diff options
| author | Keith Packard <keithp@keithp.com> | 2016-12-17 20:58:36 -0800 |
|---|---|---|
| committer | Keith Packard <keithp@keithp.com> | 2016-12-17 21:04:33 -0800 |
| commit | 89ecc32b90565ace078c4a84d4406a4d1f86821a (patch) | |
| tree | 3b32f1d922380b3dfd25db75552a30dc84c24d41 /src/drivers/ao_trng_send.c | |
| parent | f650211f9e99e1d3d0ae13ae559dd1c082f71545 (diff) | |
altos/arm: Align data so that gcc 5.4 doesn't do byte-accesses. Add -Wcast-align
Gcc 5.4.1 tracks alignment of data through assignments, so that a
uint32_t pointer which comes from byte-aligned uint8_t data:
extern uint8_t foo[];
uint32_t *q = (void *) foo;
Fetches and stores through this pointer are done bytewise. This is
slow (meh), but if q references a device register, things to bad very
quickly.
This patch works around this bug in the compiler by adding
__attribute__((aligned(4))) tags to some variables, or changing them
from uint8_t to uint32_t. Places doing this will now be caught as I've
added -Wcast-align to the compiler flags. That required adding (void
*) casts, after the relevant code was checked to make sure the
compiler could tell that the addresses were aligned.
Signed-off-by: Keith Packard <keithp@keithp.com>
Diffstat (limited to 'src/drivers/ao_trng_send.c')
| -rw-r--r-- | src/drivers/ao_trng_send.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/src/drivers/ao_trng_send.c b/src/drivers/ao_trng_send.c index 85034efd..b1227aaa 100644 --- a/src/drivers/ao_trng_send.c +++ b/src/drivers/ao_trng_send.c @@ -104,7 +104,7 @@ ao_trng_get_cooked(uint16_t *buf) { uint16_t i; uint16_t t; - uint32_t *rnd = (uint32_t *) ao_adc_ring; + uint32_t *rnd = (uint32_t *) (void *) ao_adc_ring; uint8_t mismatch = 0; t = ao_adc_get(AO_USB_IN_SIZE) >> 1; /* one 16-bit value per output byte */ |