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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 196 deletions

diff --git a/arch/ia64/kernel/ftrace.c b/arch/ia64/kernel/ftrace.c
deleted file mode 100644
index d6360fd404ab..000000000000
--- a/arch/ia64/kernel/ftrace.c
+++ /dev/null
@@ -1,196 +0,0 @@
-/*
- * Dynamic function tracing support.
- *
- * Copyright (C) 2008 Shaohua Li <shaohua.li@intel.com>
- *
- * For licencing details, see COPYING.
- *
- * Defines low-level handling of mcount calls when the kernel
- * is compiled with the -pg flag. When using dynamic ftrace, the
- * mcount call-sites get patched lazily with NOP till they are
- * enabled. All code mutation routines here take effect atomically.
- */
-
-#include <linux/uaccess.h>
-#include <linux/ftrace.h>
-
-#include <asm/cacheflush.h>
-#include <asm/patch.h>
-
-/* In IA64, each function will be added below two bundles with -pg option */
-static unsigned char __attribute__((aligned(8)))
-ftrace_orig_code[MCOUNT_INSN_SIZE] = {
-	0x02, 0x40, 0x31, 0x10, 0x80, 0x05, /* alloc r40=ar.pfs,12,8,0 */
-	0xb0, 0x02, 0x00, 0x00, 0x42, 0x40, /* mov r43=r0;; */
-	0x05, 0x00, 0xc4, 0x00,             /* mov r42=b0 */
-	0x11, 0x48, 0x01, 0x02, 0x00, 0x21, /* mov r41=r1 */
-	0x00, 0x00, 0x00, 0x02, 0x00, 0x00, /* nop.i 0x0 */
-	0x08, 0x00, 0x00, 0x50              /* br.call.sptk.many b0 = _mcount;; */
-};
-
-struct ftrace_orig_insn {
-	u64 dummy1, dummy2, dummy3;
-	u64 dummy4:64-41+13;
-	u64 imm20:20;
-	u64 dummy5:3;
-	u64 sign:1;
-	u64 dummy6:4;
-};
-
-/* mcount stub will be converted below for nop */
-static unsigned char ftrace_nop_code[MCOUNT_INSN_SIZE] = {
-	0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
-	0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
-	0x00, 0x00, 0x04, 0x00,             /* nop.i 0x0 */
-	0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
-	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* nop.x 0x0;; */
-	0x00, 0x00, 0x04, 0x00
-};
-
-static unsigned char *ftrace_nop_replace(void)
-{
-	return ftrace_nop_code;
-}
-
-/*
- * mcount stub will be converted below for call
- * Note: Just the last instruction is changed against nop
- * */
-static unsigned char __attribute__((aligned(8)))
-ftrace_call_code[MCOUNT_INSN_SIZE] = {
-	0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
-	0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
-	0x00, 0x00, 0x04, 0x00,             /* nop.i 0x0 */
-	0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
-	0xff, 0xff, 0xff, 0xff, 0x7f, 0x00, /* brl.many .;;*/
-	0xf8, 0xff, 0xff, 0xc8
-};
-
-struct ftrace_call_insn {
-	u64 dummy1, dummy2;
-	u64 dummy3:48;
-	u64 imm39_l:16;
-	u64 imm39_h:23;
-	u64 dummy4:13;
-	u64 imm20:20;
-	u64 dummy5:3;
-	u64 i:1;
-	u64 dummy6:4;
-};
-
-static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
-{
-	struct ftrace_call_insn *code = (void *)ftrace_call_code;
-	unsigned long offset = addr - (ip + 0x10);
-
-	code->imm39_l = offset >> 24;
-	code->imm39_h = offset >> 40;
-	code->imm20 = offset >> 4;
-	code->i = offset >> 63;
-	return ftrace_call_code;
-}
-
-static int
-ftrace_modify_code(unsigned long ip, unsigned char *old_code,
-		   unsigned char *new_code, int do_check)
-{
-	unsigned char replaced[MCOUNT_INSN_SIZE];
-
-	/*
-	 * Note:
-	 * We are paranoid about modifying text, as if a bug was to happen, it
-	 * could cause us to read or write to someplace that could cause harm.
-	 * Carefully read and modify the code with probe_kernel_*(), and make
-	 * sure what we read is what we expected it to be before modifying it.
-	 */
-
-	if (!do_check)
-		goto skip_check;
-
-	/* read the text we want to modify */
-	if (copy_from_kernel_nofault(replaced, (void *)ip, MCOUNT_INSN_SIZE))
-		return -EFAULT;
-
-	/* Make sure it is what we expect it to be */
-	if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
-		return -EINVAL;
-
-skip_check:
-	/* replace the text with the new text */
-	if (copy_to_kernel_nofault(((void *)ip), new_code, MCOUNT_INSN_SIZE))
-		return -EPERM;
-	flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
-
-	return 0;
-}
-
-static int ftrace_make_nop_check(struct dyn_ftrace *rec, unsigned long addr)
-{
-	unsigned char __attribute__((aligned(8))) replaced[MCOUNT_INSN_SIZE];
-	unsigned long ip = rec->ip;
-
-	if (copy_from_kernel_nofault(replaced, (void *)ip, MCOUNT_INSN_SIZE))
-		return -EFAULT;
-	if (rec->flags & FTRACE_FL_CONVERTED) {
-		struct ftrace_call_insn *call_insn, *tmp_call;
-
-		call_insn = (void *)ftrace_call_code;
-		tmp_call = (void *)replaced;
-		call_insn->imm39_l = tmp_call->imm39_l;
-		call_insn->imm39_h = tmp_call->imm39_h;
-		call_insn->imm20 = tmp_call->imm20;
-		call_insn->i = tmp_call->i;
-		if (memcmp(replaced, ftrace_call_code, MCOUNT_INSN_SIZE) != 0)
-			return -EINVAL;
-		return 0;
-	} else {
-		struct ftrace_orig_insn *call_insn, *tmp_call;
-
-		call_insn = (void *)ftrace_orig_code;
-		tmp_call = (void *)replaced;
-		call_insn->sign = tmp_call->sign;
-		call_insn->imm20 = tmp_call->imm20;
-		if (memcmp(replaced, ftrace_orig_code, MCOUNT_INSN_SIZE) != 0)
-			return -EINVAL;
-		return 0;
-	}
-}
-
-int ftrace_make_nop(struct module *mod,
-		    struct dyn_ftrace *rec, unsigned long addr)
-{
-	int ret;
-	char *new;
-
-	ret = ftrace_make_nop_check(rec, addr);
-	if (ret)
-		return ret;
-	new = ftrace_nop_replace();
-	return ftrace_modify_code(rec->ip, NULL, new, 0);
-}
-
-int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
-{
-	unsigned long ip = rec->ip;
-	unsigned char *old, *new;
-
-	old=  ftrace_nop_replace();
-	new = ftrace_call_replace(ip, addr);
-	return ftrace_modify_code(ip, old, new, 1);
-}
-
-/* in IA64, _mcount can't directly call ftrace_stub. Only jump is ok */
-int ftrace_update_ftrace_func(ftrace_func_t func)
-{
-	unsigned long ip;
-	unsigned long addr = ((struct fnptr *)ftrace_call)->ip;
-
-	if (func == ftrace_stub)
-		return 0;
-	ip = ((struct fnptr *)func)->ip;
-
-	ia64_patch_imm64(addr + 2, ip);
-
-	flush_icache_range(addr, addr + 16);
-	return 0;
-}