On Tue, Jul 16, 2019 at 06:28:17PM -0700, Andrey Smirnov wrote:
> On Tue, Jul 16, 2019 at 6:50 AM Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> wrote:
> >
> > Not all toolchains use pc relative addresses for global variables.
> > Apparently the gcc 8.3.0 YOCTO toolchain uses absolute addresses.
>
> Just out of curiosity, can this behavior be changed with -mcmodel=tiny
> or maybe -mpc-relative-literal-loads ?
This doesn't seem to have any influence with one toolchain or the other.
BTW with this diff:
diff --git a/arch/arm/cpu/common.c b/arch/arm/cpu/common.c
index 4d957da1dc..65cf90f553 100644
--- a/arch/arm/cpu/common.c
+++ b/arch/arm/cpu/common.c
@@ -60,6 +60,14 @@ void pbl_barebox_break(void)
);
}
+static noinline void _puthex_ll(unsigned long val)
+{
+ putc_ll('a');
+ putc_ll(':');
+ puthex_ll(val);
+ putc_ll('\n');
+}
+
/*
* relocate binary to the currently running address
*/
@@ -69,6 +77,8 @@ void relocate_to_current_adr(void)
unsigned long __maybe_unused *dynsym, *dynend;
void *dstart, *dend;
+ _puthex_ll((unsigned long)__rel_dyn_start);
+
/* Get offset between linked address and runtime address */
offset = get_runtime_offset();
offset_var = global_variable_offset();
This is what the two toolchains make from it (stripped some irrelevant instructions):
YOCTO:
0000000000003c38 <relocate_to_current_adr>:
3c3c: b0000100 adrp x0, 24000 <__dtb_imx8mq_evk_start+0x5c40>
3c48: f943e013 ldr x19, [x0, #1984]
3c4c: aa1303e0 mov x0, x19
3c50: 97ffffd1 bl 3b94 <_puthex_ll>
OSELAS:
0000000000003c20 <relocate_to_current_adr>:
3c24: b0000100 adrp x0, 24000 <__dtb_imx8mq_evk_start+0x5c60>
3c30: 911ee013 add x19, x0, #0x7b8
3c34: aa1303e0 mov x0, x19
3c38: 97ffffd1 bl 3b7c <_puthex_ll>
Sascha
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