Re: [PATCH] x86: Remove a.out support

Re: [PATCH] x86: Remove a.out support

[James Jones]

> From: Borislav Petkov <bp@suse.de>
>
> Commit
>
>   eac616557050 ("x86: Deprecate a.out support")
>
> deprecated a.out support with the promise to remove it a couple of
> releases later. That commit landed in v5.1.
>
> Now it is more than a couple of releases later, no one has complained so
> remove it.

Sorry for taking so long to complain, but I have been meaning to note
that I and a few others are still using a.out. I saw it go by in my
morning Google news skim that this went in, and figured it was now or
never. The use case is running an old set of tools to build programs for
the Atari Jaguar. Namely, Atari's assembler (mac) and linker (aln). The
alternative is running windows versions in dosbox, or using some
replacements that have been developed based on an even older,
less-featureful version of the source code for mac and aln, but which
still haven't managed to add back in all the features needed to build
some programs or use the Atari debugging tools (Also available in a.out
only).

I've been running with a few local patches to fix the a.out build and
add the Kconfig options back for the last year or so to enable this on a
few of my machines, and it's been working fine. I know of at least one
other person doing this. If the code itself and supporting
syscalls/other code go away though, it'll probably become impractical.
If others are open to it, I can share my small local patches along with
a revert of this change. I'd also like to ask whether much is gained by
deleting this code as far as reducing maintenance burden. It has
survived nearly untouched since the deprecation notice and still works
modulo a broken preprocessor macro in fs/exec.c.

For the curious, or if anyone wants proof I'm not making this up and
really do spend time on these things, my amalgamation of Jaguar tools &
docs, including copies of the old mac and aln a.out binaries, is
available here:

https://github.com/cubanismo/jaguar-sdk

Thanks,
-James

> Signed-off-by: Borislav Petkov <bp@suse.de>
> ---
>  arch/x86/Kconfig          |   7 -
>  arch/x86/ia32/Makefile    |   2 -
>  arch/x86/ia32/ia32_aout.c | 325 --------------------------------------
>  3 files changed, 334 deletions(-)
>  delete mode 100644 arch/x86/ia32/ia32_aout.c
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 976dd6b532bf..6f3d63dbbddf 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2835,13 +2835,6 @@ config IA32_EMULATION
>  	  64-bit kernel. You should likely turn this on, unless you're
>  	  100% sure that you don't have any 32-bit programs left.
>
> -config IA32_AOUT
> -	tristate "IA32 a.out support"
> -	depends on IA32_EMULATION
> -	depends on BROKEN
> -	help
> -	  Support old a.out binaries in the 32bit emulation.
> -
>  config X86_X32
>  	bool "x32 ABI for 64-bit mode"
>  	depends on X86_64
> diff --git a/arch/x86/ia32/Makefile b/arch/x86/ia32/Makefile
> index 8e4d0391ff6c..e481056698de 100644
> --- a/arch/x86/ia32/Makefile
> +++ b/arch/x86/ia32/Makefile
> @@ -5,7 +5,5 @@
>
>  obj-$(CONFIG_IA32_EMULATION) := ia32_signal.o
>
> -obj-$(CONFIG_IA32_AOUT) += ia32_aout.o
> -
>  audit-class-$(CONFIG_AUDIT) := audit.o
>  obj-$(CONFIG_IA32_EMULATION) += $(audit-class-y)
> diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
> deleted file mode 100644
> index 9bd15241fadb..000000000000
> --- a/arch/x86/ia32/ia32_aout.c
> +++ /dev/null
> @@ -1,325 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0-only
> -/*
> - *  a.out loader for x86-64
> - *
> - *  Copyright (C) 1991, 1992, 1996  Linus Torvalds
> - *  Hacked together by Andi Kleen
> - */
> -
> -#include <linux/module.h>
> -
> -#include <linux/time.h>
> -#include <linux/kernel.h>
> -#include <linux/mm.h>
> -#include <linux/mman.h>
> -#include <linux/a.out.h>
> -#include <linux/errno.h>
> -#include <linux/signal.h>
> -#include <linux/string.h>
> -#include <linux/fs.h>
> -#include <linux/file.h>
> -#include <linux/stat.h>
> -#include <linux/fcntl.h>
> -#include <linux/ptrace.h>
> -#include <linux/user.h>
> -#include <linux/binfmts.h>
> -#include <linux/personality.h>
> -#include <linux/init.h>
> -#include <linux/jiffies.h>
> -#include <linux/perf_event.h>
> -#include <linux/sched/task_stack.h>
> -
> -#include <linux/uaccess.h>
> -#include <asm/cacheflush.h>
> -#include <asm/user32.h>
> -#include <asm/ia32.h>
> -
> -#undef WARN_OLD
> -
> -static int load_aout_binary(struct linux_binprm *);
> -static int load_aout_library(struct file *);
> -
> -static struct linux_binfmt aout_format = {
> -	.module		= THIS_MODULE,
> -	.load_binary	= load_aout_binary,
> -	.load_shlib	= load_aout_library,
> -};
> -
> -static int set_brk(unsigned long start, unsigned long end)
> -{
> -	start = PAGE_ALIGN(start);
> -	end = PAGE_ALIGN(end);
> -	if (end <= start)
> -		return 0;
> -	return vm_brk(start, end - start);
> -}
> -
> -
> -/*
> - * create_aout_tables() parses the env- and arg-strings in new user
> - * memory and creates the pointer tables from them, and puts their
> - * addresses on the "stack", returning the new stack pointer value.
> - */
> -static u32 __user *create_aout_tables(char __user *p, struct linux_binprm *bprm)
> -{
> -	u32 __user *argv, *envp, *sp;
> -	int argc = bprm->argc, envc = bprm->envc;
> -
> -	sp = (u32 __user *) ((-(unsigned long)sizeof(u32)) & (unsigned long) p);
> -	sp -= envc+1;
> -	envp = sp;
> -	sp -= argc+1;
> -	argv = sp;
> -	put_user((unsigned long) envp, --sp);
> -	put_user((unsigned long) argv, --sp);
> -	put_user(argc, --sp);
> -	current->mm->arg_start = (unsigned long) p;
> -	while (argc-- > 0) {
> -		char c;
> -
> -		put_user((u32)(unsigned long)p, argv++);
> -		do {
> -			get_user(c, p++);
> -		} while (c);
> -	}
> -	put_user(0, argv);
> -	current->mm->arg_end = current->mm->env_start = (unsigned long) p;
> -	while (envc-- > 0) {
> -		char c;
> -
> -		put_user((u32)(unsigned long)p, envp++);
> -		do {
> -			get_user(c, p++);
> -		} while (c);
> -	}
> -	put_user(0, envp);
> -	current->mm->env_end = (unsigned long) p;
> -	return sp;
> -}
> -
> -/*
> - * These are the functions used to load a.out style executables and shared
> - * libraries.  There is no binary dependent code anywhere else.
> - */
> -static int load_aout_binary(struct linux_binprm *bprm)
> -{
> -	unsigned long error, fd_offset, rlim;
> -	struct pt_regs *regs = current_pt_regs();
> -	struct exec ex;
> -	int retval;
> -
> -	ex = *((struct exec *) bprm->buf);		/* exec-header */
> -	if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
> -	     N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
> -	    N_TRSIZE(ex) || N_DRSIZE(ex) ||
> -	    i_size_read(file_inode(bprm->file)) <
> -	    ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
> -		return -ENOEXEC;
> -	}
> -
> -	fd_offset = N_TXTOFF(ex);
> -
> -	/* Check initial limits. This avoids letting people circumvent
> -	 * size limits imposed on them by creating programs with large
> -	 * arrays in the data or bss.
> -	 */
> -	rlim = rlimit(RLIMIT_DATA);
> -	if (rlim >= RLIM_INFINITY)
> -		rlim = ~0;
> -	if (ex.a_data + ex.a_bss > rlim)
> -		return -ENOMEM;
> -
> -	/* Flush all traces of the currently running executable */
> -	retval = begin_new_exec(bprm);
> -	if (retval)
> -		return retval;
> -
> -	/* OK, This is the point of no return */
> -	set_personality(PER_LINUX);
> -	set_personality_ia32(false);
> -
> -	setup_new_exec(bprm);
> -
> -	regs->cs = __USER32_CS;
> -	regs->r8 = regs->r9 = regs->r10 = regs->r11 = regs->r12 =
> -		regs->r13 = regs->r14 = regs->r15 = 0;
> -
> -	current->mm->end_code = ex.a_text +
> -		(current->mm->start_code = N_TXTADDR(ex));
> -	current->mm->end_data = ex.a_data +
> -		(current->mm->start_data = N_DATADDR(ex));
> -	current->mm->brk = ex.a_bss +
> -		(current->mm->start_brk = N_BSSADDR(ex));
> -
> -	retval = setup_arg_pages(bprm, IA32_STACK_TOP, EXSTACK_DEFAULT);
> -	if (retval < 0)
> -		return retval;
> -
> -	if (N_MAGIC(ex) == OMAGIC) {
> -		unsigned long text_addr, map_size;
> -
> -		text_addr = N_TXTADDR(ex);
> -		map_size = ex.a_text+ex.a_data;
> -
> -		error = vm_brk(text_addr & PAGE_MASK, map_size);
> -
> -		if (error)
> -			return error;
> -
> -		error = read_code(bprm->file, text_addr, 32,
> -				  ex.a_text + ex.a_data);
> -		if ((signed long)error < 0)
> -			return error;
> -	} else {
> -#ifdef WARN_OLD
> -		static unsigned long error_time, error_time2;
> -		if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
> -		    (N_MAGIC(ex) != NMAGIC) &&
> -				time_after(jiffies, error_time2 + 5*HZ)) {
> -			printk(KERN_NOTICE "executable not page aligned\n");
> -			error_time2 = jiffies;
> -		}
> -
> -		if ((fd_offset & ~PAGE_MASK) != 0 &&
> -			    time_after(jiffies, error_time + 5*HZ)) {
> -			printk(KERN_WARNING
> -			       "fd_offset is not page aligned. Please convert "
> -			       "program: %pD\n",
> -			       bprm->file);
> -			error_time = jiffies;
> -		}
> -#endif
> -
> -		if (!bprm->file->f_op->mmap || (fd_offset & ~PAGE_MASK) != 0) {
> -			error = vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
> -			if (error)
> -				return error;
> -
> -			read_code(bprm->file, N_TXTADDR(ex), fd_offset,
> -					ex.a_text+ex.a_data);
> -			goto beyond_if;
> -		}
> -
> -		error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
> -				PROT_READ | PROT_EXEC,
> -				MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
> -				fd_offset);
> -
> -		if (error != N_TXTADDR(ex))
> -			return error;
> -
> -		error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
> -				PROT_READ | PROT_WRITE | PROT_EXEC,
> -				MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
> -				fd_offset + ex.a_text);
> -		if (error != N_DATADDR(ex))
> -			return error;
> -	}
> -
> -beyond_if:
> -	error = set_brk(current->mm->start_brk, current->mm->brk);
> -	if (error)
> -		return error;
> -
> -	set_binfmt(&aout_format);
> -
> -	current->mm->start_stack =
> -		(unsigned long)create_aout_tables((char __user *)bprm->p, bprm);
> -	/* start thread */
> -	loadsegment(fs, 0);
> -	loadsegment(ds, __USER32_DS);
> -	loadsegment(es, __USER32_DS);
> -	load_gs_index(0);
> -	(regs)->ip = ex.a_entry;
> -	(regs)->sp = current->mm->start_stack;
> -	(regs)->flags = 0x200;
> -	(regs)->cs = __USER32_CS;
> -	(regs)->ss = __USER32_DS;
> -	regs->r8 = regs->r9 = regs->r10 = regs->r11 =
> -	regs->r12 = regs->r13 = regs->r14 = regs->r15 = 0;
> -	return 0;
> -}
> -
> -static int load_aout_library(struct file *file)
> -{
> -	unsigned long bss, start_addr, len, error;
> -	int retval;
> -	struct exec ex;
> -	loff_t pos = 0;
> -
> -	retval = -ENOEXEC;
> -	error = kernel_read(file, &ex, sizeof(ex), &pos);
> -	if (error != sizeof(ex))
> -		goto out;
> -
> -	/* We come in here for the regular a.out style of shared libraries */
> -	if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
> -	    N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
> -	    i_size_read(file_inode(file)) <
> -	    ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
> -		goto out;
> -	}
> -
> -	if (N_FLAGS(ex))
> -		goto out;
> -
> -	/* For  QMAGIC, the starting address is 0x20 into the page.  We mask
> -	   this off to get the starting address for the page */
> -
> -	start_addr =  ex.a_entry & 0xfffff000;
> -
> -	if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
> -#ifdef WARN_OLD
> -		static unsigned long error_time;
> -		if (time_after(jiffies, error_time + 5*HZ)) {
> -			printk(KERN_WARNING
> -			       "N_TXTOFF is not page aligned. Please convert "
> -			       "library: %pD\n",
> -			       file);
> -			error_time = jiffies;
> -		}
> -#endif
> -		retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
> -		if (retval)
> -			goto out;
> -
> -		read_code(file, start_addr, N_TXTOFF(ex),
> -			  ex.a_text + ex.a_data);
> -		retval = 0;
> -		goto out;
> -	}
> -	/* Now use mmap to map the library into memory. */
> -	error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
> -			PROT_READ | PROT_WRITE | PROT_EXEC,
> -			MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
> -			N_TXTOFF(ex));
> -	retval = error;
> -	if (error != start_addr)
> -		goto out;
> -
> -	len = PAGE_ALIGN(ex.a_text + ex.a_data);
> -	bss = ex.a_text + ex.a_data + ex.a_bss;
> -	if (bss > len) {
> -		retval = vm_brk(start_addr + len, bss - len);
> -		if (retval)
> -			goto out;
> -	}
> -	retval = 0;
> -out:
> -	return retval;
> -}
> -
> -static int __init init_aout_binfmt(void)
> -{
> -	register_binfmt(&aout_format);
> -	return 0;
> -}
> -
> -static void __exit exit_aout_binfmt(void)
> -{
> -	unregister_binfmt(&aout_format);
> -}
> -
> -module_init(init_aout_binfmt);
> -module_exit(exit_aout_binfmt);
> -MODULE_LICENSE("GPL");
> --
> 2.29.2

Re: [PATCH] x86: Remove a.out support

[James Jones]

On 3/12/22 9:54 AM, James Jones wrote:
>> From: Borislav Petkov <bp@suse.de>
>>
>> Commit
>>
>>    eac616557050 ("x86: Deprecate a.out support")
>>
>> deprecated a.out support with the promise to remove it a couple of
>> releases later. That commit landed in v5.1.
>>
>> Now it is more than a couple of releases later, no one has complained so
>> remove it.
>
> Sorry for taking so long to complain, but I have been meaning to note
> that I and a few others are still using a.out. I saw it go by in my
> morning Google news skim that this went in, and figured it was now or
> never. The use case is running an old set of tools to build programs for
> the Atari Jaguar. Namely, Atari's assembler (mac) and linker (aln). The
> alternative is running windows versions in dosbox, or using some
> replacements that have been developed based on an even older,
> less-featureful version of the source code for mac and aln, but which
> still haven't managed to add back in all the features needed to build
> some programs or use the Atari debugging tools (Also available in a.out
> only).
>
> I've been running with a few local patches to fix the a.out build and
> add the Kconfig options back for the last year or so to enable this on a
> few of my machines, and it's been working fine. I know of at least one
> other person doing this. If the code itself and supporting
> syscalls/other code go away though, it'll probably become impractical.
> If others are open to it, I can share my small local patches along with
> a revert of this change. I'd also like to ask whether much is gained by
> deleting this code as far as reducing maintenance burden. It has
> survived nearly untouched since the deprecation notice and still works
> modulo a broken preprocessor macro in fs/exec.c.
>
> For the curious, or if anyone wants proof I'm not making this up and
> really do spend time on these things, my amalgamation of Jaguar tools &
> docs, including copies of the old mac and aln a.out binaries, is
> available here:
>
> https://github.com/cubanismo/jaguar-sdk

Apologies, fixing x86 maintainer alias address.

