| Message ID | 20200429194420.21147-4-dbuono@linux.vnet.ibm.com |
|---|---|
| State | New |
| Headers | show |
| Series | Add support for SafeStack | expand |
On Wed, Apr 29, 2020 at 03:44:19PM -0400, Daniele Buono wrote: > This patch adds a flag to enable the SafeStack instrumentation provided > by LLVM. > The checks make sure that the compiler supports the flags, and that we > are using the proper coroutine implementation (coroutine-ucontext). > While SafeStack is supported only on Linux, NetBSD, FreeBSD and macOS, > we are not checking for the O.S. since this is already done by LLVM. > > Signed-off-by: Daniele Buono <dbuono@linux.vnet.ibm.com> > --- > configure | 29 +++++++++++++++++++++++++++++ > 1 file changed, 29 insertions(+) Great, this can become Patch 1 and it can set CONFIG_SAFESTACK as mentioned in my earlier reply. > diff --git a/configure b/configure > index 23b5e93752..f37e4ae0bd 100755 > --- a/configure > +++ b/configure > @@ -302,6 +302,7 @@ audio_win_int="" > libs_qga="" > debug_info="yes" > stack_protector="" > +safe_stack="no" The comment above this says: # Always add --enable-foo and --disable-foo command line args. Please add --disable-safe-stack.
Hi Stefan, I would feel more confident by adding another check in configure to make sure that the user didn't enable SafeStack manually through other means, like manually setting the option through extra_cflags. What do you think? On 5/21/2020 5:52 AM, Stefan Hajnoczi wrote: > On Wed, Apr 29, 2020 at 03:44:19PM -0400, Daniele Buono wrote: >> This patch adds a flag to enable the SafeStack instrumentation provided >> by LLVM. >> The checks make sure that the compiler supports the flags, and that we >> are using the proper coroutine implementation (coroutine-ucontext). >> While SafeStack is supported only on Linux, NetBSD, FreeBSD and macOS, >> we are not checking for the O.S. since this is already done by LLVM. >> >> Signed-off-by: Daniele Buono <dbuono@linux.vnet.ibm.com> >> --- >> configure | 29 +++++++++++++++++++++++++++++ >> 1 file changed, 29 insertions(+) > > Great, this can become Patch 1 and it can set CONFIG_SAFESTACK as > mentioned in my earlier reply. > >> diff --git a/configure b/configure >> index 23b5e93752..f37e4ae0bd 100755 >> --- a/configure >> +++ b/configure >> @@ -302,6 +302,7 @@ audio_win_int="" >> libs_qga="" >> debug_info="yes" >> stack_protector="" >> +safe_stack="no" > > The comment above this says: > > # Always add --enable-foo and --disable-foo command line args. > > Please add --disable-safe-stack. >
On Fri, May 22, 2020 at 11:24:46AM -0400, Daniele Buono wrote: > I would feel more confident by adding another check in configure to make > sure that the user didn't enable SafeStack manually through other means, > like manually setting the option through extra_cflags. > What do you think? Sure, a compile_prog call could check if SafeStack is enable when it shouldn't be. This can be done together with a --disable option. Stefan
Hi Stefan, a quick clarification on configure: right now, in configure, there's * "Advanced Options (experts only)" which usually don't have both enable and disable for each option, and * "Optional features, enabled with --enable-FEATURE and disabled with --disable-FEATURE, default is enabled if available:" How do you think SafeStack should be classified? * If we do it as Advanced option, we should probably force it disabled unless --enable-safe-stack is provided. In this case --disable-safe-stack is not really necessary. * If we do it as optional feature, I have two ways to handle the default: 1. enable/disable based on the compilation flags given to configure 2. enable every time the provided compiler supports it On 5/27/2020 7:12 AM, Stefan Hajnoczi wrote: > On Fri, May 22, 2020 at 11:24:46AM -0400, Daniele Buono wrote: >> I would feel more confident by adding another check in configure to make >> sure that the user didn't enable SafeStack manually through other means, >> like manually setting the option through extra_cflags. >> What do you think? > > Sure, a compile_prog call could check if SafeStack is enable when it > shouldn't be. > > This can be done together with a --disable option. > > Stefan >
diff --git a/configure b/configure index 23b5e93752..f37e4ae0bd 100755 --- a/configure +++ b/configure @@ -302,6 +302,7 @@ audio_win_int="" libs_qga="" debug_info="yes" stack_protector="" +safe_stack="no" use_containers="yes" gdb_bin=$(command -v "gdb") @@ -1275,6 +1276,8 @@ for opt do ;; --disable-stack-protector) stack_protector="no" ;; + --enable-safe-stack) safe_stack="yes" + ;; --disable-curses) curses="no" ;; --enable-curses) curses="yes" @@ -1774,6 +1777,8 @@ Advanced options (experts only): --with-coroutine=BACKEND coroutine backend. Supported options: ucontext, sigaltstack, windows --enable-gcov enable test coverage analysis with gcov + --enable-safe-stack enable the SafeStack stack protection. Depends on + clang/llvm >= 3.7 and coroutine backend ucontext. --gcov=GCOV use specified gcov [$gcov_tool] --disable-blobs disable installing provided firmware blobs --with-vss-sdk=SDK-path enable Windows VSS support in QEMU Guest Agent @@ -5501,6 +5506,29 @@ if test "$debug_stack_usage" = "yes"; then fi fi +################################################## +# Check if SafeStack is enabled and supported + +if test "$safe_stack" = "yes"; then + cat > $TMPC << EOF +int main(int argc, char *argv[]) +{ + return 0; +} +EOF + flag="-fsanitize=safe-stack" + # Check that safe-stack is supported. + if compile_prog "-Werror $flag" ""; then + # Flag needed both at compilation and at linking + QEMU_CFLAGS="$QEMU_CFLAGS $flag" + QEMU_LDFLAGS="$QEMU_LDFLAGS $flag" + else + error_exit "SafeStack not supported by your compiler" + fi + if test "$coroutine" != "ucontext"; then + error_exit "SafeStack is only supported by the coroutine backend ucontext" + fi +fi ########################################## # check if we have open_by_handle_at @@ -6595,6 +6623,7 @@ echo "sparse enabled $sparse" echo "strip binaries $strip_opt" echo "profiler $profiler" echo "static build $static" +echo "safe stack $safe_stack" if test "$darwin" = "yes" ; then echo "Cocoa support $cocoa" fi
This patch adds a flag to enable the SafeStack instrumentation provided by LLVM. The checks make sure that the compiler supports the flags, and that we are using the proper coroutine implementation (coroutine-ucontext). While SafeStack is supported only on Linux, NetBSD, FreeBSD and macOS, we are not checking for the O.S. since this is already done by LLVM. Signed-off-by: Daniele Buono <dbuono@linux.vnet.ibm.com> --- configure | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+)