[PATCH for-5.0 v3 0/7] configure: Improve PIE and other linkage

[PATCH for-5.0 v3 0/7] configure: Improve PIE and other linkage

[Richard Henderson]

Version 3 is a rebase from January, with s/LDCONFIG/QEMU_LDCONFIG/.
I plan on including this in the next tcg-next pull request, if there
is no other commentary.


r~


Richard Henderson (7):
  configure: Drop adjustment of textseg
  tcg: Remove softmmu code_gen_buffer fixed address
  configure: Do not force pie=no for non-x86
  configure: Always detect -no-pie toolchain support
  configure: Unnest detection of -z,relro and -z,now
  configure: Override the os default with --disable-pie
  configure: Support -static-pie if requested

 configure                 | 116 +++++++++++---------------------------
 Makefile                  |   2 +-
 accel/tcg/translate-all.c |  37 ++----------
 3 files changed, 38 insertions(+), 117 deletions(-)

-- 
2.20.1

[PATCH for-5.0 v3 1/7] configure: Drop adjustment of textseg

[Richard Henderson]

This adjustment was random and unnecessary.  The user mode
startup code in probe_guest_base() will choose a value for
guest_base that allows the host qemu binary to not conflict
with the guest binary.

With modern distributions, this isn't even used, as the default
is PIE, which does the same job in a more portable way.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
v2: Remove mention of config-host.ld from make distclean
---
 configure | 47 -----------------------------------------------
 Makefile  |  2 +-
 2 files changed, 1 insertion(+), 48 deletions(-)

diff --git a/configure b/configure
index 89fe881dd4..2afcae61df 100755
--- a/configure
+++ b/configure
@@ -6498,49 +6498,6 @@ if test "$cpu" = "s390x" ; then
   fi
 fi
 
-# Probe for the need for relocating the user-only binary.
-if ( [ "$linux_user" = yes ] || [ "$bsd_user" = yes ] ) && [ "$pie" = no ]; then
-  textseg_addr=
-  case "$cpu" in
-    arm | i386 | ppc* | s390* | sparc* | x86_64 | x32)
-      # ??? Rationale for choosing this address
-      textseg_addr=0x60000000
-      ;;
-    mips)
-      # A 256M aligned address, high in the address space, with enough
-      # room for the code_gen_buffer above it before the stack.
-      textseg_addr=0x60000000
-      ;;
-  esac
-  if [ -n "$textseg_addr" ]; then
-    cat > $TMPC <<EOF
-    int main(void) { return 0; }
-EOF
-    textseg_ldflags="-Wl,-Ttext-segment=$textseg_addr"
-    if ! compile_prog "" "$textseg_ldflags"; then
-      # In case ld does not support -Ttext-segment, edit the default linker
-      # script via sed to set the .text start addr.  This is needed on FreeBSD
-      # at least.
-      if ! $ld --verbose >/dev/null 2>&1; then
-        error_exit \
-            "We need to link the QEMU user mode binaries at a" \
-            "specific text address. Unfortunately your linker" \
-            "doesn't support either the -Ttext-segment option or" \
-            "printing the default linker script with --verbose." \
-            "If you don't want the user mode binaries, pass the" \
-            "--disable-user option to configure."
-      fi
-
-      $ld --verbose | sed \
-        -e '1,/==================================================/d' \
-        -e '/==================================================/,$d' \
-        -e "s/[.] = [0-9a-fx]* [+] SIZEOF_HEADERS/. = $textseg_addr + SIZEOF_HEADERS/" \
-        -e "s/__executable_start = [0-9a-fx]*/__executable_start = $textseg_addr/" > config-host.ld
-      textseg_ldflags="-Wl,-T../config-host.ld"
-    fi
-  fi
-fi
-
 # Check that the C++ compiler exists and works with the C compiler.
 # All the QEMU_CXXFLAGS are based on QEMU_CFLAGS. Keep this at the end to don't miss any other that could be added.
 if has $cxx; then
@@ -8175,10 +8132,6 @@ if test "$gprof" = "yes" ; then
   fi
 fi
 
-if test "$target_linux_user" = "yes" || test "$target_bsd_user" = "yes" ; then
-  ldflags="$ldflags $textseg_ldflags"
-fi
-
 # Newer kernels on s390 check for an S390_PGSTE program header and
 # enable the pgste page table extensions in that case. This makes
 # the vm.allocate_pgste sysctl unnecessary. We enable this program
diff --git a/Makefile b/Makefile
index fc2808fb4b..84ef881600 100644
--- a/Makefile
+++ b/Makefile
@@ -795,7 +795,7 @@ rm -f $(MANUAL_BUILDDIR)/$1/objects.inv $(MANUAL_BUILDDIR)/$1/searchindex.js $(M
 endef
 
 distclean: clean
-	rm -f config-host.mak config-host.h* config-host.ld $(DOCS)
+	rm -f config-host.mak config-host.h* $(DOCS)
 	rm -f tests/tcg/config-*.mak
 	rm -f config-all-devices.mak config-all-disas.mak config.status
 	rm -f $(SUBDIR_DEVICES_MAK)
-- 
2.20.1

[PATCH for-5.0 v3 2/7] tcg: Remove softmmu code_gen_buffer fixed address

[Richard Henderson]

The commentary talks about "in concert with the addresses
assigned in the relevant linker script", except there is no
linker script for softmmu, nor has there been for some time.

