Rework linker scripts.

Having separate linker scripts for all the boards is a bad idea. Most
boards really only need to specify MEMORY and the appropriate
REGION_ALIASES() so that support/ld/common.inc can do its work. Not
having infrastructure for this leads to duplication -- viz. the Maple
Mini linker scripts are identical to the Maple's, and the
olimex_stm32_h103 linker directory is just a symlink to
Maple's. Clearly, the current structure is wrong.

To fix it, instead of having per-board subdirectories of support/ld/,
add per-MEMORY subdirectories of (new) support/ld/stm32/mem/. The
per-board .mk files under support/mk/board-includes/ now reference
these directly, and target-config.mk and the Makefile handle this
appropriately. We move some other stuff around in target-config.mk to
make this all more convenient, and even allow more overriding of the
libmaple defaults on a per-board basis. Custom board hacks will be
easier now.

Unfortunately, lots of duplication under support/ld/stm32/mem/ is
necessary, as the LENGTH attribute in a MEMORY region specification
doesn't support arithmetic expressions, and ld doesn't seem to have
any way to specify MEMORY at the command line (why?!). If we find a
better way than this, we should do it.

If a board (e.g. Maple Native) _does_ really need special
memory-related configuration, you can always put a per-board
subdirectory of support/ld/stm32/mem. We do this here to configure the
heap.

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/support/ld/ram.ld b/support/ld/ram.ld
new file mode 100644
index 0000000..34b468e
--- /dev/null
+++ b/support/ld/ram.ld
@@ -0,0 +1,25 @@
+/*
+ * libmaple linker script for RAM builds.
+ *
+ * A Flash build puts .text, .rodata, and .data/.bss/heap (of course)
+ * in SRAM, but offsets the sections by enough space to store the
+ * Maple bootloader, which uses low memory.
+ */
+
+/*
+ * This pulls in the appropriate MEMORY declaration from the right
+ * subdirectory of stm32/mem/ (the environment must call ld with the
+ * right include directory flags to make this happen). Boards can also
+ * use this file to use any of libmaple's memory-related hooks (like
+ * where the heap should live).
+ */
+INCLUDE mem-ram.inc
+
+/* Provide memory region aliases for common.inc */
+REGION_ALIAS("REGION_TEXT", ram);
+REGION_ALIAS("REGION_DATA", ram);
+REGION_ALIAS("REGION_BSS", ram);
+REGION_ALIAS("REGION_RODATA", ram);
+
+/* Let common.inc handle the real work. */
+INCLUDE common.inc