Christopher Collins created MYNEWT-477:
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Summary: newt - Split image requires split startup .s file to be
in BSP package
Key: MYNEWT-477
URL: https://issues.apache.org/jira/browse/MYNEWT-477
Project: Mynewt
Issue Type: Bug
Components: Newt
Reporter: Christopher Collins
Assignee: Sterling Hughes
It would be better if all the startup code could go in the MCU package. If the
split startup file is put in the MCU package, a split image build results in an
empty second-slot image and the following warning:
{noformat}
arm-none-eabi/bin/ld: warning: cannot find entry symbol Reset_Handler_split;
defaulting to 0000000000042020
{noformat}
Newt thinks the second-stage app uses no symbols from the MCU package, so it
doesn't include the MCU .a file in the final link phace. The app does use a
symbol from the MCU app; namely Reset_Handler_split. This symbol is designated
as the entry point in the split linker script, but not referenced anywhere else.
The reason newt doesn't honor the linker script's reference to
Reset_Handler_split has to do with the way it builds split images. Before
performing the final link of the second-stage app, newt performs some "test
links" to determine which packages and symbols are shared among the two apps.
The test links are done using the regular stage 1 (loader) linker script.
Hence, newt determines early that the second-stage app does not reference the
MCU package at all.
This problem does not occur when the split startup code is in the BSP package,
because the second-stage app directly calls BSP functions in main(), namely
bsp_init() (called via sysinit()). Therefore, newt recognizes that the app
depends on the BSP package, and includes this package in the final link phase.
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