(Do not confuse the user-only linker script editing that was
removed in the previous patch, because user-only does not
use this code_gen_buffer allocation method.)

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 accel/tcg/translate-all.c | 37 +++++--------------------------------
 1 file changed, 5 insertions(+), 32 deletions(-)

diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index 78914154bf..9924e66d1f 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -1043,47 +1043,20 @@ static inline void *alloc_code_gen_buffer(void)
 {
     int prot = PROT_WRITE | PROT_READ | PROT_EXEC;
     int flags = MAP_PRIVATE | MAP_ANONYMOUS;
-    uintptr_t start = 0;
     size_t size = tcg_ctx->code_gen_buffer_size;
     void *buf;
 
-    /* Constrain the position of the buffer based on the host cpu.
-       Note that these addresses are chosen in concert with the
-       addresses assigned in the relevant linker script file.  */
-# if defined(__PIE__) || defined(__PIC__)
-    /* Don't bother setting a preferred location if we're building
-       a position-independent executable.  We're more likely to get
-       an address near the main executable if we let the kernel
-       choose the address.  */
-# elif defined(__x86_64__) && defined(MAP_32BIT)
-    /* Force the memory down into low memory with the executable.
-       Leave the choice of exact location with the kernel.  */
-    flags |= MAP_32BIT;
-    /* Cannot expect to map more than 800MB in low memory.  */
-    if (size > 800u * 1024 * 1024) {
-        tcg_ctx->code_gen_buffer_size = size = 800u * 1024 * 1024;
-    }
-# elif defined(__sparc__)
-    start = 0x40000000ul;
-# elif defined(__s390x__)
-    start = 0x90000000ul;
-# elif defined(__mips__)
-#  if _MIPS_SIM == _ABI64
-    start = 0x128000000ul;
-#  else
-    start = 0x08000000ul;
-#  endif
-# endif
-
-    buf = mmap((void *)start, size, prot, flags, -1, 0);
+    buf = mmap(NULL, size, prot, flags, -1, 0);
     if (buf == MAP_FAILED) {
         return NULL;
     }
 
 #ifdef __mips__
     if (cross_256mb(buf, size)) {
-        /* Try again, with the original still mapped, to avoid re-acquiring
-           that 256mb crossing.  This time don't specify an address.  */
+        /*
+         * Try again, with the original still mapped, to avoid re-acquiring
+         * the same 256mb crossing.
+         */
         size_t size2;
         void *buf2 = mmap(NULL, size, prot, flags, -1, 0);
         switch ((int)(buf2 != MAP_FAILED)) {
-- 
2.20.1

[PATCH for-5.0 v3 3/7] configure: Do not force pie=no for non-x86

[Richard Henderson]

PIE is supported on many other hosts besides x86.

The default for non-x86 is now the same as x86: pie is used
if supported, and may be forced via --enable/--disable-pie.

The original commit (40d6444e91c) said:

  "Non-x86 are not changed, as they require TCG changes"

but I think that's wrong -- there's nothing about PIE that
affects TCG one way or another.

Tested on aarch64 (bionic) and ppc64le (centos 7) hosts.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 configure | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/configure b/configure
index 2afcae61df..cbde833f6e 100755
--- a/configure
+++ b/configure
@@ -2107,16 +2107,6 @@ if ! compile_prog "-Werror" "" ; then
 	"Thread-Local Storage (TLS). Please upgrade to a version that does."
 fi
 
-if test "$pie" = ""; then
-  case "$cpu-$targetos" in
-    i386-Linux|x86_64-Linux|x32-Linux|i386-OpenBSD|x86_64-OpenBSD)
-      ;;
-    *)
-      pie="no"
-      ;;
-  esac
-fi
-
 if test "$pie" != "no" ; then
   cat > $TMPC << EOF
 
-- 
2.20.1

[PATCH for-5.0 v3 4/7] configure: Always detect -no-pie toolchain support

[Richard Henderson]

The CFLAGS_NOPIE and LDFLAGS_NOPIE variables are used
in pc-bios/optionrom/Makefile, which has nothing to do
with the PIE setting of the main qemu executables.

This overrides any operating system default to build
all executables as PIE, which is important for ROMs.

