linux-kernel - [PATCH] alpha/elf: Fix misc/setarch test of util-linux by removing 32bit support

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Message-ID: <87jzb2tdb7.fsf_-_@email.froward.int.ebiederm.org>
Date: Fri, 10 Jan 2025 18:16:28 -0600
From: "Eric W. Biederman" <ebiederm@...ssion.com>
To: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc: Arnd Bergmann <arnd@...db.de>,  Richard Henderson
 <richard.henderson@...aro.org>,  Matt Turner <mattst88@...il.com>,  Kees
 Cook <kees@...nel.org>,  "Paul E. McKenney" <paulmck@...nel.org>,
  linux-alpha@...r.kernel.org,  linux-mm@...ck.org,
  linux-kernel@...r.kernel.org,  Michael Cree <mcree@...on.net.nz>,  Sam
 James <sam@...too.org>,  "Maciej W. Rozycki" <macro@...am.me.uk>,  Geert
 Uytterhoeven <geert@...ux-m68k.org>,  Michael Karcher
 <kernel@...rcher.dialup.fu-berlin.de>,  Chris Hofstaedtler
 <zeha@...ian.org>,  util-linux@...r.kernel.org,
  linux-mips@...r.kernel.org,  loongarch@...ts.linux.dev
Subject: [PATCH] alpha/elf: Fix misc/setarch test of util-linux by removing
 32bit support


Richard Henderson <richard.henderson@...aro.org> writes[1]:

> There was a Spec benchmark (I forget which) which was memory bound and ran
> twice as fast with 32-bit pointers.
>
> I copied the idea from DEC to the ELF abi, but never did all the other work
> to allow the toolchain to take advantage.
>
> Amusingly, a later Spec changed the benchmark data sets to not fit into a
> 32-bit address space, specifically because of this.
>
> I expect one could delete the ELF bit and personality and no one would
> notice. Not even the 10 remaining Alpha users.

In [2] it was pointed out that parts of setarch weren't working
properly on alpha because it has it's own SET_PERSONALITY
implementation.  In the discussion that followed Richard Henderson
pointed out that the 32bit pointer support for alpha was never
completed.

Fix this by removing alpha's 32bit pointer support.

As a bit of paranoia refuse to execute any alpha binaries that hafe
the EF_ALPHA_32BIT flag set.  Just to fail explicitly in case someone
somewhere has binaries that trying to use alpha's 32bit pointer
support.

[1] https://lkml.kernel.org/r/CAFXwXrkgu=4Qn-v1PjnOR4SG0oUb9LSa0g6QXpBq4ttm52pJOQ@mail.gmail.com
[2] https://lkml.kernel.org/r/20250103140148.370368-1-glaubitz@physik.fu-berlin.de
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 arch/alpha/include/asm/elf.h       |  6 +-----
 arch/alpha/include/asm/pgtable.h   |  2 +-
 arch/alpha/include/asm/processor.h |  8 ++------
 arch/alpha/kernel/osf_sys.c        | 11 ++---------
 4 files changed, 6 insertions(+), 21 deletions(-)

diff --git a/arch/alpha/include/asm/elf.h b/arch/alpha/include/asm/elf.h
index 4d7c46f50382..50c82187e60e 100644
--- a/arch/alpha/include/asm/elf.h
+++ b/arch/alpha/include/asm/elf.h
@@ -74,7 +74,7 @@ typedef elf_fpreg_t elf_fpregset_t[ELF_NFPREG];
 /*
  * This is used to ensure we don't load something for the wrong architecture.
  */
-#define elf_check_arch(x) ((x)->e_machine == EM_ALPHA)
+#define elf_check_arch(x) (((x)->e_machine == EM_ALPHA) && !((x)->e_flags & EF_ALPHA_32BIT))
 
 /*
  * These are used to set parameters in the core dumps.
@@ -137,10 +137,6 @@ extern int dump_elf_task(elf_greg_t *dest, struct task_struct *task);
 	: amask (AMASK_CIX) ? "ev6" : "ev67");	\
 })
 
-#define SET_PERSONALITY(EX)					\
-	set_personality(((EX).e_flags & EF_ALPHA_32BIT)		\
-	   ? PER_LINUX_32BIT : PER_LINUX)
-
 extern int alpha_l1i_cacheshape;
 extern int alpha_l1d_cacheshape;
 extern int alpha_l2_cacheshape;
diff --git a/arch/alpha/include/asm/pgtable.h b/arch/alpha/include/asm/pgtable.h
index 635f0a5f5bbd..02e8817a8921 100644
--- a/arch/alpha/include/asm/pgtable.h
+++ b/arch/alpha/include/asm/pgtable.h
@@ -360,7 +360,7 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte)
 
 extern void paging_init(void);
 
-/* We have our own get_unmapped_area to cope with ADDR_LIMIT_32BIT.  */
+/* We have our own get_unmapped_area */
 #define HAVE_ARCH_UNMAPPED_AREA
 
 #endif /* _ALPHA_PGTABLE_H */
diff --git a/arch/alpha/include/asm/processor.h b/arch/alpha/include/asm/processor.h
index 55bb1c09fd39..5dce5518a211 100644
--- a/arch/alpha/include/asm/processor.h
+++ b/arch/alpha/include/asm/processor.h
@@ -8,23 +8,19 @@
 #ifndef __ASM_ALPHA_PROCESSOR_H
 #define __ASM_ALPHA_PROCESSOR_H
 
-#include <linux/personality.h>	/* for ADDR_LIMIT_32BIT */
-
 /*
  * We have a 42-bit user address space: 4TB user VM...
  */
 #define TASK_SIZE (0x40000000000UL)
 
-#define STACK_TOP \
-  (current->personality & ADDR_LIMIT_32BIT ? 0x80000000 : 0x00120000000UL)
+#define STACK_TOP (0x00120000000UL)
 
 #define STACK_TOP_MAX	0x00120000000UL
 
 /* This decides where the kernel will search for a free chunk of vm
  * space during mmap's.
  */
-#define TASK_UNMAPPED_BASE \
-  ((current->personality & ADDR_LIMIT_32BIT) ? 0x40000000 : TASK_SIZE / 2)
+#define TASK_UNMAPPED_BASE (TASK_SIZE / 2)
 
 /* This is dead.  Everything has been moved to thread_info.  */
 struct thread_struct { };
diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c
index 86185021f75a..a08e8edef1a4 100644
--- a/arch/alpha/kernel/osf_sys.c
+++ b/arch/alpha/kernel/osf_sys.c
@@ -1210,8 +1210,7 @@ SYSCALL_DEFINE1(old_adjtimex, struct timex32 __user *, txc_p)
 	return ret;
 }
 
-/* Get an address range which is currently unmapped.  Similar to the
-   generic version except that we know how to honor ADDR_LIMIT_32BIT.  */
+/* Get an address range which is currently unmapped. */
 
 static unsigned long
 arch_get_unmapped_area_1(unsigned long addr, unsigned long len,
@@ -1230,13 +1229,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
 		       unsigned long len, unsigned long pgoff,
 		       unsigned long flags, vm_flags_t vm_flags)
 {
-	unsigned long limit;
-
-	/* "32 bit" actually means 31 bit, since pointers sign extend.  */
-	if (current->personality & ADDR_LIMIT_32BIT)
-		limit = 0x80000000;
-	else
-		limit = TASK_SIZE;
+	unsigned long limit = TASK_SIZE;
 
 	if (len > limit)
 		return -ENOMEM;
-- 
2.41.0