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MIPS support for GNU hash

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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.
This commit is contained in:
Mihailo Stojanovic 2019-08-29 20:11:42 +00:00 committed by Joseph Myers
parent 605f38177d
commit 23c1c256ae
9 changed files with 70 additions and 8 deletions
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21
ChangeLog
View File

@ -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.

5
elf/dl-addr.c
View File

@ -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);
}

10
elf/dl-lookup.c
View File

@ -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;
}

5
elf/elf.h
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@ -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. */

17
sysdeps/generic/ldsodefs.h
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@ -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)

15
sysdeps/mips/ldsodefs.h
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@ -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 *, \

1
sysdeps/mips/linkmap.h
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@ -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 */
};

2
sysdeps/unix/sysv/linux/mips/ldsodefs.h
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@ -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 */

2
sysdeps/unix/sysv/linux/mips/libc-abis
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@ -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