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/kernel | |
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/kernel')
-rw-r--r-- | src/kernel/ao_list.h | 2 | ||||
-rw-r--r-- | src/kernel/ao_pyro.c | 4 | ||||
-rw-r--r-- | src/kernel/ao_task.h | 13 |
3 files changed, 15 insertions, 4 deletions
diff --git a/src/kernel/ao_list.h b/src/kernel/ao_list.h index e2df6885..45a3df5b 100644 --- a/src/kernel/ao_list.h +++ b/src/kernel/ao_list.h @@ -138,7 +138,7 @@ ao_list_is_empty(struct ao_list *head) * @return A pointer to the data struct containing the list head. */ #define ao_container_of(ptr, type, member) \ - ((type *)((char *)(ptr) - offsetof(type, member))) + ((type *)((void *) ((char *)(ptr) - offsetof(type, member)))) /** * Alias of ao_container_of diff --git a/src/kernel/ao_pyro.c b/src/kernel/ao_pyro.c index b11d1080..a0881f9e 100644 --- a/src/kernel/ao_pyro.c +++ b/src/kernel/ao_pyro.c @@ -438,7 +438,7 @@ ao_pyro_show(void) if (ao_pyro_values[v].flag & AO_PYRO_8_BIT_VALUE) value = *((uint8_t *) ((char *) pyro + ao_pyro_values[v].offset)); else - value = *((int16_t *) ((char *) pyro + ao_pyro_values[v].offset)); + value = *((int16_t *) (void *) ((char *) pyro + ao_pyro_values[v].offset)); printf ("%6d ", value); } else { printf (" "); @@ -517,7 +517,7 @@ ao_pyro_set(void) } else { if (negative) ao_cmd_lex_i = -ao_cmd_lex_i; - *((int16_t *) ((char *) &pyro_tmp + ao_pyro_values[v].offset)) = ao_cmd_lex_i; + *((int16_t *) (void *) ((char *) &pyro_tmp + ao_pyro_values[v].offset)) = ao_cmd_lex_i; } } } diff --git a/src/kernel/ao_task.h b/src/kernel/ao_task.h index f1dbd654..30b018ff 100644 --- a/src/kernel/ao_task.h +++ b/src/kernel/ao_task.h @@ -26,6 +26,17 @@ #define HAS_TASK_INFO 1 #endif +/* arm stacks must be 32-bit aligned */ +#ifdef __arm__ +#define AO_STACK_ALIGNMENT __attribute__ ((aligned(4))) +#endif +#ifdef SDCC +#define AO_STACK_ALIGNMENT +#endif +#ifdef __AVR__ +#define AO_STACK_ALIGNMENT +#endif + /* An AltOS task */ struct ao_task { __xdata void *wchan; /* current wait channel (NULL if running) */ @@ -37,7 +48,7 @@ struct ao_task { struct ao_list queue; struct ao_list alarm_queue; #endif - uint8_t stack[AO_STACK_SIZE]; /* saved stack */ + uint8_t stack[AO_STACK_SIZE] AO_STACK_ALIGNMENT; /* saved stack */ #if HAS_SAMPLE_PROFILE uint32_t ticks; uint32_t yields; |