From 0dcd91a9e6cc0a401416bbdd34b0a255cde0aee1 Mon Sep 17 00:00:00 2001 From: Sebastian Ott Date: Thu, 12 Oct 2017 13:57:26 +0200 Subject: s390/debug: only write data once debug_event_common memsets the active debug entry with zeros to prevent stale data leakage. This is overwritten with the actual debug data in the next step. Only write zeros to that part of the debug entry that's not used by new debug data. Micro benchmarks show a 2-10% reduction of cpu cycles with this approach. Signed-off-by: Sebastian Ott Acked-by: Michael Holzheu Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/debug.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'arch/s390') diff --git a/arch/s390/kernel/debug.c b/arch/s390/kernel/debug.c index df916738fbd8..2df679d75454 100644 --- a/arch/s390/kernel/debug.c +++ b/arch/s390/kernel/debug.c @@ -902,8 +902,9 @@ debug_entry_t *debug_event_common(debug_info_t *id, int level, const void *buf, } do { active = get_active_entry(id); - memset(DEBUG_DATA(active), 0, id->buf_size); memcpy(DEBUG_DATA(active), buf, min(len, id->buf_size)); + if (len < id->buf_size) + memset((DEBUG_DATA(active)) + len, 0, id->buf_size - len); debug_finish_entry(id, active, level, 0); len -= id->buf_size; buf += id->buf_size; @@ -934,8 +935,9 @@ debug_entry_t *debug_exception_common(debug_info_t *id, int level, } do { active = get_active_entry(id); - memset(DEBUG_DATA(active), 0, id->buf_size); memcpy(DEBUG_DATA(active), buf, min(len, id->buf_size)); + if (len < id->buf_size) + memset((DEBUG_DATA(active)) + len, 0, id->buf_size - len); debug_finish_entry(id, active, level, len <= id->buf_size); len -= id->buf_size; buf += id->buf_size; -- cgit