> Thanks,
> -James
>
>> Signed-off-by: Borislav Petkov <bp@suse.de>
>> ---
>>   arch/x86/Kconfig          |   7 -
>>   arch/x86/ia32/Makefile    |   2 -
>>   arch/x86/ia32/ia32_aout.c | 325 --------------------------------------
>>   3 files changed, 334 deletions(-)
>>   delete mode 100644 arch/x86/ia32/ia32_aout.c
>>
>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>> index 976dd6b532bf..6f3d63dbbddf 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -2835,13 +2835,6 @@ config IA32_EMULATION
>>   	  64-bit kernel. You should likely turn this on, unless you're
>>   	  100% sure that you don't have any 32-bit programs left.
>>
>> -config IA32_AOUT
>> -	tristate "IA32 a.out support"
>> -	depends on IA32_EMULATION
>> -	depends on BROKEN
>> -	help
>> -	  Support old a.out binaries in the 32bit emulation.
>> -
>>   config X86_X32
>>   	bool "x32 ABI for 64-bit mode"
>>   	depends on X86_64
>> diff --git a/arch/x86/ia32/Makefile b/arch/x86/ia32/Makefile
>> index 8e4d0391ff6c..e481056698de 100644
>> --- a/arch/x86/ia32/Makefile
>> +++ b/arch/x86/ia32/Makefile
>> @@ -5,7 +5,5 @@
>>
>>   obj-$(CONFIG_IA32_EMULATION) := ia32_signal.o
>>
>> -obj-$(CONFIG_IA32_AOUT) += ia32_aout.o
>> -
>>   audit-class-$(CONFIG_AUDIT) := audit.o
>>   obj-$(CONFIG_IA32_EMULATION) += $(audit-class-y)
>> diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
>> deleted file mode 100644
>> index 9bd15241fadb..000000000000
>> --- a/arch/x86/ia32/ia32_aout.c
>> +++ /dev/null
>> @@ -1,325 +0,0 @@
>> -// SPDX-License-Identifier: GPL-2.0-only
>> -/*
>> - *  a.out loader for x86-64
>> - *
>> - *  Copyright (C) 1991, 1992, 1996  Linus Torvalds
>> - *  Hacked together by Andi Kleen
>> - */
>> -
>> -#include <linux/module.h>
>> -
>> -#include <linux/time.h>
>> -#include <linux/kernel.h>
>> -#include <linux/mm.h>
>> -#include <linux/mman.h>
>> -#include <linux/a.out.h>
>> -#include <linux/errno.h>
>> -#include <linux/signal.h>
>> -#include <linux/string.h>
>> -#include <linux/fs.h>
>> -#include <linux/file.h>
>> -#include <linux/stat.h>
>> -#include <linux/fcntl.h>
>> -#include <linux/ptrace.h>
>> -#include <linux/user.h>
>> -#include <linux/binfmts.h>
>> -#include <linux/personality.h>
>> -#include <linux/init.h>
>> -#include <linux/jiffies.h>
>> -#include <linux/perf_event.h>
>> -#include <linux/sched/task_stack.h>
>> -
>> -#include <linux/uaccess.h>
>> -#include <asm/cacheflush.h>
>> -#include <asm/user32.h>
>> -#include <asm/ia32.h>
>> -
>> -#undef WARN_OLD
>> -
>> -static int load_aout_binary(struct linux_binprm *);
>> -static int load_aout_library(struct file *);
>> -
>> -static struct linux_binfmt aout_format = {
>> -	.module		= THIS_MODULE,
>> -	.load_binary	= load_aout_binary,
>> -	.load_shlib	= load_aout_library,
>> -};
>> -
>> -static int set_brk(unsigned long start, unsigned long end)
>> -{
>> -	start = PAGE_ALIGN(start);
>> -	end = PAGE_ALIGN(end);
>> -	if (end <= start)
>> -		return 0;
>> -	return vm_brk(start, end - start);
>> -}
>> -
>> -
>> -/*
>> - * create_aout_tables() parses the env- and arg-strings in new user
>> - * memory and creates the pointer tables from them, and puts their
>> - * addresses on the "stack", returning the new stack pointer value.
>> - */
>> -static u32 __user *create_aout_tables(char __user *p, struct linux_binprm *bprm)
>> -{
>> -	u32 __user *argv, *envp, *sp;
>> -	int argc = bprm->argc, envc = bprm->envc;
>> -
>> -	sp = (u32 __user *) ((-(unsigned long)sizeof(u32)) & (unsigned long) p);
>> -	sp -= envc+1;
>> -	envp = sp;
>> -	sp -= argc+1;
>> -	argv = sp;
>> -	put_user((unsigned long) envp, --sp);
>> -	put_user((unsigned long) argv, --sp);
>> -	put_user(argc, --sp);
>> -	current->mm->arg_start = (unsigned long) p;
>> -	while (argc-- > 0) {
>> -		char c;
>> -
>> -		put_user((u32)(unsigned long)p, argv++);
>> -		do {
>> -			get_user(c, p++);
>> -		} while (c);
>> -	}
>> -	put_user(0, argv);
>> -	current->mm->arg_end = current->mm->env_start = (unsigned long) p;
>> -	while (envc-- > 0) {
>> -		char c;
>> -
>> -		put_user((u32)(unsigned long)p, envp++);
>> -		do {
>> -			get_user(c, p++);
>> -		} while (c);
>> -	}
>> -	put_user(0, envp);
>> -	current->mm->env_end = (unsigned long) p;
>> -	return sp;
>> -}
>> -
>> -/*
>> - * These are the functions used to load a.out style executables and shared
>> - * libraries.  There is no binary dependent code anywhere else.
>> - */
>> -static int load_aout_binary(struct linux_binprm *bprm)
>> -{
>> -	unsigned long error, fd_offset, rlim;
>> -	struct pt_regs *regs = current_pt_regs();
>> -	struct exec ex;
>> -	int retval;
>> -
>> -	ex = *((struct exec *) bprm->buf);		/* exec-header */
>> -	if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
>> -	     N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
>> -	    N_TRSIZE(ex) || N_DRSIZE(ex) ||
>> -	    i_size_read(file_inode(bprm->file)) <
>> -	    ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
>> -		return -ENOEXEC;
>> -	}
>> -
>> -	fd_offset = N_TXTOFF(ex);
>> -
>> -	/* Check initial limits. This avoids letting people circumvent
>> -	 * size limits imposed on them by creating programs with large
>> -	 * arrays in the data or bss.
>> -	 */
>> -	rlim = rlimit(RLIMIT_DATA);
>> -	if (rlim >= RLIM_INFINITY)
>> -		rlim = ~0;
>> -	if (ex.a_data + ex.a_bss > rlim)
>> -		return -ENOMEM;
>> -
>> -	/* Flush all traces of the currently running executable */
>> -	retval = begin_new_exec(bprm);
>> -	if (retval)
>> -		return retval;
>> -
>> -	/* OK, This is the point of no return */
>> -	set_personality(PER_LINUX);
>> -	set_personality_ia32(false);
>> -
>> -	setup_new_exec(bprm);
>> -
>> -	regs->cs = __USER32_CS;
>> -	regs->r8 = regs->r9 = regs->r10 = regs->r11 = regs->r12 =
>> -		regs->r13 = regs->r14 = regs->r15 = 0;
>> -
>> -	current->mm->end_code = ex.a_text +
>> -		(current->mm->start_code = N_TXTADDR(ex));
>> -	current->mm->end_data = ex.a_data +
>> -		(current->mm->start_data = N_DATADDR(ex));
>> -	current->mm->brk = ex.a_bss +
>> -		(current->mm->start_brk = N_BSSADDR(ex));
>> -
>> -	retval = setup_arg_pages(bprm, IA32_STACK_TOP, EXSTACK_DEFAULT);
>> -	if (retval < 0)
>> -		return retval;
>> -
>> -	if (N_MAGIC(ex) == OMAGIC) {
>> -		unsigned long text_addr, map_size;
>> -
>> -		text_addr = N_TXTADDR(ex);
>> -		map_size = ex.a_text+ex.a_data;
>> -
>> -		error = vm_brk(text_addr & PAGE_MASK, map_size);
>> -
>> -		if (error)
>> -			return error;
>> -
>> -		error = read_code(bprm->file, text_addr, 32,
>> -				  ex.a_text + ex.a_data);
>> -		if ((signed long)error < 0)
>> -			return error;
>> -	} else {
>> -#ifdef WARN_OLD
>> -		static unsigned long error_time, error_time2;
>> -		if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
>> -		    (N_MAGIC(ex) != NMAGIC) &&
>> -				time_after(jiffies, error_time2 + 5*HZ)) {
>> -			printk(KERN_NOTICE "executable not page aligned\n");
>> -			error_time2 = jiffies;
>> -		}
>> -
>> -		if ((fd_offset & ~PAGE_MASK) != 0 &&
>> -			    time_after(jiffies, error_time + 5*HZ)) {
>> -			printk(KERN_WARNING
>> -			       "fd_offset is not page aligned. Please convert "
>> -			       "program: %pD\n",
>> -			       bprm->file);
>> -			error_time = jiffies;
>> -		}
>> -#endif
>> -
>> -		if (!bprm->file->f_op->mmap || (fd_offset & ~PAGE_MASK) != 0) {
>> -			error = vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
>> -			if (error)
>> -				return error;
>> -
>> -			read_code(bprm->file, N_TXTADDR(ex), fd_offset,
>> -					ex.a_text+ex.a_data);
>> -			goto beyond_if;
>> -		}
>> -
>> -		error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
>> -				PROT_READ | PROT_EXEC,
>> -				MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
>> -				fd_offset);
>> -
>> -		if (error != N_TXTADDR(ex))
>> -			return error;
>> -
>> -		error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
>> -				PROT_READ | PROT_WRITE | PROT_EXEC,
>> -				MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
>> -				fd_offset + ex.a_text);
>> -		if (error != N_DATADDR(ex))
>> -			return error;
>> -	}
>> -
>> -beyond_if:
>> -	error = set_brk(current->mm->start_brk, current->mm->brk);
>> -	if (error)
>> -		return error;
>> -
>> -	set_binfmt(&aout_format);
>> -
>> -	current->mm->start_stack =
>> -		(unsigned long)create_aout_tables((char __user *)bprm->p, bprm);
>> -	/* start thread */
>> -	loadsegment(fs, 0);
>> -	loadsegment(ds, __USER32_DS);
>> -	loadsegment(es, __USER32_DS);
>> -	load_gs_index(0);
>> -	(regs)->ip = ex.a_entry;
>> -	(regs)->sp = current->mm->start_stack;
>> -	(regs)->flags = 0x200;
>> -	(regs)->cs = __USER32_CS;
>> -	(regs)->ss = __USER32_DS;
>> -	regs->r8 = regs->r9 = regs->r10 = regs->r11 =
>> -	regs->r12 = regs->r13 = regs->r14 = regs->r15 = 0;
>> -	return 0;
>> -}
>> -
>> -static int load_aout_library(struct file *file)
>> -{
>> -	unsigned long bss, start_addr, len, error;
>> -	int retval;
>> -	struct exec ex;
>> -	loff_t pos = 0;
>> -
>> -	retval = -ENOEXEC;
>> -	error = kernel_read(file, &ex, sizeof(ex), &pos);
>> -	if (error != sizeof(ex))
>> -		goto out;
>> -
>> -	/* We come in here for the regular a.out style of shared libraries */
>> -	if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
>> -	    N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
>> -	    i_size_read(file_inode(file)) <
>> -	    ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
>> -		goto out;
>> -	}
>> -
>> -	if (N_FLAGS(ex))
>> -		goto out;
>> -
>> -	/* For  QMAGIC, the starting address is 0x20 into the page.  We mask
>> -	   this off to get the starting address for the page */
>> -
>> -	start_addr =  ex.a_entry & 0xfffff000;
>> -
>> -	if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
>> -#ifdef WARN_OLD
>> -		static unsigned long error_time;
>> -		if (time_after(jiffies, error_time + 5*HZ)) {
>> -			printk(KERN_WARNING
>> -			       "N_TXTOFF is not page aligned. Please convert "
>> -			       "library: %pD\n",
>> -			       file);
>> -			error_time = jiffies;
>> -		}
>> -#endif
>> -		retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
>> -		if (retval)
>> -			goto out;
>> -
>> -		read_code(file, start_addr, N_TXTOFF(ex),
>> -			  ex.a_text + ex.a_data);
>> -		retval = 0;
>> -		goto out;
>> -	}
>> -	/* Now use mmap to map the library into memory. */
>> -	error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
>> -			PROT_READ | PROT_WRITE | PROT_EXEC,
>> -			MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
>> -			N_TXTOFF(ex));
>> -	retval = error;
>> -	if (error != start_addr)
>> -		goto out;
>> -
>> -	len = PAGE_ALIGN(ex.a_text + ex.a_data);
>> -	bss = ex.a_text + ex.a_data + ex.a_bss;
>> -	if (bss > len) {
>> -		retval = vm_brk(start_addr + len, bss - len);
>> -		if (retval)
>> -			goto out;
>> -	}
>> -	retval = 0;
>> -out:
>> -	return retval;
>> -}
>> -
>> -static int __init init_aout_binfmt(void)
>> -{
>> -	register_binfmt(&aout_format);
>> -	return 0;
>> -}
>> -
>> -static void __exit exit_aout_binfmt(void)
>> -{
>> -	unregister_binfmt(&aout_format);
>> -}
>> -
>> -module_init(init_aout_binfmt);
>> -module_exit(exit_aout_binfmt);
>> -MODULE_LICENSE("GPL");
>> --
>> 2.29.2
>

Re: [PATCH] x86: Remove a.out support

[Borislav Petkov]

On Sat, Mar 12, 2022 at 06:06:26PM +0000, James Jones wrote:
> > Sorry for taking so long to complain, but I have been meaning to note
> > that I and a few others are still using a.out. I saw it go by in my
> > morning Google news skim that this went in, and figured it was now or
> > never. The use case is running an old set of tools to build programs for
> > the Atari Jaguar. Namely, Atari's assembler (mac) and linker (aln). The
> > alternative is running windows versions in dosbox, or using some
> > replacements that have been developed based on an even older,
> > less-featureful version of the source code for mac and aln, but which
> > still haven't managed to add back in all the features needed to build
> > some programs or use the Atari debugging tools (Also available in a.out
> > only).

Ok, for my own understanding only: you want to build those tools as
a.out binaries and run them on x86, correct?

Because wikipedia says that jaguar thing has a motorola m68k system
processor and looking at your makefile, you build some ancient gcc with
--target=m68k-aout so where does x86's a.out support come into play
here?

