From b46ac13504e991910127aa0ffe56a6983ffd1ce2 Mon Sep 17 00:00:00 2001
From: Justine Tunney <jtunney@gmail.com>
Date: Thu, 10 Nov 2022 20:58:48 -0800
Subject: [PATCH] Introduce new `jartsr='` ape prefix

Files beginning with "MZqFpD" are Actually Portable Executables,
which have a printf statement in the first 4096 bytes with octal
codes that specify the ELF header. APE also specifies `jartsr='`
as an alternative prefix, intended for binaries that do not want
to be identified as Windows executables. Like the \177ELF magic,
all these prefixes decode as x86 jump instructions that could be
used for 16-bit bootloaders or 32-bit / 64-bit flat executables.
Most importantly they provide a fallback path for Thompson shell
copmatible command interpreters, which do not require a shebang,
e.g. bash, zsh, fish, bourne, almquist, etc. Please note that in
order to meet the requirements of POSIX.1, the single quote must
be followed by a newline character, before any null bytes occur.
See also: https://www.austingroupbugs.net/view.php?id=1250
---
 ape/ape.S           | 27 ++++++++++++++++++++++++---
 ape/apeinstall.sh   |  4 ++--
 ape/apeuninstall.sh | 18 ++++++++----------
 3 files changed, 34 insertions(+), 15 deletions(-)

diff --git a/ape/ape.S b/ape/ape.S
index 412a03626..234b5d07d 100644
--- a/ape/ape.S
+++ b/ape/ape.S
@@ -116,11 +116,29 @@ cstr:	.endobj	cstr,globl,hidden		# ←for gdb readability
 ape_mz:
 #if SupportsWindows() || SupportsMetal()
 	.asciz	"MZqFpD='\n"		# Mark 'Zibo' Joseph Zbikowski
+//	# in real mode
+//	dec	%bp
+//	pop	%dx
+//	jno	0x4a
+//	jo	0x4a
+//
+//	# in legacy mode
+//	push	%ebp
+//	pop	%edx
+//	jno	0x4a
+//	jo	0x4a
+//
+//	# 64-bit mode
+//	rex.WRB
+//	pop	%r10
+//	jno	0x4a
+//	jo	0x4a
 #else
 //	Avoid virus scanner reputation damage when targeting System Five.
-//	WARNING: This prefix is experimental; it may be removed sometime.
-//	TODO(jart): Find another prefix that will work with BIOS loading.
-	.asciz	"JTqFpD='\n"		# Mark 'Zibo' Joseph Zbikowski
+	.asciz	"jartsr='\n"		# Justine Alexandra Roberts Tunney
+//	push	$0x61
+//	jb	0x78
+//	jae	0x78
 #endif
 	.short	0x1000			# MZ: lowers upper bound load / 16
 	.short	0xf800			# MZ: roll greed on bss
@@ -140,6 +158,9 @@ ape_mz:
 	.long	RVA(ape_pe)		# PE: the new technology
 #else
 	.long	0
+	.org	0x78
+	pop	%rax
+	jmp	_start
 #endif
 	.endfn	ape_mz,globl,hidden
 
diff --git a/ape/apeinstall.sh b/ape/apeinstall.sh
index c97d8fff7..334ed2778 100755
--- a/ape/apeinstall.sh
+++ b/ape/apeinstall.sh
@@ -97,8 +97,8 @@ if [ x"$(uname -s)" = xLinux ]; then
   echo you may need to edit configs to persist across reboot >&2
   echo '$SUDO sh -c "echo '"'"':APE:M::MZqFpD::/usr/bin/ape:'"'"' >/proc/sys/fs/binfmt_misc/register"' >&2
   $SUDO sh -c "echo ':APE:M::MZqFpD::/usr/bin/ape:' >/proc/sys/fs/binfmt_misc/register" || exit
-  echo '$SUDO sh -c "echo '"'"':APE-sysv:M::JTqFpD::/usr/bin/ape:'"'"' >/proc/sys/fs/binfmt_misc/register"' >&2
-  $SUDO sh -c "echo ':APE-sysv:M::JTqFpD::/usr/bin/ape:' >/proc/sys/fs/binfmt_misc/register" || exit
+  echo '$SUDO sh -c "echo '"'"':APE-jart:M::jartsr::/usr/bin/ape:'"'"' >/proc/sys/fs/binfmt_misc/register"' >&2
+  $SUDO sh -c "echo ':APE-jart:M::jartsr::/usr/bin/ape:' >/proc/sys/fs/binfmt_misc/register" || exit
   echo done >&2
 
   if [ x"$(cat /proc/sys/fs/binfmt_misc/status)" = xdisabled ]; then
diff --git a/ape/apeuninstall.sh b/ape/apeuninstall.sh
index 69cd41031..5cad154a8 100755
--- a/ape/apeuninstall.sh
+++ b/ape/apeuninstall.sh
@@ -8,21 +8,19 @@ fi
 
 {
   echo
-  echo "APE Uninstaller intends to run"
+  echo "APE Uninstaller intends to run (in pseudo-shell)"
   echo
-  echo "    $SUDO sh -c 'echo -1 >/proc/sys/fs/binfmt_misc/APE'"
-  echo "    $SUDO sh -c 'echo -1 >/proc/sys/fs/binfmt_misc/APE-sysv'"
-  echo "    $SUDO rm -f /usr/bin/ape ~/.ape o/tmp/.ape /tmp/.ape"
+  echo "    sudo echo -1 into /proc/sys/fs/binfmt_misc/APE*"
+  echo "    sudo rm -f /usr/bin/ape ~/.ape o/tmp/.ape /tmp/.ape"
   echo
   echo "You may then use ape/apeinstall.sh to reinstall it"
   echo
 } >&2
 
 set -ex
-if [ -f /proc/sys/fs/binfmt_misc/APE ]; then
-  $SUDO sh -c 'echo -1 >/proc/sys/fs/binfmt_misc/APE' || exit
-fi
-if [ -f /proc/sys/fs/binfmt_misc/APE-sysv ]; then
-  $SUDO sh -c 'echo -1 >/proc/sys/fs/binfmt_misc/APE-sysv' || exit
-fi
+for f in /proc/sys/fs/binfmt_misc/APE*; do
+  if [ -f $f ]; then
+    $SUDO sh -c "echo -1 >$f" || exit
+  fi
+done
 $SUDO rm -f /usr/bin/ape ~/.ape o/tmp/.ape o/tmp/ape /tmp/.ape /tmp/ape || exit