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modmachine: Implement physical memory access using /dev/mem (Linux, etc).

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This requires root access. And on recent Linux kernels, with
CONFIG_STRICT_DEVMEM option enabled, only address ranges listed in
/proc/iomem can be accessed. The above compiled-time option can be
however overriden with boot-time option "iomem=relaxed".

This also removed separate read/write paths - there unlikely would
be a case when they're different.
This commit is contained in:
Paul Sokolovsky
2015-07-06 00:08:33 +03:00
parent a0a3de60be
commit 354d17523f
6 changed files with 54 additions and 27 deletions
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42
extmod/modmachine.c
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@@ -29,22 +29,44 @@
#include "py/nlr.h"
#include "py/obj.h"
#if MICROPY_PLAT_DEV_MEM
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#endif
#if MICROPY_PY_MACHINE
STATIC mp_uint_t get_read_addr(mp_obj_t addr_o, uint align) {
mp_uint_t addr = mp_obj_int_get_truncated(addr_o);
if ((addr & (align - 1)) != 0) {
nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "address %08x is not aligned to %d bytes", addr, align));
}
return addr;
}
#define PAGE_SIZE 4096
#define PAGE_MASK (PAGE_SIZE - 1)
STATIC mp_uint_t get_write_addr(mp_obj_t addr_o, uint align) {
STATIC mp_uint_t get_addr(mp_obj_t addr_o, uint align) {
mp_uint_t addr = mp_obj_int_get_truncated(addr_o);
if ((addr & (align - 1)) != 0) {
nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "address %08x is not aligned to %d bytes", addr, align));
}
#if MICROPY_PLAT_DEV_MEM
{
// Not thread-safe
static int fd;
static mp_uint_t last_base = (mp_uint_t)-1;
static mp_uint_t map_page;
if (!fd) {
fd = open("/dev/mem", O_RDWR | O_SYNC);
if (fd == -1) {
nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(errno)));
}
}
mp_uint_t cur_base = addr & ~PAGE_MASK;
if (cur_base != last_base) {
map_page = (mp_uint_t)mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, cur_base);
last_base = cur_base;
}
addr = map_page + (addr & PAGE_MASK);
}
#endif
return addr;
}
@@ -67,7 +89,7 @@ STATIC mp_obj_t machine_mem_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t va
return MP_OBJ_NULL; // op not supported
} else if (value == MP_OBJ_SENTINEL) {
// load
mp_uint_t addr = get_read_addr(index, self->elem_size);
mp_uint_t addr = get_addr(index, self->elem_size);
uint32_t val;
switch (self->elem_size) {
case 1: val = (*(uint8_t*)addr); break;
@@ -77,7 +99,7 @@ STATIC mp_obj_t machine_mem_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t va
return mp_obj_new_int(val);
} else {
// store
mp_uint_t addr = get_write_addr(index, self->elem_size);
mp_uint_t addr = get_addr(index, self->elem_size);
uint32_t val = mp_obj_get_int(value);
switch (self->elem_size) {
case 1: (*(uint8_t*)addr) = val; break;