Add NO_EXEC_STACK_DIRECTIVE to chkstk and chkstk2 sources

[dim]

Summary

As reported in bug 35739, the arch-specific sources for the chkstk and
chkstk2 functions do not contain NO_EXEC_STACK_DIRECTIVE macros, and
therefore have an executable stack by default. This can cause warnings
from automated vulnerability scanners.

Add the directives to make these warnings go away. This is basically a
follow-up to rL273500.

[martell]

LGTM

Also noting my comment on 35739

chkstk.S and chkstk2.S should only be included on WIN32
removing them from the (NOT MSVC) guards seems like the correct move.

[dim]

Do not build chkstk.S and chkstk2.S for non-Windows targets.

[dim]

Oops, checked in wrong revision. This has both fixes:

• Add NO_EXEC_STACK_DIRECTIVE, that can never hurt
• Remove chkstk*.S from non-Windows targets

[martell]

hmm, looking at the #define for NO_EXEC_STACK_DIRECTIVE
once the two files have been removed from non windows targets they won't do anything anymore.

Do you have commit access, it looks good as is?

[dim]

In D41567#963799, @martell wrote:

hmm looking at the #define for NO_EXEC_STACK_DIRECTIVE
once the two files have been removed from non windows targets they won't do anything anymore.

Ah yes, you're right, I didn't realize that. Those won't really be needed then.

Do you have commit access, it looks good as is?

Yes, I'll commit.

[mstorsjo]

In D41567#963799, @martell wrote:

hmm, looking at the #define for NO_EXEC_STACK_DIRECTIVE
once the two files have been removed from non windows targets they won't do anything anymore.

Yes, it's not really needed for chkstk for windows. As for what the condition should be, MINGW or "WIN32 and NOT MSVC", I don't have much of an opinion. (The comment I got in the mail said something about that, but this comment seems to have been revised?)

lib/builtins/CMakeLists.txt

set(x86_ARCH_SOURCES
   floatundixf.c
   floatuntixf.c
   mulxc3.c
   powixf2.c
 )
 
 if (NOT MSVC)
   set(x86_64_SOURCES
-      x86_64/chkstk.S
-      x86_64/chkstk2.S
       x86_64/floatdidf.c
       x86_64/floatdisf.c
       x86_64/floatdixf.c
       x86_64/floatundidf.S
       x86_64/floatundisf.S
       x86_64/floatundixf.S)
   filter_builtin_sources(x86_64_SOURCES EXCLUDE x86_64_SOURCES "${x86_64_SOURCES};${GENERIC_SOURCES}")
   set(x86_64h_SOURCES ${x86_64_SOURCES})
 
   if (WIN32)
     set(x86_64_SOURCES
         ${x86_64_SOURCES}
         x86_64/chkstk.S
         x86_64/chkstk2.S)
   endif()
 
   set(i386_SOURCES
       i386/ashldi3.S
       i386/ashrdi3.S
-      i386/chkstk.S
-      i386/chkstk2.S
       i386/divdi3.S
       i386/floatdidf.S
       i386/floatdisf.S
       i386/floatdixf.S
       i386/floatundidf.S
       i386/floatundisf.S
       i386/floatundixf.S
       i386/lshrdi3.S

lib/builtins/aarch64/chkstk.S

1:
         subs   x16, x16, #PAGE_SIZE
         ldr    xzr, [x17]
         b.gt   1b
 
         ret
 END_COMPILERRT_FUNCTION(__chkstk)
 
 #endif // __aarch64__
+
+NO_EXEC_STACK_DIRECTIVE
+

lib/builtins/i386/chkstk.S

1:
         sub    %eax,%ecx
         test   %ecx,(%ecx)
         pop    %eax
         pop    %ecx
         ret
 END_COMPILERRT_FUNCTION(__chkstk_ms)
 
 #endif // __i386__
+
+NO_EXEC_STACK_DIRECTIVE
+

lib/builtins/i386/chkstk2.S

1:
         mov    -4(%eax),%ecx    // restore ecx
         push   (%eax)           // push return address onto the stack
         sub    %esp,%eax        // restore the original value in eax
         ret
 END_COMPILERRT_FUNCTION(__chkstk)
 END_COMPILERRT_FUNCTION(_alloca)
 
 #endif // __i386__
+
+NO_EXEC_STACK_DIRECTIVE
+

lib/builtins/x86_64/chkstk.S

1:
         sub    %rax,%rcx
         test   %rcx,(%rcx)
         pop    %rax
         pop    %rcx
         ret
 END_COMPILERRT_FUNCTION(___chkstk_ms)
 
 #endif // __x86_64__
+
+NO_EXEC_STACK_DIRECTIVE
+

lib/builtins/x86_64/chkstk2.S

1:
         mov    -8(%rax),%rcx    // restore rcx
         push   (%rax)           // push return address onto the stack
         sub    %rsp,%rax        // restore the original value in rax
         ret
 END_COMPILERRT_FUNCTION(___chkstk)
 END_COMPILERRT_FUNCTION(__alloca)
 
 #endif // __x86_64__
+
+NO_EXEC_STACK_DIRECTIVE
+