[PATCH] uml: fix linkage of tt mode against NPTL

With Al Viro <viro@parcelfarce.linux.theplanet.co.uk>

To make sure switcheroo() can execute when we remap all the executable
image, we used a trick to make it use a local copy of errno...  this trick
does not work with NPTL glibc, only with LinuxThreads, so use another
(simpler) one to make it work anyway.

Hopefully, a lot improved thanks to merging with the version of Al Viro
(which had his part of problems, though, i.e.  removing a fix to another
bug and not fixing the problem on i386).

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/um/Makefile

@@ -122,7 +122,7 @@ endif
 CPPFLAGS_vmlinux.lds = $(shell echo -U$(SUBARCH) \
 	-DSTART=$(START) -DELF_ARCH=$(ELF_ARCH) \
 	-DELF_FORMAT=\"$(ELF_FORMAT)\" $(CPP_MODE-y) \
-	-DKERNEL_STACK_SIZE=$(STACK_SIZE))
+	-DKERNEL_STACK_SIZE=$(STACK_SIZE) -DSUBARCH=$(SUBARCH))
 
 #The wrappers will select whether using "malloc" or the kernel allocator.
 LINK_WRAPS = -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc

arch/um/kernel/tt/Makefile

@@ -3,10 +3,6 @@
 # Licensed under the GPL
 #
 
-extra-y := unmap_fin.o
-targets := unmap.o
-clean-files := unmap_tmp.o
-
 obj-y = exec_kern.o exec_user.o gdb.o ksyms.o mem.o mem_user.o process_kern.o \
 	syscall_kern.o syscall_user.o time.o tlb.o tracer.o trap_user.o \
 	uaccess.o uaccess_user.o
@@ -16,14 +12,3 @@ obj-$(CONFIG_PT_PROXY) += gdb_kern.o ptproxy/
 USER_OBJS := gdb.o time.o tracer.o
 
 include arch/um/scripts/Makefile.rules
-
-UNMAP_CFLAGS := $(patsubst -pg -DPROFILING,,$(USER_CFLAGS))
-UNMAP_CFLAGS := $(patsubst -fprofile-arcs -ftest-coverage,,$(UNMAP_CFLAGS))
-
-#XXX: partially copied from arch/um/scripts/Makefile.rules
-$(obj)/unmap.o: c_flags = -Wp,-MD,$(depfile) $(UNMAP_CFLAGS)
-
-$(obj)/unmap_fin.o : $(obj)/unmap.o
-	$(LD) -r -o $(obj)/unmap_tmp.o $< $(shell $(CC) -print-file-name=libc.a)
-	$(OBJCOPY) $(obj)/unmap_tmp.o $@ -G switcheroo
-

arch/um/kernel/uml.lds.S

@@ -14,19 +14,10 @@ SECTIONS
   /* Used in arch/um/kernel/mem.c. Any memory between START and __binary_start
    * is remapped.*/
   __binary_start = .;
-#ifdef MODE_TT
-  .thread_private : {
-    __start_thread_private = .;
-    errno = .;
-    . += 4;
-    arch/um/kernel/tt/unmap_fin.o (.data)
-    __end_thread_private = .;
-  }
-  . = ALIGN(4096);
-  .remap : { arch/um/kernel/tt/unmap_fin.o (.text) }
 
-  /* We want it only if we are in MODE_TT. In both cases, however, when MODE_TT
-   * is off the resulting binary segfaults.*/
+#ifdef MODE_TT
+  .remap_data : { arch/um/sys-SUBARCH/unmap_fin.o (.data .bss) }
+  .remap : { arch/um/sys-SUBARCH/unmap_fin.o (.text) }
 
   . = ALIGN(4096);		/* Init code and data */
 #endif

arch/um/scripts/Makefile.rules

@@ -10,6 +10,12 @@ USER_OBJS := $(foreach file,$(USER_OBJS),$(obj)/$(file))
 $(USER_OBJS) : c_flags = -Wp,-MD,$(depfile) $(USER_CFLAGS) \
 	$(CFLAGS_$(notdir $@))
 
+# The stubs and unmap.o can't try to call mcount or update basic block data
+define unprofile
+	$(patsubst -pg,,$(patsubst -fprofile-arcs -ftest-coverage,,$(1)))
+endef
+
+
 quiet_cmd_make_link = SYMLINK $@
 cmd_make_link       = ln -sf $(srctree)/arch/$(SUBARCH)/$($(notdir $@)-dir)/$(notdir $@) $@
 

arch/um/scripts/Makefile.unmap

@@ -0,0 +1,22 @@
+clean-files += unmap_tmp.o unmap_fin.o unmap.o
+
+ifdef CONFIG_MODE_TT
+
+#Always build unmap_fin.o
+extra-y += unmap_fin.o
+#Do dependency tracking for unmap.o (it will be always built, but won't get the tracking unless we use this).
+targets += unmap.o
+
+#XXX: partially copied from arch/um/scripts/Makefile.rules
+$(obj)/unmap.o: _c_flags = $(call unprofile,$(CFLAGS))
+
+quiet_cmd_wrapld = LD      $@
+define cmd_wrapld
+	$(LD) -r -o $(obj)/unmap_tmp.o $< $(shell $(CC) -print-file-name=libc.a); \
+	$(OBJCOPY) $(obj)/unmap_tmp.o $@ -G switcheroo
+endef
+
+$(obj)/unmap_fin.o : $(obj)/unmap.o FORCE
+	$(call if_changed,wrapld)
+
+endif

arch/um/sys-i386/Makefile

@@ -17,3 +17,5 @@ highmem.c-dir = mm
 module.c-dir = kernel
 
 subdir- := util
+
+include arch/um/scripts/Makefile.unmap

arch/um/sys-i386/unmap.c

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
+ * Licensed under the GPL
+ */
+
+#include <linux/mman.h>
+#include <asm/unistd.h>
+
+static int errno;
+
+static inline _syscall2(int,munmap,void *,start,size_t,len)
+static inline _syscall6(void *,mmap2,void *,addr,size_t,len,int,prot,int,flags,int,fd,off_t,offset)
+int switcheroo(int fd, int prot, void *from, void *to, int size)
+{
+	if(munmap(to, size) < 0){
+		return(-1);
+	}
+	if(mmap2(to, size, prot, MAP_SHARED | MAP_FIXED, fd, 0) != to){
+		return(-1);
+	}
+	if(munmap(from, size) < 0){
+		return(-1);
+	}
+	return(0);
+}

arch/um/sys-x86_64/Makefile

@@ -29,3 +29,5 @@ thunk.S-dir = lib
 module.c-dir = kernel
 
 subdir- := util
+
+include arch/um/scripts/Makefile.unmap

arch/um/sys-x86_64/unmap.c

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
+ * Licensed under the GPL
+ */
+
+#include <linux/mman.h>
+#include <asm/unistd.h>
+
+static int errno;
+
+static inline _syscall2(int,munmap,void *,start,size_t,len)
+static inline _syscall6(void *,mmap,void *,addr,size_t,len,int,prot,int,flags,int,fd,off_t,offset)
+int switcheroo(int fd, int prot, void *from, void *to, int size)
+{
+	if(munmap(to, size) < 0){
+		return(-1);
+	}
+	if(mmap(to, size, prot, MAP_SHARED | MAP_FIXED, fd, 0) != to){
+		return(-1);
+	}
+	if(munmap(from, size) < 0){
+		return(-1);
+	}
+	return(0);
+}