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 configure | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/configure b/configure
index cbde833f6e..7ba18783cb 100755
--- a/configure
+++ b/configure
@@ -2107,26 +2107,24 @@ if ! compile_prog "-Werror" "" ; then
 	"Thread-Local Storage (TLS). Please upgrade to a version that does."
 fi
 
-if test "$pie" != "no" ; then
-  cat > $TMPC << EOF
+cat > $TMPC << EOF
 
 #ifdef __linux__
 #  define THREAD __thread
 #else
 #  define THREAD
 #endif
-
 static THREAD int tls_var;
-
 int main(void) { return tls_var; }
-
 EOF
-  # check we support --no-pie first...
-  if compile_prog "-Werror -fno-pie" "-no-pie"; then
-    CFLAGS_NOPIE="-fno-pie"
-    LDFLAGS_NOPIE="-nopie"
-  fi
 
+# Check we support --no-pie first; we will need this for building ROMs.
+if compile_prog "-Werror -fno-pie" "-no-pie"; then
+  CFLAGS_NOPIE="-fno-pie"
+  LDFLAGS_NOPIE="-no-pie"
+fi
+
+if test "$pie" != "no" ; then
   if compile_prog "-fPIE -DPIE" "-pie"; then
     QEMU_CFLAGS="-fPIE -DPIE $QEMU_CFLAGS"
     QEMU_LDFLAGS="-pie $QEMU_LDFLAGS"
-- 
2.20.1

Re: [PATCH for-5.0 v3 4/7] configure: Always detect -no-pie toolchain support

[Alex Bennée]

Richard Henderson <richard.henderson@linaro.org> writes:

> The CFLAGS_NOPIE and LDFLAGS_NOPIE variables are used
> in pc-bios/optionrom/Makefile, which has nothing to do
> with the PIE setting of the main qemu executables.
>
> This overrides any operating system default to build
> all executables as PIE, which is important for ROMs.
>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
>  configure | 18 ++++++++----------
>  1 file changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/configure b/configure
> index cbde833f6e..7ba18783cb 100755
> --- a/configure
> +++ b/configure
> @@ -2107,26 +2107,24 @@ if ! compile_prog "-Werror" "" ; then
>  	"Thread-Local Storage (TLS). Please upgrade to a version that does."
>  fi
>  
> -if test "$pie" != "no" ; then
> -  cat > $TMPC << EOF
> +cat > $TMPC << EOF
>  
>  #ifdef __linux__
>  #  define THREAD __thread
>  #else
>  #  define THREAD
>  #endif
> -
>  static THREAD int tls_var;
> -
>  int main(void) { return tls_var; }
> -
>  EOF
> -  # check we support --no-pie first...
> -  if compile_prog "-Werror -fno-pie" "-no-pie"; then
> -    CFLAGS_NOPIE="-fno-pie"
> -    LDFLAGS_NOPIE="-nopie"
> -  fi
>  
> +# Check we support --no-pie first; we will need this for building ROMs.
> +if compile_prog "-Werror -fno-pie" "-no-pie"; then
> +  CFLAGS_NOPIE="-fno-pie"
> +  LDFLAGS_NOPIE="-no-pie"
> +fi
> +
> +if test "$pie" != "no" ; then
>    if compile_prog "-fPIE -DPIE" "-pie"; then
>      QEMU_CFLAGS="-fPIE -DPIE $QEMU_CFLAGS"
>      QEMU_LDFLAGS="-pie $QEMU_LDFLAGS"


-- 
Alex Bennée

[PATCH for-5.0 v3 5/7] configure: Unnest detection of -z, relro and -z, now

[Richard Henderson]

There is nothing about these options that is related to PIE.
Use them unconditionally.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Fangrui Song <i@maskray.me>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
v2: Do not split into two tests.
v3: Update to QEMU_LDFLAGS.
---
 configure | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index 7ba18783cb..4dead416ae 100755
--- a/configure
+++ b/configure
@@ -2129,9 +2129,6 @@ if test "$pie" != "no" ; then
     QEMU_CFLAGS="-fPIE -DPIE $QEMU_CFLAGS"
     QEMU_LDFLAGS="-pie $QEMU_LDFLAGS"
     pie="yes"
-    if compile_prog "" "-Wl,-z,relro -Wl,-z,now" ; then
-      QEMU_LDFLAGS="-Wl,-z,relro -Wl,-z,now $QEMU_LDFLAGS"
-    fi
   else
     if test "$pie" = "yes"; then
       error_exit "PIE not available due to missing toolchain support"
@@ -2142,6 +2139,12 @@ if test "$pie" != "no" ; then
   fi
 fi
 
+# Detect support for PT_GNU_RELRO + DT_BIND_NOW.
+# The combination is known as "full relro", because .got.plt is read-only too.
+if compile_prog "" "-Wl,-z,relro -Wl,-z,now" ; then
+  QEMU_LDFLAGS="-Wl,-z,relro -Wl,-z,now $QEMU_LDFLAGS"
+fi
+
 ##########################################
 # __sync_fetch_and_and requires at least -march=i486. Many toolchains
 # use i686 as default anyway, but for those that don't, an explicit
-- 
2.20.1

[PATCH for-5.0 v3 6/7] configure: Override the os default with --disable-pie

[Richard Henderson]

Some distributions, e.g. Ubuntu 19.10, enable PIE by default.
If for some reason one wishes to build a non-pie binary, we
must provide additional options to override.

