coreboot: introduce CONFIG_RELOCATABLE_RAMSTAGE

This patch adds an option to build the ramstage as a reloctable binary.
It uses the rmodule library for the relocation. The main changes
consist of the following:

1. The ramstage is loaded just under the cmbem space.
2. Payloads cannot be loaded over where ramstage is loaded. If a payload
   is attempted to load where the relocatable ramstage resides the load
   is aborted.
3. The memory occupied by the ramstage is reserved from the OS's usage
   using the romstage_handoff structure stored in cbmem. This region is
   communicated to ramstage by an CBMEM_ID_ROMSTAGE_INFO entry in cbmem.
4. There is no need to reserve cbmem space for the OS controlled memory for
   the resume path because the ramsage region has been reserved in #3.
5. Since no memory needs to be preserved in the wake path, the loading
   and begin of execution of a elf payload is straight forward.

Change-Id: Ia66cf1be65c29fa25ca7bd9ea6c8f11d7eee05f5
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/2792
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>

3 files changed, 78 insertions, 0 deletions

diff --git a/src/lib/Makefile.inc b/src/lib/Makefile.inc
index d08ee7a4e0..97baaa2be0 100644
--- a/src/lib/Makefile.inc
+++ b/src/lib/Makefile.inc
@@ -110,6 +110,7 @@ $(obj)/lib/uart8250.smm.o : $(OPTION_TABLE_H)
 
 ifeq ($(CONFIG_RELOCATABLE_MODULES),y)
 ramstage-y += rmodule.c
+romstage-$(CONFIG_RELOCATABLE_RAMSTAGE) += rmodule.c
 
 RMODULE_LDSCRIPT := $(src)/lib/rmodule.ld
 RMODULE_LDFLAGS  := -nostartfiles -shared -z defs -nostdlib -Bsymbolic -T $(RMODULE_LDSCRIPT)
diff --git a/src/lib/cbfs.c b/src/lib/cbfs.c
index c56f550e17..4dac4bb5c2 100644
--- a/src/lib/cbfs.c
+++ b/src/lib/cbfs.c
@@ -36,6 +36,7 @@
 
 #include <cbfs.h>
 #include <string.h>
+#include <cbmem.h>
 
 #ifdef LIBPAYLOAD
 # include <stdio.h>
@@ -114,6 +115,65 @@ void *cbfs_load_optionrom(struct cbfs_media *media, uint16_t vendor,
 	return dest;
 }
 
+#if CONFIG_RELOCATABLE_RAMSTAGE && defined(__PRE_RAM__)
+
+#include <rmodule.h>
+#include <romstage_handoff.h>
+/* When CONFIG_RELOCATABLE_RAMSTAGE is enabled and this file is being compiled
+ * for the romstage the rmodule loader is used. The ramstage is placed just
+ * below the cbemem location. */
+
+void * cbfs_load_stage(struct cbfs_media *media, const char *name)
+{
+	struct cbfs_stage *stage;
+	struct rmodule ramstage;
+	void *cbmem_base;
+	void *ramstage_base;
+	void *decompression_loc;
+	void *ramstage_loc;
+	struct romstage_handoff *handoff;
+
+	stage = (struct cbfs_stage *)
+		cbfs_get_file_content(media, name, CBFS_TYPE_STAGE);
+
+	if (stage == NULL)
+		return (void *) -1;
+
+	cbmem_base = get_cbmem_toc();
+	if (cbmem_base == NULL)
+		return (void *) -1;
+
+	ramstage_base = rmodule_find_region_below(cbmem_base, stage->memlen,
+	                                          &ramstage_loc,
+	                                          &decompression_loc);
+
+	LOG("Decompressing stage %s @ 0x%p (%d bytes)\n",
+	    name, decompression_loc, stage->memlen);
+
+	if (cbfs_decompress(stage->compression, &stage[1],
+	                    decompression_loc, stage->len))
+		return (void *) -1;
+
+	if (rmodule_parse(decompression_loc, &ramstage))
+		return (void *) -1;
+
+	/* The ramstage is responsible for clearing its own bss. */
+	if (rmodule_load(ramstage_loc, &ramstage))
+		return (void *) -1;
+
+	handoff = cbmem_add(CBMEM_ID_ROMSTAGE_INFO, sizeof(*handoff));
+	if (handoff) {
+		handoff->reserve_base = (uint32_t)ramstage_base;
+		handoff->reserve_size = (uint32_t)cbmem_base -
+		                        (uint32_t)ramstage_base;
+	} else
+		LOG("Couldn't allocate romstage handoff.\n");
+
+	return rmodule_entry(&ramstage);
+}
+
+#else
+
 void * cbfs_load_stage(struct cbfs_media *media, const char *name)
 {
 	struct cbfs_stage *stage = (struct cbfs_stage *)
@@ -146,6 +206,7 @@ void * cbfs_load_stage(struct cbfs_media *media, const char *name)
 
 	return (void *) entry;
 }
+#endif /* CONFIG_RELOCATABLE_RAMSTAGE */
 
 int cbfs_execute_stage(struct cbfs_media *media, const char *name)
 {
diff --git a/src/lib/selfboot.c b/src/lib/selfboot.c
index f32bb814fb..f933142144 100644
--- a/src/lib/selfboot.c
+++ b/src/lib/selfboot.c
@@ -78,6 +78,16 @@ struct segment {
 
 static unsigned long bounce_size, bounce_buffer;
 
+#if CONFIG_RELOCATABLE_RAMSTAGE
+static void get_bounce_buffer(struct lb_memory *mem, unsigned long req_size)
+{
+	/* When the ramstage is relocatable there is no need for a bounce
+	 * buffer. All payloads should not overlap the ramstage.
+	 */
+	bounce_buffer = ~0UL;
+	bounce_size = 0;
+}
+#else
 static void get_bounce_buffer(struct lb_memory *mem, unsigned long req_size)
 {
 	unsigned long lb_size;
@@ -114,6 +124,7 @@ static void get_bounce_buffer(struct lb_memory *mem, unsigned long req_size)
 	bounce_buffer = buffer;
 	bounce_size = req_size;
 }
+#endif /* CONFIG_RELOCATABLE_RAMSTAGE */
 
 static int valid_area(struct lb_memory *mem, unsigned long buffer,
 	unsigned long start, unsigned long len)
@@ -394,8 +405,13 @@ static int load_self_segments(
 	for(ptr = head->next; ptr != head; ptr = ptr->next) {
 		if (!overlaps_coreboot(ptr))
 			continue;
+#if CONFIG_RELOCATABLE_RAMSTAGE
+		/* payloads are required to not overlap ramstage. */
+		return 0;
+#else
 		if (ptr->s_dstaddr + ptr->s_memsz > bounce_high)
 			bounce_high = ptr->s_dstaddr + ptr->s_memsz;
+#endif
 	}
 	get_bounce_buffer(mem, bounce_high - lb_start);
 	if (!bounce_buffer) {