[PATCH v4 2/2] xen: Populate xen.lds.h and make use of its macros

[Michal Orzel <michal.orzel@arm.com>]

Populate header file xen.lds.h with the first portion of macros storing
constructs common to x86 and arm linker scripts. Replace the original
constructs with these helpers.

No functional improvements to x86 linker script.

Making use of common macros improves arm linker script with:
- explicit list of debug sections that otherwise are seen as "orphans"
  by the linker. This will allow to fix issues after enabling linker
  option --orphan-handling one day,
- extended list of discarded section to include: .discard, destructors
  related sections, .fini_array which can reference .text.exit,
- sections not related to debugging that are placed by ld.lld. Even
  though we do not support linking with LLD on Arm, these sections do
  not cause problem to GNU ld.

Please note that this patch does not aim to perform the full sync up
between the linker scripts. It creates a base for further work.

Signed-off-by: Michal Orzel <michal.orzel@arm.com>
---
Changes since v3:
-use POINTER_ALIGN in debug sections when needed
-modify comment about ELF_DETAILS_SECTIONS
Changes since v2:
-refactor commit msg
-move constructs together with surrounding ifdefery
-list constructs other than *_SECTIONS in alphabetical order
-add comment about EFI vs EFI support
Changes since v1:
-merge x86 and arm changes into single patch
-do not propagate issues by generalizing CTORS
-extract sections not related to debugging into separate macro
-get rid of _SECTION suffix in favor of using more meaningful suffixes
---
 xen/arch/arm/xen.lds.S    |  44 +++----------
 xen/arch/x86/xen.lds.S    |  96 +++-------------------------
 xen/include/xen/xen.lds.h | 129 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 147 insertions(+), 122 deletions(-)

diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index c666fc3e69..649aa04f7f 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -68,12 +68,7 @@ SECTIONS
        *(.proc.info)
        __proc_info_end = .;
 
-#ifdef CONFIG_HAS_VPCI
-       . = ALIGN(POINTER_ALIGN);
-       __start_vpci_array = .;
-       *(SORT(.data.vpci.*))
-       __end_vpci_array = .;
-#endif
+       VPCI_ARRAY
   } :text
 
 #if defined(BUILD_ID)
@@ -109,12 +104,7 @@ SECTIONS
        *(.data.schedulers)
        __end_schedulers_array = .;
 
-#ifdef CONFIG_HYPFS
-       . = ALIGN(8);
-       __paramhypfs_start = .;
-       *(.data.paramhypfs)
-       __paramhypfs_end = .;
-#endif
+       HYPFS_PARAM
 
        *(.data .data.*)
        CONSTRUCTORS
@@ -178,12 +168,7 @@ SECTIONS
        *(.altinstructions)
        __alt_instructions_end = .;
 
-#ifdef CONFIG_DEBUG_LOCK_PROFILE
-       . = ALIGN(POINTER_ALIGN);
-       __lock_profile_start = .;
-       *(.lockprofile.data)
-       __lock_profile_end = .;
-#endif
+       LOCK_PROFILE_DATA
 
        *(.init.data)
        *(.init.data.rel)
@@ -222,22 +207,13 @@ SECTIONS
   /* Section for the device tree blob (if any). */
   .dtb : { *(.dtb) } :text
 
-  /* Sections to be discarded */
-  /DISCARD/ : {
-       *(.exit.text)
-       *(.exit.data)
-       *(.exitcall.exit)
-       *(.eh_frame)
-  }
-
-  /* Stabs debugging sections.  */
-  .stab 0 : { *(.stab) }
-  .stabstr 0 : { *(.stabstr) }
-  .stab.excl 0 : { *(.stab.excl) }
-  .stab.exclstr 0 : { *(.stab.exclstr) }
-  .stab.index 0 : { *(.stab.index) }
-  .stab.indexstr 0 : { *(.stab.indexstr) }
-  .comment 0 : { *(.comment) }
+  DWARF2_DEBUG_SECTIONS
+
+  DISCARD_SECTIONS
+
+  STABS_DEBUG_SECTIONS
+
+  ELF_DETAILS_SECTIONS
 }
 
