[U-Boot] Can not access global variable in uboot command function?
mips64 , xlr732
I've added a test command in uboot, say, U_BOOT_CMD(test_globa,...do_test_global) ,which is in cmd_command.c .
And in cmd_command.c, there is also a global string array ,say ,char* p = "test";
In do_test_global, I used pointer to access elements of array p like this:
char c = *(char*)p;
it seemd that , the code above caused uboot dead and print nothing ,I guess that,maybe there was a memory access violation.
Any suggestions on how could this happended? Thank you in advance
my code is like this:
/* cmd_command.c*/
char* p = "test";
U_BOOT_CMD(test_globa,do_test_global) ;
int do_test_global() { char c = *(char*)p; //when called , uboot was dead here... return 0; }
Hi Wilbur,
wilbur.chan wrote:
mips64 , xlr732
I've added a test command in uboot, say, U_BOOT_CMD(test_globa,...do_test_global) ,which is in cmd_command.c
And in cmd_command.c, there is also a global string array ,say ,char* p = "test";
In do_test_global, I used pointer to access elements of array p like this:
char c = *(char*)p;
it seemd that , the code above caused uboot dead and print nothing ,I guess that,maybe there was a memory access violation.
Any suggestions on how could this happended? Thank you in advance
Just a guess, but I suspect your are getting bitten by the manual pointer relocation issue.
Your char *p is pointing into flash, but you are dereferencing the pointer after relocation to RAM, running out of RAM with a different memory map than power-on-reset (initialization has completed). I suspect your flash image is no longer where it was on release of reset and thus dereferencing *p now tries to read an invalid memory location, causing your "hang."
If you really need the pointers, you need to manually relocate them. See ./include/asm-mips/global_data.h and the function void board_init_r (gd_t *id, ulong dest_addr) in lib_mips/board.c.
The bottom line is that you probably need to add gd->reloc_off to your compiled-in pointers: *(p + gd->reloc_off)
[snip]
gvb
participants (2)
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Jerry Van Baren -
wilbur.chan