> > If others are open to it, I can share my small local patches along with
> > a revert of this change. I'd also like to ask whether much is gained by
> > deleting this code as far as reducing maintenance burden. It has
> > survived nearly untouched since the deprecation notice and still works
> > modulo a broken preprocessor macro in fs/exec.c.

I personally don't mind if you fix it up and take care of it going
forward, shouldn't be too much of a maintenance overhead - I'd just like
you to document somewhere in those files what is still using this so
that when you don't care for that project anymore or you stop needing
it for whatever reason, we can look up the URL and check whether we can
remove a.out support then.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH] x86: Remove a.out support

[James Jones]

On 3/13/22 4:56 AM, Borislav Petkov wrote:
> On Sat, Mar 12, 2022 at 06:06:26PM +0000, James Jones wrote:
>>> Sorry for taking so long to complain, but I have been meaning to note
>>> that I and a few others are still using a.out. I saw it go by in my
>>> morning Google news skim that this went in, and figured it was now or
>>> never. The use case is running an old set of tools to build programs for
>>> the Atari Jaguar. Namely, Atari's assembler (mac) and linker (aln). The
>>> alternative is running windows versions in dosbox, or using some
>>> replacements that have been developed based on an even older,
>>> less-featureful version of the source code for mac and aln, but which
>>> still haven't managed to add back in all the features needed to build
>>> some programs or use the Atari debugging tools (Also available in a.out
>>> only).
>
> Ok, for my own understanding only: you want to build those tools as
> a.out binaries and run them on x86, correct?

The 'mac' and 'aln' tools are only available as x86 a.out binaries. I
can't build them. They're in 'jaguar/bin/linux/[aln,mac]' in the
referenced jaguar-sdk project, along with a few others.

> Because wikipedia says that jaguar thing has a motorola m68k system
> processor and looking at your makefile, you build some ancient gcc with
> --target=m68k-aout so where does x86's a.out support come into play
> here?

Sorry for not being clearer. The 'mac' and 'aln' x86 a.out binaries
generate and consume m68k a.out object files. So if you want to use some
C code in addition to assembly listings, you'd use this separate m68k
a.out build of gcc (itself an ELF executable) to compile the C code to
object files, then link everything with 'aln'.

The real value of 'mac' and 'aln' though isn't their m68k support.
binutils can assemble and link that, as can the version of 'mac' and
'aln' that source is available for. These builds of 'mac' also support
the Jaguar's custom RISC instruction set, allowing you to add this RISC
code in the same assembly listings as the m68k code using a few
directives. This version of 'aln' has a few options to support
Jaguar-specific stuff as well.

This all probably seems absurd now, but note the newest version of these
tools was released in 1995, when Linux ELF support would have been brand
new. I don't know when the tools first shipped on Linux, but it would
have been a few years before that, so a.out would have been the only
option. It seems some Atari Jaguar developers were rather early Linux
adopters.

>>> If others are open to it, I can share my small local patches along with
>>> a revert of this change. I'd also like to ask whether much is gained by
>>> deleting this code as far as reducing maintenance burden. It has
>>> survived nearly untouched since the deprecation notice and still works
>>> modulo a broken preprocessor macro in fs/exec.c.
>
> I personally don't mind if you fix it up and take care of it going
> forward, shouldn't be too much of a maintenance overhead - I'd just like
> you to document somewhere in those files what is still using this so
> that when you don't care for that project anymore or you stop needing
> it for whatever reason, we can look up the URL and check whether we can
> remove a.out support then.

OK, will do. I appreciate the consideration.

-James

> Thx.
>
> --
> Regards/Gruss,
>      Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH] x86: Remove a.out support

[Borislav Petkov]

On Sun, Mar 13, 2022 at 06:26:31PM +0000, James Jones wrote:
> ...
> This all probably seems absurd now, but note the newest version of these
> tools was released in 1995, when Linux ELF support would have been brand
> new. I don't know when the tools first shipped on Linux, but it would
> have been a few years before that, so a.out would have been the only
> option. It seems some Atari Jaguar developers were rather early Linux
> adopters.

Ok, that explains it fine, thanks.

Please put that explanation in a text file somewhere in
Documentation/x86/ so that we know why we're keeping a.out support.

I'll zap the removing patch from the lineup now and you can send me your
fixes whenever you're ready.

If you're wondering on how to format them and what to do, we have it all
documented in Documentation/process/. I'd especially suggest reading
Documentation/process/submitting-patches.rst

HTH.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH] x86: Remove a.out support

[Kees Cook]

On Sat, Mar 12, 2022 at 06:06:26PM +0000, James Jones wrote:
> [...]
> > docs, including copies of the old mac and aln a.out binaries, is
> > available here:
> >
> > https://github.com/cubanismo/jaguar-sdk

Do these end up requiring libc4, etc? I see "uselib" syscalls in the
disassembly...

$ for i in $(objdump -b binary -D -m i386 aln mac | grep -B4 'int.*$0x80' \
	| grep -E 'int|eax' | grep mov | awk '{print $8}' | cut -d, -f1 \
	| cut -c2- | sort -u); do printf "%d\n" $i; done | sort -n
1       exit
3       read
4       write
5       open
6       close
10      unlink
13      time
19      lseek
20      getpid
37      kill
45      brk
54      ioctl
55      fcntl
86      uselib
89      readdir
91      munmap
106     stat
107     lstat
108     fstat
126     sigprocmask

It seems like it should be possible to create an ELF wrapper for simple
a.out binaries...

-- 
Kees Cook

Re: [PATCH] x86: Remove a.out support

[James Jones]

On 3/15/22 12:51 PM, Kees Cook wrote:
> On Sat, Mar 12, 2022 at 06:06:26PM +0000, James Jones wrote:
>> [...]
>>> docs, including copies of the old mac and aln a.out binaries, is
>>> available here:
>>>
>>> https://github.com/cubanismo/jaguar-sdk
>
> Do these end up requiring libc4, etc? I see "uselib" syscalls in the
> disassembly...
>
> $ for i in $(objdump -b binary -D -m i386 aln mac | grep -B4 'int.*$0x80' \
> 	| grep -E 'int|eax' | grep mov | awk '{print $8}' | cut -d, -f1 \
> 	| cut -c2- | sort -u); do printf "%d\n" $i; done | sort -n
> 1       exit
> 3       read
> 4       write
> 5       open
> 6       close
> 10      unlink
> 13      time
> 19      lseek
> 20      getpid
> 37      kill
> 45      brk
> 54      ioctl
> 55      fcntl
> 86      uselib
> 89      readdir
> 91      munmap
> 106     stat
> 107     lstat
> 108     fstat
> 126     sigprocmask
>
> It seems like it should be possible to create an ELF wrapper for simple
> a.out binaries...

I didn't need to dig up any ancient libraries to get these working. They
seem to be completely statically linked.

Probably getting a bit off topic, but I did spend a few hours searching
around for any existing tools to convert a binary from a.out->ELF, and
trying to come up with something myself by extracting the sections with
objdump and re-combining them into an ELF using a linker script placing
the sections at the same locations. I couldn't get it working in an
evening or two messing with it so I moved on, but I agree something like
this seems possible in theory. I got 'mac' converted to an ELF that
would load up and print its input prompt if run without parameters, but
only if run as root. As a regular user, it segfaults somewhere before it
even starts executing in the text section AFAICT. Any actual assembling
segfaults even when running as root. I never got 'aln' to do anything
but segfault.

I dug the scripts up in the state they were in when I gave up (September
2020 according to mtime), and put them on github in case anyone wants to
have a go at it:

https://github.com/cubanismo/aout-to-elf/

It was an interesting problem in its own right, and I'd be curious to
know what I missed.

Thanks,
-James

> --
> Kees Cook

Re: [PATCH] x86: Remove a.out support

[Arnd Bergmann]

On Wed, Mar 16, 2022 James Jones <linux@theinnocuous.com> wrote:
> On 3/15/22 12:51 PM, Kees Cook wrote:
>
> Probably getting a bit off topic, but I did spend a few hours searching
> around for any existing tools to convert a binary from a.out->ELF, and
> trying to come up with something myself by extracting the sections with
> objdump and re-combining them into an ELF using a linker script placing
> the sections at the same locations. I couldn't get it working in an
> evening or two messing with it so I moved on, but I agree something like
> this seems possible in theory. I got 'mac' converted to an ELF that
> would load up and print its input prompt if run without parameters, but
> only if run as root. As a regular user, it segfaults somewhere before it
> even starts executing in the text section AFAICT. Any actual assembling
> segfaults even when running as root. I never got 'aln' to do anything
> but segfault.
>
> I dug the scripts up in the state they were in when I gave up (September
> 2020 according to mtime), and put them on github in case anyone wants to
> have a go at it:
>
> https://github.com/cubanismo/aout-to-elf/
>
> It was an interesting problem in its own right, and I'd be curious to
> know what I missed.

I noticed that qemu-user has code to run the two other native binary
formats (elf and flat) that the kernel supports, in
https://github.com/qemu/qemu/blob/master/linux-user/linuxload.c

The qemu code is fairly close to the kernel version it is derived
from, and the a.out loader in the kernel is the simplest of those.

If performance is not overly important, I think it should be possible
to turn the Linux binfmt_aout.c code into something that works
in qemu, allowing you to run these executables through CPU
emulation on any architecture. No idea how much work this
is in the end, but it's likely easier than a standalone a.out loader
in user space, or a conversion to ELF format.

       Arnd

Re: [PATCH] x86: Remove a.out support

[Kees Cook]

On Wed, Mar 16, 2022 at 01:38:31PM +0100, Arnd Bergmann wrote:
> is in the end, but it's likely easier than a standalone a.out loader
> in user space, or a conversion to ELF format.

Yeah, the exec format is really simple. The only tricky bit was preparing
the stack and making sure everything landed in the right place for text
and data. James, can you try this? aln and mac run for me, but I'm not
actually exercising them beyond dumping argument lists, etc:

https://github.com/kees/kernel-tools/tree/trunk/a.out

$ make
cc -Wall -m32    aout.c   -o aout
$ ./aout aln --help
mmap: Operation not permitted
/proc/sys/vm/mmap_min_addr is set to 65536 but QMAGIC a.out binaries must be mapped at 4096.
To temporarily change this, run: sudo sysctl -w vm.mmap_min_addr=4096
$ sudo sysctl -w vm.mmap_min_addr=4096
vm.mmap_min_addr = 4096
$ ./aout aln --help
aln: unrecognized option `--help'
Usage: aln [-options] <files|-x file|-i[i] <fname> <label>>
Where options are:
?: print this
a <text> <data> <bss>: output absolute file
        hex value: segment address
        r: relocatable segment
        x: contiguous segment
...



/*
 * Execute a static QMAGIC ia32 a.out binary.
 * Copyright 2022 Kees Cook <keescook@chromium.org>
 * License: GPLv2
 */
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <string.h>
#include <sys/time.h>
#include <sys/resource.h>

/* Locally define the stuff from a.out.h since that file may disappear. */
struct a_out
{
	unsigned int a_info;	/* machine type, magic, etc */
	unsigned int a_text;	/* text size */
	unsigned int a_data;	/* data size */
	unsigned int a_bss;	/* desired bss size */
	unsigned int a_syms;	/* symbol table size */
	unsigned int a_entry;	/* entry address */
	unsigned int a_trsize;	/* text relocation size */
	unsigned int a_drsize;	/* data relocation size */
};

#define Q_MAGIC_LOAD_ADDR	0x1000
#define MMAP_MIN_ADDR_PATH	"/proc/sys/vm/mmap_min_addr"

#define ALIGN(x, a)		ALIGN_MASK(x, (unsigned long)(a) - 1)
#define ALIGN_MASK(x, mask)	(typeof(x))(((unsigned long)(x) + (mask)) & ~(mask))

static void check_mmap_min_addr(void)
{
	unsigned long addr;
	char buf[128], *result;
	FILE *proc;

	proc = fopen(MMAP_MIN_ADDR_PATH, "r");
	if (!proc)
		return;
	result = fgets(buf, sizeof(buf), proc);
	fclose(proc);
	if (!result)
		return;

	addr = strtoul(result, NULL, 0);
	if (addr <= Q_MAGIC_LOAD_ADDR)
		return;

	fprintf(stderr, "%s is set to %lu but QMAGIC a.out binaries must be mapped at %u.\n",
		MMAP_MIN_ADDR_PATH, addr, Q_MAGIC_LOAD_ADDR);
	fprintf(stderr, "To temporarily change this, run: sudo sysctl -w vm.mmap_min_addr=%u\n",
		Q_MAGIC_LOAD_ADDR);
}

int main(int argc, char *argv[], char *envp[])
{
	const unsigned long qmagic = 0x006400cc;
	struct a_out *aout;
	struct stat info;
	unsigned char *image, *image_end, *bss, *bss_end, *stack, *stack_end;
	char **p;
	unsigned long *sp;
	struct rlimit rlim;
	int pagesize;
	int fd;
	int argc_copy, envc_copy;
	char **argv_copy, **envp_copy;

	if (sizeof(void *) != 4) {
		fprintf(stderr, "Eek: I was compiled in 64-bit mode. Please build with -m32.\n");
		return 1;
	}

	if (argc < 2) {
		fprintf(stderr, "Usage: %s a.out [arg ...]\n", argv[0]);
		return 1;
	}

	fd = open(argv[1], O_RDONLY);
	if (fd < 0) {
		perror(argv[1]);
		return 1;
	}

	if (fstat(fd, &info) < 0) {
		perror(argv[1]);
		return 1;
	}

	if (info.st_size < sizeof(*aout)) {
		fprintf(stderr, "%s: too small to read a.out header\n", argv[1]);
		return 1;
	}

	/* Load file into memory at Q_MAGIC_LOAD_ADDR. */
	pagesize = getpagesize();
	image = mmap((void *)Q_MAGIC_LOAD_ADDR, info.st_size, PROT_EXEC | PROT_READ | PROT_WRITE,
			MAP_FIXED | MAP_PRIVATE, fd, 0);
	if (image == MAP_FAILED) {
		perror("mmap");
		check_mmap_min_addr();
		return 1;
	}
	image_end = ALIGN(image + info.st_size, pagesize);

	aout = (struct a_out *)image;
	if (aout->a_info != qmagic) {
		fprintf(stderr, "%s: not ia32 QMAGIC a.out binary (header 0x%x != expected 0x%lx)\n",
			argv[1], aout->a_info, qmagic);
		return 1;
	}

	if (aout->a_syms != 0) {
		fprintf(stderr, "%s: a.out header a_syms must be 0.\n", argv[1]);
		return 1;
	}

	if (aout->a_trsize != 0) {
		fprintf(stderr, "%s: a.out header a_trsize must be 0.\n", argv[1]);
		return 1;
	}

	if (aout->a_drsize != 0) {
		fprintf(stderr, "%s: a.out header a_drsize must be 0.\n", argv[1]);
		return 1;
	}

	/* See if .bss needs to extend beyond end of the file mmap. */
	bss = image + aout->a_text + aout->a_data;
	bss_end = bss + aout->a_bss;
	if (bss_end > image_end) {
		bss = mmap(bss, aout->a_bss, PROT_READ | PROT_WRITE,
			   MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
		if (bss == MAP_FAILED) {
			perror("mmap bss");
			return 1;
		}
	}
	/* Zero out .bss. */
	memset(bss, 0, ALIGN(aout->a_bss, pagesize));

	/* Prepare stack, based on current stack. */
	if (getrlimit(RLIMIT_STACK, &rlim) < 0) {
		perror("getrlimit");
		return 1;
	}

