[xen staging] x86/EFI: redo .reloc section bounds determination

[patchbot@xxxxxxx]

commit d4057f3732baeeeed7f88e8b9b9f27b89fd7ef12
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Apr 22 13:27:47 2021 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Apr 22 13:27:47 2021 +0200

    x86/EFI: redo .reloc section bounds determination
    
    There's no need to link relocs-dummy.o into the ELF binary. The two
    symbols needed can as well be provided by the linker script. Then our
    mkreloc tool also doesn't need to put them in the generated assembler
    source.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/Makefile           |  5 ++---
 xen/arch/x86/efi/mkreloc.c      |  6 +-----
 xen/arch/x86/efi/relocs-dummy.S |  2 --
 xen/arch/x86/xen.lds.S          | 31 ++++++++++++++-----------------
 4 files changed, 17 insertions(+), 27 deletions(-)

diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 053206e4f0..0b4c24112d 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -136,7 +136,6 @@ XEN_NO_PE_FIXUPS := $(if $(XEN_BUILD_EFI), \
 endif
 
 ALL_OBJS := $(BASEDIR)/arch/x86/boot/built_in.o 
$(BASEDIR)/arch/x86/efi/built_in.o $(ALL_OBJS)
-EFI_OBJS-$(XEN_BUILD_EFI) := efi/relocs-dummy.o
 
 ifeq ($(CONFIG_LTO),y)
 # Gather all LTO objects together
@@ -144,13 +143,13 @@ prelink_lto.o: $(ALL_OBJS) $(ALL_LIBS)
        $(LD_LTO) -r -o $@ $(filter-out %.a,$^) --start-group $(filter %.a,$^) 
--end-group
 
 # Link it with all the binary objects
-prelink.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o 
$(EFI_OBJS-y) FORCE
+prelink.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o 
FORCE
        $(call if_changed,ld)
 
 prelink-efi.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) 
prelink_lto.o FORCE
        $(call if_changed,ld)
 else
-prelink.o: $(ALL_OBJS) $(ALL_LIBS) $(EFI_OBJS-y) FORCE
+prelink.o: $(ALL_OBJS) $(ALL_LIBS) FORCE
        $(call if_changed,ld)
 
 prelink-efi.o: $(ALL_OBJS) $(ALL_LIBS) FORCE
diff --git a/xen/arch/x86/efi/mkreloc.c b/xen/arch/x86/efi/mkreloc.c
index 9efeaee7c5..083740ab8a 100644
--- a/xen/arch/x86/efi/mkreloc.c
+++ b/xen/arch/x86/efi/mkreloc.c
@@ -320,9 +320,7 @@ int main(int argc, char *argv[])
     }
 
     puts("\t.section .reloc, \"a\", @progbits\n"
-         "\t.balign 4\n"
-         "\t.globl __base_relocs_start, __base_relocs_end\n"
-         "__base_relocs_start:");
+         "\t.balign 4");
 
     for ( i = 0; i < nsec; ++i )
     {
@@ -373,8 +371,6 @@ int main(int argc, char *argv[])
 
     diff_sections(NULL, NULL, NULL, 0, 0, 0, 0);
 
-    puts("__base_relocs_end:");
-
     close(in1);
     close(in2);
 
diff --git a/xen/arch/x86/efi/relocs-dummy.S b/xen/arch/x86/efi/relocs-dummy.S
index d928a82d53..b95fa444da 100644
--- a/xen/arch/x86/efi/relocs-dummy.S
+++ b/xen/arch/x86/efi/relocs-dummy.S
@@ -1,10 +1,8 @@
 
        .section .reloc, "a", @progbits
        .balign 4
-GLOBAL(__base_relocs_start)
        .long 0
        .long 8
-GLOBAL(__base_relocs_end)
 
        .globl VIRT_START, ALT_START
        .equ VIRT_START, XEN_VIRT_START
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 3e29147b6a..5fadb02b7f 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -170,18 +170,6 @@ SECTIONS
 #endif
 #endif
 
-/*
- * ELF builds are linked to a fixed virtual address, and in principle
- * shouldn't have a .reloc section.  However, due to the way EFI support is
- * currently implemented, retaining the .reloc section is necessary.
- */
-#if defined(XEN_BUILD_EFI) && !defined(EFI)
-  . = ALIGN(4);
-  DECL_SECTION(.reloc) {
-    *(.reloc)
-  } PHDR(text)
-#endif
-
   _erodata = .;
 
   . = ALIGN(SECTION_ALIGN);
@@ -319,18 +307,27 @@ SECTIONS
   __2M_rwdata_end = .;
 
 #ifdef EFI
-  . = ALIGN(4);
-  DECL_SECTION(.reloc) {
+  .reloc ALIGN(4) : {
+    __base_relocs_start = .;
     *(.reloc)
+    __base_relocs_end = .;
   }
   /* Trick the linker into setting the image size to exactly 16Mb. */
   . = ALIGN(__section_alignment__);
   DECL_SECTION(.pad) {
     . = ALIGN(MB(16));
   }
-#endif
-
-#ifndef XEN_BUILD_EFI
+#elif defined(XEN_BUILD_EFI)
+  /*
+   * Due to the way EFI support is currently implemented, these two symbols
+   * need to be defined.  Their precise values shouldn't matter (the consuming
+   * function doesn't get called), but to be on the safe side both values would
+   * better match.  Of course the need to be reachable by the relocations
+   * referencing them.
+   */
+  PROVIDE(__base_relocs_start = .);
+  PROVIDE(__base_relocs_end = .);
+#else
   efi = .;
 #endif
 
--
generated by git-patchbot for /home/xen/git/xen.git#staging