 /*
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 3e65c09bb3..65cc4c9231 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -13,13 +13,6 @@
 #undef __XEN_VIRT_START
 #define __XEN_VIRT_START __image_base__
 #define DECL_SECTION(x) x :
-/*
- * Use the NOLOAD directive, despite currently ignored by (at least) GNU ld
- * for PE output, in order to record that we'd prefer these sections to not
- * be loaded into memory.
- */
-#define DECL_DEBUG(x, a) #x ALIGN(a) (NOLOAD) : { *(x) }
-#define DECL_DEBUG2(x, y, a) #x ALIGN(a) (NOLOAD) : { *(x) *(y) }
 
 ENTRY(efi_start)
 
@@ -27,8 +20,6 @@ ENTRY(efi_start)
 
 #define FORMAT "elf64-x86-64"
 #define DECL_SECTION(x) #x : AT(ADDR(#x) - __XEN_VIRT_START)
-#define DECL_DEBUG(x, a) #x 0 : { *(x) }
-#define DECL_DEBUG2(x, y, a) #x 0 : { *(x) *(y) }
 
 ENTRY(start_pa)
 
@@ -159,12 +150,7 @@ SECTIONS
        *(.note.gnu.build-id)
        __note_gnu_build_id_end = .;
 #endif
-#ifdef CONFIG_HAS_VPCI
-       . = ALIGN(POINTER_ALIGN);
-       __start_vpci_array = .;
-       *(SORT(.data.vpci.*))
-       __end_vpci_array = .;
-#endif
+       VPCI_ARRAY
   } PHDR(text)
 
 #if defined(CONFIG_PVH_GUEST) && !defined(EFI)
@@ -278,12 +264,7 @@ SECTIONS
         *(.altinstructions)
         __alt_instructions_end = .;
 
-#ifdef CONFIG_DEBUG_LOCK_PROFILE
-       . = ALIGN(POINTER_ALIGN);
-       __lock_profile_start = .;
-       *(.lockprofile.data)
-       __lock_profile_end = .;
-#endif
+       LOCK_PROFILE_DATA
 
        . = ALIGN(8);
        __ctors_start = .;
@@ -335,12 +316,7 @@ SECTIONS
        *(.data.schedulers)
        __end_schedulers_array = .;
 
-#ifdef CONFIG_HYPFS
-       . = ALIGN(8);
-       __paramhypfs_start = .;
-       *(.data.paramhypfs)
-       __paramhypfs_end = .;
-#endif
+       HYPFS_PARAM
   } PHDR(text)
 
   DECL_SECTION(.data) {
@@ -387,33 +363,7 @@ SECTIONS
   efi = .;
 #endif
 
-  /*
-   * Explicitly list debug sections, first of all to avoid these sections being
-   * viewed as "orphan" by the linker.
-   *
-   * For the PE output this is further necessary so that they don't end up at
-   * VA 0, which is below image base and thus invalid.  Note that we're past
-   * _end here, so if these sections get loaded they'll be discarded at runtime
-   * anyway.
-   */
-  DECL_DEBUG(.debug_abbrev, 1)
-  DECL_DEBUG2(.debug_info, .gnu.linkonce.wi.*, 1)
-  DECL_DEBUG(.debug_types, 1)
-  DECL_DEBUG(.debug_str, 1)
-  DECL_DEBUG2(.debug_line, .debug_line.*, 1)
-  DECL_DEBUG(.debug_line_str, 1)
-  DECL_DEBUG(.debug_names, 4)
-  DECL_DEBUG(.debug_frame, 4)
-  DECL_DEBUG(.debug_loc, 1)
-  DECL_DEBUG(.debug_loclists, 4)
-  DECL_DEBUG(.debug_macinfo, 1)
-  DECL_DEBUG(.debug_macro, 1)
-  DECL_DEBUG(.debug_ranges, 8)
-  DECL_DEBUG(.debug_rnglists, 4)
-  DECL_DEBUG(.debug_addr, 8)
-  DECL_DEBUG(.debug_aranges, 1)
-  DECL_DEBUG(.debug_pubnames, 1)
-  DECL_DEBUG(.debug_pubtypes, 1)
+  DWARF2_DEBUG_SECTIONS
 