	/* Default to 8MiB */
	if (rlim.rlim_cur == RLIM_INFINITY)
		rlim.rlim_cur = 8 * 1024 * 1024;

	stack = mmap(NULL, rlim.rlim_cur, PROT_EXEC | PROT_READ | PROT_WRITE,
			MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
	if (stack == MAP_FAILED) {
		perror("mmap stack");
		return 1;
	}
	stack_end = ALIGN(stack + rlim.rlim_cur, pagesize);

	/* Fill top of stack with arg/env pointers. */
	sp = (unsigned long *)stack_end;
	sp--;

	/* do not include argv[0] */
	argc_copy = argc - 1;
	argv++;

	/* count envp */
	for (envc_copy = 0, p = envp; *p; envc_copy++, p++) ;

	/* make room for envp pointers */
	sp -= envc_copy + 1;
	envp_copy = (char **)sp;
	/* make room for argv pointers */
	sp -= argc_copy + 1;
	argv_copy = (char **)sp;

	/* store pointers and argc */
	*--sp = (unsigned long)envp_copy;
	*--sp = (unsigned long)argv_copy;
	*--sp = (unsigned long)argc_copy;

	/* copy argv pointer (contents can stay where they already are) */
	while (argc_copy--)
		*argv_copy++ = *argv++;
	*argv_copy = 0;

	/* copy envp (contents can stay where they already are) */
	while (envc_copy--)
		*envp_copy++ = *envp++;

	/* Aim sp at argc, and jump! */
	asm volatile ("movl %0, %%esp\njmp *%1\n" : : "rm" (sp), "r"(aout->a_entry) );

	/* This should be unreachable. */
	fprintf(stderr, "They found me. I don't how, but they found me.\n");
	return 2;
}

-- 
Kees Cook

Re: [PATCH] x86: Remove a.out support

[James Jones]

On 3/16/22 3:30 PM, Kees Cook wrote:
> On Wed, Mar 16, 2022 at 01:38:31PM +0100, Arnd Bergmann wrote:
>> is in the end, but it's likely easier than a standalone a.out loader
>> in user space, or a conversion to ELF format.
>
> Yeah, the exec format is really simple. The only tricky bit was preparing
> the stack and making sure everything landed in the right place for text
> and data. James, can you try this? aln and mac run for me, but I'm not
> actually exercising them beyond dumping argument lists, etc:
>
> https://github.com/kees/kernel-tools/tree/trunk/a.out

Yes, works perfectly, thank you. I like the idea of using this much
better than getting emailed every time someone wants to delete the a.out
code again. Consider my use case withdrawn. I've already pushed an
update to my jaguar-sdk project to use this tool instead.

-James

> $ make
> cc -Wall -m32    aout.c   -o aout
> $ ./aout aln --help
> mmap: Operation not permitted
> /proc/sys/vm/mmap_min_addr is set to 65536 but QMAGIC a.out binaries must be mapped at 4096.
> To temporarily change this, run: sudo sysctl -w vm.mmap_min_addr=4096
> $ sudo sysctl -w vm.mmap_min_addr=4096
> vm.mmap_min_addr = 4096
> $ ./aout aln --help
> aln: unrecognized option `--help'
> Usage: aln [-options] <files|-x file|-i[i] <fname> <label>>
> Where options are:
> ?: print this
> a <text> <data> <bss>: output absolute file
>          hex value: segment address
>          r: relocatable segment
>          x: contiguous segment
> ...
>
>
>
> /*
>   * Execute a static QMAGIC ia32 a.out binary.
>   * Copyright 2022 Kees Cook <keescook@chromium.org>
>   * License: GPLv2
>   */
> #include <stdint.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <unistd.h>
> #include <sys/mman.h>
> #include <string.h>
> #include <sys/time.h>
> #include <sys/resource.h>
>
> /* Locally define the stuff from a.out.h since that file may disappear. */
> struct a_out
> {
> 	unsigned int a_info;	/* machine type, magic, etc */
> 	unsigned int a_text;	/* text size */
> 	unsigned int a_data;	/* data size */
> 	unsigned int a_bss;	/* desired bss size */
> 	unsigned int a_syms;	/* symbol table size */
> 	unsigned int a_entry;	/* entry address */
> 	unsigned int a_trsize;	/* text relocation size */
> 	unsigned int a_drsize;	/* data relocation size */
> };
>
> #define Q_MAGIC_LOAD_ADDR	0x1000
> #define MMAP_MIN_ADDR_PATH	"/proc/sys/vm/mmap_min_addr"
>
> #define ALIGN(x, a)		ALIGN_MASK(x, (unsigned long)(a) - 1)
> #define ALIGN_MASK(x, mask)	(typeof(x))(((unsigned long)(x) + (mask)) & ~(mask))
>
> static void check_mmap_min_addr(void)
> {
> 	unsigned long addr;
> 	char buf[128], *result;
> 	FILE *proc;
>
> 	proc = fopen(MMAP_MIN_ADDR_PATH, "r");
> 	if (!proc)
> 		return;
> 	result = fgets(buf, sizeof(buf), proc);
> 	fclose(proc);
> 	if (!result)
> 		return;
>
> 	addr = strtoul(result, NULL, 0);
> 	if (addr <= Q_MAGIC_LOAD_ADDR)
> 		return;
>
> 	fprintf(stderr, "%s is set to %lu but QMAGIC a.out binaries must be mapped at %u.\n",
> 		MMAP_MIN_ADDR_PATH, addr, Q_MAGIC_LOAD_ADDR);
> 	fprintf(stderr, "To temporarily change this, run: sudo sysctl -w vm.mmap_min_addr=%u\n",
> 		Q_MAGIC_LOAD_ADDR);
> }
>
> int main(int argc, char *argv[], char *envp[])
> {
> 	const unsigned long qmagic = 0x006400cc;
> 	struct a_out *aout;
> 	struct stat info;
> 	unsigned char *image, *image_end, *bss, *bss_end, *stack, *stack_end;
> 	char **p;
> 	unsigned long *sp;
> 	struct rlimit rlim;
> 	int pagesize;
> 	int fd;
> 	int argc_copy, envc_copy;
> 	char **argv_copy, **envp_copy;
>
> 	if (sizeof(void *) != 4) {
> 		fprintf(stderr, "Eek: I was compiled in 64-bit mode. Please build with -m32.\n");
> 		return 1;
> 	}
>
> 	if (argc < 2) {
> 		fprintf(stderr, "Usage: %s a.out [arg ...]\n", argv[0]);
> 		return 1;
> 	}
>
> 	fd = open(argv[1], O_RDONLY);
> 	if (fd < 0) {
> 		perror(argv[1]);
> 		return 1;
> 	}
>
> 	if (fstat(fd, &info) < 0) {
> 		perror(argv[1]);
> 		return 1;
> 	}
>
> 	if (info.st_size < sizeof(*aout)) {
> 		fprintf(stderr, "%s: too small to read a.out header\n", argv[1]);
> 		return 1;
> 	}
>
> 	/* Load file into memory at Q_MAGIC_LOAD_ADDR. */
> 	pagesize = getpagesize();
> 	image = mmap((void *)Q_MAGIC_LOAD_ADDR, info.st_size, PROT_EXEC | PROT_READ | PROT_WRITE,
> 			MAP_FIXED | MAP_PRIVATE, fd, 0);
> 	if (image == MAP_FAILED) {
> 		perror("mmap");
> 		check_mmap_min_addr();
> 		return 1;
> 	}
> 	image_end = ALIGN(image + info.st_size, pagesize);
>
> 	aout = (struct a_out *)image;
> 	if (aout->a_info != qmagic) {
> 		fprintf(stderr, "%s: not ia32 QMAGIC a.out binary (header 0x%x != expected 0x%lx)\n",
> 			argv[1], aout->a_info, qmagic);
> 		return 1;
> 	}
>
> 	if (aout->a_syms != 0) {
> 		fprintf(stderr, "%s: a.out header a_syms must be 0.\n", argv[1]);
> 		return 1;
> 	}
>
> 	if (aout->a_trsize != 0) {
> 		fprintf(stderr, "%s: a.out header a_trsize must be 0.\n", argv[1]);
> 		return 1;
> 	}
>
> 	if (aout->a_drsize != 0) {
> 		fprintf(stderr, "%s: a.out header a_drsize must be 0.\n", argv[1]);
> 		return 1;
> 	}
>
> 	/* See if .bss needs to extend beyond end of the file mmap. */
> 	bss = image + aout->a_text + aout->a_data;
> 	bss_end = bss + aout->a_bss;
> 	if (bss_end > image_end) {
> 		bss = mmap(bss, aout->a_bss, PROT_READ | PROT_WRITE,
> 			   MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
> 		if (bss == MAP_FAILED) {
> 			perror("mmap bss");
> 			return 1;
> 		}
> 	}
> 	/* Zero out .bss. */
> 	memset(bss, 0, ALIGN(aout->a_bss, pagesize));
>
> 	/* Prepare stack, based on current stack. */
> 	if (getrlimit(RLIMIT_STACK, &rlim) < 0) {
> 		perror("getrlimit");
> 		return 1;
> 	}
>
> 	/* Default to 8MiB */
> 	if (rlim.rlim_cur == RLIM_INFINITY)
> 		rlim.rlim_cur = 8 * 1024 * 1024;
>
> 	stack = mmap(NULL, rlim.rlim_cur, PROT_EXEC | PROT_READ | PROT_WRITE,
> 			MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
> 	if (stack == MAP_FAILED) {
> 		perror("mmap stack");
> 		return 1;
> 	}
> 	stack_end = ALIGN(stack + rlim.rlim_cur, pagesize);
>
> 	/* Fill top of stack with arg/env pointers. */
> 	sp = (unsigned long *)stack_end;
> 	sp--;
>
> 	/* do not include argv[0] */
> 	argc_copy = argc - 1;
> 	argv++;
>
> 	/* count envp */
> 	for (envc_copy = 0, p = envp; *p; envc_copy++, p++) ;
>
> 	/* make room for envp pointers */
> 	sp -= envc_copy + 1;
> 	envp_copy = (char **)sp;
> 	/* make room for argv pointers */
> 	sp -= argc_copy + 1;
> 	argv_copy = (char **)sp;
>
> 	/* store pointers and argc */
> 	*--sp = (unsigned long)envp_copy;
> 	*--sp = (unsigned long)argv_copy;
> 	*--sp = (unsigned long)argc_copy;
>
> 	/* copy argv pointer (contents can stay where they already are) */
> 	while (argc_copy--)
> 		*argv_copy++ = *argv++;
> 	*argv_copy = 0;
>
> 	/* copy envp (contents can stay where they already are) */
> 	while (envc_copy--)
> 		*envp_copy++ = *envp++;
>
> 	/* Aim sp at argc, and jump! */
> 	asm volatile ("movl %0, %%esp\njmp *%1\n" : : "rm" (sp), "r"(aout->a_entry) );
>
> 	/* This should be unreachable. */
> 	fprintf(stderr, "They found me. I don't how, but they found me.\n");
> 	return 2;
> }
>
> --
> Kees Cook

RE: [PATCH] x86: Remove a.out support

[David Laight]

From: James Jones
> Sent: 17 March 2022 02:05
> 
> On 3/16/22 3:30 PM, Kees Cook wrote:
> > On Wed, Mar 16, 2022 at 01:38:31PM +0100, Arnd Bergmann wrote:
> >> is in the end, but it's likely easier than a standalone a.out loader
> >> in user space, or a conversion to ELF format.
> >
> > Yeah, the exec format is really simple. The only tricky bit was preparing
> > the stack and making sure everything landed in the right place for text
> > and data. James, can you try this? aln and mac run for me, but I'm not
> > actually exercising them beyond dumping argument lists, etc:
> >
> > https://github.com/kees/kernel-tools/tree/trunk/a.out
> 
> Yes, works perfectly, thank you. I like the idea of using this much
> better than getting emailed every time someone wants to delete the a.out
> code again. Consider my use case withdrawn. I've already pushed an
> update to my jaguar-sdk project to use this tool instead.

Just every time the someone wants to delete the associated
system calls :-)

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH] x86: Remove a.out support

[Borislav Petkov]

On Thu, Mar 17, 2022 at 02:04:46AM +0000, James Jones wrote:
> Yes, works perfectly, thank you. I like the idea of using this much
> better than getting emailed every time someone wants to delete the a.out
> code again. Consider my use case withdrawn. I've already pushed an
> update to my jaguar-sdk project to use this tool instead.

Ok, pls do test this solution extensively and let us know if there are
other problems. I'll schedule a.out removal then for the next kernel so
you have a month or two time to experiment.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH] x86: Remove a.out support

[Kees Cook]

On Thu, Mar 17, 2022 at 02:04:46AM +0000, James Jones wrote:
> On 3/16/22 3:30 PM, Kees Cook wrote:
> > On Wed, Mar 16, 2022 at 01:38:31PM +0100, Arnd Bergmann wrote:
> >> is in the end, but it's likely easier than a standalone a.out loader
> >> in user space, or a conversion to ELF format.
> >
> > Yeah, the exec format is really simple. The only tricky bit was preparing
> > the stack and making sure everything landed in the right place for text
> > and data. James, can you try this? aln and mac run for me, but I'm not
> > actually exercising them beyond dumping argument lists, etc:
> >
> > https://github.com/kees/kernel-tools/tree/trunk/a.out
> 
> Yes, works perfectly, thank you. I like the idea of using this much

Hurray!

> better than getting emailed every time someone wants to delete the a.out
> code again. Consider my use case withdrawn. I've already pushed an
> update to my jaguar-sdk project to use this tool instead.

Nice; I see there are other binaries besides aln and mac that are
working with this too? *whew* I'm glad it was relatively straight
forward. :)

-- 
Kees Cook

RE: [PATCH] x86: Remove a.out support

[David Laight]

From: Kees Cook
> Sent: 16 March 2022 22:30
> 
> On Wed, Mar 16, 2022 at 01:38:31PM +0100, Arnd Bergmann wrote:
> > is in the end, but it's likely easier than a standalone a.out loader
> > in user space, or a conversion to ELF format.
> 
> Yeah, the exec format is really simple. The only tricky bit was preparing
> the stack and making sure everything landed in the right place for text
> and data. James, can you try this? aln and mac run for me, but I'm not
> actually exercising them beyond dumping argument lists, etc:

Doesn't that restrict the a.out program to the address space below
the normal base address for elf programs?
So you'll only be able to load small programs - which might be ok here.

OTOH it might be possible to link the 'loader program' to a high
address - the elf loader will probably just load it.
Best to link it static to avoid shared lib mmaps
and probably try to avoid libc calls.

I was wondering what happens when malloc() starts using
sbrk() - but I guess it sees the top of the bss for the
loaded and it all works fine.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH] x86: Remove a.out support

[Kees Cook]

On Thu, Mar 17, 2022 at 02:32:29AM +0000, David Laight wrote:
> From: Kees Cook
> > Sent: 16 March 2022 22:30
> > 
> > On Wed, Mar 16, 2022 at 01:38:31PM +0100, Arnd Bergmann wrote:
> > > is in the end, but it's likely easier than a standalone a.out loader
> > > in user space, or a conversion to ELF format.
> > 
> > Yeah, the exec format is really simple. The only tricky bit was preparing
> > the stack and making sure everything landed in the right place for text
> > and data. James, can you try this? aln and mac run for me, but I'm not
> > actually exercising them beyond dumping argument lists, etc:
> 
> Doesn't that restrict the a.out program to the address space below
> the normal base address for elf programs?
> So you'll only be able to load small programs - which might be ok here.
> 
> OTOH it might be possible to link the 'loader program' to a high
> address - the elf loader will probably just load it.
> Best to link it static to avoid shared lib mmaps
> and probably try to avoid libc calls.
> 
> I was wondering what happens when malloc() starts using
> sbrk() - but I guess it sees the top of the bss for the
> loaded and it all works fine.

