From 1b310030bb855b9b13d1c0a9feffdb54883b06ab Mon Sep 17 00:00:00 2001 From: Douglas Anderson Date: Thu, 7 May 2020 16:11:46 -0700 Subject: kdb: Cleanup math with KDB_CMD_HISTORY_COUNT From code inspection the math in handle_ctrl_cmd() looks super sketchy because it subjects -1 from cmdptr and then does a "% KDB_CMD_HISTORY_COUNT". It turns out that this code works because "cmdptr" is unsigned and KDB_CMD_HISTORY_COUNT is a nice power of 2. Let's make this a little less sketchy. This patch should be a no-op. Signed-off-by: Douglas Anderson Link: https://lore.kernel.org/r/20200507161125.1.I2cce9ac66e141230c3644b8174b6c15d4e769232@changeid Reviewed-by: Sumit Garg Signed-off-by: Daniel Thompson --- kernel/debug/kdb/kdb_main.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel/debug') diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 515379cbf209..6865a0f58d38 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -1108,7 +1108,8 @@ static int handle_ctrl_cmd(char *cmd) switch (*cmd) { case CTRL_P: if (cmdptr != cmd_tail) - cmdptr = (cmdptr-1) % KDB_CMD_HISTORY_COUNT; + cmdptr = (cmdptr + KDB_CMD_HISTORY_COUNT - 1) % + KDB_CMD_HISTORY_COUNT; strscpy(cmd_cur, cmd_hist[cmdptr], CMD_BUFLEN); return 1; case CTRL_N: -- cgit v1.2.3