[v2,2/5] LoongArch: Fix bad reloc with mixed visibility ifunc symbols in shared libraries
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Commit Message
With a simple test case:
.globl ifunc
.globl ifunc_hidden
.hidden ifunc_hidden
.type ifunc, %gnu_indirect_function
.type ifunc_hidden, %gnu_indirect_function
.text
.align 2
ifunc: ret
ifunc_hidden: ret
test:
bl ifunc
bl ifunc_hidden
"ld -shared" produces a shared object with one R_LARCH_NONE (instead of
R_LARCH_JUMP_SLOT as we expect) to relocate the GOT entry of "ifunc".
It's because the indices in .plt and .rela.plt mismatches for
STV_DEFAULT STT_IFUNC symbols when another PLT entry exists for a
STV_HIDDEN STT_IFUNC symbol, and such a mismatch breaks the logic of
loongarch_elf_finish_dynamic_symbol. Fix the issue by reordering .plt
so the indices no longer mismatch.
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
---
bfd/elfnn-loongarch.c | 77 ++++++++++++++++---
ld/testsuite/ld-loongarch-elf/ifunc-reloc.d | 19 +++++
ld/testsuite/ld-loongarch-elf/ifunc-reloc.s | 55 +++++++++++++
.../ld-loongarch-elf/ld-loongarch-elf.exp | 1 +
4 files changed, 140 insertions(+), 12 deletions(-)
create mode 100644 ld/testsuite/ld-loongarch-elf/ifunc-reloc.d
create mode 100644 ld/testsuite/ld-loongarch-elf/ifunc-reloc.s
Comments
On 2024-06-26 18:04, Xi Ruoyao wrote:
> With a simple test case:
>
> .globl ifunc
> .globl ifunc_hidden
> .hidden ifunc_hidden
> .type ifunc, %gnu_indirect_function
> .type ifunc_hidden, %gnu_indirect_function
>
> .text
> .align 2
> ifunc: ret
> ifunc_hidden: ret
>
> test:
> bl ifunc
> bl ifunc_hidden
>
> "ld -shared" produces a shared object with one R_LARCH_NONE (instead of
> R_LARCH_JUMP_SLOT as we expect) to relocate the GOT entry of "ifunc".
> It's because the indices in .plt and .rela.plt mismatches for
> STV_DEFAULT STT_IFUNC symbols when another PLT entry exists for a
> STV_HIDDEN STT_IFUNC symbol, and such a mismatch breaks the logic of
> loongarch_elf_finish_dynamic_symbol. Fix the issue by reordering .plt
> so the indices no longer mismatch.
>
> Signed-off-by: Xi Ruoyao <xry111@xry111.site>
> ---
> bfd/elfnn-loongarch.c | 77 ++++++++++++++++---
> ld/testsuite/ld-loongarch-elf/ifunc-reloc.d | 19 +++++
> ld/testsuite/ld-loongarch-elf/ifunc-reloc.s | 55 +++++++++++++
> .../ld-loongarch-elf/ld-loongarch-elf.exp | 1 +
> 4 files changed, 140 insertions(+), 12 deletions(-)
> create mode 100644 ld/testsuite/ld-loongarch-elf/ifunc-reloc.d
> create mode 100644 ld/testsuite/ld-loongarch-elf/ifunc-reloc.s
>
> diff --git a/bfd/elfnn-loongarch.c b/bfd/elfnn-loongarch.c
> index 3a55ac93e20..c02e3f4bd9c 100644
> --- a/bfd/elfnn-loongarch.c
> +++ b/bfd/elfnn-loongarch.c
> @@ -1691,9 +1691,10 @@ local_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
> ifunc dynamic relocs. */
>
> static bool
> -elfNN_allocate_ifunc_dynrelocs (struct elf_link_hash_entry *h, void *inf)
> +elfNN_allocate_ifunc_dynrelocs (struct elf_link_hash_entry *h,
> + struct bfd_link_info *info,
> + bool ref_local)
> {
> - struct bfd_link_info *info;
> /* An example of a bfd_link_hash_indirect symbol is versioned
> symbol. For example: __gxx_personality_v0(bfd_link_hash_indirect)