I'll wait unless something breaks. :) Right now I just wanted to get aln
and mac working -- and that's a pretty small subset of all a.out
binaries. :)

-- 
Kees Cook

Re: [PATCH] x86: Remove a.out support

[Kees Cook]

On Wed, Mar 16, 2022 at 05:06:10AM +0000, James Jones wrote:
> I dug the scripts up in the state they were in when I gave up (September
> 2020 according to mtime), and put them on github in case anyone wants to
> have a go at it:
> 
> https://github.com/cubanismo/aout-to-elf/
> 
> It was an interesting problem in its own right, and I'd be curious to
> know what I missed.

Yeah, this is a good start. I think the main problem is with how program
entry works, specifically that %esp is pointing to argc (with all the
args in memory above there), which isn't the way ELF sets %esp.

It might be possible to make a userspace loader, though. Hmm.

-- 
Kees Cook

RE: [PATCH] x86: Remove a.out support

[David Laight]

From: Kees Cook
> Sent: 16 March 2022 16:11
> 
> On Wed, Mar 16, 2022 at 05:06:10AM +0000, James Jones wrote:
> > I dug the scripts up in the state they were in when I gave up (September
> > 2020 according to mtime), and put them on github in case anyone wants to
> > have a go at it:
> >
> > https://github.com/cubanismo/aout-to-elf/
> >
> > It was an interesting problem in its own right, and I'd be curious to
> > know what I missed.
> 
> Yeah, this is a good start. I think the main problem is with how program
> entry works, specifically that %esp is pointing to argc (with all the
> args in memory above there), which isn't the way ELF sets %esp.
> 
> It might be possible to make a userspace loader, though. Hmm.

Could it be fixed up by a small bit of code that the elf interpreter
runs just before jumping the a.out entry point?

Depending on the elf layout it might be enough to just reset %esp.
But if the strings are the wrong side of argv[] and enpv[] the
vectors themselves might need copying further down the stack.

Should be possible to do it as PIC code.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH] x86: Remove a.out support

[Maciej W. Rozycki]

On Wed, 16 Mar 2022, James Jones wrote:

> Probably getting a bit off topic, but I did spend a few hours searching
> around for any existing tools to convert a binary from a.out->ELF, and
> trying to come up with something myself by extracting the sections with
> objdump and re-combining them into an ELF using a linker script placing
> the sections at the same locations. I couldn't get it working in an
> evening or two messing with it so I moved on, but I agree something like
> this seems possible in theory.

 Chiming in late as I'm scanning outstanding mailing list traffic: if this 
is as you say all statically linked stuff, then converting from a.out to 
ELF might be as easy as:

$ objcopy -I a.out-i386-linux -O elf32-i386 a.out-binary elf-binary

though you may have to build yourself suitably old i386-linux-gnu binutils 
(from ftp.gnu.org), e.g. this version does support a.out:

$ objcopy --info
BFD header file version 2.15.91 20040527
elf32-i386
 (header little endian, data little endian)
  i386
a.out-i386-linux
 (header little endian, data little endian)
  i386
efi-app-ia32
 (header little endian, data little endian)
  i386
elf32-little
 (header little endian, data little endian)
  i386
elf32-big
 (header big endian, data big endian)
  i386
srec
 (header endianness unknown, data endianness unknown)
  i386
symbolsrec
 (header endianness unknown, data endianness unknown)
  i386
tekhex
 (header endianness unknown, data endianness unknown)
  i386
binary
 (header endianness unknown, data endianness unknown)
  i386
ihex
 (header endianness unknown, data endianness unknown)
  i386
trad-core
 (header endianness unknown, data endianness unknown)

               elf32-i386 a.out-i386-linux efi-app-ia32 elf32-little elf32-big 
          i386 elf32-i386 a.out-i386-linux efi-app-ia32 elf32-little elf32-big 

               srec symbolsrec tekhex binary ihex trad-core 
          i386 srec symbolsrec tekhex binary ihex --------- 

The last binutils version to support a.out-i386-linux was 2.30 I believe.  
Just configuring for i386-linux-gnu should do as a.out used to be included 
as a secondary BFD target (you can also do `--enable-targets=all' to get 
support for all kinds of the exotic and less exotic BFD targets).

 HTH,

  Maciej

Re: [PATCH] x86: Remove a.out support

[Kees Cook]

On April 2, 2022 3:14:43 PM PDT, "Maciej W. Rozycki" <macro@orcam.me.uk> wrote:
>On Wed, 16 Mar 2022, James Jones wrote:
>
>> Probably getting a bit off topic, but I did spend a few hours searching
>> around for any existing tools to convert a binary from a.out->ELF, and
>> trying to come up with something myself by extracting the sections with
>> objdump and re-combining them into an ELF using a linker script placing
>> the sections at the same locations. I couldn't get it working in an
>> evening or two messing with it so I moved on, but I agree something like
>> this seems possible in theory.
>
> Chiming in late as I'm scanning outstanding mailing list traffic: if this 
>is as you say all statically linked stuff, then converting from a.out to 
>ELF might be as easy as:
>
>$ objcopy -I a.out-i386-linux -O elf32-i386 a.out-binary elf-binary

Based on my research (and the wrapper I ended up writing), I don't think this is sufficient because entry point handling is different between ELF and a.out (specifically the stack layout and initial sp register value).

-Kees

-- 
Kees Cook

Re: [PATCH] x86: Remove a.out support

[Maciej W. Rozycki]

On Sat, 2 Apr 2022, Kees Cook wrote:

> > Chiming in late as I'm scanning outstanding mailing list traffic: if this 
> >is as you say all statically linked stuff, then converting from a.out to 
> >ELF might be as easy as:
> >
> >$ objcopy -I a.out-i386-linux -O elf32-i386 a.out-binary elf-binary
> 
> Based on my research (and the wrapper I ended up writing), I don't think 
> this is sufficient because entry point handling is different between ELF 
> and a.out (specifically the stack layout and initial sp register value).

 Fair enough.  I guess the exact value of %esp doesn't matter that much 
(why would it?), but the arguments and environment may well be structured 
differently (and indeed based on a glance over binfmt_aout.c there's extra 
indirection involved compared to the ELF i386 psABI).

  Maciej

RE: [PATCH] x86: Remove a.out support

[David Laight]

From: Maciej W. Rozycki
> Sent: 04 April 2022 12:04
> 
> On Sat, 2 Apr 2022, Kees Cook wrote:
> 
> > > Chiming in late as I'm scanning outstanding mailing list traffic: if this
> > >is as you say all statically linked stuff, then converting from a.out to
> > >ELF might be as easy as:
> > >
> > >$ objcopy -I a.out-i386-linux -O elf32-i386 a.out-binary elf-binary
> >
> > Based on my research (and the wrapper I ended up writing), I don't think
> > this is sufficient because entry point handling is different between ELF
> > and a.out (specifically the stack layout and initial sp register value).
> 
>  Fair enough.  I guess the exact value of %esp doesn't matter that much
> (why would it?), but the arguments and environment may well be structured
> differently (and indeed based on a glance over binfmt_aout.c there's extra
> indirection involved compared to the ELF i386 psABI).

You could write a custom 'elf interpreter'.
Hacking at those isn't for the faint-hearted :-)

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH] x86: Remove a.out support

[Kees Cook]

On Mon, Apr 04, 2022 at 05:07:11PM +0000, David Laight wrote:
> From: Maciej W. Rozycki
> > Sent: 04 April 2022 12:04
> > 
> > On Sat, 2 Apr 2022, Kees Cook wrote:
> > 
> > > > Chiming in late as I'm scanning outstanding mailing list traffic: if this
> > > >is as you say all statically linked stuff, then converting from a.out to
> > > >ELF might be as easy as:
> > > >
> > > >$ objcopy -I a.out-i386-linux -O elf32-i386 a.out-binary elf-binary
> > >
> > > Based on my research (and the wrapper I ended up writing), I don't think
> > > this is sufficient because entry point handling is different between ELF
> > > and a.out (specifically the stack layout and initial sp register value).
> > 
> >  Fair enough.  I guess the exact value of %esp doesn't matter that much
> > (why would it?), but the arguments and environment may well be structured
> > differently (and indeed based on a glance over binfmt_aout.c there's extra
> > indirection involved compared to the ELF i386 psABI).
> 
> You could write a custom 'elf interpreter'.
> Hacking at those isn't for the faint-hearted :-)

A thread on LWN pointed to:
https://github.com/siegfriedpammer/run-aout
which appears to be a much more complete a.out wrapper.

-- 
Kees Cook

Re: [PATCH] x86: Remove a.out support

[Geert Uytterhoeven]

On Sun, Apr 3, 2022 at 6:46 PM Maciej W. Rozycki <macro@orcam.me.uk> wrote:
> On Wed, 16 Mar 2022, James Jones wrote:
> > Probably getting a bit off topic, but I did spend a few hours searching
> > around for any existing tools to convert a binary from a.out->ELF, and
> > trying to come up with something myself by extracting the sections with
> > objdump and re-combining them into an ELF using a linker script placing
> > the sections at the same locations. I couldn't get it working in an
> > evening or two messing with it so I moved on, but I agree something like
> > this seems possible in theory.
>
>  Chiming in late as I'm scanning outstanding mailing list traffic: if this
> is as you say all statically linked stuff, then converting from a.out to
> ELF might be as easy as:

Probably, as https://lwn.net/Articles/889952/ claims dynamically linked
a.out was broken in v5.1.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

[PATCH] x86: Remove a.out support

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

Commit

  eac616557050 ("x86: Deprecate a.out support")

deprecated a.out support with the promise to remove it a couple of
releases later. That commit landed in v5.1.

Now it is more than a couple of releases later, no one has complained so
remove it.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/Kconfig          |   7 -
 arch/x86/ia32/Makefile    |   2 -
 arch/x86/ia32/ia32_aout.c | 325 --------------------------------------
 3 files changed, 334 deletions(-)
 delete mode 100644 arch/x86/ia32/ia32_aout.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 976dd6b532bf..6f3d63dbbddf 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2835,13 +2835,6 @@ config IA32_EMULATION
 	  64-bit kernel. You should likely turn this on, unless you're
 	  100% sure that you don't have any 32-bit programs left.
 
-config IA32_AOUT
-	tristate "IA32 a.out support"
-	depends on IA32_EMULATION
-	depends on BROKEN
-	help
-	  Support old a.out binaries in the 32bit emulation.
-
 config X86_X32
 	bool "x32 ABI for 64-bit mode"
 	depends on X86_64
diff --git a/arch/x86/ia32/Makefile b/arch/x86/ia32/Makefile
index 8e4d0391ff6c..e481056698de 100644
--- a/arch/x86/ia32/Makefile
+++ b/arch/x86/ia32/Makefile
@@ -5,7 +5,5 @@
 
