commit 23c1c256ae7b0f010d0fcaff60682b620887b164

Author: Mihailo Stojanovic <mihailo.stojanovic@rt-rk.com>

Date:   Thu Aug 29 20:11:42 2019 +0000

    MIPS support for GNU hash

    This patch is a reimplementation of [1], which was submitted back in

    2015. Copyright issue has been sorted [2] last year. It proposed a new

    section (.gnu.xhash) and related dynamic tag (GT_GNU_XHASH). The new

    section would be virtually identical to the existing .gnu.hash except

    for the translation table (xlat) which would contain correct MIPS

    .dynsym indexes corresponding to the hashvals in chains. This is because

    MIPS ABI imposes a different ordering of the dynsyms than the one

    expected by the .gnu.hash section. Another addition would be a leading

    word at the beggining of the section, which would contain the number of

    entries in the translation table.

    In this patch, the new section name and dynamic tag are changed to

    reflect the fact that the section should be treated as MIPS specific

    (.MIPS.xhash and DT_MIPS_XHASH).

    This patch addresses the alignment issue reported in [3] which is caused

    by the leading word of the .MIPS.xhash section. Leading word is now

    removed in the corresponding binutils patch, and the number of entries

    in the translation table is computed using DT_MIPS_SYMTABNO dynamic tag.

    Since the MIPS specific dl-lookup.c file was removed following the

    initial patch submission, I opted for the definition of three new macros

    in the generic ldsodefs.h. ELF_MACHINE_GNU_HASH_ADDRIDX defines the

    index of the dynamic tag in the l_info array. ELF_MACHINE_HASH_SYMIDX is

    used to calculate the index of a symbol in GNU hash. On MIPS, it is

    defined to look up the symbol index in the translation table.

    ELF_MACHINE_XHASH_SETUP is defined for MIPS only. It initializes the

    .MIPS.xhash pointer in the link_map_machine struct.

    The other major change is bumping the highest EI_ABIVERSION value for

    MIPS to suggest that the dynamic linker now supports GNU hash.

    The patch was tested by running the glibc testsuite for the three MIPS

    ABIs (o32, n32 and n64) and for x86_64-linux-gnu.

    [1] https://sourceware.org/ml/binutils/2015-10/msg00057.html

    [2] https://sourceware.org/ml/binutils/2018-03/msg00025.html

    [3] https://sourceware.org/ml/binutils/2016-01/msg00006.html

            * elf/dl-addr.c (determine_info): Calculate the symbol index

            using the newly defined ELF_MACHINE_HASH_SYMIDX macro.

            * elf/dl-lookup.c (do_lookup_x): Ditto.

            (_dl_setup_hash): Initialize MIPS xhash translation table.

            * elf/elf.h (SHT_MIPS_XHASH): New define.

            (DT_MIPS_XHASH): New define.

            * sysdeps/generic/ldsodefs.h (ELF_MACHINE_GNU_HASH_ADDRIDX): New

            define.

            (ELF_MACHINE_HASH_SYMIDX): Ditto.

            (ELF_MACHINE_XHASH_SETUP): Ditto.

            * sysdeps/mips/ldsodefs.h (ELF_MACHINE_GNU_HASH_ADDRIDX): New

            define.

            (ELF_MACHINE_HASH_SYMIDX): Ditto.

            (ELF_MACHINE_XHASH_SETUP): Ditto.

            * sysdeps/mips/linkmap.h (struct link_map_machine): New member.

            * sysdeps/unix/sysv/linux/mips/ldsodefs.h: Increment valid ABI

            version.

            * sysdeps/unix/sysv/linux/mips/libc-abis: New ABI version.

diff --git a/elf/dl-addr.c b/elf/dl-addr.c

index e6c7d020945c51d2..b146fed09a46ff76 100644

--- a/elf/dl-addr.c

+++ b/elf/dl-addr.c

@@ -42,7 +42,7 @@ determine_info (const ElfW(Addr) addr, struct link_map *match, Dl_info *info,

   ElfW(Word) strtabsize = match->l_info[DT_STRSZ]->d_un.d_val;

   const ElfW(Sym) *matchsym = NULL;

-  if (match->l_info[ADDRIDX (DT_GNU_HASH)] != NULL)

+  if (match->l_info[ELF_MACHINE_GNU_HASH_ADDRIDX] != NULL)

     {

       /* We look at all symbol table entries referenced by the hash

 	 table.  */

@@ -57,6 +57,7 @@ determine_info (const ElfW(Addr) addr, struct link_map *match, Dl_info *info,