At the same time, reorg the code to an elif chain.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
v3: Update for QEMU_LDFLAGS.
---
 configure | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/configure b/configure
index 4dead416ae..b304bd0cf8 100755
--- a/configure
+++ b/configure
@@ -2124,19 +2124,18 @@ if compile_prog "-Werror -fno-pie" "-no-pie"; then
   LDFLAGS_NOPIE="-no-pie"
 fi
 
-if test "$pie" != "no" ; then
-  if compile_prog "-fPIE -DPIE" "-pie"; then
-    QEMU_CFLAGS="-fPIE -DPIE $QEMU_CFLAGS"
-    QEMU_LDFLAGS="-pie $QEMU_LDFLAGS"
-    pie="yes"
-  else
-    if test "$pie" = "yes"; then
-      error_exit "PIE not available due to missing toolchain support"
-    else
-      echo "Disabling PIE due to missing toolchain support"
-      pie="no"
-    fi
-  fi
+if test "$pie" = "no"; then
+  QEMU_CFLAGS="$CFLAGS_NOPIE $QEMU_CFLAGS"
+  QEMU_LDFLAGS="$LDFLAGS_NOPIE $QEMU_LDFLAGS"
+elif compile_prog "-fPIE -DPIE" "-pie"; then
+  QEMU_CFLAGS="-fPIE -DPIE $QEMU_CFLAGS"
+  QEMU_LDFLAGS="-pie $QEMU_LDFLAGS"
+  pie="yes"
+elif test "$pie" = "yes"; then
+  error_exit "PIE not available due to missing toolchain support"
+else
+  echo "Disabling PIE due to missing toolchain support"
+  pie="no"
 fi
 
 # Detect support for PT_GNU_RELRO + DT_BIND_NOW.
-- 
2.20.1

[PATCH for-5.0 v3 7/7] configure: Support -static-pie if requested

[Richard Henderson]

Recent toolchains support static and pie at the same time.

As with normal dynamic builds, allow --static to default to PIE
if supported by the toolchain.  Allow --enable/--disable-pie to
override the default.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
v2: Fix --disable-pie --static
v3: Update for QEMU_LDFLAGS.
---
 configure | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/configure b/configure
index b304bd0cf8..a16ae9a2be 100755
--- a/configure
+++ b/configure
@@ -1067,7 +1067,6 @@ for opt do
   ;;
   --static)
     static="yes"
-    QEMU_LDFLAGS="-static $QEMU_LDFLAGS"
     QEMU_PKG_CONFIG_FLAGS="--static $QEMU_PKG_CONFIG_FLAGS"
   ;;
   --mandir=*) mandir="$optarg"
@@ -2089,11 +2088,6 @@ if test "$static" = "yes" ; then
   if test "$modules" = "yes" ; then
     error_exit "static and modules are mutually incompatible"
   fi
-  if test "$pie" = "yes" ; then
-    error_exit "static and pie are mutually incompatible"
-  else
-    pie="no"
-  fi
 fi
 
 # Unconditional check for compiler __thread support
@@ -2124,7 +2118,18 @@ if compile_prog "-Werror -fno-pie" "-no-pie"; then
   LDFLAGS_NOPIE="-no-pie"
 fi
 
-if test "$pie" = "no"; then
+if test "$static" = "yes"; then
+  if test "$pie" != "no" && compile_prog "-fPIE -DPIE" "-static-pie"; then
+    QEMU_CFLAGS="-fPIE -DPIE $QEMU_CFLAGS"
+    QEMU_LDFLAGS="-static-pie $QEMU_LDFLAGS"
+    pie="yes"
+  elif test "$pie" = "yes"; then
+    error_exit "-static-pie not available due to missing toolchain support"
+  else
+    QEMU_LDFLAGS="-static $QEMU_LDFLAGS"
+    pie="no"
+  fi
+elif test "$pie" = "no"; then
   QEMU_CFLAGS="$CFLAGS_NOPIE $QEMU_CFLAGS"
   QEMU_LDFLAGS="$LDFLAGS_NOPIE $QEMU_LDFLAGS"
 elif compile_prog "-fPIE -DPIE" "-pie"; then
-- 
2.20.1