 obj-$(CONFIG_IA32_EMULATION) := ia32_signal.o
 
-obj-$(CONFIG_IA32_AOUT) += ia32_aout.o
-
 audit-class-$(CONFIG_AUDIT) := audit.o
 obj-$(CONFIG_IA32_EMULATION) += $(audit-class-y)
diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
deleted file mode 100644
index 9bd15241fadb..000000000000
--- a/arch/x86/ia32/ia32_aout.c
+++ /dev/null
@@ -1,325 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- *  a.out loader for x86-64
- *
- *  Copyright (C) 1991, 1992, 1996  Linus Torvalds
- *  Hacked together by Andi Kleen
- */
-
-#include <linux/module.h>
-
-#include <linux/time.h>
-#include <linux/kernel.h>
-#include <linux/mm.h>
-#include <linux/mman.h>
-#include <linux/a.out.h>
-#include <linux/errno.h>
-#include <linux/signal.h>
-#include <linux/string.h>
-#include <linux/fs.h>
-#include <linux/file.h>
-#include <linux/stat.h>
-#include <linux/fcntl.h>
-#include <linux/ptrace.h>
-#include <linux/user.h>
-#include <linux/binfmts.h>
-#include <linux/personality.h>
-#include <linux/init.h>
-#include <linux/jiffies.h>
-#include <linux/perf_event.h>
-#include <linux/sched/task_stack.h>
-
-#include <linux/uaccess.h>
-#include <asm/cacheflush.h>
-#include <asm/user32.h>
-#include <asm/ia32.h>
-
-#undef WARN_OLD
-
-static int load_aout_binary(struct linux_binprm *);
-static int load_aout_library(struct file *);
-
-static struct linux_binfmt aout_format = {
-	.module		= THIS_MODULE,
-	.load_binary	= load_aout_binary,
-	.load_shlib	= load_aout_library,
-};
-
-static int set_brk(unsigned long start, unsigned long end)
-{
-	start = PAGE_ALIGN(start);
-	end = PAGE_ALIGN(end);
-	if (end <= start)
-		return 0;
-	return vm_brk(start, end - start);
-}
-
-
-/*
- * create_aout_tables() parses the env- and arg-strings in new user
- * memory and creates the pointer tables from them, and puts their
- * addresses on the "stack", returning the new stack pointer value.
- */
-static u32 __user *create_aout_tables(char __user *p, struct linux_binprm *bprm)
-{
-	u32 __user *argv, *envp, *sp;
-	int argc = bprm->argc, envc = bprm->envc;
-
-	sp = (u32 __user *) ((-(unsigned long)sizeof(u32)) & (unsigned long) p);
-	sp -= envc+1;
-	envp = sp;
-	sp -= argc+1;
-	argv = sp;
-	put_user((unsigned long) envp, --sp);
-	put_user((unsigned long) argv, --sp);
-	put_user(argc, --sp);
-	current->mm->arg_start = (unsigned long) p;
-	while (argc-- > 0) {
-		char c;
-
-		put_user((u32)(unsigned long)p, argv++);
-		do {
-			get_user(c, p++);
-		} while (c);
-	}
-	put_user(0, argv);
-	current->mm->arg_end = current->mm->env_start = (unsigned long) p;
-	while (envc-- > 0) {
-		char c;
-
-		put_user((u32)(unsigned long)p, envp++);
-		do {
-			get_user(c, p++);
-		} while (c);
-	}
-	put_user(0, envp);
-	current->mm->env_end = (unsigned long) p;
-	return sp;
-}
-
-/*
- * These are the functions used to load a.out style executables and shared
- * libraries.  There is no binary dependent code anywhere else.
- */
-static int load_aout_binary(struct linux_binprm *bprm)
-{
-	unsigned long error, fd_offset, rlim;
-	struct pt_regs *regs = current_pt_regs();
-	struct exec ex;
-	int retval;
-
-	ex = *((struct exec *) bprm->buf);		/* exec-header */
-	if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
-	     N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
-	    N_TRSIZE(ex) || N_DRSIZE(ex) ||
-	    i_size_read(file_inode(bprm->file)) <
-	    ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
-		return -ENOEXEC;
-	}
-
-	fd_offset = N_TXTOFF(ex);
-
-	/* Check initial limits. This avoids letting people circumvent
-	 * size limits imposed on them by creating programs with large
-	 * arrays in the data or bss.
-	 */
-	rlim = rlimit(RLIMIT_DATA);
-	if (rlim >= RLIM_INFINITY)
-		rlim = ~0;
-	if (ex.a_data + ex.a_bss > rlim)
-		return -ENOMEM;
-
-	/* Flush all traces of the currently running executable */
-	retval = begin_new_exec(bprm);
-	if (retval)
-		return retval;
-
-	/* OK, This is the point of no return */
-	set_personality(PER_LINUX);
-	set_personality_ia32(false);
-
-	setup_new_exec(bprm);
-
-	regs->cs = __USER32_CS;
-	regs->r8 = regs->r9 = regs->r10 = regs->r11 = regs->r12 =
-		regs->r13 = regs->r14 = regs->r15 = 0;
-
-	current->mm->end_code = ex.a_text +
-		(current->mm->start_code = N_TXTADDR(ex));
-	current->mm->end_data = ex.a_data +
-		(current->mm->start_data = N_DATADDR(ex));
-	current->mm->brk = ex.a_bss +
-		(current->mm->start_brk = N_BSSADDR(ex));
-
-	retval = setup_arg_pages(bprm, IA32_STACK_TOP, EXSTACK_DEFAULT);
-	if (retval < 0)
-		return retval;
-
-	if (N_MAGIC(ex) == OMAGIC) {
-		unsigned long text_addr, map_size;
-
-		text_addr = N_TXTADDR(ex);
-		map_size = ex.a_text+ex.a_data;
-
-		error = vm_brk(text_addr & PAGE_MASK, map_size);
-
-		if (error)
-			return error;
-
-		error = read_code(bprm->file, text_addr, 32,
-				  ex.a_text + ex.a_data);
-		if ((signed long)error < 0)
-			return error;
-	} else {
-#ifdef WARN_OLD
-		static unsigned long error_time, error_time2;
-		if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
-		    (N_MAGIC(ex) != NMAGIC) &&
-				time_after(jiffies, error_time2 + 5*HZ)) {
-			printk(KERN_NOTICE "executable not page aligned\n");
-			error_time2 = jiffies;
-		}
-
-		if ((fd_offset & ~PAGE_MASK) != 0 &&
-			    time_after(jiffies, error_time + 5*HZ)) {
-			printk(KERN_WARNING
-			       "fd_offset is not page aligned. Please convert "
-			       "program: %pD\n",
-			       bprm->file);
-			error_time = jiffies;
-		}
-#endif
-
-		if (!bprm->file->f_op->mmap || (fd_offset & ~PAGE_MASK) != 0) {
-			error = vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
-			if (error)
-				return error;
-
-			read_code(bprm->file, N_TXTADDR(ex), fd_offset,
-					ex.a_text+ex.a_data);
-			goto beyond_if;
-		}
-
-		error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
-				PROT_READ | PROT_EXEC,
-				MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
-				fd_offset);
-
-		if (error != N_TXTADDR(ex))
-			return error;
-
-		error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
-				PROT_READ | PROT_WRITE | PROT_EXEC,
-				MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
-				fd_offset + ex.a_text);
-		if (error != N_DATADDR(ex))
-			return error;
-	}
-
-beyond_if:
-	error = set_brk(current->mm->start_brk, current->mm->brk);
-	if (error)
-		return error;
-
-	set_binfmt(&aout_format);
-
-	current->mm->start_stack =
-		(unsigned long)create_aout_tables((char __user *)bprm->p, bprm);
-	/* start thread */
-	loadsegment(fs, 0);
-	loadsegment(ds, __USER32_DS);
-	loadsegment(es, __USER32_DS);
-	load_gs_index(0);
-	(regs)->ip = ex.a_entry;
-	(regs)->sp = current->mm->start_stack;
-	(regs)->flags = 0x200;
-	(regs)->cs = __USER32_CS;
-	(regs)->ss = __USER32_DS;
-	regs->r8 = regs->r9 = regs->r10 = regs->r11 =
-	regs->r12 = regs->r13 = regs->r14 = regs->r15 = 0;
-	return 0;
-}
-
-static int load_aout_library(struct file *file)
-{
-	unsigned long bss, start_addr, len, error;
-	int retval;
-	struct exec ex;
-	loff_t pos = 0;
-
-	retval = -ENOEXEC;
-	error = kernel_read(file, &ex, sizeof(ex), &pos);
-	if (error != sizeof(ex))
-		goto out;
-
-	/* We come in here for the regular a.out style of shared libraries */
-	if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
-	    N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
-	    i_size_read(file_inode(file)) <
-	    ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
-		goto out;
-	}
-
-	if (N_FLAGS(ex))
-		goto out;
-
-	/* For  QMAGIC, the starting address is 0x20 into the page.  We mask
-	   this off to get the starting address for the page */
-
-	start_addr =  ex.a_entry & 0xfffff000;
-
-	if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
-#ifdef WARN_OLD
-		static unsigned long error_time;
-		if (time_after(jiffies, error_time + 5*HZ)) {
-			printk(KERN_WARNING
-			       "N_TXTOFF is not page aligned. Please convert "
-			       "library: %pD\n",
-			       file);
-			error_time = jiffies;
-		}
-#endif
-		retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
-		if (retval)
-			goto out;
-
-		read_code(file, start_addr, N_TXTOFF(ex),
-			  ex.a_text + ex.a_data);
-		retval = 0;
-		goto out;
-	}
-	/* Now use mmap to map the library into memory. */
-	error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
-			PROT_READ | PROT_WRITE | PROT_EXEC,
-			MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
-			N_TXTOFF(ex));
-	retval = error;
-	if (error != start_addr)
-		goto out;
-
-	len = PAGE_ALIGN(ex.a_text + ex.a_data);
-	bss = ex.a_text + ex.a_data + ex.a_bss;
-	if (bss > len) {
-		retval = vm_brk(start_addr + len, bss - len);
-		if (retval)
-			goto out;
-	}
-	retval = 0;
-out:
-	return retval;
-}
-
-static int __init init_aout_binfmt(void)
-{
-	register_binfmt(&aout_format);
-	return 0;
-}
-
-static void __exit exit_aout_binfmt(void)
-{
-	unregister_binfmt(&aout_format);
-}
-
-module_init(init_aout_binfmt);
-module_exit(exit_aout_binfmt);
-MODULE_LICENSE("GPL");
-- 
2.29.2

Re: [PATCH] x86: Remove a.out support

[Kees Cook]

On Thu, Jan 13, 2022 at 05:01:15PM +0100, Borislav Petkov wrote:
> From: Borislav Petkov <bp@suse.de>
> 
> Commit
> 
>   eac616557050 ("x86: Deprecate a.out support")
> 
> deprecated a.out support with the promise to remove it a couple of
> releases later. That commit landed in v5.1.
> 
> Now it is more than a couple of releases later, no one has complained so
> remove it.
> 
> Signed-off-by: Borislav Petkov <bp@suse.de>

Yes please. :)

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH] x86: Remove a.out support

[Theodore Ts'o]

On Thu, Jan 13, 2022 at 05:01:15PM +0100, Borislav Petkov wrote:
> From: Borislav Petkov <bp@suse.de>
> 
> Commit
> 
>   eac616557050 ("x86: Deprecate a.out support")
> 
> deprecated a.out support with the promise to remove it a couple of
> releases later. That commit landed in v5.1.
> 
> Now it is more than a couple of releases later, no one has complained so
> remove it.
> 
> Signed-off-by: Borislav Petkov <bp@suse.de>

Let's pour one out for being able to run Minix binaries on Linux.  :-)

Speaking of which, if we're doing this, are there some old system
calls that we could remove at the same time?

      	       	       	     	  - Ted

Re: [PATCH] x86: Remove a.out support

[Borislav Petkov]

On Thu, Jan 13, 2022 at 01:47:34PM -0500, Theodore Ts'o wrote:
> Let's pour one out for being able to run Minix binaries on Linux.  :-)

https://en.wikipedia.org/wiki/Minix_3:

"2013-02-21 ... Dropped support for a.out binaries"

They themselves killed that support a lot earlier. :-)

> Speaking of which, if we're doing this, are there some old system
> calls that we could remove at the same time?

Good question.

Unfortunately, I'm just the janitor removing this and a.out is waaay
before my time. :-)

But I'm open to suggestions on how to determine which are those obsolete
syscalls.

Btw, pls do note that this is removing only the x86 a.out support -
other arches (m68k and alpha) still select HAVE_AOUT and thus the
respective glue in fs/binfmt_aout.c

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH] x86: Remove a.out support

[Theodore Ts'o]

On Thu, Jan 13, 2022 at 11:56:53PM +0100, Borislav Petkov wrote:
> On Thu, Jan 13, 2022 at 01:47:34PM -0500, Theodore Ts'o wrote:
> > Let's pour one out for being able to run Minix binaries on Linux.  :-)
> 
> https://en.wikipedia.org/wiki/Minix_3:
> 
> "2013-02-21 ... Dropped support for a.out binaries"
> 
> They themselves killed that support a lot earlier. :-)

Well, Minix 3 is a very different beast than the Minix 1.x that Linus
used when he was boot-strapping Linux back in 1991.  :-)

Among other things Minux 1.x is system call compatible with the
original V7 Unix from AT&T, whereas Minux 2.x and higher switch to
having system calls that were Posix comaptible --- and Minix 2, being
at teaching OS, wouldn't have kept any backwards compatibility when
Prof. Tannenbaum released the 2nd edition of his Operating Systems
Design and Implementation book in 1997.

> > Speaking of which, if we're doing this, are there some old system
> > calls that we could remove at the same time?
> 
> Good question.
> 
> Unfortunately, I'm just the janitor removing this and a.out is waaay
> before my time. :-)
> 
> But I'm open to suggestions on how to determine which are those obsolete
> syscalls.

Historically there were a couple of different C libraries
which x86 binaries for Linux could use:

A) minix's libc -- used by binaries compiled using the Minix 1 toolchain
B) Libc 4 -- a fork of GNU Libc version 1, for a.out execuables
C) Libc 5 -- a fork of GNU Libc version 1, for ELF execuables
D) Libc 6 -- GNU Libc version 2, for ELF executables

So I think what this would boil down to is finding those system calls
that were used by (A) and (B), but not referenced in (C) and (D).  I
guess we'd also have to check to make sure that some of these ancient
system calls might still be used by some of the micro libc's, such as
dietlibc, musl, etc.

Is it worth doing?  Perhaps; perhaps not.  It probably wouldn't reduce
the size of the kernel by all *that* much, but getting rid of cruft is
kind of a good thing for its own sake.

Cheers.

						- Ted

Re: [PATCH] x86: Remove a.out support

[Arnd Bergmann]

On Fri, Jan 14, 2022 at 5:06 AM Theodore Ts'o <tytso@mit.edu> wrote:
> On Thu, Jan 13, 2022 at 11:56:53PM +0100, Borislav Petkov wrote:
> >
> > But I'm open to suggestions on how to determine which are those obsolete
> > syscalls.
>
> Historically there were a couple of different C libraries
> which x86 binaries for Linux could use:
>
> A) minix's libc -- used by binaries compiled using the Minix 1 toolchain
> B) Libc 4 -- a fork of GNU Libc version 1, for a.out execuables
> C) Libc 5 -- a fork of GNU Libc version 1, for ELF execuables
> D) Libc 6 -- GNU Libc version 2, for ELF executables
>
> So I think what this would boil down to is finding those system calls
> that were used by (A) and (B), but not referenced in (C) and (D).  I
> guess we'd also have to check to make sure that some of these ancient
> system calls might still be used by some of the micro libc's, such as
> dietlibc, musl, etc.
>
> Is it worth doing?  Perhaps; perhaps not.  It probably wouldn't reduce
> the size of the kernel by all *that* much, but getting rid of cruft is
> kind of a good thing for its own sake.

For reference, these are the system calls that are implemented on i386
as of 5.16 but have been replaced on modern architectures, from
ooking only in the linux sources:

2 i386 fork sys_fork
5 i386 open sys_open compat_sys_open
7 i386 waitpid sys_waitpid
8 i386 creat sys_creat
9 i386 link sys_link
10 i386 unlink sys_unlink
13 i386 time sys_time32
14 i386 mknod sys_mknod
15 i386 chmod sys_chmod
16 i386 lchown sys_lchown16
16 i386 lchown sys_lchown16
18 i386 oldstat sys_stat
22 i386 umount sys_oldumount
23 i386 setuid sys_setuid16
24 i386 getuid sys_getuid16
25 i386 stime sys_stime32
27 i386 alarm sys_alarm
28 i386 oldfstat sys_fstat
29 i386 pause sys_pause
30 i386 utime sys_utime32
33 i386 access sys_access
34 i386 nice sys_nice
38 i386 rename sys_rename
39 i386 mkdir sys_mkdir
40 i386 rmdir sys_rmdir
42 i386 pipe sys_pipe
46 i386 setgid sys_setgid16
47 i386 getgid sys_getgid16
48 i386 signal sys_signal
49 i386 geteuid sys_geteuid16
50 i386 getegid sys_getegid16
59 i386 oldolduname sys_olduname
62 i386 ustat sys_ustat compat_sys_ustat
63 i386 dup2 sys_dup2
65 i386 getpgrp sys_getpgrp
67 i386 sigaction sys_sigaction compat_sys_sigaction
68 i386 sgetmask sys_sgetmask
69 i386 ssetmask sys_ssetmask
70 i386 setreuid sys_setreuid16
71 i386 setregid sys_setregid16
72 i386 sigsuspend sys_sigsuspend
73 i386 sigpending sys_sigpending compat_sys_sigpending
80 i386 getgroups sys_getgroups16
81 i386 setgroups sys_setgroups16
82 i386 select sys_old_select compat_sys_old_select
83 i386 symlink sys_symlink
84 i386 oldlstat sys_lstat
85 i386 readlink sys_readlink
86 i386 uselib sys_uselib
89 i386 readdir sys_old_readdir compat_sys_old_readdir
95 i386 fchown sys_fchown16
101 i386 ioperm sys_ioperm
102 i386 socketcall sys_socketcall compat_sys_socketcall
109 i386 olduname sys_uname
110 i386 iopl sys_iopl
117 i386 ipc sys_ipc compat_sys_ipc
119 i386 sigreturn sys_sigreturn compat_sys_sigreturn
123 i386 modify_ldt sys_modify_ldt
126 i386 sigprocmask sys_sigprocmask compat_sys_sigprocmask
135 i386 sysfs sys_sysfs
138 i386 setfsuid sys_setfsuid16
139 i386 setfsgid sys_setfsgid16
141 i386 getdents sys_getdents compat_sys_getdents
142 i386 _newselect sys_select compat_sys_select
164 i386 setresuid sys_setresuid16
165 i386 getresuid sys_getresuid16
168 i386 poll sys_poll
170 i386 setresgid sys_setresgid16
171 i386 getresgid sys_getresgid
182 i386 chown sys_chown16
190 i386 vfork sys_vfork
243 i386 set_thread_area sys_set_thread_area
244 i386 get_thread_area sys_get_thread_area
254 i386 epoll_create sys_epoll_create
256 i386 epoll_wait sys_epoll_wait
271 i386 utimes sys_utimes_time32
291 i386 inotify_init sys_inotify_init
299 i386 futimesat sys_futimesat_time32
321 i386 signalfd sys_signalfd compat_sys_signalfd
323 i386 eventfd sys_eventfd
384 i386 arch_prctl sys_arch_prctl compat_sys_arch_prctl

Looking at libc-4.7.2 from Slackware-3.0, the highest syscall number
used there is 182 (chown16), anything later is presumably added
after the ELF transition was done. All of the syscalls referenced in
libc-4.7 are still referenced in libc-5.0, so nothing is obviously changed
between those.

