[kvm-unit-tests PATCH v1 2/3] s390x/Makefile: snippets: Avoid creation of .eh_frame and .eh_frame_hdr sections

[Marc Hartmayer <mhartmay@linux.ibm.com>]

Use `-fno-asynchronous-unwind-tables` and `-fno-exceptions` to avoid creating
`.eh_frame` and `.eh_frame_hdr` sections. They are not used by the snippets and
the creation of the sections may result in the creation of an RWX
segment (depending on the toolchain used).

Before this change:

$ make -j s390x/snippets/c/spec_ex.elf >/dev/null && readelf -l s390x/snippets/c/spec_ex.elf
/usr/bin/s390x-linux-gnu-ld: warning: s390x/snippets/c/spec_ex.elf has a LOAD segment with RWX permissions

Elf file type is EXEC (Executable file)
Entry point 0x4000
There are 4 program headers, starting at offset 64

Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  LOAD           0x0000000000001000 0x0000000000000000 0x0000000000000000
                 0x00000000000001b0 0x00000000000001b0  RW     0x1000
  LOAD           0x0000000000002000 0x0000000000004000 0x0000000000004000
                 0x000000000000104c 0x0000000000001060  RWE    0x1000
  GNU_EH_FRAME   0x0000000000003038 0x0000000000005038 0x0000000000005038
                 0x0000000000000014 0x0000000000000014  R      0x4
  GNU_STACK      0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000000 0x0000000000000000  RW     0x10

 Section to Segment mapping:
  Segment Sections...
   00     .lowcore
   01     .text .eh_frame .eh_frame_hdr .bss
   02     .eh_frame_hdr
   03

After this change, there is no warning and no RWX ELF segment:

$ make -j s390x/snippets/c/spec_ex.elf >/dev/null && readelf -l s390x/snippets/c/spec_ex.elf
Elf file type is EXEC (Executable file)
Entry point 0x4000
There are 4 program headers, starting at offset 64

Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  LOAD           0x0000000000001000 0x0000000000000000 0x0000000000000000
                 0x00000000000001b0 0x00000000000001b0  RW     0x1000
  LOAD           0x0000000000002000 0x0000000000004000 0x0000000000004000
                 0x00000000000000a8 0x00000000000000a8  R E    0x1000
  LOAD           0x0000000000000000 0x0000000000005000 0x0000000000005000
                 0x0000000000000000 0x0000000000000010  RW     0x1000
  GNU_STACK      0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000000 0x0000000000000000  RW     0x10

 Section to Segment mapping:
  Segment Sections...
   00     .lowcore
   01     .text
   02     .bss
   03

Linker used:

$ s390x-linux-gnu-ld -v
GNU ld version 2.41-1.fc40

Therefore the commit 9801dbbe9ea4 ("s390x: Specify program headers with flags to
avoid linker warnings") can be reverted.
---
Note: we have to double check whether__builtin_frame_address() in s390x/stack.c
needs the .eh_frame or not.
---
Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
---
 s390x/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/s390x/Makefile b/s390x/Makefile
index 784818b2883e..f1bbf5e9f457 100644
--- a/s390x/Makefile
+++ b/s390x/Makefile
@@ -148,10 +148,10 @@ endif
 
 # the asm/c snippets %.o have additional generated files as dependencies
 $(SNIPPET_DIR)/asm/%.o: $(SNIPPET_DIR)/asm/%.S $(asm-offsets)
-	$(CC) $(CFLAGS) -c -nostdlib -o $@ $<
+	$(CC) $(CFLAGS) -c -nostdlib -fno-asynchronous-unwind-tables -fno-exceptions -o $@ $<
 
 $(SNIPPET_DIR)/c/%.o: $(SNIPPET_DIR)/c/%.c $(asm-offsets)
-	$(CC) $(CFLAGS) -c -nostdlib -o $@ $<
+	$(CC) $(CFLAGS) -c -nostdlib -fno-asynchronous-unwind-tables -fno-exceptions -o $@ $<
 
 $(SNIPPET_DIR)/asm/%.elf: $(SNIPPET_DIR)/asm/%.o $(SNIPPET_DIR)/asm/flat.lds
 	$(CC) $(LDFLAGS) -o $@ -T $(SNIPPET_DIR)/asm/flat.lds $<
-- 
2.34.1