> -> __gxx_personality_v0(bfd_link_hash_defined)
> @@ -1709,20 +1710,18 @@ elfNN_allocate_ifunc_dynrelocs (struct elf_link_hash_entry *h, void *inf)
> if (h->root.type == bfd_link_hash_warning)
> h = (struct elf_link_hash_entry *) h->root.u.i.link;
>
> - info = (struct bfd_link_info *) inf;
> -
> /* Since STT_GNU_IFUNC symbol must go through PLT, we handle it
> here if it is defined and referenced in a non-shared object. */
> if (h->type == STT_GNU_IFUNC && h->def_regular)
> {
> - if (SYMBOL_REFERENCES_LOCAL (info, h))
> + if (ref_local && SYMBOL_REFERENCES_LOCAL (info, h))
> return local_allocate_ifunc_dyn_relocs (info, h,
> &h->dyn_relocs,
> PLT_ENTRY_SIZE,
> PLT_HEADER_SIZE,
> GOT_ENTRY_SIZE,
> false);
> - else
> + else if (!ref_local && !SYMBOL_REFERENCES_LOCAL (info, h))
> return _bfd_elf_allocate_ifunc_dyn_relocs (info, h,
> &h->dyn_relocs,
> PLT_ENTRY_SIZE,
> @@ -1734,6 +1733,23 @@ elfNN_allocate_ifunc_dynrelocs (struct elf_link_hash_entry *h, void *inf)
> return true;
> }
>
> +static bool
> +elfNN_allocate_ifunc_dynrelocs_ref_local (struct elf_link_hash_entry *h,
> + void *info)
> +{
> + return elfNN_allocate_ifunc_dynrelocs (h, (struct bfd_link_info *) info,
> + true);
> +}
> +
> +static bool
> +elfNN_allocate_ifunc_dynrelocs_ref_global (struct elf_link_hash_entry *h,
> + void *info)
> +{
> + return elfNN_allocate_ifunc_dynrelocs (h, (struct bfd_link_info *) info,
> + false);
> +}
> +
> +
> /* Allocate space in .plt, .got and associated reloc sections for
> ifunc dynamic relocs. */
>
> @@ -1749,7 +1765,7 @@ elfNN_allocate_local_ifunc_dynrelocs (void **slot, void *inf)
> || h->root.type != bfd_link_hash_defined)
> abort ();
>
> - return elfNN_allocate_ifunc_dynrelocs (h, inf);
> + return elfNN_allocate_ifunc_dynrelocs_ref_local (h, inf);
> }
>
> /* Set DF_TEXTREL if we find any dynamic relocs that apply to
> @@ -1909,11 +1925,48 @@ loongarch_elf_late_size_sections (bfd *output_bfd,
> sym dynamic relocs. */
> elf_link_hash_traverse (&htab->elf, allocate_dynrelocs, info);
>
> - /* Allocate global ifunc sym .plt and .got entries, and space for global
> - ifunc sym dynamic relocs. */
> - elf_link_hash_traverse (&htab->elf, elfNN_allocate_ifunc_dynrelocs, info);
> -
> - /* Allocate .plt and .got entries, and space for local ifunc symbols. */
> + /* Allocate global ifunc sym .plt and .got entries, and space for
> + *preemptible* ifunc sym dynamic relocs. Note that we must do it
> + for *all* preemptible ifunc (including local ifuncs and STV_HIDDEN
> + ifuncs) before doing it for any non-preemptible ifunc symbol:
> + assuming we are not so careful, when we link a shared library the
> + correlation of .plt and .rela.plt might look like:
> +
> + idx in .plt idx in .rela.plt
> + ext_func1@plt 0 0
> + ext_func2@plt 1 1
> + ext_func3@plt 2 2
> + hidden_ifunc1@plt 3 None: it's in .rela.got
> + hidden_ifunc2@plt 4 None: it's in .rela.got
> + normal_ifunc1@plt 5 != 3
> + normal_ifunc2@plt 6 != 4
> + local_ifunc@plt 7 None: it's in .rela.got
> +
> + Now oops the indices for normal_ifunc{1,2} in .rela.plt were different
> + from the indices in .plt :(. This would break finish_dynamic_symbol
> + which assumes the index in .rela.plt matches the index in .plt.
