[U-Boot] ARM: problem with linker option -pie
Darius Augulis
augulis.darius at gmail.com
Sat Oct 30 22:37:26 CEST 2010
Hi all,
I've found solution which solves problem of empty command table.
Actually the problem is -pie linker option. I removed it and added -fPIC
flag to compiler options. Because relocation with such changes fails, I
set TEXT_BASE equal to runtime calculated relocation address.
And it works! All commands are there.
There is this dummy patch:
diff --git a/arch/arm/config.mk b/arch/arm/config.mk
index 4e165bf..2046c32 100644
--- a/arch/arm/config.mk
+++ b/arch/arm/config.mk
@@ -33,7 +33,7 @@ STANDALONE_LOAD_ADDR = 0xc100000
endif
endif
-PLATFORM_CPPFLAGS += -DCONFIG_ARM -D__ARM__
+PLATFORM_CPPFLAGS += -DCONFIG_ARM -D__ARM__ -fPIC
# Explicitly specifiy 32-bit ARM ISA since toolchain default can be
-mthumb:
PLATFORM_CPPFLAGS += $(call cc-option,-marm,)
@@ -67,5 +67,4 @@ LDSCRIPT := $(SRCTREE)/$(CPUDIR)/u-boot.lds
# needed for relocation
ifndef CONFIG_NAND_SPL
-PLATFORM_LDFLAGS += -pie
endif
And there is small patch for debugging command table:
diff --git a/common/hush.c b/common/hush.c
index 2188fd4..be92968 100644
--- a/common/hush.c
+++ b/common/hush.c
@@ -1675,6 +1675,10 @@ static int run_pipe_real(struct pipe *pi)
/* Look up command in command table */
+ printf("%s %d: cmd_tbl_s: %X, cmd_tbl_e: %X,
len: %d\n",
+ __func__, __LINE__,
+ &__u_boot_cmd_start, &__u_boot_cmd_end,
+ &__u_boot_cmd_end - &__u_boot_cmd_start);
if ((cmdtp = find_cmd(child->argv[i])) == NULL) {
printf ("Unknown command '%s' - try
'help'\n", child->argv[i]);
return -1; /* give up after bad
command */
Also I did one test with linker script.
I defined variable in start.S:
.globl _cmd_start
_cmd_start:
.word __u_boot_cmd_start
__u_boot_cmd_start is exported in linker script.
Without my patch, disassembled elf looks like this:
<...>
57e00048 <_cmd_start>:
57e00048: 00000000 .word 0x00000000
<...>
while with patch applied:
<..>
57fcb048 <_cmd_start>:
57fcb048: 57fea2b0 .word 0x57fea2b0
<..>
Also disassembling u-boot-spl shows good result because there isn't -pie
linker option.
It's interesting, because if I define .word __u_boot_cmd_start - _start,
then *offset* is calculated correctly.
So, I assume, with -pie, linker doesn't export variables correctly and
in my case pointer to command table is always null.
Eric, could your please test your board in the same way I have described
and find out whether it helps? This could be toolchain version dependent
and other people may not have this problem.
Darius.
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