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Handle AARCH64_TLS_TPREL relas #29

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merged 1 commit into from
Jun 7, 2024
Merged

Handle AARCH64_TLS_TPREL relas #29

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1 change: 1 addition & 0 deletions include/compartment.h
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Original file line number Diff line number Diff line change
Expand Up @@ -92,6 +92,7 @@ struct LibRelaMapping
char *rela_name;
void *rela_address; // address of relocation in compartment
void *target_func_address; // address of actual function
unsigned short rela_type; // type of relocation
unsigned short rela_sym_type; // type of underlying symbol
unsigned short rela_sym_bind; // bind of underlying symbol
};
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35 changes: 20 additions & 15 deletions src/compartment.c
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Expand Up @@ -664,7 +664,7 @@ parse_lib_rela(Elf64_Shdr *rela_shdr, Elf64_Ehdr *lib_ehdr, int lib_fd,
// Prepare TLS look-up function relocation (will be copied for each TLS
// relocation entry
static struct LibRelaMapping tls_lrm
= { NULL, 0x0, 0x0, STT_FUNC, STB_GLOBAL };
= { NULL, 0x0, 0x0, -1, STT_FUNC, STB_GLOBAL };

// Log symbols that will need to be relocated eagerly at maptime
Elf64_Rela curr_rela;
Expand All @@ -675,7 +675,7 @@ parse_lib_rela(Elf64_Shdr *rela_shdr, Elf64_Ehdr *lib_ehdr, int lib_fd,
size_t curr_rela_sym_idx = ELF64_R_SYM(curr_rela.r_info);
size_t curr_rela_type = ELF64_R_TYPE(curr_rela.r_info);

struct LibRelaMapping lrm = { NULL, 0x0, 0x0, -1, -1 };
struct LibRelaMapping lrm = { NULL, 0x0, 0x0, curr_rela_type, -1, -1 };

// XXX We handle `TLS` symbols differently. It seems the way
// AARCH64 handles TLS variables is preferentially via
Expand Down Expand Up @@ -736,11 +736,12 @@ parse_lib_rela(Elf64_Shdr *rela_shdr, Elf64_Ehdr *lib_ehdr, int lib_fd,
// function relocation
lrm.rela_address = curr_rela.r_offset
+ (char *) lib_dep->lib_mem_base + sizeof(void *);
memcpy(
new_relas + actual_relas, &lrm, sizeof(struct LibRelaMapping));

actual_relas += 1;
continue;
}
else if (curr_rela_type == R_AARCH64_TLS_TPREL64)
{
lrm.target_func_address = (char *) curr_rela.r_addend;
lrm.rela_address
= curr_rela.r_offset + (char *) lib_dep->lib_mem_base;
}
else
{
Expand Down Expand Up @@ -796,13 +797,9 @@ parse_lib_rela(Elf64_Shdr *rela_shdr, Elf64_Ehdr *lib_ehdr, int lib_fd,
}
lrm.rela_address
= curr_rela.r_offset + (char *) lib_dep->lib_mem_base;
memcpy(
new_relas + actual_relas, &lrm, sizeof(struct LibRelaMapping));

actual_relas += 1;
continue;
}
errx(1, "Unhandled relocation\n");
memcpy(new_relas + actual_relas, &lrm, sizeof(struct LibRelaMapping));
actual_relas += 1;
}
lib_dep->rela_maps = realloc(lib_dep->rela_maps,
(lib_dep->rela_maps_count + actual_relas)
Expand Down Expand Up @@ -890,12 +887,14 @@ resolve_rela_syms(struct Compartment *new_comp)
continue;
}

if (curr_rela_map->target_func_address != 0)
if (curr_rela_map->target_func_address != 0
|| curr_rela_map->rela_type == R_AARCH64_TLS_TPREL64)
{
continue;
}

if (!strcmp(curr_rela_map->rela_name, tls_rtld_dropin))
if (curr_rela_map->rela_name
&& !strcmp(curr_rela_map->rela_name, tls_rtld_dropin))
{
curr_rela_map->target_func_address = new_comp->tls_lookup_func;
continue;
Expand Down Expand Up @@ -961,6 +960,12 @@ find_lib_dep_sym_in_comp(const char *to_find,
{
for (size_t j = 0; j < comp_to_search->libs[i]->lib_syms_count; ++j)
{
// Ignore non-symbol relocations
if (!comp_to_search->libs[i]->lib_syms[j].sym_name)
{
continue;
}

// TODO eyeball performance of this approach versus using `&&`
// Ignore `LOCAL` bind symbols - they cannot be relocated against
bool cond
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1 change: 1 addition & 0 deletions tests/CMakeLists.txt
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Expand Up @@ -162,6 +162,7 @@ set(tests
"simple_libc"
"simple_malloc"
"simple_open_write"
"simple_printf"
"simple_static_var"
"simple_syscall_getpid"
"simple_syscall_write"
Expand Down