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authorTom Rini <trini@ti.com>2012-09-20 06:02:43 +0000
committerTom Rini <trini@ti.com>2012-09-26 11:08:32 -0700
commit2d1d65838eacd314b989701bd2f9e2b657bbf62b (patch)
tree25644feecf696bc101c9be34f6a69329845ee817 /doc/README.commands
parent244e6f97055aa86e446ed3a925fdfa3f2b8f8207 (diff)
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README.commands: Document what UNDEF_SYM does
Changes in v2: - Reword a bit more Signed-off-by: Tom Rini <trini@ti.com>
Diffstat (limited to 'doc/README.commands')
-rw-r--r--doc/README.commands7
1 files changed, 7 insertions, 0 deletions
diff --git a/doc/README.commands b/doc/README.commands
index 27815d2..125f077 100644
--- a/doc/README.commands
+++ b/doc/README.commands
@@ -22,6 +22,13 @@ This makes it possible for the final link to extract all commands
compiled into any object code and construct a static array so the
command can be found in an array starting at __u_boot_cmd_start.
+To ensure that the linker does not discard these symbols when linking
+full U-Boot we generate a list of all the commands we have built (based
+on the sections mentioned above) and use that to force the linker to
+first enter the symbol as undefined in the output object so that there
+is then a need for the symbol to be kept (this is the UNDEF_SYM logic in
+the Makefile).
+
If a new board is defined do not forget to define the command section
by writing in u-boot.lds ($(TOPDIR)/board/boardname/u-boot.lds) these
3 lines: