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The Itanium architecture is obsolete, and an informal survey [0] reveals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, 165 deletions

diff --git a/arch/ia64/kernel/unwind_i.h b/arch/ia64/kernel/unwind_i.h
deleted file mode 100644
index 1dd57ba44327..000000000000
--- a/arch/ia64/kernel/unwind_i.h
+++ /dev/null
@@ -1,165 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Copyright (C) 2000, 2002-2003 Hewlett-Packard Co
- *	David Mosberger-Tang <davidm@hpl.hp.com>
- *
- * Kernel unwind support.
- */
-
-#define UNW_VER(x)		((x) >> 48)
-#define UNW_FLAG_MASK		0x0000ffff00000000
-#define UNW_FLAG_OSMASK		0x0000f00000000000
-#define UNW_FLAG_EHANDLER(x)	((x) & 0x0000000100000000L)
-#define UNW_FLAG_UHANDLER(x)	((x) & 0x0000000200000000L)
-#define UNW_LENGTH(x)		((x) & 0x00000000ffffffffL)
-
-enum unw_register_index {
-	/* primary unat: */
-	UNW_REG_PRI_UNAT_GR,
-	UNW_REG_PRI_UNAT_MEM,
-
-	/* register stack */
-	UNW_REG_BSP,					/* register stack pointer */
-	UNW_REG_BSPSTORE,
-	UNW_REG_PFS,					/* previous function state */
-	UNW_REG_RNAT,
-	/* memory stack */
-	UNW_REG_PSP,					/* previous memory stack pointer */
-	/* return pointer: */
-	UNW_REG_RP,
-
-	/* preserved registers: */
-	UNW_REG_R4, UNW_REG_R5, UNW_REG_R6, UNW_REG_R7,
-	UNW_REG_UNAT, UNW_REG_PR, UNW_REG_LC, UNW_REG_FPSR,
-	UNW_REG_B1, UNW_REG_B2, UNW_REG_B3, UNW_REG_B4, UNW_REG_B5,
-	UNW_REG_F2, UNW_REG_F3, UNW_REG_F4, UNW_REG_F5,
-	UNW_REG_F16, UNW_REG_F17, UNW_REG_F18, UNW_REG_F19,
-	UNW_REG_F20, UNW_REG_F21, UNW_REG_F22, UNW_REG_F23,
-	UNW_REG_F24, UNW_REG_F25, UNW_REG_F26, UNW_REG_F27,
-	UNW_REG_F28, UNW_REG_F29, UNW_REG_F30, UNW_REG_F31,
-	UNW_NUM_REGS
-};
-
-struct unw_info_block {
-	u64 header;
-	u64 desc[];		/* unwind descriptors */
-	/* personality routine and language-specific data follow behind descriptors */
-};
-
-struct unw_table {
-	struct unw_table *next;		/* must be first member! */
-	const char *name;
-	unsigned long gp;		/* global pointer for this load-module */
-	unsigned long segment_base;	/* base for offsets in the unwind table entries */
-	unsigned long start;
-	unsigned long end;
-	const struct unw_table_entry *array;
-	unsigned long length;
-};
-
-enum unw_where {
-	UNW_WHERE_NONE,			/* register isn't saved at all */
-	UNW_WHERE_GR,			/* register is saved in a general register */
-	UNW_WHERE_FR,			/* register is saved in a floating-point register */
-	UNW_WHERE_BR,			/* register is saved in a branch register */
-	UNW_WHERE_SPREL,		/* register is saved on memstack (sp-relative) */
-	UNW_WHERE_PSPREL,		/* register is saved on memstack (psp-relative) */
-	/*
-	 * At the end of each prologue these locations get resolved to
-	 * UNW_WHERE_PSPREL and UNW_WHERE_GR, respectively:
-	 */
-	UNW_WHERE_SPILL_HOME,		/* register is saved in its spill home */
-	UNW_WHERE_GR_SAVE		/* register is saved in next general register */
-};
-
-#define UNW_WHEN_NEVER	0x7fffffff
-
-struct unw_reg_info {
-	unsigned long val;		/* save location: register number or offset */
-	enum unw_where where;		/* where the register gets saved */
-	int when;			/* when the register gets saved */
-};
-
-struct unw_reg_state {
