[PATCH v3 2/2] RISC-V: Fix that IRELATIVE relocs may be inserted to the wrong place.
Nelson Chu
nelson.chu@sifive.com
Wed Oct 7 03:48:23 GMT 2020
For the ifunc symbol, which is referenced by GOT rather than PLT relocs,
we should add the dynamic reloc (usually IRELATIVE) into the .rel.iplt
when generating the static executable. But if we use riscv_elf_append_rela
to add the dynamic relocs into .rela.iplt, this may cause the overwrite
problem.
The reason is that we don't handle the `reloc_index` of .rela.iplt, but
the riscv_elf_append_rela adds the relocs to the place that are calculated
from the reloc_index (in seqential). Therefore, we may overwrite the
dynamic relocs when the `reloc_index` of .rela.iplt isn't handled correctly.
One solution is that we can add these dynamic relocs (GOT ifunc) from
the last of .rela.iplt section. But I'm not sure if it is the best way.
bfd/
* elfnn-riscv.c (riscv_elf_link_hash_table): Add last_iplt_index.
(riscv_elf_size_dynamic_sections): Initialize the last_iplt_index.
(riscv_elf_relocate_section): Use riscv_elf_append_rela.
(riscv_elf_finish_dynamic_symbol): If the use_elf_append_rela is
false, then we should add the dynamic relocs from the last of
the .rela.iplt, and don't use the riscv_elf_append_rela to add.
ld/
* testsuite/ld-riscv-elf/ifunc-plt-got-overwrite.s: New testcase.
* testsuite/ld-riscv-elf/ifunc-plt-got-overwrite.d: Likewise.
* testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-exe.rd: Likewise.
* testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-pic.rd: Likewise.
* testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-pie.rd: Likewise.
* testsuite/ld-riscv-elf/ld-riscv-elf.exp: Updated.
---
bfd/elfnn-riscv.c | 46 ++++++++++++++++++----
.../ld-riscv-elf/ifunc-plt-got-overwrite-exe.rd | 4 ++
.../ld-riscv-elf/ifunc-plt-got-overwrite-pic.rd | 8 ++++
.../ld-riscv-elf/ifunc-plt-got-overwrite-pie.rd | 7 ++++
.../ld-riscv-elf/ifunc-plt-got-overwrite.d | 19 +++++++++
.../ld-riscv-elf/ifunc-plt-got-overwrite.s | 38 ++++++++++++++++++
ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp | 7 ++++
7 files changed, 122 insertions(+), 7 deletions(-)
create mode 100644 ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-exe.rd
create mode 100644 ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-pic.rd
create mode 100644 ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-pie.rd
create mode 100644 ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite.d
create mode 100644 ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite.s
diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
index a26cd3f..c854957 100644
--- a/bfd/elfnn-riscv.c
+++ b/bfd/elfnn-riscv.c
@@ -120,6 +120,9 @@ struct riscv_elf_link_hash_table
/* Used by local STT_GNU_IFUNC symbols. */
htab_t loc_hash_table;
void * loc_hash_memory;
+
+ /* The index of the last unused .rel.iplt solt. */
+ bfd_vma last_iplt_index;
};
@@ -1424,6 +1427,11 @@ riscv_elf_size_dynamic_sections (bfd *output_bfd, struct bfd_link_info *info)
local ifunc symbols. */
htab_traverse (htab->loc_hash_table, allocate_local_ifunc_dynrelocs, info);
+ /* Used to resolve the dynamic relocs overwite problems when
+ generating static executable. */
+ if (htab->elf.irelplt)
+ htab->last_iplt_index = htab->elf.irelplt->reloc_count - 1;
+
if (htab->elf.sgotplt)
{
struct elf_link_hash_entry *got;
@@ -2904,6 +2912,7 @@ riscv_elf_finish_dynamic_symbol (bfd *output_bfd,
asection *sgot;
asection *srela;
Elf_Internal_Rela rela;
+ bfd_boolean use_elf_append_rela = TRUE;
/* This symbol has an entry in the GOT. Set it up. */
@@ -2920,12 +2929,18 @@ riscv_elf_finish_dynamic_symbol (bfd *output_bfd,
if (h->plt.offset == (bfd_vma) -1)
{
/* STT_GNU_IFUNC is referenced without PLT. */
+
if (htab->elf.splt == NULL)
{
- /* use .rel[a].iplt section to store .got relocations
+ /* Use .rela.iplt section to store .got relocations
in static executable. */
srela = htab->elf.irelplt;
+
+ /* Do not use riscv_elf_append_rela to add dynamic
+ relocs. */
+ use_elf_append_rela = FALSE;
}
+
if (SYMBOL_REFERENCES_LOCAL (info, h))
{
info->callbacks->minfo (_("Local IFUNC function `%s' in %pB\n"),
@@ -2973,14 +2988,14 @@ riscv_elf_finish_dynamic_symbol (bfd *output_bfd,
return TRUE;
}
}
- /* If this is a local symbol reference, we just want to emit a RELATIVE
- reloc. This can happen if it is a -Bsymbolic link, or a pie link, or
- the symbol was forced to be local because of a version file.