 #ifdef EFI
   /* Trick the linker into setting the image size to no less than 16Mb. */
@@ -427,42 +377,12 @@ SECTIONS
   hv_hcall_page = ABSOLUTE(HV_HCALL_PAGE - XEN_VIRT_START + __XEN_VIRT_START);
 #endif
 
-  /* Sections to be discarded */
-  /DISCARD/ : {
-       *(.text.exit)
-       *(.exit.text)
-       *(.exit.data)
-       *(.exitcall.exit)
-       *(.discard)
-       *(.discard.*)
-       *(.eh_frame)
-       *(.dtors)
-       *(.dtors.*)
-       *(.fini_array)
-       *(.fini_array.*)
-#ifdef EFI
-       *(.comment)
-       *(.comment.*)
-       *(.note.*)
-#endif
-  }
+  DISCARD_SECTIONS
 
 #ifndef EFI
-  /* Stabs debugging sections.  */
-  .stab 0 : { *(.stab) }
-  .stabstr 0 : { *(.stabstr) }
-  .stab.excl 0 : { *(.stab.excl) }
-  .stab.exclstr 0 : { *(.stab.exclstr) }
-  .stab.index 0 : { *(.stab.index) }
-  .stab.indexstr 0 : { *(.stab.indexstr) }
-  .comment 0 : { *(.comment) *(.comment.*) }
-  /*
-   * LLVM ld also wants .symtab, .strtab, and .shstrtab placed. These look to
-   * be benign to GNU ld, so we can have them here unconditionally.
-   */
-  .symtab 0 : { *(.symtab) }
-  .strtab 0 : { *(.strtab) }
-  .shstrtab 0 : { *(.shstrtab) }
+  STABS_DEBUG_SECTIONS
+
+  ELF_DETAILS_SECTIONS
 #endif
 }
 
diff --git a/xen/include/xen/xen.lds.h b/xen/include/xen/xen.lds.h
index dd292fa7dc..fc47bb1ccc 100644
--- a/xen/include/xen/xen.lds.h
+++ b/xen/include/xen/xen.lds.h
@@ -5,4 +5,133 @@
  * Common macros to be used in architecture specific linker scripts.
  */
 
