a.out: remove core dumping support

We're (finally) phasing out a.out support for good.  As Borislav Petkov
points out, we've supported ELF binaries for about 25 years by now, and
coredumping in particular has bitrotted over the years.

None of the tool chains even support generating a.out binaries any more,
and the plan is to deprecate a.out support entirely for the kernel.  But
I want to start with just removing the core dumping code, because I can
still imagine that somebody actually might want to support a.out as a
simpler biinary format.

Particularly if you generate some random binaries on the fly, ELF is a
much more complicated format (admittedly ELF also does have a lot of
toolchain support, mitigating that complexity a lot and you really
should have moved over in the last 25 years).

So it's at least somewhat possible that somebody out there has some
workflow that still involves generating and running a.out executables.

In contrast, it's very unlikely that anybody depends on debugging any
legacy a.out core files.  But regardless, I want this phase-out to be
done in two steps, so that we can resurrect a.out support (if needed)
without having to resurrect the core file dumping that is almost
certainly not needed.

Jann Horn pointed to the <asm/a.out-core.h> file that my first trivial
cut at this had missed.

And Alan Cox points out that the a.out binary loader _could_ be done in
user space if somebody wants to, but we might keep just the loader in
the kernel if somebody really wants it, since the loader isn't that big
and has no really odd special cases like the core dumping does.

Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: Jann Horn <jannh@google.com>
Cc: Richard Weinberger <richard@nod.at>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 83 deletions

diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c
index ca9725f18e00..1fefd87eb4b4 100644
--- a/fs/binfmt_aout.c
+++ b/fs/binfmt_aout.c
@@ -29,97 +29,14 @@
 
 #include <linux/uaccess.h>
 #include <asm/cacheflush.h>
-#include <asm/a.out-core.h>
 
 static int load_aout_binary(struct linux_binprm *);
 static int load_aout_library(struct file*);
 
-#ifdef CONFIG_COREDUMP
-/*
- * Routine writes a core dump image in the current directory.
- * Currently only a stub-function.
- *
- * Note that setuid/setgid files won't make a core-dump if the uid/gid
- * changed due to the set[u|g]id. It's enforced by the "current->mm->dumpable"
- * field, which also makes sure the core-dumps won't be recursive if the
- * dumping of the process results in another error..
- */
-static int aout_core_dump(struct coredump_params *cprm)
-{
-	mm_segment_t fs;
-	int has_dumped = 0;
-	void __user *dump_start;
-	int dump_size;
-	struct user dump;
-#ifdef __alpha__
-#       define START_DATA(u)	((void __user *)u.start_data)
-#else
-#	define START_DATA(u)	((void __user *)((u.u_tsize << PAGE_SHIFT) + \
-				 u.start_code))
-#endif
-#       define START_STACK(u)   ((void __user *)u.start_stack)
-
-	fs = get_fs();
-	set_fs(KERNEL_DS);
-	has_dumped = 1;
-       	strncpy(dump.u_comm, current->comm, sizeof(dump.u_comm));
-	dump.u_ar0 = offsetof(struct user, regs);
-	dump.signal = cprm->siginfo->si_signo;
-	aout_dump_thread(cprm->regs, &dump);
-
-/* If the size of the dump file exceeds the rlimit, then see what would happen
-   if we wrote the stack, but not the data area.  */
-	if ((dump.u_dsize + dump.u_ssize+1) * PAGE_SIZE > cprm->limit)
-		dump.u_dsize = 0;
-
-/* Make sure we have enough room to write the stack and data areas. */
-	if ((dump.u_ssize + 1) * PAGE_SIZE > cprm->limit)
-		dump.u_ssize = 0;
-
-/* make sure we actually have a data and stack area to dump */
-	set_fs(USER_DS);
-	if (!access_ok(START_DATA(dump), dump.u_dsize << PAGE_SHIFT))
-		dump.u_dsize = 0;
-	if (!access_ok(START_STACK(dump), dump.u_ssize << PAGE_SHIFT))
-		dump.u_ssize = 0;
-
-	set_fs(KERNEL_DS);
-/* struct user */
-	if (!dump_emit(cprm, &dump, sizeof(dump)))
-		goto end_coredump;
-/* Now dump all of the user data.  Include malloced stuff as well */
-	if (!dump_skip(cprm, PAGE_SIZE - sizeof(dump)))
-		goto end_coredump;
-/* now we start writing out the user space info */
-	set_fs(USER_DS);
-/* Dump the data area */
-	if (dump.u_dsize != 0) {
-		dump_start = START_DATA(dump);
-		dump_size = dump.u_dsize << PAGE_SHIFT;
-		if (!dump_emit(cprm, dump_start, dump_size))
-			goto end_coredump;
-	}
-/* Now prepare to dump the stack area */
-	if (dump.u_ssize != 0) {
-		dump_start = START_STACK(dump);
-		dump_size = dump.u_ssize << PAGE_SHIFT;
-		if (!dump_emit(cprm, dump_start, dump_size))
-			goto end_coredump;
-	}
-end_coredump:
-	set_fs(fs);
-	return has_dumped;
-}
-#else
-#define aout_core_dump NULL
-#endif
-
 static struct linux_binfmt aout_format = {
 	.module		= THIS_MODULE,
 	.load_binary	= load_aout_binary,
 	.load_shlib	= load_aout_library,
-	.core_dump	= aout_core_dump,
-	.min_coredump	= PAGE_SIZE
 };
 
 #define BAD_ADDR(x)	((unsigned long)(x) >= TASK_SIZE)