- The entry in the global offset table will already have been
- initialized in the relocate_section function. */
else if (bfd_link_pic (info)
&& SYMBOL_REFERENCES_LOCAL (info, h))
{
+ /* If this is a local symbol reference, we just want to emit
+ a RELATIVE reloc. This can happen if it is a -Bsymbolic link,
+ or a pie link, or the symbol was forced to be local because
+ of a version file. The entry in the global offset table will
+ already have been initialized in the relocate_section function. */
BFD_ASSERT((h->got.offset & 1) != 0);
asection *sec = h->root.u.def.section;
rela.r_info = ELFNN_R_INFO (0, R_RISCV_RELATIVE);
@@ -2998,7 +3013,24 @@ riscv_elf_finish_dynamic_symbol (bfd *output_bfd,
bfd_put_NN (output_bfd, 0,
sgot->contents + (h->got.offset & ~(bfd_vma) 1));
- riscv_elf_append_rela (output_bfd, srela, &rela);
+
+ if (use_elf_append_rela)
+ riscv_elf_append_rela (output_bfd, srela, &rela);
+ else
+ {
+ /* Use riscv_elf_append_rela to add the dynamic relocs into
+ .rela.iplt may cause the overwrite problems. Since we insert
+ the relocs for PLT didn't handle the reloc_index of .rela.iplt,
+ but the riscv_elf_append_rela adds the relocs to the place
+ that are calculated from the reloc_index (in seqential).
+
+ One solution is that add these dynamic relocs (GOT IFUNC)
+ from the last of .rela.iplt section. */
+ bfd_vma iplt_idx = htab->last_iplt_index--;
+ bfd_byte *loc = srela->contents
+ + iplt_idx * sizeof (ElfNN_External_Rela);
+ bed->s->swap_reloca_out (output_bfd, &rela, loc);
+ }
}
if (h->needs_copy)
diff --git a/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-exe.rd b/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-exe.rd
new file mode 100644
index 0000000..0de47a4
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-exe.rd
@@ -0,0 +1,4 @@
+Relocation section '.rela.plt' at .*
+[ ]+Offset[ ]+Info[ ]+Type[ ]+.*
+[0-9a-f]+[ ]+[0-9a-f]+[ ]+R_RISCV_IRELATIVE[ ]+[0-9a-f]*
+[0-9a-f]+[ ]+[0-9a-f]+[ ]+R_RISCV_IRELATIVE[ ]+[0-9a-f]*
diff --git a/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-pic.rd b/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-pic.rd
new file mode 100644
index 0000000..f65d789
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-pic.rd
@@ -0,0 +1,8 @@
+Relocation section '.rela.got' at .*
+[ ]+Offset[ ]+Info[ ]+Type[ ]+.*
+[0-9a-f]+[ ]+[0-9a-f]+[ ]+R_RISCV_(32|64)[ ]+foo2\(\)[ ]+foo2 \+ 0
+[0-9a-f]+[ ]+[0-9a-f]+[ ]+R_RISCV_(32|64)[ ]+foo1\(\)[ ]+foo1 \+ 0
+#...
