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powerpc: Add PowerPC Capabilities ELF note 

Add the PowerPC name and the PPC_ELFNOTE_CAPABILITIES type in the
kernel binary ELF note. This type is a bitmap that can be used to
advertise kernel capabilities to userland.

This patch also defines PPCCAP_ULTRAVISOR_BIT as being the bit zero.

Suggested-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com>
[ maxiwell: Define the 'PowerPC' type in the elfnote.h ]
Signed-off-by: Maxiwell S. Garcia <maxiwell@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190829155021.2915-2-maxiwell@linux.ibm.com
This commit is contained in:
Claudio Carvalho 2019-08-29 12:50:20 -03:00 committed by Michael Ellerman
parent a102f139aa
commit 70ed86f4de
3 changed files with 65 additions and 1 deletions
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24
arch/powerpc/include/asm/elfnote.h Normal file
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@ -0,0 +1,24 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* PowerPC ELF notes.
*
* Copyright 2019, IBM Corporation
*/
#ifndef __ASM_POWERPC_ELFNOTE_H__
#define __ASM_POWERPC_ELFNOTE_H__
/*
* These note types should live in a SHT_NOTE segment and have
* "PowerPC" in the name field.
*/
/*
* The capabilities supported/required by this kernel (bitmap).
*
* This type uses a bitmap as "desc" field. Each bit is described
* in arch/powerpc/kernel/note.S
*/
#define PPC_ELFNOTE_CAPABILITIES 1
#endif /* __ASM_POWERPC_ELFNOTE_H__ */

2
arch/powerpc/kernel/Makefile
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@ -53,7 +53,7 @@ obj-y := cputable.o ptrace.o syscalls.o \
dma-common.o
obj-$(CONFIG_PPC64) += setup_64.o sys_ppc32.o \
signal_64.o ptrace32.o \
paca.o nvram_64.o firmware.o
paca.o nvram_64.o firmware.o note.o
obj-$(CONFIG_VDSO32) += vdso32/
obj-$(CONFIG_PPC_WATCHDOG) += watchdog.o
obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o

40
arch/powerpc/kernel/note.S Normal file
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@ -0,0 +1,40 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* PowerPC ELF notes.
*
* Copyright 2019, IBM Corporation
*/
#include <linux/elfnote.h>
#include <asm/elfnote.h>
/*
* Ultravisor-capable bit (PowerNV only).
*
* Bit 0 indicates 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.
*/
#ifdef CONFIG_PPC_POWERNV
#define PPCCAP_ULTRAVISOR_BIT (1 << 0)
#else
#define PPCCAP_ULTRAVISOR_BIT 0
#endif
/*
* Add the PowerPC Capabilities in the binary ELF note. It is a bitmap that
* can be used to advertise kernel capabilities to userland.
*/
#define PPC_CAPABILITIES_BITMAP (PPCCAP_ULTRAVISOR_BIT)
ELFNOTE(PowerPC, PPC_ELFNOTE_CAPABILITIES,
.long PPC_CAPABILITIES_BITMAP)