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boot: introduce seL4_BootInfoFrameSize

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Provide seL4_BootInfoFrameSize (and seL4_BootInfoFrameBits) for
userland, to there is no longer a need to hard-code the 4 KiByte
assumption.

Signed-off-by: Axel Heider <axelheider@gmx.de>
This commit is contained in:
Axel Heider
2023-04-10 21:34:28 +02:00
committed by Gerwin Klein
parent 8153bc569e
commit b8c0b1cb02
4 changed files with 35 additions and 20 deletions
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17
manual/parts/bootup.tex
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@@ -118,14 +118,15 @@ of slots in the initial thread's CNode, starting with CPTR \texttt{start} and wi
\end{center}
\end{table}
Depending on the architecture and platform there might be additional pieces of boot
information. If \texttt{extraLen} is greater than zero, then 4K after the start of bootinfo
is a region of extraLen bytes containing additional bootinfo structures. Each chunk starts
with a \texttt{seL4\_BootInfoHeader}, described in \autoref{tab:bi_header_struct}, that
describes what the chunk is and how long it is, where the length includes the header. The
length can be used to skip over chunks that you do not understand. The only generally
defined chunk type is \texttt{SEL4\_BOOTINFO\_HEADER\_PADDING} and describes an empty
chunk that has no data, any other types are platform or architecture specific. The
The size of the fixed Boot Info Frame is \texttt{seL4\_BootInfoFrameSize}. In the standard
configuration, this is one page, which is 4 KiByte on x86, ARM and RISC-V. Depending on the
architecture and platform, there might be additional pieces of variable boot information
following afterwards. The overall size of this data is \texttt{extraLen}, it contains a
sequence of blobs, where each one start with a \texttt{seL4\_BootInfoHeader} described in
\autoref{tab:bi_header_struct}. This header describes what the blob is and how long it is,
where the length includes the header. Thus, the length can be used to skip over unknown
chunks. The only generally defined chunk type is \texttt{SEL4\_BOOTINFO\_HEADER\_PADDING}
and describes a blob where any payload data exists for padding only. The
\texttt{extraBIPages} slot region gives the frames capabilities for the pages that make up
the additional boot info region.