arch: Remove Itanium (IA-64) architecture

The Itanium architecture is obsolete, and an informal survey [0] reveals
that any residual use of Itanium hardware in production is mostly HP-UX
or OpenVMS based. The use of Linux on Itanium appears to be limited to
enthusiasts that occasionally boot a fresh Linux kernel to see whether
things are still working as intended, and perhaps to churn out some
distro packages that are rarely used in practice.

None of the original companies behind Itanium still produce or support
any hardware or software for the architecture, and it is listed as
'Orphaned' in the MAINTAINERS file, as apparently, none of the engineers
that contributed on behalf of those companies (nor anyone else, for that
matter) have been willing to support or maintain the architecture
upstream or even be responsible for applying the odd fix. The Intel
firmware team removed all IA-64 support from the Tianocore/EDK2
reference implementation of EFI in 2018. (Itanium is the original
architecture for which EFI was developed, and the way Linux supports it
deviates significantly from other architectures.) Some distros, such as
Debian and Gentoo, still maintain [unofficial] ia64 ports, but many have
dropped support years ago.

While the argument is being made [1] that there is a 'for the common
good' angle to being able to build and run existing projects such as the
Grid Community Toolkit [2] on Itanium for interoperability testing, the
fact remains that none of those projects are known to be deployed on
Linux/ia64, and very few people actually have access to such a system in
the first place. Even if there were ways imaginable in which Linux/ia64
could be put to good use today, what matters is whether anyone is
actually doing that, and this does not appear to be the case.

There are no emulators widely available, and so boot testing Itanium is
generally infeasible for ordinary contributors. GCC still supports IA-64
but its compile farm [3] no longer has any IA-64 machines. GLIBC would
like to get rid of IA-64 [4] too because it would permit some overdue
code cleanups. In summary, the benefits to the ecosystem of having IA-64
be part of it are mostly theoretical, whereas the maintenance overhead
of keeping it supported is real.

So let's rip off the band aid, and remove the IA-64 arch code entirely.
This follows the timeline proposed by the Debian/ia64 maintainer [5],
which removes support in a controlled manner, leaving IA-64 in a known
good state in the most recent LTS release. Other projects will follow
once the kernel support is removed.

[0] https://lore.kernel.org/all/CAMj1kXFCMh_578jniKpUtx_j8ByHnt=s7S+yQ+vGbKt9ud7+kQ@mail.gmail.com/
[1] https://lore.kernel.org/all/0075883c-7c51-00f5-2c2d-5119c1820410@web.de/
[2] https://gridcf.org/gct-docs/latest/index.html
[3] https://cfarm.tetaneutral.net/machines/list/
[4] https://lore.kernel.org/all/87bkiilpc4.fsf@mid.deneb.enyo.de/
[5] https://lore.kernel.org/all/ff58a3e76e5102c94bb5946d99187b358def688a.camel@physik.fu-berlin.de/

Acked-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

1 files changed, 0 insertions, 116 deletions

diff --git a/arch/ia64/include/asm/kprobes.h b/arch/ia64/include/asm/kprobes.h
deleted file mode 100644
index 9e956768946c..000000000000
--- a/arch/ia64/include/asm/kprobes.h
+++ /dev/null
@@ -1,116 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
-#ifndef _ASM_KPROBES_H
-#define _ASM_KPROBES_H
-/*
- *  Kernel Probes (KProbes)
- *
- * Copyright (C) IBM Corporation, 2002, 2004
- * Copyright (C) Intel Corporation, 2005
- *
- * 2005-Apr     Rusty Lynch <rusty.lynch@intel.com> and Anil S Keshavamurthy
- *              <anil.s.keshavamurthy@intel.com> adapted from i386
- */
-#include <asm-generic/kprobes.h>
-#include <asm/break.h>
-
-#define BREAK_INST	(long)(__IA64_BREAK_KPROBE << 6)
-
-#ifdef CONFIG_KPROBES
-
-#include <linux/types.h>
-#include <linux/ptrace.h>
-#include <linux/percpu.h>
-
-#define __ARCH_WANT_KPROBES_INSN_SLOT
-#define MAX_INSN_SIZE   2	/* last half is for kprobe-booster */
-#define NOP_M_INST	(long)(1<<27)
-#define BRL_INST(i1, i2) ((long)((0xcL << 37) |	/* brl */ \
-				(0x1L << 12) |	/* many */ \
-				(((i1) & 1) << 36) | ((i2) << 13))) /* imm */
-
-typedef union cmp_inst {
-	struct {
-	unsigned long long qp : 6;
-	unsigned long long p1 : 6;
-	unsigned long long c  : 1;
-	unsigned long long r2 : 7;
-	unsigned long long r3 : 7;
-	unsigned long long p2 : 6;
-	unsigned long long ta : 1;
-	unsigned long long x2 : 2;
-	unsigned long long tb : 1;
-	unsigned long long opcode : 4;
-	unsigned long long reserved : 23;
-	}f;
-	unsigned long long l;
-} cmp_inst_t;
-
-struct kprobe;
-
-typedef struct _bundle {
-	struct {
-		unsigned long long template : 5;
-		unsigned long long slot0 : 41;
-		unsigned long long slot1_p0 : 64-46;
-	} quad0;
-	struct {
-		unsigned long long slot1_p1 : 41 - (64-46);
-		unsigned long long slot2 : 41;
-	} quad1;
-} __attribute__((__aligned__(16)))  bundle_t;
-
-struct prev_kprobe {
-	struct kprobe *kp;
-	unsigned long status;
-};
-
-#define	MAX_PARAM_RSE_SIZE	(0x60+0x60/0x3f)
-/* per-cpu kprobe control block */
-#define ARCH_PREV_KPROBE_SZ 2
-struct kprobe_ctlblk {
-	unsigned long kprobe_status;
-	unsigned long *bsp;
-	unsigned long cfm;
-	atomic_t prev_kprobe_index;
-	struct prev_kprobe prev_kprobe[ARCH_PREV_KPROBE_SZ];
-};
-
-#define kretprobe_blacklist_size 0
-
-#define SLOT0_OPCODE_SHIFT	(37)
-#define SLOT1_p1_OPCODE_SHIFT	(37 - (64-46))
-#define SLOT2_OPCODE_SHIFT 	(37)
-
-#define INDIRECT_CALL_OPCODE		(1)
-#define IP_RELATIVE_CALL_OPCODE		(5)
-#define IP_RELATIVE_BRANCH_OPCODE	(4)
-#define IP_RELATIVE_PREDICT_OPCODE	(7)
-#define LONG_BRANCH_OPCODE		(0xC)
-#define LONG_CALL_OPCODE		(0xD)
-#define flush_insn_slot(p)		do { } while (0)
-
-typedef struct kprobe_opcode {
-	bundle_t bundle;
-} kprobe_opcode_t;
-
-/* Architecture specific copy of original instruction*/
-struct arch_specific_insn {
-	/* copy of the instruction to be emulated */
-	kprobe_opcode_t *insn;
- #define INST_FLAG_FIX_RELATIVE_IP_ADDR		1
- #define INST_FLAG_FIX_BRANCH_REG		2
- #define INST_FLAG_BREAK_INST			4
- #define INST_FLAG_BOOSTABLE			8
- 	unsigned long inst_flag;
- 	unsigned short target_br_reg;
-	unsigned short slot;
-};
-
-extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
-extern int kprobe_exceptions_notify(struct notifier_block *self,
-				    unsigned long val, void *data);
-
-extern void arch_remove_kprobe(struct kprobe *p);
-
-#endif /* CONFIG_KPROBES */
-#endif /* _ASM_KPROBES_H */