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| author | Maxiwell S. Garcia <maxiwell@linux.ibm.com> | 2019-08-29 12:50:21 -0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2019-08-30 09:40:15 +1000 |
| commit | 134cb3ab71c0736da0ec66d2cfd7f6ebba96c8cf (patch) | |
| tree | c4528f487f5bb55a6f1b0887508db5ffcde2e4eb /Documentation/powerpc | |
| parent | 70ed86f4de5bd74dd2d884dcd2f3275c4cfe665f (diff) | |
| download | lwn-134cb3ab71c0736da0ec66d2cfd7f6ebba96c8cf.tar.gz lwn-134cb3ab71c0736da0ec66d2cfd7f6ebba96c8cf.zip | |
Documentation/powerpc: Add ELF note documentation
The ELF note documentation describes the types and descriptors to be
used with the PowerPC namespace.
Signed-off-by: Maxiwell S. Garcia <maxiwell@linux.ibm.com>
Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190829155021.2915-3-maxiwell@linux.ibm.com
Diffstat (limited to 'Documentation/powerpc')
| -rw-r--r-- | Documentation/powerpc/elfnote.rst | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/Documentation/powerpc/elfnote.rst b/Documentation/powerpc/elfnote.rst new file mode 100644 index 000000000000..2a5c4beeb809 --- /dev/null +++ b/Documentation/powerpc/elfnote.rst @@ -0,0 +1,42 @@ +========================== +ELF Note PowerPC Namespace +========================== + +The PowerPC namespace in an ELF Note of the kernel binary is used to store +capabilities and information which can be used by a bootloader or userland. + +Types and Descriptors +--------------------- + +The types to be used with the "PowerPC" namesapce are defined in the +include/uapi/asm/elfnote.h + + 1) PPC_ELFNOTE_CAPABILITIES + +Define the capabilities supported/required by the kernel. This type uses a +bitmap as "descriptor" field. Each bit is described below: + +- Ultravisor-capable bit (PowerNV only). + + #define PPCCAP_ULTRAVISOR_BIT (1 << 0) + + Indicate that the powerpc kernel binary knows how to run in an + ultravisor-enabled system. + + In an ultravisor-enabled system, some machine resources are now controlled + by the ultravisor. If the kernel is not ultravisor-capable, but it ends up + being run on a machine with ultravisor, the kernel will probably crash + trying to access ultravisor resources. For instance, it may crash in early + boot trying to set the partition table entry 0. + + In an ultravisor-enabled system, a bootloader could warn the user or prevent + the kernel from being run if the PowerPC ultravisor capability doesn't exist + or the Ultravisor-capable bit is not set. + +References +---------- + +arch/powerpc/include/asm/elfnote.h +arch/powerpc/kernel/note.S + + |