> +
> + So let's be careful and make it correct:
> +
> + idx in .plt idx in .rela.plt
> + ext_func1@plt 0 0
> + ext_func2@plt 1 1
> + ext_func3@plt 2 2
> + normal_ifunc1@plt 3 3
> + normal_ifunc2@plt 4 4
> + hidden_ifunc1@plt 5 None: it's in .rela.got
> + hidden_ifunc2@plt 6 None: it's in .rela.got
> + local_ifunc@plt 7 None: it's in .rela.got
> +
> + Now normal_ifuncs first. */
> + elf_link_hash_traverse (&htab->elf,
> + elfNN_allocate_ifunc_dynrelocs_ref_global, info);
> +
> + /* Now hidden_ifuncs ifuncs. */
LGTM. It makes logic clear and simple!
Update "hidden_ifuncs" in the third patch?
Thanks.
> + elf_link_hash_traverse (&htab->elf,
> + elfNN_allocate_ifunc_dynrelocs_ref_local, info);
> +
> + /* Finally local ifuncs. */
> htab_traverse (htab->loc_hash_table,
> elfNN_allocate_local_ifunc_dynrelocs, info);
>
> diff --git a/ld/testsuite/ld-loongarch-elf/ifunc-reloc.d b/ld/testsuite/ld-loongarch-elf/ifunc-reloc.d
> new file mode 100644
> index 00000000000..cb592874b1e
> --- /dev/null
> +++ b/ld/testsuite/ld-loongarch-elf/ifunc-reloc.d
> @@ -0,0 +1,19 @@
> +#ld: -shared
> +#readelf: -Wr
> +
> +#...
> +.*'\.rela\.dyn'.*
> +#...
> +.* R_LARCH_RELATIVE .*
> +.* R_LARCH_IRELATIVE .*
> +.* R_LARCH_IRELATIVE .*
> +.* R_LARCH_IRELATIVE .*
> +#...
> +.*'\.rela\.plt'.*
> +#...
> +.* R_LARCH_JUMP_SLOT .*
> +.* R_LARCH_JUMP_SLOT .*
> +.* R_LARCH_JUMP_SLOT .*
> +.* R_LARCH_JUMP_SLOT .*
> +.* R_LARCH_JUMP_SLOT .*
> +.* R_LARCH_JUMP_SLOT .*
> diff --git a/ld/testsuite/ld-loongarch-elf/ifunc-reloc.s b/ld/testsuite/ld-loongarch-elf/ifunc-reloc.s
> new file mode 100644
> index 00000000000..e59f2b20e36
> --- /dev/null
> +++ b/ld/testsuite/ld-loongarch-elf/ifunc-reloc.s
> @@ -0,0 +1,55 @@
> +.globl foo
> +.globl foo_hidden1
> +.globl foo_hidden2
> +.globl foo_protected
> +
> +.type foo, %gnu_indirect_function
> +.type foo_hidden1, %gnu_indirect_function
> +.type foo_hidden2, %gnu_indirect_function
> +.type foo_protected, %gnu_indirect_function
> +.type foo_internal, %gnu_indirect_function
> +
> +.hidden foo_hidden1
> +.hidden foo_hidden2
> +
> +.protected foo_protected
> +
> +.globl ext_ifunc1
> +.globl ext_ifunc2
> +.type ext_ifunc1, %gnu_indirect_function
> +.type ext_ifunc2, %gnu_indirect_function
> +
> +.text
> +.align 2
> +foo:
> + ret
> +
> +foo_hidden1:
> + ret
> +
> +foo_hidden2:
> + ret
> +
> +foo_protected:
> + ret
> +
> +foo_internal:
> + ret
> +
> +test:
> + la.got $a0, num
> + # The order is deliberately shuffled.
> + bl ext_ifunc1
> + bl foo
> + bl foo_hidden1
> + bl ext_func1
> + bl foo_protected
> + bl foo_internal
> + bl foo_hidden2
> + bl ext_func2
> + bl ext_ifunc2
> +
> +.data
> +.align 3
> +num:
> + .quad 114514
> diff --git a/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp b/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
> index 4d9f4aebaff..6cff117e29b 100644
> --- a/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
> +++ b/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
> @@ -133,6 +133,7 @@ if [istarget "loongarch64-*-*"] {
> run_dump_test "reloc_ler_with_shared"
> run_dump_test "reloc_abs_with_shared"
> run_dump_test "r_larch_32_elf64"
> + run_dump_test "ifunc-reloc"
> }
>
> if [check_pie_support] {
On Fri, 2024-06-28 at 17:40 +0800, Jinyang He wrote:
> > + Now normal_ifuncs first. */
> > + elf_link_hash_traverse (&htab->elf,
> > + elfNN_allocate_ifunc_dynrelocs_ref_global, info);
> > +
> > + /* Now hidden_ifuncs ifuncs. */
>
> LGTM. It makes logic clear and simple!
