[glibc/google/grte/v5-2.27/master] elf: Support DT_RELR relative relocation format

[Fangrui Song <maskray@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d59cb9842ce708bd4fc057aaf143e4afab921197

commit d59cb9842ce708bd4fc057aaf143e4afab921197
Author: Fangrui Song <maskray@google.com>
Date:   Fri Nov 19 13:21:57 2021 -0800

    elf: Support DT_RELR relative relocation format
    
    Upstream patch: https://sourceware.org/pipermail/libc-alpha/2021-October/132029.html
    Bikeshedding: https://sourceware.org/pipermail/libc-alpha/2021-November/133009.html
    
    This commit removes configure.ac and test changes to avoid conflict when
    the upstream finally gets the feature.

Diff:
---
 elf/dynamic-link.h     | 28 ++++++++++++++++++++++++++++
 elf/elf.h              | 16 +++++++++++++---
 elf/get-dynamic-info.h |  3 +++
 3 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/elf/dynamic-link.h b/elf/dynamic-link.h
index f576d787e3..5e72ddc972 100644
--- a/elf/dynamic-link.h
+++ b/elf/dynamic-link.h
@@ -253,6 +253,33 @@ elf_machine_lazy_rel (struct link_map *map,
 #  define ELF_DYNAMIC_DO_RELA(map, lazy, skip_ifunc, boot_map) /* Nothing to do.  */
 # endif
 
+# define ELF_DYNAMIC_DO_RELR(map)					      \
+  do {									      \
+    ElfW(Addr) l_addr = (map)->l_addr, *where = 0;			      \
+    const ElfW(Relr) *r, *end;						      \
+    if (!(map)->l_info[DT_RELR])					      \
+      break;								      \
+    r = (const ElfW(Relr) *)D_PTR((map), l_info[DT_RELR]);		      \
+    end = (const ElfW(Relr) *)((const char *)r +			      \
+                               (map)->l_info[DT_RELRSZ]->d_un.d_val);	      \
+    for (; r < end; r++)						      \
+      {									      \
+	ElfW(Relr) entry = *r;						      \
+	if ((entry & 1) == 0)						      \
+	  {								      \
+	    where = (ElfW(Addr) *)(l_addr + entry);			      \
+	    *where++ += l_addr;						      \
+	  }								      \
+	else 								      \
+	  {								      \
+	    for (long i = 0; (entry >>= 1) != 0; i++)			      \
+	      if ((entry & 1) != 0)					      \
+		where[i] += l_addr;					      \
+	    where += CHAR_BIT * sizeof(ElfW(Relr)) - 1;			      \
+	  }								      \
+      }									      \
+  } while (0);
+
 /* This can't just be an inline function because GCC is too dumb
    to inline functions containing inlines themselves.  */
 # define ELF_DYNAMIC_RELOCATE(map, lazy, consider_profile, skip_ifunc, boot_map) \
@@ -261,6 +288,7 @@ elf_machine_lazy_rel (struct link_map *map,
 					      (consider_profile));	      \
     ELF_DYNAMIC_DO_REL ((map), edr_lazy, skip_ifunc, boot_map);			\
     ELF_DYNAMIC_DO_RELA ((map), edr_lazy, skip_ifunc, boot_map);			\
+    ELF_DYNAMIC_DO_RELR ((map));					      \
   } while (0)
 #else /* NESTING */
 # if ! ELF_MACHINE_NO_REL
diff --git a/elf/elf.h b/elf/elf.h
index 954f3266f7..9635285d9a 100644
--- a/elf/elf.h
+++ b/elf/elf.h
@@ -444,8 +444,9 @@ typedef struct
 #define SHT_FINI_ARRAY	  15		/* Array of destructors */
 #define SHT_PREINIT_ARRAY 16		/* Array of pre-constructors */
 #define SHT_GROUP	  17		/* Section group */
-#define SHT_SYMTAB_SHNDX  18		/* Extended section indeces */
-#define	SHT_NUM		  19		/* Number of defined types.  */
+#define SHT_SYMTAB_SHNDX  18		/* Extended section indices */
+#define SHT_RELR	  19            /* RELR relative relocations */
+#define	SHT_NUM		  20		/* Number of defined types.  */
 #define SHT_LOOS	  0x60000000	/* Start OS-specific.  */
 #define SHT_GNU_ATTRIBUTES 0x6ffffff5	/* Object attributes.  */
 #define SHT_GNU_HASH	  0x6ffffff6	/* GNU-style hash table.  */
@@ -663,6 +664,11 @@ typedef struct
   Elf64_Sxword	r_addend;		/* Addend */
 } Elf64_Rela;
 
+/* RELR relocation table entry */
+
+typedef Elf32_Word	Elf32_Relr;
+typedef Elf64_Xword	Elf64_Relr;
+
 /* How to extract and insert information held in the r_info field.  */
 
 #define ELF32_R_SYM(val)		((val) >> 8)
@@ -861,7 +867,11 @@ typedef struct
 #define DT_ENCODING	32		/* Start of encoded range */
 #define DT_PREINIT_ARRAY 32		/* Array with addresses of preinit fct*/
 #define DT_PREINIT_ARRAYSZ 33		/* size in bytes of DT_PREINIT_ARRAY */
-#define	DT_NUM		34		/* Number used */
+#define DT_SYMTAB_SHNDX	34		/* Address of SYMTAB_SHNDX section */
+#define DT_RELRSZ	35		/* Total size of RELR relative relocations */
+#define DT_RELR		36		/* Address of RELR relative relocations */
+#define DT_RELRENT	37		/* Size of one RELR relative relocaction */
+#define	DT_NUM		38		/* Number used */
 #define DT_LOOS		0x6000000d	/* Start of OS-specific */
 #define DT_HIOS		0x6ffff000	/* End of OS-specific */
 #define DT_LOPROC	0x70000000	/* Start of processor-specific */
diff --git a/elf/get-dynamic-info.h b/elf/get-dynamic-info.h
index f9c5b84d6a..631f794765 100644
--- a/elf/get-dynamic-info.h
+++ b/elf/get-dynamic-info.h
@@ -110,6 +110,7 @@ elf_get_dynamic_info (struct link_map *l, ElfW(Dyn) *temp)
 # if ! ELF_MACHINE_NO_REL
       ADJUST_DYN_INFO (DT_REL);
 # endif
+      ADJUST_DYN_INFO (DT_RELR);
       ADJUST_DYN_INFO (DT_JMPREL);
       ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
       ADJUST_DYN_INFO (DT_ADDRTAGIDX (DT_GNU_HASH) + DT_NUM + DT_THISPROCNUM
@@ -137,6 +138,8 @@ elf_get_dynamic_info (struct link_map *l, ElfW(Dyn) *temp)
   if (info[DT_REL] != NULL)
     assert (info[DT_RELENT]->d_un.d_val == sizeof (ElfW(Rel)));
 #endif
+  if (info[DT_RELR] != NULL)
+    assert (info[DT_RELRENT]->d_un.d_val == sizeof (ElfW(Relr)));
 #ifdef RTLD_BOOTSTRAP
   /* Only the bind now flags are allowed.  */
   assert (info[VERSYMIDX (DT_FLAGS_1)] == NULL