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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 251 deletions

diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
deleted file mode 100644
index 5458b52b4009..000000000000
--- a/arch/ia64/mm/fault.c
+++ /dev/null
@@ -1,251 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * MMU fault handling support.
- *
- * Copyright (C) 1998-2002 Hewlett-Packard Co
- *	David Mosberger-Tang <davidm@hpl.hp.com>
- */
-#include <linux/sched/signal.h>
-#include <linux/kernel.h>
-#include <linux/mm.h>
-#include <linux/extable.h>
-#include <linux/interrupt.h>
-#include <linux/kprobes.h>
-#include <linux/kdebug.h>
-#include <linux/prefetch.h>
-#include <linux/uaccess.h>
-#include <linux/perf_event.h>
-
-#include <asm/processor.h>
-#include <asm/exception.h>
-
-extern int die(char *, struct pt_regs *, long);
-
-/*
- * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
- * (inside region 5, on ia64) and that page is present.
- */
-static int
-mapped_kernel_page_is_present (unsigned long address)
-{
-	pgd_t *pgd;
-	p4d_t *p4d;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *ptep, pte;
-
-	pgd = pgd_offset_k(address);
-	if (pgd_none(*pgd) || pgd_bad(*pgd))
-		return 0;
-
-	p4d = p4d_offset(pgd, address);
-	if (p4d_none(*p4d) || p4d_bad(*p4d))
-		return 0;
-
-	pud = pud_offset(p4d, address);
-	if (pud_none(*pud) || pud_bad(*pud))
-		return 0;
-
-	pmd = pmd_offset(pud, address);
-	if (pmd_none(*pmd) || pmd_bad(*pmd))
-		return 0;
-
-	ptep = pte_offset_kernel(pmd, address);
-	if (!ptep)
-		return 0;
-
-	pte = *ptep;
-	return pte_present(pte);
-}
-
-#	define VM_READ_BIT	0
-#	define VM_WRITE_BIT	1
-#	define VM_EXEC_BIT	2
-
-void __kprobes
-ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
-{
-	int signal = SIGSEGV, code = SEGV_MAPERR;
-	struct vm_area_struct *vma, *prev_vma;
-	struct mm_struct *mm = current->mm;
-	unsigned long mask;
-	vm_fault_t fault;
-	unsigned int flags = FAULT_FLAG_DEFAULT;
-
-	mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
-		| (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));
-
-	/* mmap_lock is performance critical.... */
-	prefetchw(&mm->mmap_lock);
-
-	/*
-	 * If we're in an interrupt or have no user context, we must not take the fault..
-	 */
-	if (faulthandler_disabled() || !mm)
-		goto no_context;
-
-	/*
-	 * This is to handle the kprobes on user space access instructions
-	 */
-	if (kprobe_page_fault(regs, TRAP_BRKPT))
-		return;
-
-	if (user_mode(regs))
-		flags |= FAULT_FLAG_USER;
-	if (mask & VM_WRITE)
-		flags |= FAULT_FLAG_WRITE;
-
-	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
-retry:
-	mmap_read_lock(mm);
-
-	vma = find_vma_prev(mm, address, &prev_vma);
-	if (!vma && !prev_vma )
-		goto bad_area;
-
-        /*
-         * find_vma_prev() returns vma such that address < vma->vm_end or NULL
-         *
-         * May find no vma, but could be that the last vm area is the
-         * register backing store that needs to expand upwards, in
-         * this case vma will be null, but prev_vma will ne non-null
-         */
-        if (( !vma && prev_vma ) || (address < vma->vm_start) ) {
-		vma = expand_stack(mm, address);
-		if (!vma)
-			goto bad_area_nosemaphore;
-	}
-
-	code = SEGV_ACCERR;
-
-	/* OK, we've got a good vm_area for this memory area.  Check the access permissions: */
-
-#	if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
-	    || (1 << VM_EXEC_BIT) != VM_EXEC)
-#		error File is out of sync with <linux/mm.h>.  Please update.
