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-rw-r--r--miscutils/devmem.c79
1 files changed, 42 insertions, 37 deletions
diff --git a/miscutils/devmem.c b/miscutils/devmem.c
index 8b8edbe7c..4903b5dcb 100644
--- a/miscutils/devmem.c
+++ b/miscutils/devmem.c
@@ -6,9 +6,6 @@
#include "libbb.h"
-#define DEVMEM_MAP_SIZE 4096
-#define DEVMEM_MAP_MASK (off_t)(DEVMEM_MAP_SIZE - 1)
-
int devmem_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int devmem_main(int argc UNUSED_PARAM, char **argv)
{
@@ -16,10 +13,16 @@ int devmem_main(int argc UNUSED_PARAM, char **argv)
uint64_t read_result;
uint64_t writeval = writeval; /* for compiler */
off_t target;
+ unsigned page_size = getpagesize();
int fd;
int width = 8 * sizeof(int);
/* devmem ADDRESS [WIDTH [VALUE]] */
+// TODO: options?
+// -r: read and output only the value in hex, with 0x prefix
+// -w: write only, no reads before or after, and no output
+// or make this behavior default?
+// Let's try this and see how users react.
/* ADDRESS */
if (!argv[1])
@@ -54,67 +57,69 @@ int devmem_main(int argc UNUSED_PARAM, char **argv)
bb_show_usage(); /* bb_strtouXX failed */
fd = xopen("/dev/mem", argv[3] ? (O_RDWR | O_SYNC) : (O_RDONLY | O_SYNC));
-
map_base = mmap(NULL,
- DEVMEM_MAP_SIZE * 2 /* in case value spans page */,
+ page_size * 2 /* in case value spans page */,
argv[3] ? (PROT_READ | PROT_WRITE) : PROT_READ,
MAP_SHARED,
fd,
- target & ~DEVMEM_MAP_MASK);
+ target & ~(off_t)(page_size - 1));
if (map_base == MAP_FAILED)
bb_perror_msg_and_die("mmap");
// printf("Memory mapped at address %p.\n", map_base);
- virt_addr = (char*)map_base + (target & DEVMEM_MAP_MASK);
-
- switch (width) {
- case 8:
- read_result = *(volatile uint8_t*)virt_addr;
- break;
- case 16:
- read_result = *(volatile uint16_t*)virt_addr;
- break;
- case 32:
- read_result = *(volatile uint32_t*)virt_addr;
- break;
- case 64:
- read_result = *(volatile uint64_t*)virt_addr;
- break;
- default:
- bb_error_msg_and_die("bad width");
- }
-
- printf("Value at address 0x%"OFF_FMT"X (%p): 0x%llX\n",
- target, virt_addr,
- (unsigned long long)read_result);
+ virt_addr = (char*)map_base + (target & (page_size - 1));
- if (argv[3]) {
+ if (!argv[3]) {
switch (width) {
case 8:
- *(volatile uint8_t*)virt_addr = writeval;
read_result = *(volatile uint8_t*)virt_addr;
break;
case 16:
- *(volatile uint16_t*)virt_addr = writeval;
read_result = *(volatile uint16_t*)virt_addr;
break;
case 32:
- *(volatile uint32_t*)virt_addr = writeval;
read_result = *(volatile uint32_t*)virt_addr;
break;
case 64:
- *(volatile uint64_t*)virt_addr = writeval;
read_result = *(volatile uint64_t*)virt_addr;
break;
+ default:
+ bb_error_msg_and_die("bad width");
+ }
+// printf("Value at address 0x%"OFF_FMT"X (%p): 0x%llX\n",
+// target, virt_addr,
+// (unsigned long long)read_result);
+ /* Zero-padded output shows the width of access just done */
+ printf("0x%0*llX\n", (width >> 2), (unsigned long long)read_result);
+ } else {
+ switch (width) {
+ case 8:
+ *(volatile uint8_t*)virt_addr = writeval;
+// read_result = *(volatile uint8_t*)virt_addr;
+ break;
+ case 16:
+ *(volatile uint16_t*)virt_addr = writeval;
+// read_result = *(volatile uint16_t*)virt_addr;
+ break;
+ case 32:
+ *(volatile uint32_t*)virt_addr = writeval;
+// read_result = *(volatile uint32_t*)virt_addr;
+ break;
+ case 64:
+ *(volatile uint64_t*)virt_addr = writeval;
+// read_result = *(volatile uint64_t*)virt_addr;
+ break;
+ default:
+ bb_error_msg_and_die("bad width");
}
- printf("Written 0x%llX; readback 0x%llX\n",
- (unsigned long long)writeval,
- (unsigned long long)read_result);
+// printf("Written 0x%llX; readback 0x%llX\n",
+// (unsigned long long)writeval,
+// (unsigned long long)read_result);
}
if (ENABLE_FEATURE_CLEAN_UP) {
- if (munmap(map_base, DEVMEM_MAP_SIZE) == -1)
+ if (munmap(map_base, page_size) == -1)
bb_perror_msg_and_die("munmap");
close(fd);
}