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/ChangeLog b/ChangeLog
index 73b4d11c1abd31e74aa1aaf22f09258210f84424..87d43d425e9331696bc935d150ac053b560c297a 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,24 @@
+2019-08-29  Mihailo Stojanovic  <mihailo.stojanovic@rt-rk.com>
+
+       * 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.
+
 2019-08-29  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
        * sysdeps/sh/preconfigure.ac: New file.

diff --git a/elf/dl-addr.c b/elf/dl-addr.c
index 9d285d76a728a1c378d9f202e31bdc816e16f665..3f2297af554074b5f53bcfaa6e39cc3ee598de08 100644 (file)
--- 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 eb23cca4e30bb2f1bcce37dee5dea9e52fc5bd91..f9d6c36b398052eb1de3afb2365e1b8701650774 100644 (file)
--- a/elf/dl-lookup.c
+++ b/elf/dl-lookup.c
@@ -403,7 +403,7 @@ 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,
@@ -909,10 +909,10 @@ _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++;
@@ -927,6 +927,10 @@ _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 7c6d6094edbe3b09dd8eadbe0b635d315a3ac35a..5b6ea638b4dda19b3e9dd5cf1987547b1fa6eb41 100644 (file)
--- a/elf/elf.h
+++ b/elf/elf.h
@@ -1715,6 +1715,7 @@ 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.  */
 
@@ -1962,7 +1963,9 @@ 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 b1fc5c31f972bbb8eae42a7afbfc10cd81aa165f..1e193b05b0a8f34e1c6415b17ca24b579a54713c 100644 (file)
--- 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 f0acb020f5d8fa45d833e158553f05ae11c218b8..95cd38e48639b4722b4d25e452071ea2e5942e92 100644 (file)
--- 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 1fb9678a6d1625fd9d31a356cf4faccbf7d1cf1e..1e640c3ba9bd18e4bce43b53441f575d81fc26ba 100644 (file)
--- 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 28257f83ae7255074dd8b93549f5630415d8c21f..ce7b2f98850c18574f8b85a431e507dcad76802c 100644 (file)
--- 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 eaea558720f42a488836eddfbaa380af878cb781..c0b67dae3ece15118451a634c13e5fc905bd6881 100644 (file)
--- 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