+/*
+ * To avoid any confusion, please note that the EFI macro does not correspond
+ * to EFI support and is used when linking a native EFI (i.e. PE/COFF) binary,
+ * hence its usage in this header.
+ */
+
+/* Macros to declare debug sections. */
+#ifdef EFI
+/*
+ * Use the NOLOAD directive, despite currently ignored by (at least) GNU ld
+ * for PE output, in order to record that we'd prefer these sections to not
+ * be loaded into memory.
+ */
+#define DECL_DEBUG(x, a) #x ALIGN(a) (NOLOAD) : { *(x) }
+#define DECL_DEBUG2(x, y, a) #x ALIGN(a) (NOLOAD) : { *(x) *(y) }
+#else
+#define DECL_DEBUG(x, a) #x 0 : { *(x) }
+#define DECL_DEBUG2(x, y, a) #x 0 : { *(x) *(y) }
+#endif
+
+/*
+ * DWARF2+ debug sections.
+ * Explicitly list debug sections, first of all to avoid these sections being
+ * viewed as "orphan" by the linker.
+ *
+ * For the PE output this is further necessary so that they don't end up at
+ * VA 0, which is below image base and thus invalid. Note that this macro is
+ * to be used after _end, so if these sections get loaded they'll be discarded
+ * at runtime anyway.
+ */
+#define DWARF2_DEBUG_SECTIONS                     \
+  DECL_DEBUG(.debug_abbrev, 1)                    \
+  DECL_DEBUG2(.debug_info, .gnu.linkonce.wi.*, 1) \
+  DECL_DEBUG(.debug_types, 1)                     \
+  DECL_DEBUG(.debug_str, 1)                       \
+  DECL_DEBUG2(.debug_line, .debug_line.*, 1)      \
+  DECL_DEBUG(.debug_line_str, 1)                  \
+  DECL_DEBUG(.debug_names, 4)                     \
+  DECL_DEBUG(.debug_frame, 4)                     \
+  DECL_DEBUG(.debug_loc, 1)                       \
+  DECL_DEBUG(.debug_loclists, 4)                  \
+  DECL_DEBUG(.debug_macinfo, 1)                   \
+  DECL_DEBUG(.debug_macro, 1)                     \
+  DECL_DEBUG(.debug_ranges, POINTER_ALIGN)        \
+  DECL_DEBUG(.debug_rnglists, 4)                  \
+  DECL_DEBUG(.debug_addr, POINTER_ALIGN)          \
+  DECL_DEBUG(.debug_aranges, 1)                   \
+  DECL_DEBUG(.debug_pubnames, 1)                  \
+  DECL_DEBUG(.debug_pubtypes, 1)
+
+/* Stabs debug sections. */
+#define STABS_DEBUG_SECTIONS                 \
+  .stab 0 : { *(.stab) }                     \
+  .stabstr 0 : { *(.stabstr) }               \
+  .stab.excl 0 : { *(.stab.excl) }           \
+  .stab.exclstr 0 : { *(.stab.exclstr) }     \
+  .stab.index 0 : { *(.stab.index) }         \
+  .stab.indexstr 0 : { *(.stab.indexstr) }
+
+/*
+ * ELF sections.
+ *
+ * LLVM ld also wants .symtab, .strtab, and .shstrtab placed. These look to
+ * be benign to GNU ld, so we can have them here unconditionally.
+ */
+#define ELF_DETAILS_SECTIONS                 \
+  .comment 0 : { *(.comment) *(.comment.*) } \
+  .symtab 0 : { *(.symtab) }                 \
+  .strtab 0 : { *(.strtab) }                 \
+  .shstrtab 0 : { *(.shstrtab) }
+
+#ifdef EFI
+#define DISCARD_EFI_SECTIONS \
+       *(.comment)   \
+       *(.comment.*) \
+       *(.note.*)
+#else
+#define DISCARD_EFI_SECTIONS
+#endif
+
+/* Sections to be discarded. */
+#define DISCARD_SECTIONS     \
+  /DISCARD/ : {              \
+       *(.text.exit)         \
+       *(.exit.text)         \
+       *(.exit.data)         \
+       *(.exitcall.exit)     \
+       *(.discard)           \
+       *(.discard.*)         \
+       *(.eh_frame)          \
+       *(.dtors)             \
+       *(.dtors.*)           \
+       *(.fini_array)        \
+       *(.fini_array.*)      \
+       DISCARD_EFI_SECTIONS  \
+  }
+
+/* List of constructs other than *_SECTIONS in alphabetical order. */
+
+#ifdef CONFIG_HYPFS
+#define HYPFS_PARAM              \
+       . = ALIGN(POINTER_ALIGN); \
+       __paramhypfs_start = .;   \
+       *(.data.paramhypfs)       \
+       __paramhypfs_end = .;
+#else
+#define HYPFS_PARAM
+#endif
+
+#ifdef CONFIG_DEBUG_LOCK_PROFILE
+#define LOCK_PROFILE_DATA        \
+       . = ALIGN(POINTER_ALIGN); \
+       __lock_profile_start = .; \
+       *(.lockprofile.data)      \
+       __lock_profile_end = .;
+#else
+#define LOCK_PROFILE_DATA
+#endif
+
+#ifdef CONFIG_HAS_VPCI
+#define VPCI_ARRAY               \
+       . = ALIGN(POINTER_ALIGN); \
+       __start_vpci_array = .;   \
+       *(SORT(.data.vpci.*))     \
+       __end_vpci_array = .;
+#else
+#define VPCI_ARRAY
+#endif
+
 #endif /* __XEN_LDS_H__ */
-- 
2.25.1