[glibc] csu: Disable stack protector for static-reloc for static-pie

[glibc] csu: Disable stack protector for static-reloc for static-pie

[Adhemerval Zanella]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e82aab227bdf3faa0f28a69dbf50b5562659d1cf

commit e82aab227bdf3faa0f28a69dbf50b5562659d1cf
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Wed Oct 5 14:07:28 2022 -0300

    csu: Disable stack protector for static-reloc for static-pie
    
    For instance on x86_64 with gcc 12.1.1 andwith fstack-protector
    enabled the empty function still generates a stack protector code
    sequence:
    
      0000000000000000 <_dl_relocate_static_pie>:
         0:   48 83 ec 18             sub    $0x18,%rsp
         4:   64 48 8b 04 25 28 00    mov    %fs:0x28,%rax
         b:   00 00
         d:   48 89 44 24 08          mov    %rax,0x8(%rsp)
        12:   31 c0                   xor    %eax,%eax
        14:   48 8b 44 24 08          mov    0x8(%rsp),%rax
        19:   64 48 2b 04 25 28 00    sub    %fs:0x28,%rax
        20:   00 00
        22:   75 05                   jne    29 <_dl_relocate_static_pie+0x29>
        24:   48 83 c4 18             add    $0x18,%rsp
        28:   c3                      ret
        29:   e8 00 00 00 00          call   2e <_dl_relocate_static_pie+0x2e>
    
    And since the function is called prior thread pointer setup, it
    triggers a invalid memory access (this is shown with the failure
    of elf/tst-tls1-static-non-pie).
    
    Although it might characterizes as compiler issue or missed
    optimization, to be safe also disables stack protector on
    static-reloc object.
    
    Checked on x86_64-linux-gnu and sparc64-linux-gnu.
    Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

Diff:
---
 csu/Makefile | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/csu/Makefile b/csu/Makefile
index 2e8a28e851..f71a5eb6c6 100644
--- a/csu/Makefile
+++ b/csu/Makefile
@@ -50,15 +50,21 @@ tests =
 # applications, so that build flags matter.
 # See <https://sourceware.org/ml/libc-alpha/2018-07/msg00101.html>.
 #
+# The function is called prior the thread pointer setup, and if stack
+# protector is enabled the compiler might still generate the stack check
+# (which requires the thread pointer correctly set).
+extra-no-ssp = static-reloc
+
 # libc-start.os is safe to be built with stack protector since
 # __libc_start_main is called after stack canary setup is done.
-ssp-safe.os = static-reloc libc-start
+ssp-safe.os = libc-start
 
-CFLAGS-.o += $(call elide-stack-protector,.o,$(routines))
-CFLAGS-.op += $(call elide-stack-protector,.op,$(routines))
-CFLAGS-.oS += $(call elide-stack-protector,.oS,$(routines))
+CFLAGS-.o += $(call elide-stack-protector,.o,$(routines) $(extra-no-ssp))
+CFLAGS-.op += $(call elide-stack-protector,.op,$(routines) $(extra-no-ssp))
+CFLAGS-.oS += $(call elide-stack-protector,.oS,$(routines) $(extra-no-ssp))
 CFLAGS-.os += $(call elide-stack-protector,.os,$(filter-out \
-						 $(ssp-safe.os),$(routines)))
+						 $(ssp-safe.os), \
+						 $(routines) $(extra-no-ssp)))
 
 ifeq (yes,$(build-shared))
 extra-objs += S$(start-installed-name) gmon-start.os