arm: move gd handling outside of C code

As of gcc 5.2.1 for Thumb-1, it is not possible any
more to assign gd from C code, as gd is mapped to r9,
and r9 may now be saved in the prolog sequence, and
restored in the epilog sequence, of any C functions.

Therefore arch_setup_gd(), which is supposed to set
r9, may actually have no effect, causing U-Boot to
use a bad address to access GD.

Fix this by never calling arch_setup_gd() for ARM,
and instead setting r9 in arch/arm/lib/crt0.S, to
the value returned by board_init_f_alloc_reserve().

Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
Reviewed-by: Simon Glass <sjg@chromium.org>

diff --git a/arch/arm/lib/crt0.S b/arch/arm/lib/crt0.S
index 4f2a712..2f4c14e 100644 (file)
--- a/arch/arm/lib/crt0.S
+++ b/arch/arm/lib/crt0.S
@@ -85,6 +85,8 @@ ENTRY(_main)
        mov     r0, sp
        bl      board_init_f_alloc_reserve
        mov     sp, r0
+       /* set up gd here, outside any C code */
+       mov     r9, r0
        bl      board_init_f_init_reserve
 
        mov     r0, #0
@@ -134,6 +136,7 @@ here:
        bl      spl_relocate_stack_gd
        cmp     r0, #0
        movne   sp, r0
+       movne   r9, r0
 # endif
        ldr     r0, =__bss_start        /* this is auto-relocated! */
 

diff --git a/common/init/board_init.c b/common/init/board_init.c
index e649e07..d98648e 100644 (file)
--- a/common/init/board_init.c
+++ b/common/init/board_init.c
@@ -21,13 +21,13 @@ DECLARE_GLOBAL_DATA_PTR;
 #define _USE_MEMCPY
 #endif
 
-/* Unfortunately x86 can't compile this code as gd cannot be assigned */
-#ifndef CONFIG_X86
+/* Unfortunately x86 or ARM can't compile this code as gd cannot be assigned */
+#if !defined(CONFIG_X86) && !defined(CONFIG_ARM)
 __weak void arch_setup_gd(struct global_data *gd_ptr)
 {
        gd = gd_ptr;
 }
-#endif /* !CONFIG_X86 */
+#endif /* !CONFIG_X86 && !CONFIG_ARM */
 
 /*
  * Allocate reserved space for use as 'globals' from 'top' address and
@@ -128,7 +128,7 @@ void board_init_f_init_reserve(ulong base)
                *ptr++ = 0;
 #endif
        /* set GD unless architecture did it already */
-#ifndef CONFIG_X86
+#if !defined(CONFIG_X86) && !defined(CONFIG_ARM)
        arch_setup_gd(gd_ptr);
 #endif
        /* next alloc will be higher by one GD plus 16-byte alignment */

diff --git a/common/spl/spl.c b/common/spl/spl.c
index 6e6dee7..e5167bf 100644 (file)
--- a/common/spl/spl.c
+++ b/common/spl/spl.c
@@ -431,8 +431,13 @@ void preloader_console_init(void)
  * more stack space for things like the MMC sub-system.
  *
  * This function calculates the stack position, copies the global_data into
- * place and returns the new stack position. The caller is responsible for
- * setting up the sp register.
+ * place, sets the new gd (except for ARM, for which setting GD within a C
+ * function may not always work) and returns the new stack position. The
+ * caller is responsible for setting up the sp register and, in the case
+ * of ARM, setting up gd.
+ *
+ * All of this is done using the same layout and alignments as done in
+ * board_init_f_init_reserve() / board_init_f_alloc_reserve().
  *
  * @return new stack location, or 0 to use the same stack
  */
@@ -440,14 +445,7 @@ ulong spl_relocate_stack_gd(void)
 {
 #ifdef CONFIG_SPL_STACK_R
        gd_t *new_gd;
-       ulong ptr;
-
-       /* Get stack position: use 8-byte alignment for ABI compliance */
-       ptr = CONFIG_SPL_STACK_R_ADDR - sizeof(gd_t);
-       ptr &= ~7;
-       new_gd = (gd_t *)ptr;
-       memcpy(new_gd, (void *)gd, sizeof(gd_t));
-       gd = new_gd;
+       ulong ptr = CONFIG_SPL_STACK_R_ADDR;
 
 #ifdef CONFIG_SPL_SYS_MALLOC_SIMPLE
        if (CONFIG_SPL_STACK_R_MALLOC_SIMPLE_LEN) {
@@ -460,7 +458,13 @@ ulong spl_relocate_stack_gd(void)
                gd->malloc_ptr = 0;
        }
 #endif
-
+       /* Get stack position: use 8-byte alignment for ABI compliance */
+       ptr = CONFIG_SPL_STACK_R_ADDR - roundup(sizeof(gd_t),16);
+       new_gd = (gd_t *)ptr;
+       memcpy(new_gd, (void *)gd, sizeof(gd_t));
+#if !defined(CONFIG_ARM)
+       gd = new_gd;
+#endif
        return ptr;
 #else
        return 0;