>
> Update "hidden_ifuncs" in the third patch?
Yes absolutely. Actually I've seen this typo at least twice myself but
I just forgot to fix it each time :(.
Thanks for the reminder.
> > + elf_link_hash_traverse (&htab->elf,
> > + elfNN_allocate_ifunc_dynrelocs_ref_local, info);
> > +
> > + /* Finally local ifuncs. */
> > htab_traverse (htab->loc_hash_table,
> > elfNN_allocate_local_ifunc_dynrelocs, info);
@@ -1691,9 +1691,10 @@ local_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
ifunc dynamic relocs. */
static bool
-elfNN_allocate_ifunc_dynrelocs (struct elf_link_hash_entry *h, void *inf)
+elfNN_allocate_ifunc_dynrelocs (struct elf_link_hash_entry *h,
+ struct bfd_link_info *info,
+ bool ref_local)
{
- struct bfd_link_info *info;
/* An example of a bfd_link_hash_indirect symbol is versioned
symbol. For example: __gxx_personality_v0(bfd_link_hash_indirect)
-> __gxx_personality_v0(bfd_link_hash_defined)
@@ -1709,20 +1710,18 @@ elfNN_allocate_ifunc_dynrelocs (struct elf_link_hash_entry *h, void *inf)
if (h->root.type == bfd_link_hash_warning)
h = (struct elf_link_hash_entry *) h->root.u.i.link;
- info = (struct bfd_link_info *) inf;
-
/* Since STT_GNU_IFUNC symbol must go through PLT, we handle it
here if it is defined and referenced in a non-shared object. */
if (h->type == STT_GNU_IFUNC && h->def_regular)
{
- if (SYMBOL_REFERENCES_LOCAL (info, h))
+ if (ref_local && SYMBOL_REFERENCES_LOCAL (info, h))
return local_allocate_ifunc_dyn_relocs (info, h,
&h->dyn_relocs,
PLT_ENTRY_SIZE,
PLT_HEADER_SIZE,
GOT_ENTRY_SIZE,
false);
- else
+ else if (!ref_local && !SYMBOL_REFERENCES_LOCAL (info, h))
return _bfd_elf_allocate_ifunc_dyn_relocs (info, h,
&h->dyn_relocs,
PLT_ENTRY_SIZE,
@@ -1734,6 +1733,23 @@ elfNN_allocate_ifunc_dynrelocs (struct elf_link_hash_entry *h, void *inf)
return true;
}
+static bool
+elfNN_allocate_ifunc_dynrelocs_ref_local (struct elf_link_hash_entry *h,
+ void *info)
+{
+ return elfNN_allocate_ifunc_dynrelocs (h, (struct bfd_link_info *) info,
+ true);
+}
+
+static bool
+elfNN_allocate_ifunc_dynrelocs_ref_global (struct elf_link_hash_entry *h,
+ void *info)
+{
+ return elfNN_allocate_ifunc_dynrelocs (h, (struct bfd_link_info *) info,
+ false);
+}
+
+
/* Allocate space in .plt, .got and associated reloc sections for
ifunc dynamic relocs. */
@@ -1749,7 +1765,7 @@ elfNN_allocate_local_ifunc_dynrelocs (void **slot, void *inf)
|| h->root.type != bfd_link_hash_defined)
abort ();
- return elfNN_allocate_ifunc_dynrelocs (h, inf);
+ return elfNN_allocate_ifunc_dynrelocs_ref_local (h, inf);
}
/* Set DF_TEXTREL if we find any dynamic relocs that apply to
@@ -1909,11 +1925,48 @@ loongarch_elf_late_size_sections (bfd *output_bfd,
sym dynamic relocs. */
elf_link_hash_traverse (&htab->elf, allocate_dynrelocs, info);
- /* Allocate global ifunc sym .plt and .got entries, and space for global
- ifunc sym dynamic relocs. */
- elf_link_hash_traverse (&htab->elf, elfNN_allocate_ifunc_dynrelocs, info);
-
- /* Allocate .plt and .got entries, and space for local ifunc symbols. */
+ /* Allocate global ifunc sym .plt and .got entries, and space for
+ *preemptible* ifunc sym dynamic relocs. Note that we must do it
+ for *all* preemptible ifunc (including local ifuncs and STV_HIDDEN
+ ifuncs) before doing it for any non-preemptible ifunc symbol:
+ assuming we are not so careful, when we link a shared library the
+ correlation of .plt and .rela.plt might look like:
+
+ idx in .plt idx in .rela.plt
+ ext_func1@plt 0 0
+ ext_func2@plt 1 1
+ ext_func3@plt 2 2
+ hidden_ifunc1@plt 3 None: it's in .rela.got
+ hidden_ifunc2@plt 4 None: it's in .rela.got
+ normal_ifunc1@plt 5 != 3
+ normal_ifunc2@plt 6 != 4
+ local_ifunc@plt 7 None: it's in .rela.got
+
+ Now oops the indices for normal_ifunc{1,2} in .rela.plt were different
+ from the indices in .plt :(. This would break finish_dynamic_symbol
+ which assumes the index in .rela.plt matches the index in .plt.