 		{

 		  /* The hash table never references local symbols so

 		     we can omit that test here.  */

+		  symndx = ELF_MACHINE_HASH_SYMIDX (match, hasharr);

 		  if ((symtab[symndx].st_shndx != SHN_UNDEF

 		       || symtab[symndx].st_value != 0)

 		      && symtab[symndx].st_shndx != SHN_ABS

@@ -65,8 +66,6 @@ determine_info (const ElfW(Addr) addr, struct link_map *match, Dl_info *info,

 					    matchsym, addr)

 		      && symtab[symndx].st_name < strtabsize)

 		    matchsym = (ElfW(Sym) *) &symtab[symndx];

-

-		  ++symndx;

 		}

 	      while ((*hasharr++ & 1u) == 0);

 	    }

diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c

index 01724a54f8840f9f..42fdaed99296137f 100644

--- a/elf/dl-lookup.c

+++ b/elf/dl-lookup.c

@@ -432,7 +432,7 @@ do_lookup_x (const char *undef_name, uint_fast32_t new_hash,

 		  do

 		    if (((*hasharr ^ new_hash) >> 1) == 0)

 		      {

-			symidx = hasharr - map->l_gnu_chain_zero;

+			symidx = ELF_MACHINE_HASH_SYMIDX (map, hasharr);

 			sym = check_match (undef_name, ref, version, flags,

 					   type_class, &symtab[symidx], symidx,

 					   strtab, map, &versioned_sym,

@@ -961,10 +961,10 @@ _dl_setup_hash (struct link_map *map)

 {

   Elf_Symndx *hash;

-  if (__glibc_likely (map->l_info[ADDRIDX (DT_GNU_HASH)] != NULL))

+  if (__glibc_likely (map->l_info[ELF_MACHINE_GNU_HASH_ADDRIDX] != NULL))

     {

       Elf32_Word *hash32

-	= (void *) D_PTR (map, l_info[ADDRIDX (DT_GNU_HASH)]);

+	= (void *) D_PTR (map, l_info[ELF_MACHINE_GNU_HASH_ADDRIDX]);

       map->l_nbuckets = *hash32++;

       Elf32_Word symbias = *hash32++;

       Elf32_Word bitmask_nwords = *hash32++;

@@ -979,6 +979,10 @@ _dl_setup_hash (struct link_map *map)

       map->l_gnu_buckets = hash32;

       hash32 += map->l_nbuckets;

       map->l_gnu_chain_zero = hash32 - symbias;

+

+      /* Initialize MIPS xhash translation table.  */

+      ELF_MACHINE_XHASH_SETUP (hash32, symbias, map);

+

       return;

     }

diff --git a/elf/elf.h b/elf/elf.h

index 74f7f479ce817040..d6506ea1c7160dea 100644

--- a/elf/elf.h

+++ b/elf/elf.h

@@ -1698,6 +1698,7 @@ typedef struct

 #define SHT_MIPS_EH_REGION	0x70000027

 #define SHT_MIPS_XLATE_OLD	0x70000028

 #define SHT_MIPS_PDR_EXCEPTION	0x70000029

+#define SHT_MIPS_XHASH		0x7000002b

 /* Legal values for sh_flags field of Elf32_Shdr.  */

@@ -1945,7 +1946,9 @@ typedef struct

    in a PIE as it stores a relative offset from the address of the tag

    rather than an absolute address.  */

 #define DT_MIPS_RLD_MAP_REL  0x70000035

-#define DT_MIPS_NUM	     0x36

+/* GNU-style hash table with xlat.  */

+#define DT_MIPS_XHASH	     0x70000036

+#define DT_MIPS_NUM	     0x37

 /* Legal values for DT_MIPS_FLAGS Elf32_Dyn entry.  */

diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h

index f0185ce0d16c0f69..3bdbdd6e67dacc85 100644

--- a/sysdeps/generic/ldsodefs.h

+++ b/sysdeps/generic/ldsodefs.h

@@ -47,6 +47,23 @@ __BEGIN_DECLS

 #define ADDRIDX(tag)	(DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGNUM \

 			 + DT_EXTRANUM + DT_VALNUM + DT_ADDRTAGIDX (tag))

+/* Type of GNU hash which the machine uses.  */

+#ifndef ELF_MACHINE_GNU_HASH_ADDRIDX

+# define ELF_MACHINE_GNU_HASH_ADDRIDX ADDRIDX (DT_GNU_HASH)

