root/arch/powerpc/kernel/note.S

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * PowerPC ELF notes.
   4  *
   5  * Copyright 2019, IBM Corporation
   6  */
   7 
   8 #include <linux/elfnote.h>
   9 #include <asm/elfnote.h>
  10 
  11 /*
  12  * Ultravisor-capable bit (PowerNV only).
  13  *
  14  * Bit 0 indicates that the powerpc kernel binary knows how to run in an
  15  * ultravisor-enabled system.
  16  *
  17  * In an ultravisor-enabled system, some machine resources are now controlled
  18  * by the ultravisor. If the kernel is not ultravisor-capable, but it ends up
  19  * being run on a machine with ultravisor, the kernel will probably crash
  20  * trying to access ultravisor resources. For instance, it may crash in early
  21  * boot trying to set the partition table entry 0.
  22  *
  23  * In an ultravisor-enabled system, a bootloader could warn the user or prevent
  24  * the kernel from being run if the PowerPC ultravisor capability doesn't exist
  25  * or the Ultravisor-capable bit is not set.
  26  */
  27 #ifdef CONFIG_PPC_POWERNV
  28 #define PPCCAP_ULTRAVISOR_BIT           (1 << 0)
  29 #else
  30 #define PPCCAP_ULTRAVISOR_BIT           0
  31 #endif
  32 
  33 /*
  34  * Add the PowerPC Capabilities in the binary ELF note. It is a bitmap that
  35  * can be used to advertise kernel capabilities to userland.
  36  */
  37 #define PPC_CAPABILITIES_BITMAP (PPCCAP_ULTRAVISOR_BIT)
  38 
  39 ELFNOTE(PowerPC, PPC_ELFNOTE_CAPABILITIES,
  40         .long PPC_CAPABILITIES_BITMAP)