Excluding the syscalls that are referenced in libc5 brings the
candidates down to

7       i386    waitpid                 sys_waitpid
16      i386    lchown                  sys_lchown16
18      i386    oldstat                 sys_stat
28      i386    oldfstat                sys_fstat
48      i386    signal                  sys_signal
59      i386    oldolduname             sys_olduname
68      i386    sgetmask                sys_sgetmask
69      i386    ssetmask                sys_ssetmask
84      i386    oldlstat                sys_lstat
109     i386    olduname                sys_uname
119     i386    sigreturn               sys_sigreturn
123     i386    modify_ldt              sys_modify_ldt
135     i386    sysfs                   sys_sysfs
141     i386    getdents                sys_getdents
142     i386    _newselect              sys_select
164     i386    setresuid               sys_setresuid16
165     i386    getresuid               sys_getresuid16
168     i386    poll                    sys_poll
170     i386    setresgid               sys_setresgid16
171     i386    getresgid               sys_getresgid16

This is probably a mix of some things that are too old
for libc5, some that are too new, and some that were never
part of libc but are called from other places.

Some may be misrepresented here because the macros got
renamed: libc5 calls 'uname' but expects it to be what the
kernel now calls '__NR_olduname'. I could not find out
which of the 'stat' family it expects because the headers
are incomplete in the slackware source package.

       Arnd

Re: [PATCH] x86: Remove a.out support

[Borislav Petkov]

Just to answer the "do we still wanna support running original a.out
binaries" aspect...

On Thu, Jan 13, 2022 at 11:06:03PM -0500, Theodore Ts'o wrote:
> > > Let's pour one out for being able to run Minix binaries on Linux.  :-)
> > 
> > https://en.wikipedia.org/wiki/Minix_3:
> > 
> > "2013-02-21 ... Dropped support for a.out binaries"
> > 
> > They themselves killed that support a lot earlier. :-)
> 
> Well, Minix 3 is a very different beast than the Minix 1.x

Right, but if the Minix 1.x successor has deemed a.out support obsolete
and has removed in 2013 I figure we can too. :-)

And, btw, Alan had a good, practical idea at the time we talked about
deprecating a.out support:

https://lore.kernel.org/all/20190305134347.4be2449c@alans-desktop/

And that is probably the best thing to do: if people wanna run old a.out
binaries, they can either write an a.out loader as an ELF program or
slap an old linux distro in a VM and do that there just fine.

If you look at the original thread which started this:

https://lore.kernel.org/all/CAG48ez1RVd5mQ_Pb6eygQESaZhpQz765OAZYSoPE0kPqfZEXQg@mail.gmail.com/

it looked even back then like a.out support is so rusty, bitrotten and
broken that we're probably even doing ourselves a favor to remove it.

Especially if not even the toolchains would even create an a.out
executable and no one even noticed.

So...

> that Linus used when he was boot-strapping Linux back in 1991. :-)
>
> Among other things Minux 1.x is system call compatible with the
> original V7 Unix from AT&T, whereas Minux 2.x and higher switch to
> having system calls that were Posix comaptible --- and Minix 2, being
> at teaching OS, wouldn't have kept any backwards compatibility when
> Prof. Tannenbaum released the 2nd edition of his Operating Systems
> Design and Implementation book in 1997.

I had a lot of fun reading that book. :-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

RE: [PATCH] x86: Remove a.out support

[David Laight]

From: Borislav Petkov
> Sent: 13 January 2022 22:57
...
> 
> Btw, pls do note that this is removing only the x86 a.out support -
> other arches (m68k and alpha) still select HAVE_AOUT and thus the
> respective glue in fs/binfmt_aout.c

I didn't think alpha was that old :-)
m68k is another matter.
But I've probably dismembered the only old m68k system disk I've had
to extract the magnets.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH] x86: Remove a.out support

[Geert Uytterhoeven]

Hi Boris,

On Fri, Jan 14, 2022 at 3:36 PM Borislav Petkov <bp@alien8.de> wrote:
> Btw, pls do note that this is removing only the x86 a.out support -
> other arches (m68k and alpha) still select HAVE_AOUT and thus the
> respective glue in fs/binfmt_aout.c

Quoting myself (do I need a canned response for this? ;-):
   "I think it's safe to assume no one still runs a.out binaries on m68k."

https://lore.kernel.org/r/CAMuHMdVGT1QN8WUqNcU8ihPLncUGfrjV49wb-8nHUgHhOzLeNw@mail.gmail.com/
https://lore.kernel.org/r/CAMuHMdW+m0Q+j3rsQdMXnrEPm+XB5Y2AQrxW5sD1mZAKgmEqoA@mail.gmail.com

Of course, m68k is not encumbered by a.out Netscape binaries, unlike
ia32 and alpha ;-)

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] x86: Remove a.out support

[Theodore Ts'o]

On Fri, Jan 14, 2022 at 03:52:29PM +0100, Geert Uytterhoeven wrote:
> Hi Boris,
> 
> On Fri, Jan 14, 2022 at 3:36 PM Borislav Petkov <bp@alien8.de> wrote:
> > Btw, pls do note that this is removing only the x86 a.out support -
> > other arches (m68k and alpha) still select HAVE_AOUT and thus the
> > respective glue in fs/binfmt_aout.c
> 
> Quoting myself (do I need a canned response for this? ;-):
>    "I think it's safe to assume no one still runs a.out binaries on m68k."
> 
> https://lore.kernel.org/r/CAMuHMdVGT1QN8WUqNcU8ihPLncUGfrjV49wb-8nHUgHhOzLeNw@mail.gmail.com/
> https://lore.kernel.org/r/CAMuHMdW+m0Q+j3rsQdMXnrEPm+XB5Y2AQrxW5sD1mZAKgmEqoA@mail.gmail.com
> 
> Of course, m68k is not encumbered by a.out Netscape binaries, unlike
> ia32 and alpha ;-)

And Alpha's a.out Netscape binary is what required OSF/1 compatible
system calls, so if and when we ever can nuke a.out Alpha support, so
perhaps there might also be an opporunity to remove OSF/1
compatibility support...

						- Ted

Re: [PATCH] x86: Remove a.out support

[Geert Uytterhoeven]

Hi Ted,

On Fri, Jan 14, 2022 at 7:58 PM Theodore Ts'o <tytso@mit.edu> wrote:
> On Fri, Jan 14, 2022 at 03:52:29PM +0100, Geert Uytterhoeven wrote:
> > On Fri, Jan 14, 2022 at 3:36 PM Borislav Petkov <bp@alien8.de> wrote:
> > > Btw, pls do note that this is removing only the x86 a.out support -
> > > other arches (m68k and alpha) still select HAVE_AOUT and thus the
> > > respective glue in fs/binfmt_aout.c
> >
> > Quoting myself (do I need a canned response for this? ;-):
> >    "I think it's safe to assume no one still runs a.out binaries on m68k."
> >
> > https://lore.kernel.org/r/CAMuHMdVGT1QN8WUqNcU8ihPLncUGfrjV49wb-8nHUgHhOzLeNw@mail.gmail.com/
> > https://lore.kernel.org/r/CAMuHMdW+m0Q+j3rsQdMXnrEPm+XB5Y2AQrxW5sD1mZAKgmEqoA@mail.gmail.com
> >
> > Of course, m68k is not encumbered by a.out Netscape binaries, unlike
> > ia32 and alpha ;-)
>
> And Alpha's a.out Netscape binary is what required OSF/1 compatible
> system calls, so if and when we ever can nuke a.out Alpha support, so
> perhaps there might also be an opporunity to remove OSF/1
> compatibility support...

As we seem to be reiterating a discussion from 2019, let's read last
time's summary first:
https://www.linuxjournal.com/content/deprecating-aout-binaries

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] x86: Remove a.out support

[Borislav Petkov]

On Fri, Jan 14, 2022 at 03:52:29PM +0100, Geert Uytterhoeven wrote:
> Quoting myself (do I need a canned response for this? ;-):
>    "I think it's safe to assume no one still runs a.out binaries on m68k."

I remember now that I've looked at the thread from back then but what
are you trying to say with your quote?

Do you wanna see another patch which rips out a.out support from m68k?

I could do one ontop but besides build-testing I can't test any other
way on m68k...

:-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH] x86: Remove a.out support

[Geert Uytterhoeven]

Hi Boris,

On Fri, Jan 14, 2022 at 8:12 PM Borislav Petkov <bp@alien8.de> wrote:
> On Fri, Jan 14, 2022 at 03:52:29PM +0100, Geert Uytterhoeven wrote:
> > Quoting myself (do I need a canned response for this? ;-):
> >    "I think it's safe to assume no one still runs a.out binaries on m68k."
>
> I remember now that I've looked at the thread from back then but what
> are you trying to say with your quote?
>
> Do you wanna see another patch which rips out a.out support from m68k?
>
> I could do one ontop but besides build-testing I can't test any other
> way on m68k...
>
> :-)

I mean that I can rip it out on m68k.

Who's gonna take care of alpha?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] x86: Remove a.out support

[Borislav Petkov]

On Fri, Jan 14, 2022 at 08:21:36PM +0100, Geert Uytterhoeven wrote:
> I mean that I can rip it out on m68k.
> 
> Who's gonna take care of alpha?

I'm sceptical anyone would:

$ ./scripts/get_maintainer.pl -f arch/alpha/
Richard Henderson <rth@twiddle.net> (odd fixer:ALPHA PORT)
Ivan Kokshaysky <ink@jurassic.park.msu.ru> (odd fixer:ALPHA PORT)

which leaves me. I could give it a try.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH] x86: Remove a.out support

[Borislav Petkov]

On Fri, Jan 14, 2022 at 08:35:53PM +0100, Borislav Petkov wrote:
> On Fri, Jan 14, 2022 at 08:21:36PM +0100, Geert Uytterhoeven wrote:
> > I mean that I can rip it out on m68k.
> > 
> > Who's gonna take care of alpha?
> 
> I'm sceptical anyone would:
> 
> $ ./scripts/get_maintainer.pl -f arch/alpha/
> Richard Henderson <rth@twiddle.net> (odd fixer:ALPHA PORT)
> Ivan Kokshaysky <ink@jurassic.park.msu.ru> (odd fixer:ALPHA PORT)
> 
> which leaves me. I could give it a try.

Well, on that old thread from 2019 people expressed the wish to be able
to run a.out binaries on Alpha. Let's see whether that has changed in
the meantime.

/me CCs them.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCH] x86: Remove a.out support

[John Paul Adrian Glaubitz]

Hi Borislav!

On 1/15/22 12:37, Borislav Petkov wrote:
> On Fri, Jan 14, 2022 at 08:35:53PM +0100, Borislav Petkov wrote:
>> On Fri, Jan 14, 2022 at 08:21:36PM +0100, Geert Uytterhoeven wrote:
>>> I mean that I can rip it out on m68k.
>>>
>>> Who's gonna take care of alpha?
>>
>> I'm sceptical anyone would:
>>
>> $ ./scripts/get_maintainer.pl -f arch/alpha/
>> Richard Henderson <rth@twiddle.net> (odd fixer:ALPHA PORT)
>> Ivan Kokshaysky <ink@jurassic.park.msu.ru> (odd fixer:ALPHA PORT)
>>
>> which leaves me. I could give it a try.
> 
> Well, on that old thread from 2019 people expressed the wish to be able
> to run a.out binaries on Alpha. Let's see whether that has changed in
> the meantime.

Checking on the message I sent three years ago, it didn't seem that I was opposed
to removing a.out support, but that I would be happy to help test the patches.

I don't have any particular use case for a.out support either.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

[PATCH] a.out: Stop building a.out/osf1 support on alpha and m68k

[Eric W. Biederman]

There has been repeated discussion on removing a.out support, the most
recent was[1].  Having read through a bunch of the discussion it looks
like no one has see any reason why we need to keep a.out support.

The m68k maintainer has even come out in favor of removing a.out
support[2].

At a practical level with only two rarely used architectures building
a.out support, it gets increasingly hard to test and to care about.
Which means the code will almost certainly bit-rot.

Let's see if anyone cares about a.out support on the last two
architectures that build it, by disabling the build of the support in
Kconfig.  If anyone cares, this can be easily reverted, and we can then
have a discussion about what it is going to take to support a.out
binaries in the long term.

Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: linux-alpha@vger.kernel.org
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: linux-m68k@lists.linux-m68k.org
[1] https://lkml.kernel.org/r/20220113160115.5375-1-bp@alien8.de
[2] https://lkml.kernel.org/r/CAMuHMdUbTNNr16YY1TFe=-uRLjg6yGzgw_RqtAFpyhnOMM5Pvw@mail.gmail.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---

Kees do you think you could add this to your execve branch?

I think this should be a complimentary patch to Borislav Petkov's patch
at the top of this tread to remove a.out support on x86.

 arch/alpha/Kconfig | 1 -
 arch/m68k/Kconfig  | 1 -
 2 files changed, 2 deletions(-)

diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 4e87783c90ad..14c97acea351 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -12,7 +12,6 @@ config ALPHA
 	select FORCE_PCI if !ALPHA_JENSEN
 	select PCI_DOMAINS if PCI
 	select PCI_SYSCALL if PCI
-	select HAVE_AOUT
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_PCSPKR_PLATFORM
 	select HAVE_PERF_EVENTS
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index 936e1803c7c7..268b3860d40d 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -17,7 +17,6 @@ config M68K
 	select GENERIC_CPU_DEVICES
 	select GENERIC_IOMAP
 	select GENERIC_IRQ_SHOW
-	select HAVE_AOUT if MMU
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_DEBUG_BUGVERBOSE
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS if !CPU_HAS_NO_UNALIGNED
-- 
2.29.2

Re: [PATCH] a.out: Stop building a.out/osf1 support on alpha and m68k

[Kees Cook]

On Wed, 09 Mar 2022 14:03:42 -0600, Eric W. Biederman wrote:
> There has been repeated discussion on removing a.out support, the most
> recent was[1].  Having read through a bunch of the discussion it looks
> like no one has see any reason why we need to keep a.out support.
> 
> The m68k maintainer has even come out in favor of removing a.out
> support[2].
> 
> [...]

Applied to for-next/execve, thanks!

[1/1] a.out: Stop building a.out/osf1 support on alpha and m68k
      https://git.kernel.org/kees/c/f451569b9da8

-- 
Kees Cook

[PATCH] x86: Remove a.out support

[Eric W. Biederman]

From: Borislav Petkov <bp@suse.de>
Date: Thu, 13 Jan 2022 17:01:15 +0100
Subject: [PATCH] x86: Remove a.out support

Commit

  eac616557050 ("x86: Deprecate a.out support")

deprecated a.out support with the promise to remove it a couple of
releases later. That commit landed in v5.1.

Now it is more than a couple of releases later, no one has complained so
remove it.

Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20220113160115.5375-1-bp@alien8.de
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---

Kees can you pick this one up in for-next/execve as well?

It still applies cleanly and the actual patch seems to have gotten lost
in the conversation about what more we could do.

