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Fix symbol versions with shared libs

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ELF files that refer to shared libs containing sym-versions, but
don't refer to any dynamic symbols with symbol versions (should happen
only with very simple shared libs) would generate an empty .gnu.version_r
section.  Some dynamic linker contain bugs in that they don't check
the section size or DT_VERNEEDNUM (which are both zero for such files
we generate) before accessing the first entry, and then bail out with
a message like

./a.exe: error while loading shared libraries: ./a1.so: unsupported
 version 25960 of Verneed record

(where the "version number" actually comes from neighboring bytes
from different sections).

So, there's not much choice, we simply must not generate such section.
This commit is contained in:
Michael Matz 2020-01-20 05:31:09 +01:00
parent d79e1dee8c
commit fdeeb62e28
1 changed files with 46 additions and 40 deletions
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86
tccelf.c
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@ -558,9 +558,7 @@ version_add (TCCState *s1)
return;
versym_section = new_section(s1, ".gnu.version", SHT_GNU_versym, SHF_ALLOC);
versym_section->sh_entsize = sizeof(ElfW(Half));
verneed_section = new_section(s1, ".gnu.version_r", SHT_GNU_verneed, SHF_ALLOC);
versym_section->link = s1->dynsym;
verneed_section->link = s1->dynsym->link;
/* add needed symbols */
symtab = s1->dynsym;
@ -580,43 +578,50 @@ version_add (TCCState *s1)
} else
versym[sym_index] = 0;
}
/* generate verneed section */
for (i = nb_sym_versions; i-- > 0;) {
struct sym_version *sv = &sym_versions[i];
int n_same_libs = 0, prev;
size_t vnofs;
ElfW(Vernaux) *vna = 0;
if (sv->out_index < 1)
continue;
vnofs = section_add(verneed_section, sizeof(*vn), 1);
vn = (ElfW(Verneed)*)(verneed_section->data + vnofs);
vn->vn_version = 1;
vn->vn_file = put_elf_str(verneed_section->link, sv->lib);
vn->vn_aux = sizeof (*vn);
do {
prev = sv->prev_same_lib;
if (sv->out_index > 0) {
vna = section_ptr_add(verneed_section, sizeof(*vna));
vna->vna_hash = elf_hash ((const unsigned char *)sv->version);
vna->vna_flags = 0;
vna->vna_other = sv->out_index;
sv->out_index = -2;
vna->vna_name = put_elf_str(verneed_section->link, sv->version);
vna->vna_next = sizeof (*vna);
n_same_libs++;
}
if (prev >= 0)
sv = &sym_versions[prev];
} while(prev >= 0);
vna->vna_next = 0;
vn = (ElfW(Verneed)*)(verneed_section->data + vnofs);
vn->vn_cnt = n_same_libs;
vn->vn_next = sizeof(*vn) + n_same_libs * sizeof(*vna);
nb_entries++;
/* generate verneed section, but not when it will be empty. Some
dynamic linkers look at their contents even when DTVERNEEDNUM and
section size is zero. */
if (nb_versions > 2) {
verneed_section = new_section(s1, ".gnu.version_r",
SHT_GNU_verneed, SHF_ALLOC);
verneed_section->link = s1->dynsym->link;
for (i = nb_sym_versions; i-- > 0;) {
struct sym_version *sv = &sym_versions[i];
int n_same_libs = 0, prev;
size_t vnofs;
ElfW(Vernaux) *vna = 0;
if (sv->out_index < 1)
continue;
vnofs = section_add(verneed_section, sizeof(*vn), 1);
vn = (ElfW(Verneed)*)(verneed_section->data + vnofs);
vn->vn_version = 1;
vn->vn_file = put_elf_str(verneed_section->link, sv->lib);
vn->vn_aux = sizeof (*vn);
do {
prev = sv->prev_same_lib;
if (sv->out_index > 0) {
vna = section_ptr_add(verneed_section, sizeof(*vna));
vna->vna_hash = elf_hash ((const unsigned char *)sv->version);
vna->vna_flags = 0;
vna->vna_other = sv->out_index;
sv->out_index = -2;
vna->vna_name = put_elf_str(verneed_section->link, sv->version);
vna->vna_next = sizeof (*vna);
n_same_libs++;
}
if (prev >= 0)
sv = &sym_versions[prev];
} while(prev >= 0);
vna->vna_next = 0;
vn = (ElfW(Verneed)*)(verneed_section->data + vnofs);
vn->vn_cnt = n_same_libs;
vn->vn_next = sizeof(*vn) + n_same_libs * sizeof(*vna);
nb_entries++;
}
if (vn)
vn->vn_next = 0;
verneed_section->sh_info = nb_entries;
}
if (vn)
vn->vn_next = 0;
verneed_section->sh_info = nb_entries;
dt_verneednum = nb_entries;
}
#endif
@ -2045,10 +2050,11 @@ static void fill_dynamic(TCCState *s1, struct dyn_inf *dyninf)
put_dt(dynamic, DT_RELENT, sizeof(ElfW_Rel));
#endif
#endif
if (versym_section) {
if (versym_section)
put_dt(dynamic, DT_VERSYM, versym_section->sh_addr);
if (verneed_section) {
put_dt(dynamic, DT_VERNEED, verneed_section->sh_addr);
put_dt(dynamic, DT_VERNEEDNUM, dt_verneednum);
put_dt(dynamic, DT_VERSYM, versym_section->sh_addr);
}
s = find_section_create (s1, ".preinit_array", 0);
if (s && s->data_offset) {