-	struct unw_reg_state *next;		/* next (outer) element on state stack */
-	struct unw_reg_info reg[UNW_NUM_REGS];	/* register save locations */
-};
-
-struct unw_labeled_state {
-	struct unw_labeled_state *next;		/* next labeled state (or NULL) */
-	unsigned long label;			/* label for this state */
-	struct unw_reg_state saved_state;
-};
-
-struct unw_state_record {
-	unsigned int first_region : 1;	/* is this the first region? */
-	unsigned int done : 1;		/* are we done scanning descriptors? */
-	unsigned int any_spills : 1;	/* got any register spills? */
-	unsigned int in_body : 1;	/* are we inside a body (as opposed to a prologue)? */
-	unsigned long flags;		/* see UNW_FLAG_* in unwind.h */
-
-	u8 *imask;			/* imask of spill_mask record or NULL */
-	unsigned long pr_val;		/* predicate values */
-	unsigned long pr_mask;		/* predicate mask */
-	long spill_offset;		/* psp-relative offset for spill base */
-	int region_start;
-	int region_len;
-	int epilogue_start;
-	int epilogue_count;
-	int when_target;
-
-	u8 gr_save_loc;			/* next general register to use for saving a register */
-	u8 return_link_reg;		/* branch register in which the return link is passed */
-
-	struct unw_labeled_state *labeled_states;	/* list of all labeled states */
-	struct unw_reg_state curr;	/* current state */
-};
-
-enum unw_nat_type {
-	UNW_NAT_NONE,		/* NaT not represented */
-	UNW_NAT_VAL,		/* NaT represented by NaT value (fp reg) */
-	UNW_NAT_MEMSTK,		/* NaT value is in unat word at offset OFF  */
-	UNW_NAT_REGSTK		/* NaT is in rnat */
-};
-
-enum unw_insn_opcode {
-	UNW_INSN_ADD,			/* s[dst] += val */
-	UNW_INSN_ADD_PSP,		/* s[dst] = (s.psp + val) */
-	UNW_INSN_ADD_SP,		/* s[dst] = (s.sp + val) */
-	UNW_INSN_MOVE,			/* s[dst] = s[val] */
-	UNW_INSN_MOVE2,			/* s[dst] = s[val]; s[dst+1] = s[val+1] */
-	UNW_INSN_MOVE_STACKED,		/* s[dst] = ia64_rse_skip(*s.bsp, val) */
-	UNW_INSN_SETNAT_MEMSTK,		/* s[dst+1].nat.type = MEMSTK;
-					   s[dst+1].nat.off = *s.pri_unat - s[dst] */
-	UNW_INSN_SETNAT_TYPE,		/* s[dst+1].nat.type = val */
-	UNW_INSN_LOAD,			/* s[dst] = *s[val] */
-	UNW_INSN_MOVE_SCRATCH,		/* s[dst] = scratch reg "val" */
-	UNW_INSN_MOVE_CONST,            /* s[dst] = constant reg "val" */
-};
-
-struct unw_insn {
-	unsigned int opc	:  4;
-	unsigned int dst	:  9;
-	signed int val		: 19;
-};
-
-/*
- * Preserved general static registers (r4-r7) give rise to two script
- * instructions; everything else yields at most one instruction; at
- * the end of the script, the psp gets popped, accounting for one more
- * instruction.
- */
-#define UNW_MAX_SCRIPT_LEN	(UNW_NUM_REGS + 5)
-
-struct unw_script {
-	unsigned long ip;		/* ip this script is for */
-	unsigned long pr_mask;		/* mask of predicates script depends on */
-	unsigned long pr_val;		/* predicate values this script is for */
-	rwlock_t lock;
-	unsigned int flags;		/* see UNW_FLAG_* in unwind.h */
-	unsigned short lru_chain;	/* used for least-recently-used chain */
-	unsigned short coll_chain;	/* used for hash collisions */
-	unsigned short hint;		/* hint for next script to try (or -1) */
-	unsigned short count;		/* number of instructions in script */
-	struct unw_insn insn[UNW_MAX_SCRIPT_LEN];
-};