[tip: objtool/urgent] objtool, regulator: rk808: Remove potential undefined behavior in rk806_set_mode_dcdc()

[tip-bot2 for Josh Poimboeuf]

The following commit has been merged into the objtool/urgent branch of tip:

Commit-ID:     4d014a6b8e4dba75eb0b99e6ed990bb7e38da294
Gitweb:        https://git.kernel.org/tip/4d014a6b8e4dba75eb0b99e6ed990bb7e38da294
Author:        Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate:    Mon, 24 Mar 2025 14:56:10 -07:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 25 Mar 2025 09:20:29 +01:00

objtool, regulator: rk808: Remove potential undefined behavior in rk806_set_mode_dcdc()

If 'ctr_bit' is negative, the shift counts become negative, causing a
shift of bounds and undefined behavior.

Presumably that's not possible in normal operation, but the code
generation isn't optimal.  And undefined behavior should be avoided
regardless.

Improve code generation and remove the undefined behavior by converting
the signed variables to unsigned.

Fixes the following warning with an UBSAN kernel:

  vmlinux.o: warning: objtool: rk806_set_mode_dcdc() falls through to next function rk806_get_mode_dcdc()
  vmlinux.o: warning: objtool: .text.rk806_set_mode_dcdc: unexpected end of section

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Liam Girdwood <lgirdwood@xxxxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/2023abcddf3f524ba478d64339996f25dc4097d2.1742852847.git.jpoimboe@xxxxxxxxxx
Closes: https://lore.kernel.org/oe-kbuild-all/202503182350.52KeHGD4-lkp@xxxxxxxxx/
---
 drivers/regulator/rk808-regulator.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/regulator/rk808-regulator.c b/drivers/regulator/rk808-regulator.c
index 7d82bd1..1e81424 100644
--- a/drivers/regulator/rk808-regulator.c
+++ b/drivers/regulator/rk808-regulator.c
@@ -270,8 +270,8 @@ static const unsigned int rk817_buck1_4_ramp_table[] = {
 
 static int rk806_set_mode_dcdc(struct regulator_dev *rdev, unsigned int mode)
 {
-	int rid = rdev_get_id(rdev);
-	int ctr_bit, reg;
+	unsigned int rid = rdev_get_id(rdev);
+	unsigned int ctr_bit, reg;
 
 	reg = RK806_POWER_FPWM_EN0 + rid / 8;
 	ctr_bit = rid % 8;