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Reported-by: Hulk Robot <hulkci@huawei.com> Signed-off-by: He Ying <heying24@huawei.com> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210326100853.173586-1-heying24@huawei.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
42 lines
1.3 KiB
ReStructuredText
42 lines
1.3 KiB
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==========================
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ELF Note PowerPC Namespace
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==========================
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The PowerPC namespace in an ELF Note of the kernel binary is used to store
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capabilities and information which can be used by a bootloader or userland.
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Types and Descriptors
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---------------------
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The types to be used with the "PowerPC" namespace are defined in [#f1]_.
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1) PPC_ELFNOTE_CAPABILITIES
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Define the capabilities supported/required by the kernel. This type uses a
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bitmap as "descriptor" field. Each bit is described below:
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- Ultravisor-capable bit (PowerNV only).
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.. code-block:: c
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#define PPCCAP_ULTRAVISOR_BIT (1 << 0)
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Indicate that the powerpc kernel binary knows how to run in an
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ultravisor-enabled system.
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In an ultravisor-enabled system, some machine resources are now controlled
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by the ultravisor. If the kernel is not ultravisor-capable, but it ends up
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being run on a machine with ultravisor, the kernel will probably crash
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trying to access ultravisor resources. For instance, it may crash in early
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boot trying to set the partition table entry 0.
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In an ultravisor-enabled system, a bootloader could warn the user or prevent
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the kernel from being run if the PowerPC ultravisor capability doesn't exist
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or the Ultravisor-capable bit is not set.
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References
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----------
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.. [#f1] arch/powerpc/include/asm/elfnote.h
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