[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:     29c578c848402a34e8c8e115bf66cb6008b77062
Gitweb:        https://git.kernel.org/tip/29c578c848402a34e8c8e115bf66cb6008b77062
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 23:00:29 +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>
Acked-by: Mark Brown <broonie@xxxxxxxxxx>
Cc: Liam Girdwood <lgirdwood@xxxxxxxxx>
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;