+#endif

+

+/* Calculate the index of a symbol in GNU hash.  */

+#ifndef ELF_MACHINE_HASH_SYMIDX

+# define ELF_MACHINE_HASH_SYMIDX(map, hasharr) \

+  ((hasharr) - (map)->l_gnu_chain_zero)

+#endif

+

+/* Setup MIPS xhash.  Defined only for MIPS.  */

+#ifndef ELF_MACHINE_XHASH_SETUP

+# define ELF_MACHINE_XHASH_SETUP(hash32, symbias, map) \

+  ((void) (hash32), (void) (symbias), (void) (map))

+#endif

+

 /* We use this macro to refer to ELF types independent of the native wordsize.

    `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'.  */

 #define ELFW(type)	_ElfW (ELF, __ELF_NATIVE_CLASS, type)

diff --git a/sysdeps/mips/ldsodefs.h b/sysdeps/mips/ldsodefs.h

index c6e5ce7e660325c1..35043b7c6d416c50 100644

--- a/sysdeps/mips/ldsodefs.h

+++ b/sysdeps/mips/ldsodefs.h

@@ -26,6 +26,21 @@ struct La_mips_32_retval;

 struct La_mips_64_regs;

 struct La_mips_64_retval;

+#define ELF_MACHINE_GNU_HASH_ADDRIDX (DT_MIPS_XHASH - DT_LOPROC + DT_NUM)

+

+/* Calculate the index of a symbol in MIPS xhash.  */

+#define ELF_MACHINE_HASH_SYMIDX(map, hasharr) \

+  ((map)->l_mach.mips_xlat_zero[(hasharr) - (map)->l_gnu_chain_zero])

+

+/* Setup MIPS xhash.  */

+#define ELF_MACHINE_XHASH_SETUP(hash32, symbias, map)			    \

+  do									    \

+    {									    \

+      (hash32) += (map)->l_info[DT_MIPS (SYMTABNO)]->d_un.d_val - (symbias); \

+      (map)->l_mach.mips_xlat_zero = (hash32) - (symbias);		    \

+    }									    \

+  while (0)

+

 #define ARCH_PLTENTER_MEMBERS						    \

     Elf32_Addr (*mips_o32_gnu_pltenter) (Elf32_Sym *, unsigned int,	    \

 					 uintptr_t *, uintptr_t *,	    \

diff --git a/sysdeps/mips/linkmap.h b/sysdeps/mips/linkmap.h

index 1fb9678a6d1625fd..1e640c3ba9bd18e4 100644

--- a/sysdeps/mips/linkmap.h

+++ b/sysdeps/mips/linkmap.h

@@ -3,4 +3,5 @@ struct link_map_machine

     ElfW(Addr) plt; /* Address of .plt */

     ElfW(Word) fpabi; /* FP ABI of the object */

     unsigned int odd_spreg; /* Does the object require odd_spreg support? */

+    const Elf32_Word *mips_xlat_zero; /* .MIPS.xhash */

   };

diff --git a/sysdeps/unix/sysv/linux/mips/ldsodefs.h b/sysdeps/unix/sysv/linux/mips/ldsodefs.h

index d2912cadabfd6877..03f3e12f202a0563 100644

--- a/sysdeps/unix/sysv/linux/mips/ldsodefs.h

+++ b/sysdeps/unix/sysv/linux/mips/ldsodefs.h

@@ -34,7 +34,7 @@ extern void _dl_static_init (struct link_map *map);

 #undef VALID_ELF_ABIVERSION

 #define VALID_ELF_ABIVERSION(osabi,ver)			\

   (ver == 0						\

-   || (osabi == ELFOSABI_SYSV && ver < 5)		\

+   || (osabi == ELFOSABI_SYSV && ver < 6)		\

    || (osabi == ELFOSABI_GNU && ver < LIBC_ABI_MAX))

 #endif /* ldsodefs.h */

diff --git a/sysdeps/unix/sysv/linux/mips/libc-abis b/sysdeps/unix/sysv/linux/mips/libc-abis

index eaea558720f42a48..c0b67dae3ece1511 100644

--- a/sysdeps/unix/sysv/linux/mips/libc-abis

+++ b/sysdeps/unix/sysv/linux/mips/libc-abis

@@ -16,3 +16,5 @@ UNIQUE

 MIPS_O32_FP64   mips*-*-linux*

 # Absolute (SHN_ABS) symbols working correctly.

 ABSOLUTE

+# GNU-style hash table with translation table.

+MIPS_XHASH