Thanks,
Eric


 arch/x86/Kconfig          |   7 -
 arch/x86/ia32/Makefile    |   2 -
 arch/x86/ia32/ia32_aout.c | 325 --------------------------------------
 3 files changed, 334 deletions(-)
 delete mode 100644 arch/x86/ia32/ia32_aout.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 9f5bd41bf660..b6563d6681c1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2827,13 +2827,6 @@ config IA32_EMULATION
 	  64-bit kernel. You should likely turn this on, unless you're
 	  100% sure that you don't have any 32-bit programs left.
 
-config IA32_AOUT
-	tristate "IA32 a.out support"
-	depends on IA32_EMULATION
-	depends on BROKEN
-	help
-	  Support old a.out binaries in the 32bit emulation.
-
 config X86_X32
 	bool "x32 ABI for 64-bit mode"
 	depends on X86_64
diff --git a/arch/x86/ia32/Makefile b/arch/x86/ia32/Makefile
index 8e4d0391ff6c..e481056698de 100644
--- a/arch/x86/ia32/Makefile
+++ b/arch/x86/ia32/Makefile
@@ -5,7 +5,5 @@
 
 obj-$(CONFIG_IA32_EMULATION) := ia32_signal.o
 
-obj-$(CONFIG_IA32_AOUT) += ia32_aout.o
-
 audit-class-$(CONFIG_AUDIT) := audit.o
 obj-$(CONFIG_IA32_EMULATION) += $(audit-class-y)
diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
deleted file mode 100644
index 9bd15241fadb..000000000000
--- a/arch/x86/ia32/ia32_aout.c
+++ /dev/null
@@ -1,325 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- *  a.out loader for x86-64
- *
- *  Copyright (C) 1991, 1992, 1996  Linus Torvalds
- *  Hacked together by Andi Kleen
- */
-
-#include <linux/module.h>
-
-#include <linux/time.h>
-#include <linux/kernel.h>
-#include <linux/mm.h>
-#include <linux/mman.h>
-#include <linux/a.out.h>
-#include <linux/errno.h>
-#include <linux/signal.h>
-#include <linux/string.h>
-#include <linux/fs.h>
-#include <linux/file.h>
-#include <linux/stat.h>
-#include <linux/fcntl.h>
-#include <linux/ptrace.h>
-#include <linux/user.h>
-#include <linux/binfmts.h>
-#include <linux/personality.h>
-#include <linux/init.h>
-#include <linux/jiffies.h>
-#include <linux/perf_event.h>
-#include <linux/sched/task_stack.h>
-
-#include <linux/uaccess.h>
-#include <asm/cacheflush.h>
-#include <asm/user32.h>
-#include <asm/ia32.h>
-
-#undef WARN_OLD
-
-static int load_aout_binary(struct linux_binprm *);
-static int load_aout_library(struct file *);
-
-static struct linux_binfmt aout_format = {
-	.module		= THIS_MODULE,
-	.load_binary	= load_aout_binary,
-	.load_shlib	= load_aout_library,
-};
-
-static int set_brk(unsigned long start, unsigned long end)
-{
-	start = PAGE_ALIGN(start);
-	end = PAGE_ALIGN(end);
-	if (end <= start)
-		return 0;
-	return vm_brk(start, end - start);
-}
-
-
-/*
- * create_aout_tables() parses the env- and arg-strings in new user
- * memory and creates the pointer tables from them, and puts their
- * addresses on the "stack", returning the new stack pointer value.
- */
-static u32 __user *create_aout_tables(char __user *p, struct linux_binprm *bprm)
-{
-	u32 __user *argv, *envp, *sp;
-	int argc = bprm->argc, envc = bprm->envc;
-
-	sp = (u32 __user *) ((-(unsigned long)sizeof(u32)) & (unsigned long) p);
-	sp -= envc+1;
-	envp = sp;
-	sp -= argc+1;
-	argv = sp;
-	put_user((unsigned long) envp, --sp);
-	put_user((unsigned long) argv, --sp);
-	put_user(argc, --sp);
-	current->mm->arg_start = (unsigned long) p;
-	while (argc-- > 0) {
-		char c;
-
-		put_user((u32)(unsigned long)p, argv++);
-		do {
-			get_user(c, p++);
-		} while (c);
-	}
-	put_user(0, argv);
-	current->mm->arg_end = current->mm->env_start = (unsigned long) p;
-	while (envc-- > 0) {
-		char c;
-
-		put_user((u32)(unsigned long)p, envp++);
-		do {
-			get_user(c, p++);
-		} while (c);
-	}
-	put_user(0, envp);
-	current->mm->env_end = (unsigned long) p;
-	return sp;
-}
-
-/*
- * These are the functions used to load a.out style executables and shared
- * libraries.  There is no binary dependent code anywhere else.
- */
-static int load_aout_binary(struct linux_binprm *bprm)
-{
-	unsigned long error, fd_offset, rlim;
-	struct pt_regs *regs = current_pt_regs();
-	struct exec ex;
-	int retval;
-
-	ex = *((struct exec *) bprm->buf);		/* exec-header */
-	if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
-	     N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
-	    N_TRSIZE(ex) || N_DRSIZE(ex) ||
-	    i_size_read(file_inode(bprm->file)) <
-	    ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
-		return -ENOEXEC;
-	}
-
-	fd_offset = N_TXTOFF(ex);
-
-	/* Check initial limits. This avoids letting people circumvent
-	 * size limits imposed on them by creating programs with large
-	 * arrays in the data or bss.
-	 */
-	rlim = rlimit(RLIMIT_DATA);
-	if (rlim >= RLIM_INFINITY)
-		rlim = ~0;
-	if (ex.a_data + ex.a_bss > rlim)
-		return -ENOMEM;
-
-	/* Flush all traces of the currently running executable */
-	retval = begin_new_exec(bprm);
-	if (retval)
-		return retval;
-
-	/* OK, This is the point of no return */
-	set_personality(PER_LINUX);
-	set_personality_ia32(false);
-
-	setup_new_exec(bprm);
-
-	regs->cs = __USER32_CS;
-	regs->r8 = regs->r9 = regs->r10 = regs->r11 = regs->r12 =
-		regs->r13 = regs->r14 = regs->r15 = 0;
-
-	current->mm->end_code = ex.a_text +
-		(current->mm->start_code = N_TXTADDR(ex));
-	current->mm->end_data = ex.a_data +
-		(current->mm->start_data = N_DATADDR(ex));
-	current->mm->brk = ex.a_bss +
-		(current->mm->start_brk = N_BSSADDR(ex));
-
-	retval = setup_arg_pages(bprm, IA32_STACK_TOP, EXSTACK_DEFAULT);
-	if (retval < 0)
-		return retval;
-
-	if (N_MAGIC(ex) == OMAGIC) {
-		unsigned long text_addr, map_size;
-
-		text_addr = N_TXTADDR(ex);
-		map_size = ex.a_text+ex.a_data;
-
-		error = vm_brk(text_addr & PAGE_MASK, map_size);
-
-		if (error)
-			return error;
-
-		error = read_code(bprm->file, text_addr, 32,
-				  ex.a_text + ex.a_data);
-		if ((signed long)error < 0)
-			return error;
-	} else {
-#ifdef WARN_OLD
-		static unsigned long error_time, error_time2;
-		if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
-		    (N_MAGIC(ex) != NMAGIC) &&
-				time_after(jiffies, error_time2 + 5*HZ)) {
-			printk(KERN_NOTICE "executable not page aligned\n");
-			error_time2 = jiffies;
-		}
-
-		if ((fd_offset & ~PAGE_MASK) != 0 &&
-			    time_after(jiffies, error_time + 5*HZ)) {
-			printk(KERN_WARNING
-			       "fd_offset is not page aligned. Please convert "
-			       "program: %pD\n",
-			       bprm->file);
-			error_time = jiffies;
-		}
-#endif
-
-		if (!bprm->file->f_op->mmap || (fd_offset & ~PAGE_MASK) != 0) {
-			error = vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
-			if (error)
-				return error;
-
-			read_code(bprm->file, N_TXTADDR(ex), fd_offset,
-					ex.a_text+ex.a_data);
-			goto beyond_if;
-		}
-
-		error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
-				PROT_READ | PROT_EXEC,
-				MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
-				fd_offset);
-
-		if (error != N_TXTADDR(ex))
-			return error;
-
-		error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
-				PROT_READ | PROT_WRITE | PROT_EXEC,
-				MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
-				fd_offset + ex.a_text);
-		if (error != N_DATADDR(ex))
-			return error;
-	}
-
-beyond_if:
-	error = set_brk(current->mm->start_brk, current->mm->brk);
-	if (error)
-		return error;
-
-	set_binfmt(&aout_format);
-
-	current->mm->start_stack =
-		(unsigned long)create_aout_tables((char __user *)bprm->p, bprm);
-	/* start thread */
-	loadsegment(fs, 0);
-	loadsegment(ds, __USER32_DS);
-	loadsegment(es, __USER32_DS);
-	load_gs_index(0);
-	(regs)->ip = ex.a_entry;
-	(regs)->sp = current->mm->start_stack;
-	(regs)->flags = 0x200;
-	(regs)->cs = __USER32_CS;
-	(regs)->ss = __USER32_DS;
-	regs->r8 = regs->r9 = regs->r10 = regs->r11 =
-	regs->r12 = regs->r13 = regs->r14 = regs->r15 = 0;
-	return 0;
-}
-
-static int load_aout_library(struct file *file)
-{
-	unsigned long bss, start_addr, len, error;
-	int retval;
-	struct exec ex;
-	loff_t pos = 0;
-
-	retval = -ENOEXEC;
-	error = kernel_read(file, &ex, sizeof(ex), &pos);
-	if (error != sizeof(ex))
-		goto out;
-
-	/* We come in here for the regular a.out style of shared libraries */
-	if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
-	    N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
-	    i_size_read(file_inode(file)) <
-	    ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
-		goto out;
-	}
-
-	if (N_FLAGS(ex))
-		goto out;
-
-	/* For  QMAGIC, the starting address is 0x20 into the page.  We mask
-	   this off to get the starting address for the page */
-
-	start_addr =  ex.a_entry & 0xfffff000;
-
-	if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
-#ifdef WARN_OLD
-		static unsigned long error_time;
-		if (time_after(jiffies, error_time + 5*HZ)) {
-			printk(KERN_WARNING
-			       "N_TXTOFF is not page aligned. Please convert "
-			       "library: %pD\n",
-			       file);
-			error_time = jiffies;
-		}
-#endif
-		retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
-		if (retval)
-			goto out;
-
-		read_code(file, start_addr, N_TXTOFF(ex),
-			  ex.a_text + ex.a_data);
-		retval = 0;
-		goto out;
-	}
-	/* Now use mmap to map the library into memory. */
-	error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
-			PROT_READ | PROT_WRITE | PROT_EXEC,
-			MAP_FIXED | MAP_PRIVATE | MAP_32BIT,
-			N_TXTOFF(ex));
-	retval = error;
-	if (error != start_addr)
-		goto out;
-
-	len = PAGE_ALIGN(ex.a_text + ex.a_data);
-	bss = ex.a_text + ex.a_data + ex.a_bss;
-	if (bss > len) {
-		retval = vm_brk(start_addr + len, bss - len);
-		if (retval)
-			goto out;
-	}
-	retval = 0;
-out:
-	return retval;
-}
-
-static int __init init_aout_binfmt(void)
-{
-	register_binfmt(&aout_format);
-	return 0;
-}
-
-static void __exit exit_aout_binfmt(void)
-{
-	unregister_binfmt(&aout_format);
-}
-
-module_init(init_aout_binfmt);
-module_exit(exit_aout_binfmt);
-MODULE_LICENSE("GPL");
-- 
2.29.2

Re: [PATCH] x86: Remove a.out support

[Linus Torvalds]

On Thu, Mar 10, 2022 at 3:29 PM Eric W. Biederman <ebiederm@xmission.com> wrote:
>
> Kees can you pick this one up in for-next/execve as well?
>
> It still applies cleanly and the actual patch seems to have gotten lost
> in the conversation about what more we could do.

Side note: there are similar other turds if a.out goes away, ie on
alpha it's OSF4_COMPAT, and it enables support for a couple of legacy
OSF/1 system calls.

I think that was also discussed in the (old) a.out deprecation thread
back in 2019..

               Linus

Re: [PATCH] x86: Remove a.out support

[Arnd Bergmann]

On Fri, Mar 11, 2022 at 12:35 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Thu, Mar 10, 2022 at 3:29 PM Eric W. Biederman <ebiederm@xmission.com> wrote:
> >
> > Kees can you pick this one up in for-next/execve as well?
> >
> > It still applies cleanly and the actual patch seems to have gotten lost
> > in the conversation about what more we could do.
>
> Side note: there are similar other turds if a.out goes away, ie on
> alpha it's OSF4_COMPAT, and it enables support for a couple of legacy
> OSF/1 system calls.
>
> I think that was also discussed in the (old) a.out deprecation thread
> back in 2019..

The only thing that actually depends on CONFIG_OSF4_COMPAT seems to be
the custom logic in readv() and writev(). Those are the two that you removed
in your patch back then[1].

For the other system calls, I fear we can only try to guess which of them
are used in Linux applications and which ones are not. These were always
available to normal Linux user space, so the ones that are similar to our
syscalls could have been used in glibc, e.g. mmap, wait4, stat.

         Arnd

[1] https://lore.kernel.org/all/CAHk-=wgt7M6yA5BJCJo0nF22WgPJnN8CvViL9CAJmd+S+Civ6w@mail.gmail.com/

[2] $ git grep sys_osf arch/alpha/kernel/syscalls/syscall.tbl
7 common osf_wait4 sys_osf_wait4
17 common brk sys_osf_brk
21 common osf_mount sys_osf_mount
43 common osf_set_program_attributes sys_osf_set_program_attributes
48 common osf_sigprocmask sys_osf_sigprocmask
71 common mmap sys_osf_mmap
93 common osf_select sys_osf_select
100 common getpriority sys_osf_getpriority
112 common osf_sigstack sys_osf_sigstack
116 common osf_gettimeofday sys_osf_gettimeofday
117 common osf_getrusage sys_osf_getrusage
120 common readv sys_osf_readv
121 common writev sys_osf_writev
122 common osf_settimeofday sys_osf_settimeofday
138 common osf_utimes sys_osf_utimes
156 common sigaction sys_osf_sigaction
159 common osf_getdirentries sys_osf_getdirentries
160 common osf_statfs sys_osf_statfs
161 common osf_fstatfs sys_osf_fstatfs
165 common osf_getdomainname sys_osf_getdomainname
207 common osf_utsname sys_osf_utsname
224 common osf_stat sys_osf_stat
225 common osf_lstat sys_osf_lstat
226 common osf_fstat sys_osf_fstat
227 common osf_statfs64 sys_osf_statfs64
228 common osf_fstatfs64 sys_osf_fstatfs64
241 common osf_sysinfo sys_osf_sysinfo
244 common osf_proplist_syscall sys_osf_proplist_syscall
251 common osf_usleep_thread sys_osf_usleep_thread
256 common osf_getsysinfo sys_osf_getsysinfo
257 common osf_setsysinfo sys_osf_setsysinfo

Re: [PATCH] x86: Remove a.out support

[Borislav Petkov]

On Thu, Mar 10, 2022 at 05:29:13PM -0600, Eric W. Biederman wrote:
> Kees can you pick this one up in for-next/execve as well?

I can carry it through tip, no probs.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

RE: [PATCH] x86: Remove a.out support

[David Laight]

From: Geert Uytterhoeven
> Sent: 14 January 2022 19:22
...
> Who's gonna take care of alpha?

Would anyone notice if the knife slipped?

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)