Hello Alexander Couzens, Kyösti Mälkki, Patrick Rudolph, David Hendricks, build bot (Jenkins), Patrick Georgi, Martin Roth,
I'd like you to reexamine a change. Please visit
https://review.coreboot.org/c/coreboot/+/34487
to look at the new patch set (#3).
Change subject: soc/intel/baytrail: Prevent unintended sign extensions ......................................................................
soc/intel/baytrail: Prevent unintended sign extensions
Consider the following assignment:
u64 = s32
For positive values this is fine, but if the s32 is negative, it will be sign-extended in the conversion to a very large unsigned integer. This manifests itself in two ways in the following code:
First, gpu_pipe{a,b}_port_select are defined as int, and can have the values 1 or 2. In the case when they have the value 2, the shift 2 << 30 will be a negative number, making it susceptible to the sign-extension problem above. Change these variables to something more reasonable like a uint8_t, which is unsigned.
Second, in any bit shift, any variable with width less than an int will be implicitly promoted to an int before performing the bit shift. For example, the variable gpu_pipea_power_on_delay is a uint16_t, and if its highest bit is set, the shift gpu_pipea_power_on_delay << 16 will become negative, again introducing the above problem. To prevent this, cast all smaller variables to a u32 before the shift, which will prevent the implicit promotions and sign extensions.
Change-Id: Ic5db6001504cefb501dee199590a0e961a15771b Signed-off-by: Jacob Garber jgarber1@ualberta.ca Found-by: Coverity CID 1229699, 1229700, 1229701, 1229702 --- M src/soc/intel/baytrail/chip.h M src/soc/intel/baytrail/gfx.c 2 files changed, 12 insertions(+), 12 deletions(-)
git pull ssh://review.coreboot.org:29418/coreboot refs/changes/87/34487/3