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[U-Boot,v2] README.commands: Document what UNDEF_SYM does

Message ID 1348156963-1898-1-git-send-email-trini@ti.com
State Accepted
Delegated to: Tom Rini
Headers show

Commit Message

Tom Rini Sept. 20, 2012, 4:02 p.m. UTC
Changes in v2:
- Reword a bit more

Signed-off-by: Tom Rini <trini@ti.com>
---
 doc/README.commands |    7 +++++++
 1 file changed, 7 insertions(+)
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Patch

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: