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author | Joel Sherrill <joel.sherrill@OARcorp.com> | 2003-09-26 20:43:22 +0000 |
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committer | Joel Sherrill <joel.sherrill@OARcorp.com> | 2003-09-26 20:43:22 +0000 |
commit | 92b67b18d78f9822dcd58c018c130e4bd986986b (patch) | |
tree | df313cd1b79049b08ed607e2861947c5fcc2a845 /c/src/lib/libbsp/powerpc/shared/startup/sbrk.c | |
parent | 2003-09-26 Till Straumann <strauman@slac.stanford.edu> (diff) | |
download | rtems-92b67b18d78f9822dcd58c018c130e4bd986986b.tar.bz2 |
2003-09-26 Till Strauman <strauman@slac.stanford.edu>
PR 496/bsps
* startup/sbrk.c: New file.
* startup/bspstart.c: This patch implements 'sbrk'
for the powerpc-shared BSP to work around what's known as the
'32Mb problem' in combination with run-time loaded code.
GCC normally generates (PowerPC) code doing 'short jumps' which
requires all text segments being in the same 32Mb area of memory.
However, some run-time loaders use (e.g. heap-) memory violating the
stated limitation on hardware with more than 32Mb of memory.
(NOTE: portable loaders are probably not even aware of this
GCC/CPU specific problem.)
This patch implements a simple workaround: At boot time, the system is
only provided with 32Mb of memory. The user is supposed to load all
necessary modules prior to that limit being exhausted. Once that
happens, newlib/malloc end up trying to 'sbrk()' for more memory and
the implementation provided by this patch will then make the rest of
the physical memory available.
Diffstat (limited to 'c/src/lib/libbsp/powerpc/shared/startup/sbrk.c')
-rw-r--r-- | c/src/lib/libbsp/powerpc/shared/startup/sbrk.c | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/c/src/lib/libbsp/powerpc/shared/startup/sbrk.c b/c/src/lib/libbsp/powerpc/shared/startup/sbrk.c new file mode 100644 index 0000000000..276433a5da --- /dev/null +++ b/c/src/lib/libbsp/powerpc/shared/startup/sbrk.c @@ -0,0 +1,64 @@ +/* $Id$ */ + +/* + * sbrk.c + * + * Author: Till Straumann <strauman@slac.stanford.edu>, 2002 + * + * Hack around the 32bit powerpc 32M problem: + * + * GCC by default uses relative branches which can not jump + * farther than 32M. Hence all program text is confined to + * a single 32M segment. + * This hack gives the RTEMS malloc region all memory below + * 32M at startup. Only when this region is exhausted will sbrk + * add more memory. Loading modules may fail at that point, hence + * the user is expected to load all modules at startup _prior_ + * to malloc()ing lots of memory... + * + * NOTE: it would probably be better to have a separate region + * for module code. + */ + +#include <rtems.h> + +#include <signal.h> +#include <errno.h> +#include <sys/types.h> +#include <unistd.h> + +static rtems_unsigned32 remaining_start=0; +static rtems_unsigned32 remaining_size=0; + +#define LIMIT_32M 0x02000000 + +rtems_unsigned32 +_bsp_sbrk_init(rtems_unsigned32 heap_start, rtems_unsigned32 *heap_size_p) +{ + rtems_unsigned32 rval=0; + + remaining_start = heap_start; + remaining_size =* heap_size_p; + if (remaining_start < LIMIT_32M && + remaining_start + remaining_size > LIMIT_32M) { + /* clip at LIMIT_32M */ + rval = remaining_start + remaining_size - LIMIT_32M; + *heap_size_p = LIMIT_32M - remaining_start; + } + return rval; +} + +void * sbrk(ptrdiff_t incr) +{ + void *rval=(void*)-1; + + if (incr <= remaining_size) { + remaining_size-=incr; + rval = (void*)remaining_start; + remaining_start += incr; + } else { + errno = ENOMEM; + } + return rval; +} + |