arm64: Fix relocation of env_addr if POSITION_INDEPENDENT=y

If both POSITION_INDEPENDENT and SYS_RELOC_GD_ENV_ADDR are enabled,
wherever original env is placed anywhere, it should be relocated to
the right address.

Relocation offset gd->reloc_off is calculated with SYS_TEXT_BASE in
setup_reloc() and env address gd->env_addr is relocated by the offset in
initr_reloc_global_data().

gd->env_addr
  = (orig env) + gd->reloc_off
  = (orig env) + (gd->relocaddr - SYS_TEXT_BASE)

However, SYS_TEXT_BASE isn't always runtime base address when
POSITION_INDEPENDENT is enabled. So the relocated env_addr might point to
wrong address. For example, if SYS_TEXT_BASE is zero, gd->env_addr is
out of memory location and memory exception will occur.

There is a difference between linked address such as SYS_TEXT_BASE and
runtime base address. In _main, the difference is calculated as
"run-vs-link" offset. The env_addr should also be added to the offset
to fix the address.

gd->env_addr
  = (orig env) + ("run-vs-link" offset)   + gd->reloc_off
  = (orig env) + (SYS_TEXT_BASE - _start) + (gd->relocaddr - SYS_TEXT_BASE)
  = (orig env) + (gd->relocaddr - _start)

Cc: Marek Vasut <marex@denx.de>
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Acked-by: Marek Vasut <marex@denx.de>
Tested-by: Marek Vasut <marex@denx.de>

arch/arm/lib/crt0_64.S

@@ -112,6 +112,11 @@ ENTRY(_main)
 	ldr	x9, _TEXT_BASE		/* x9 <- Linked value of _start */
 	sub	x9, x9, x0		/* x9 <- Run-vs-link offset */
 	add	lr, lr, x9
+#if defined(CONFIG_SYS_RELOC_GD_ENV_ADDR)
+	ldr	x0, [x18, #GD_ENV_ADDR]	/* x0 <- gd->env_addr */
+	add	x0, x0, x9
+	str	x0, [x18, #GD_ENV_ADDR]
+#endif
 #endif
 	/* Add in link-vs-relocation offset */
 	ldr	x9, [x18, #GD_RELOC_OFF]	/* x9 <- gd->reloc_off */

lib/asm-offsets.c

@@ -41,5 +41,7 @@ int main(void)
 
 	DEFINE(GD_NEW_GD, offsetof(struct global_data, new_gd));
 
+	DEFINE(GD_ENV_ADDR, offsetof(struct global_data, env_addr));
+
 	return 0;
 }