+Relocation section '.rela.plt' at .*
+[ ]+Offset[ ]+Info[ ]+Type[ ]+.*
+[0-9a-f]+[ ]+[0-9a-f]+[ ]+R_RISCV_JUMP_SLOT[ ]+foo1\(\)[ ]+foo1 \+ 0
diff --git a/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-pie.rd b/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-pie.rd
new file mode 100644
index 0000000..32e66f0
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite-pie.rd
@@ -0,0 +1,7 @@
+Relocation section '.rela.got' at .*
+[ ]+Offset[ ]+Info[ ]+Type[ ]+.*
+[0-9a-f]+[ ]+[0-9a-f]+[ ]+R_RISCV_IRELATIVE[ ]+[0-9a-f]*
+
+Relocation section '.rela.plt' at .*
+[ ]+Offset[ ]+Info[ ]+Type[ ]+.*
+[0-9a-f]+[ ]+[0-9a-f]+[ ]+R_RISCV_IRELATIVE[ ]+[0-9a-f]*
diff --git a/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite.d b/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite.d
new file mode 100644
index 0000000..333dea3
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite.d
@@ -0,0 +1,19 @@
+#...
+Disassembly of section .plt:
+#...
+0+[0-9a-f]+ <(\*ABS\*\+0x[0-9a-f]+@plt|foo@plt|.plt)>:
+#...
+Disassembly of section .text:
+#...
+0+[0-9a-f]+ <foo_resolver>:
+#...
+0+[0-9a-f]+ <bar>:
+.*:[ ]+[0-9a-f]+[ ]+auipc[ ]+.*
+.*:[ ]+[0-9a-f]+[ ]+(lw|ld)[ ]+.*<(_GLOBAL_OFFSET_TABLE_.*|.*)>
+.*:[ ]+[0-9a-f]+[ ]+auipc[ ]+.*
+.*:[ ]+[0-9a-f]+[ ]+jalr[ ]+.*<(.*plt.*)>
+.*:[ ]+[0-9a-f]+[ ]+auipc[ ]+.*
+.*:[ ]+[0-9a-f]+[ ]+jalr[ ]+.*<(.*plt.*)>
+.*:[ ]+[0-9a-f]+[ ]+auipc[ ]+.*
+.*:[ ]+[0-9a-f]+[ ]+(lw|ld)[ ]+.*<(_GLOBAL_OFFSET_TABLE_.*|.*)>
+#...
diff --git a/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite.s b/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite.s
new file mode 100644
index 0000000..6c2f8e8
--- /dev/null
+++ b/ld/testsuite/ld-riscv-elf/ifunc-plt-got-overwrite.s
@@ -0,0 +1,38 @@
+ .text
+
+ .type foo_resolver, @function
+foo_resolver:
+ ret
+ .size foo_resolver, .-foo_resolver
+
+ .globl foo1
+ .type foo1, %gnu_indirect_function
+ .set foo1, foo_resolver
+
+ .globl foo2
+ .type foo2, %gnu_indirect_function
+ .set foo2, foo_resolver
+
+ .globl bar
+ .type bar, @function
+bar:
+.L1:
+ auipc x1, %got_pcrel_hi (foo1)
+.ifdef __64_bit__
+ ld x1, %pcrel_lo (.L1) (x1)
+.else
+ lw x1, %pcrel_lo (.L1) (x1)
+.endif
+
+ call foo1
+ call foo1@plt
+
+.L2:
+ auipc x2, %got_pcrel_hi (foo2)
+.ifdef __64_bit__
+ ld x2, %pcrel_lo (.L2) (x2)
+.else
+ lw x2, %pcrel_lo (.L2) (x2)
+.endif
+ ret
+ .size bar, .-bar
diff --git a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
index b82e092..9834041 100644
--- a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
+++ b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
@@ -175,6 +175,13 @@ if [istarget "riscv*-*-*"] {
run_dump_test_ifunc "ifunc-plt-02" rv64 exe
run_dump_test_ifunc "ifunc-plt-02" rv64 pie
run_dump_test_ifunc "ifunc-plt-02" rv64 pic
+ # Check the .rela.iplt overwrite issue.
+ run_dump_test_ifunc "ifunc-plt-got-overwrite" rv32 exe
+ run_dump_test_ifunc "ifunc-plt-got-overwrite" rv32 pie
+ run_dump_test_ifunc "ifunc-plt-got-overwrite" rv32 pic
+ run_dump_test_ifunc "ifunc-plt-got-overwrite" rv64 exe
+ run_dump_test_ifunc "ifunc-plt-got-overwrite" rv64 pie
+ run_dump_test_ifunc "ifunc-plt-got-overwrite" rv64 pic
# Setup shared libraries.
run_ld_link_tests {
--
2.7.4
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