From 1119ffe7afa9787910e1b12c6d47b33ea3465d7a Mon Sep 17 00:00:00 2001
From: =?utf8?q?Micha=C5=82=20Januszewski?= <spock@gentoo.org>
Date: Tue, 23 Sep 2008 00:56:59 +0200
Subject: [PATCH] Remove dynamically generated code from LRMI.

LRMI dynamically generated the return to 32-bit code (int 0xff), which
causes problem with systems using PaX, where memory pages are either
executable or writable, but never both at once.  Fix this by including
this code in a separate section in the object file and mapping it
to the absolute address 0x9000.

Thanks to the PaX team for useful suggestions and discussions in
http://bugs.gentoo.org/show_bug.cgi?id=226107
---
 Makefile                |  3 +--
 libs/lrmi-0.10/Makefile |  2 +-
 libs/lrmi-0.10/lrmi.c   | 15 ++++++++++++++-
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index 3b2ae00..0d4c809 100644
--- a/Makefile
+++ b/Makefile
@@ -11,7 +11,6 @@ endif
 
 CFLAGS ?= -Wall -g -O2
 CFLAGS += -I$(KDIR)/include
-LDFLAGS += -Wl,-z,execheap
 
 ifeq ($(call config_opt,CONFIG_X86EMU),true)
 	CFLAGS += -Ilibs/x86emu
@@ -21,7 +20,7 @@ ifeq ($(call config_opt,CONFIG_X86EMU),true)
 	V86LIB = x86emu
 else
 	CFLAGS += -Ilibs/lrmi-0.10
-	LDFLAGS += -Llibs/lrmi-0.10 -static
+	LDFLAGS += -Llibs/lrmi-0.10 -static -Wl,--section-start,vm86_ret=0x9000
 	LDLIBS += -llrmi
 	V86OBJS = v86_lrmi.o
 	V86LIB = lrmi
diff --git a/libs/lrmi-0.10/Makefile b/libs/lrmi-0.10/Makefile
index c37bf4e..17896a3 100644
--- a/libs/lrmi-0.10/Makefile
+++ b/libs/lrmi-0.10/Makefile
@@ -26,7 +26,7 @@ liblrmi.a: $(objects)
 
 liblrmi.so: $(pic_objects)
 #	$(CC) $(CPPFLAGS) $(CFLAGS) -fPIC -shared -o $@ $^
-	$(CC) $(CPPFLAGS) $(CFLAGS) -Wl,-soname,$(LIBNAME).so.$(MAJOR) -fPIC -shared -o $(LIBNAME).so.$(VERSION) $^
+	$(CC) $(CPPFLAGS) $(CFLAGS) -Wl,-soname,$(LIBNAME).so.$(MAJOR) -Wl,--section-start,vm86_ret=0x9000 -fPIC -shared -o $(LIBNAME).so.$(VERSION) $^
 	ln -sf $(LIBNAME).so.$(VERSION) $(LIBNAME).so.$(MAJOR)
 	ln -sf $(LIBNAME).so.$(MAJOR) $(LIBNAME).so
 
diff --git a/libs/lrmi-0.10/lrmi.c b/libs/lrmi-0.10/lrmi.c
index 97b6ae2..7f733ef 100644
--- a/libs/lrmi-0.10/lrmi.c
+++ b/libs/lrmi-0.10/lrmi.c
@@ -372,6 +372,18 @@ LRMI_init(void)
 	context.stack_seg = (unsigned int)m >> 4;
 	context.stack_off = DEFAULT_STACK_SIZE;
 
+#if defined(__linux__)
+	/*
+	 The return to 32-bit code (vm86_ret section) is linked
+	 into the absolute address 0x9000.
+	*/
+	context.ret_seg = 0x0900;
+	context.ret_off = 0x0000;
+
+	asm (".pushsection vm86_ret, \"ax\"\nint %0\n.popsection"
+		: /* no return value */
+		: "i" (RETURN_TO_32_INT));
+#else
 	/*
 	 Allocate the return to 32 bit routine
 	*/
@@ -380,9 +392,10 @@ LRMI_init(void)
 	context.ret_seg = (unsigned int)m >> 4;
 	context.ret_off = (unsigned int)m & 0xf;
 
-	((unsigned char *)m)[0] = 0xcd; 	/* int opcode */
+	((unsigned char *)m)[0] = 0xcd;		/* int opcode */
 	((unsigned char *)m)[1] = RETURN_TO_32_INT;
 
+#endif  /* __linux__ */
 	memset(&context.vm, 0, sizeof(context.vm));
 
 	/*
-- 
2.11.4.GIT