* [PATCH v2 1/2] powerpc: Add PowerPC Capabilities ELF note
2019-08-29 15:50 [PATCH v2 0/2] powerpc: Add PowerPC Capabilities ELF note Maxiwell S. Garcia
@ 2019-08-29 15:50 ` Maxiwell S. Garcia
2019-09-02 3:06 ` Michael Ellerman
2019-08-29 15:50 ` [PATCH v2 2/2] docs: powerpc: Add ELF note documentation Maxiwell S. Garcia
1 sibling, 1 reply; 4+ messages in thread
From: Maxiwell S. Garcia @ 2019-08-29 15:50 UTC (permalink / raw)
To: linuxppc-dev
Cc: linux-arch, andmike, linuxram, linux-kernel, kvm-ppc, cclaudio,
Maxiwell S . Garcia, bauerman
From: Claudio Carvalho <cclaudio@linux.ibm.com>
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>
---
arch/powerpc/include/asm/elfnote.h | 24 ++++++++++++++++++
arch/powerpc/kernel/Makefile | 2 +-
arch/powerpc/kernel/note.S | 40 ++++++++++++++++++++++++++++++
3 files changed, 65 insertions(+), 1 deletion(-)
create mode 100644 arch/powerpc/include/asm/elfnote.h
create mode 100644 arch/powerpc/kernel/note.S
diff --git a/arch/powerpc/include/asm/elfnote.h b/arch/powerpc/include/asm/elfnote.h
new file mode 100644
index 000000000000..a201b6e9ae44
--- /dev/null
+++ b/arch/powerpc/include/asm/elfnote.h
@@ -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__ */
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 56dfa7a2a6f2..0fcd3045284f 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -52,7 +52,7 @@ obj-y := cputable.o ptrace.o syscalls.o \
of_platform.o prom_parse.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
diff --git a/arch/powerpc/kernel/note.S b/arch/powerpc/kernel/note.S
new file mode 100644
index 000000000000..bcdad15395dd
--- /dev/null
+++ b/arch/powerpc/kernel/note.S
@@ -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)
--
2.20.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v2 2/2] docs: powerpc: Add ELF note documentation
2019-08-29 15:50 [PATCH v2 0/2] powerpc: Add PowerPC Capabilities ELF note Maxiwell S. Garcia
2019-08-29 15:50 ` [PATCH v2 1/2] " Maxiwell S. Garcia
@ 2019-08-29 15:50 ` Maxiwell S. Garcia
1 sibling, 0 replies; 4+ messages in thread
From: Maxiwell S. Garcia @ 2019-08-29 15:50 UTC (permalink / raw)
To: linuxppc-dev
Cc: linux-arch, andmike, linuxram, linux-kernel, kvm-ppc, cclaudio,
Maxiwell S. Garcia, bauerman
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>
---
Documentation/powerpc/elfnote.rst | 42 +++++++++++++++++++++++++++++++
1 file changed, 42 insertions(+)
create mode 100644 Documentation/powerpc/elfnote.rst
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
+
+
--
2.20.1
^ permalink raw reply related [flat|nested] 4+ messages in thread