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

[ Upstream commit 29c578c848402a34e8c8e115bf66cb6008b77062 ]

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@intel.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Mark Brown <broonie@kernel.org>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/2023abcddf3f524ba478d64339996f25dc4097d2.1742852847.git.jpoimboe@kernel.org
Closes: https://lore.kernel.org/oe-kbuild-all/202503182350.52KeHGD4-lkp@intel.com/
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/regulator/rk808-regulator.c b/drivers/regulator/rk808-regulator.c
index 374d80dc6d17abb7d784d1c4b77ca3f1a2bd1fbf..bec22a001a5dd595f18592313e124fcb4e44b4f3 100644 (file)
--- a/drivers/regulator/rk808-regulator.c
+++ b/drivers/regulator/rk808-regulator.c
@@ -267,8 +267,8 @@ 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;