+
+ So let's be careful and make it correct:
+
+ idx in .plt idx in .rela.plt
+ ext_func1@plt 0 0
+ ext_func2@plt 1 1
+ ext_func3@plt 2 2
+ normal_ifunc1@plt 3 3
+ normal_ifunc2@plt 4 4
+ hidden_ifunc1@plt 5 None: it's in .rela.got
+ hidden_ifunc2@plt 6 None: it's in .rela.got
+ local_ifunc@plt 7 None: it's in .rela.got
+
+ Now normal_ifuncs first. */
+ elf_link_hash_traverse (&htab->elf,
+ elfNN_allocate_ifunc_dynrelocs_ref_global, info);
+
+ /* Now hidden_ifuncs ifuncs. */
+ elf_link_hash_traverse (&htab->elf,
+ elfNN_allocate_ifunc_dynrelocs_ref_local, info);
+
+ /* Finally local ifuncs. */
htab_traverse (htab->loc_hash_table,
elfNN_allocate_local_ifunc_dynrelocs, info);
new file mode 100644
@@ -0,0 +1,19 @@
+#ld: -shared
+#readelf: -Wr
+
+#...
+.*'\.rela\.dyn'.*
+#...
+.* R_LARCH_RELATIVE .*
+.* R_LARCH_IRELATIVE .*
+.* R_LARCH_IRELATIVE .*
+.* R_LARCH_IRELATIVE .*
+#...
+.*'\.rela\.plt'.*
+#...
+.* R_LARCH_JUMP_SLOT .*
+.* R_LARCH_JUMP_SLOT .*
+.* R_LARCH_JUMP_SLOT .*
+.* R_LARCH_JUMP_SLOT .*
+.* R_LARCH_JUMP_SLOT .*
+.* R_LARCH_JUMP_SLOT .*
new file mode 100644
@@ -0,0 +1,55 @@
+.globl foo
+.globl foo_hidden1
+.globl foo_hidden2
+.globl foo_protected
+
+.type foo, %gnu_indirect_function
+.type foo_hidden1, %gnu_indirect_function
+.type foo_hidden2, %gnu_indirect_function
+.type foo_protected, %gnu_indirect_function
+.type foo_internal, %gnu_indirect_function
+
+.hidden foo_hidden1
+.hidden foo_hidden2
+
+.protected foo_protected
+
+.globl ext_ifunc1
+.globl ext_ifunc2
+.type ext_ifunc1, %gnu_indirect_function
+.type ext_ifunc2, %gnu_indirect_function
+
+.text
+.align 2
+foo:
+ ret
+
+foo_hidden1:
+ ret
+
+foo_hidden2:
+ ret
+
+foo_protected:
+ ret
+
+foo_internal:
+ ret
+
+test:
+ la.got $a0, num
+ # The order is deliberately shuffled.
+ bl ext_ifunc1
+ bl foo
+ bl foo_hidden1
+ bl ext_func1
+ bl foo_protected
+ bl foo_internal
+ bl foo_hidden2
+ bl ext_func2
+ bl ext_ifunc2
+
+.data
+.align 3
+num:
+ .quad 114514
@@ -133,6 +133,7 @@ if [istarget "loongarch64-*-*"] {
run_dump_test "reloc_ler_with_shared"
run_dump_test "reloc_abs_with_shared"
run_dump_test "r_larch_32_elf64"
+ run_dump_test "ifunc-reloc"
}
if [check_pie_support] {