-#	endif
-
-	if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE))))
-		goto bad_area;
-
-	if ((vma->vm_flags & mask) != mask)
-		goto bad_area;
-
-	/*
-	 * If for any reason at all we couldn't handle the fault, make
-	 * sure we exit gracefully rather than endlessly redo the
-	 * fault.
-	 */
-	fault = handle_mm_fault(vma, address, flags, regs);
-
-	if (fault_signal_pending(fault, regs)) {
-		if (!user_mode(regs))
-			goto no_context;
-		return;
-	}
-
-	/* The fault is fully completed (including releasing mmap lock) */
-	if (fault & VM_FAULT_COMPLETED)
-		return;
-
-	if (unlikely(fault & VM_FAULT_ERROR)) {
-		/*
-		 * We ran out of memory, or some other thing happened
-		 * to us that made us unable to handle the page fault
-		 * gracefully.
-		 */
-		if (fault & VM_FAULT_OOM) {
-			goto out_of_memory;
-		} else if (fault & VM_FAULT_SIGSEGV) {
-			goto bad_area;
-		} else if (fault & VM_FAULT_SIGBUS) {
-			signal = SIGBUS;
-			goto bad_area;
-		}
-		BUG();
-	}
-
-	if (fault & VM_FAULT_RETRY) {
-		flags |= FAULT_FLAG_TRIED;
-
-		/* No need to mmap_read_unlock(mm) as we would
-		 * have already released it in __lock_page_or_retry
-		 * in mm/filemap.c.
-		 */
-
-		goto retry;
-	}
-
-	mmap_read_unlock(mm);
-	return;
-
-  bad_area:
-	mmap_read_unlock(mm);
-  bad_area_nosemaphore:
-	if ((isr & IA64_ISR_SP)
-	    || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
-	{
-		/*
-		 * This fault was due to a speculative load or lfetch.fault, set the "ed"
-		 * bit in the psr to ensure forward progress.  (Target register will get a
-		 * NaT for ld.s, lfetch will be canceled.)
-		 */
-		ia64_psr(regs)->ed = 1;
-		return;
-	}
-	if (user_mode(regs)) {
-		force_sig_fault(signal, code, (void __user *) address,
-				0, __ISR_VALID, isr);
-		return;
-	}
-
-  no_context:
-	if ((isr & IA64_ISR_SP)
-	    || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
-	{
-		/*
-		 * This fault was due to a speculative load or lfetch.fault, set the "ed"
-		 * bit in the psr to ensure forward progress.  (Target register will get a
-		 * NaT for ld.s, lfetch will be canceled.)
-		 */
-		ia64_psr(regs)->ed = 1;
-		return;
-	}
-
-	/*
-	 * Since we have no vma's for region 5, we might get here even if the address is
-	 * valid, due to the VHPT walker inserting a non present translation that becomes
-	 * stale. If that happens, the non present fault handler already purged the stale
-	 * translation, which fixed the problem. So, we check to see if the translation is
-	 * valid, and return if it is.
-	 */
-	if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
-		return;
-
-	if (ia64_done_with_exception(regs))
-		return;
-
-	/*
-	 * Oops. The kernel tried to access some bad page. We'll have to terminate things
-	 * with extreme prejudice.
-	 */
-	bust_spinlocks(1);
-
-	if (address < PAGE_SIZE)
-		printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address);
-	else
-		printk(KERN_ALERT "Unable to handle kernel paging request at "
-		       "virtual address %016lx\n", address);
-	if (die("Oops", regs, isr))
-		regs = NULL;
-	bust_spinlocks(0);
-	if (regs)
-		make_task_dead(SIGKILL);
-	return;
-
-  out_of_memory:
-	mmap_read_unlock(mm);
-	if (!user_mode(regs))
-		goto no_context;
-	pagefault_out_of_memory();
-}