Fix board init code to respect the C runtime environment

board_init_f_mem() alters the C runtime environment's
stack it is actually already using. This is not a valid
behaviour within a C runtime environment.

Split board_init_f_mem into C functions which do not alter
their own stack and always behave properly with respect to
their C runtime environment.

Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
Acked-by: Thomas Chou <thomas@wytron.com.tw>

1 files changed, 99 insertions, 10 deletions

diff --git a/common/init/board_init.c b/common/init/board_init.c
index 1c6126d8ce5..e649e078b9c 100644
--- a/common/init/board_init.c
+++ b/common/init/board_init.c
@@ -29,31 +29,120 @@ __weak void arch_setup_gd(struct global_data *gd_ptr)
 }
 #endif /* !CONFIG_X86 */
 
-ulong board_init_f_mem(ulong top)
+/*
+ * Allocate reserved space for use as 'globals' from 'top' address and
+ * return 'bottom' address of allocated space
+ *
+ * Notes:
+ *
+ * Actual reservation cannot be done from within this function as
+ * it requires altering the C stack pointer, so this will be done by
+ * the caller upon return from this function.
+ *
+ * IMPORTANT:
+ *
+ * Alignment constraints may differ for each 'chunk' allocated. For now:
+ *
+ * - GD is aligned down on a 16-byte boundary
+ *
+ *  - the early malloc arena is not aligned, therefore it follows the stack
+ *   alignment constraint of the architecture for which we are bulding.
+ *
+ *  - GD is allocated last, so that the return value of this functions is
+ *   both the bottom of the reserved area and the address of GD, should
+ *   the calling context need it.
+ */
+
+ulong board_init_f_alloc_reserve(ulong top)
+{
+	/* Reserve early malloc arena */
+#if defined(CONFIG_SYS_MALLOC_F)
+	top -= CONFIG_SYS_MALLOC_F_LEN;
+#endif
+	/* LAST : reserve GD (rounded up to a multiple of 16 bytes) */
+	top = rounddown(top-sizeof(struct global_data), 16);
+
+	return top;
+}
+
+/*
+ * Initialize reserved space (which has been safely allocated on the C
+ * stack from the C runtime environment handling code).
+ *
+ * Notes:
+ *
+ * Actual reservation was done by the caller; the locations from base
+ * to base+size-1 (where 'size' is the value returned by the allocation
+ * function above) can be accessed freely without risk of corrupting the
+ * C runtime environment.
+ *
+ * IMPORTANT:
+ *
+ * Upon return from the allocation function above, on some architectures
+ * the caller will set gd to the lowest reserved location. Therefore, in
+ * this initialization function, the global data MUST be placed at base.
+ *
+ * ALSO IMPORTANT:
+ *
+ * On some architectures, gd will already be good when entering this
+ * function. On others, it will only be good once arch_setup_gd() returns.
+ * Therefore, global data accesses must be done:
+ *
+ * - through gd_ptr if before the call to arch_setup_gd();
+ *
+ * - through gd once arch_setup_gd() has been called.
+ *
+ * Do not use 'gd->' until arch_setup_gd() has been called!
+ *
+ * IMPORTANT TOO:
+ *
+ * Initialization for each "chunk" (GD, early malloc arena...) ends with
+ * an incrementation line of the form 'base += <some size>'. The last of
+ * these incrementations seems useless, as base will not be used any
+ * more after this incrementation; but if/when a new "chunk" is appended,
+ * this increment will be essential as it will give base right value for
+ * this new chunk (which will have to end with its own incrementation
+ * statement). Besides, the compiler's optimizer will silently detect
+ * and remove the last base incrementation, therefore leaving that last
+ * (seemingly useless) incrementation causes no code increase.
+ */
+
+void board_init_f_init_reserve(ulong base)
 {
 	struct global_data *gd_ptr;
 #ifndef _USE_MEMCPY
 	int *ptr;
 #endif
 
-	/* Leave space for the stack we are running with now */
-	top -= 0x40;
+	/*
+	 * clear GD entirely and set it up.
+	 * Use gd_ptr, as gd may not be properly set yet.
+	 */
 
-	top -= sizeof(struct global_data);
-	top = ALIGN(top, 16);
-	gd_ptr = (struct global_data *)top;
+	gd_ptr = (struct global_data *)base;
+	/* zero the area */
 #ifdef _USE_MEMCPY
 	memset(gd_ptr, '\0', sizeof(*gd));
 #else
 	for (ptr = (int *)gd_ptr; ptr < (int *)(gd_ptr + 1); )
 		*ptr++ = 0;
 #endif
+	/* set GD unless architecture did it already */
+#ifndef CONFIG_X86
 	arch_setup_gd(gd_ptr);
+#endif
+	/* next alloc will be higher by one GD plus 16-byte alignment */
+	base += roundup(sizeof(struct global_data), 16);
+
+	/*
+	 * record early malloc arena start.
+	 * Use gd as it is now properly set for all architectures.
+	 */
 
 #if defined(CONFIG_SYS_MALLOC_F)
-	top -= CONFIG_SYS_MALLOC_F_LEN;
-	gd->malloc_base = top;
+	/* go down one 'early malloc arena' */
+	gd->malloc_base = base;
+	/* next alloc will be higher by one 'early malloc arena' size */
+	base += CONFIG_SYS_MALLOC_F_LEN;
 #endif
-
-	return top;
 }