be
4 bytes. Add a warning when we silently fix up the parameter so tool
developers can get notified.
This addresses the FIXME comment by adding diagnostic output rather
than breaking existing tools by returning -EINVAL.
Signed-off-by: Osama Abdelkader <osama.abdelkader@gmail.com>
---
v2: fix warning messageline splitting
---
arch/arm64/kernel/hw_breakpoint.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index ab76b36dce82..cce306145d78 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -475,11 +475,13 @@ static int arch_build_bp_info(struct perf_event *bp,
return -EINVAL;
} else if (hw->ctrl.len != ARM_BREAKPOINT_LEN_4) {
/*
- * FIXME: Some tools (I'm looking at you perf) assume
- * that breakpoints should be sizeof(long). This
- * is nonsense. For now, we fix up the parameter
- * but we should probably return -EINVAL instead.
+ * Some tools (e.g. perf) incorrectly assume that
+ * breakpoints should be sizeof(long). This is wrong
+ * for AArch64 where breakpoints must be 4 bytes.
+ * Warn the user and fix up the parameter.
*/
+ pr_warn_once("hw_breakpoint: invalid AArch64 breakpoint length %d, fixing to 4 bytes\n",
+ hw->ctrl.len);
hw->ctrl.len = ARM_BREAKPOINT_LEN_4;
}
}
--
2.43.0