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LoongArch: Check PC-relative relocations for shared libraries

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Building shared libraries should not be allowed for PC-relative
relocations against external symbols.
Currently LoongArch has no corresponding checks and silently
generates wrong shared libraries.

However, In the first version of the medium cmodel, pcalau12i+jirl was
used for function calls, in which case PC-relative relocations were
allowed.
This commit is contained in:
Lulu Cai 2024-09-30 16:08:59 +08:00 committed by liuzhensong
parent 7721dcad5c
commit 4cb77761d6
11 changed files with 80 additions and 0 deletions
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21
bfd/elfnn-loongarch.c
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@ -1079,6 +1079,18 @@ loongarch_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
h->non_got_ref = 1;
break;
/* Since shared library global symbols interpose, any
PC-relative relocations against external symbols
should not be used to build shared libraries. */
case R_LARCH_PCREL20_S2:
if (bfd_link_pic (info)
&& (sec->flags & SEC_ALLOC) != 0
&& (sec->flags & SEC_READONLY) != 0
&& ! LARCH_REF_LOCAL (info, h))
return bad_static_reloc (abfd, rel, sec, r_type, h, NULL);
break;
/* For normal cmodel, pcalau12i + addi.d/w used to data.
For first version medium cmodel, pcalau12i + jirl are used to
function call, it need to creat PLT entry for STT_FUNC and
@ -1096,6 +1108,15 @@ loongarch_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
h->pointer_equality_needed = 1;
}
/* PC-relative relocations are allowed For first version
medium cmodel function call. */
if (h != NULL && !h->needs_plt
&& bfd_link_pic (info)
&& (sec->flags & SEC_ALLOC) != 0
&& (sec->flags & SEC_READONLY) != 0
&& ! LARCH_REF_LOCAL (info, h))
return bad_static_reloc (abfd, rel, sec, r_type, h, NULL);
break;
case R_LARCH_B16:

5
ld/testsuite/ld-loongarch-elf/bad_pcala_hi20_global.d Normal file
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@ -0,0 +1,5 @@
#name: PC-relative relocation making shared
#source: bad_pcala_hi20_global.s
#target: [check_shared_lib_support]
#ld: -shared --defsym global_a=0x10 --defsym global_b=0x20
#error: .*: relocation R_LARCH_PCALA_HI20 against `global_b` can not be used when making a shared object; recompile with -fPIC

8
ld/testsuite/ld-loongarch-elf/bad_pcala_hi20_global.s Normal file
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@ -0,0 +1,8 @@
.hidden global_a
.text
.align 2
main:
# Symbols defined .hidden are bound local and
# the linker should differenciate them.
la.pcrel $a0, global_a
la.pcrel $a0, global_b

5
ld/testsuite/ld-loongarch-elf/bad_pcala_hi20_weak.d Normal file
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@ -0,0 +1,5 @@
#name: PC-relative relocation making shared
#source: bad_pcala_hi20_weak.s
#target: [check_shared_lib_support]
#ld: -shared --defsym global_a=0x10 --defsym global_b=0x20
#error: .*: relocation R_LARCH_PCALA_HI20 against `global_b` can not be used when making a shared object; recompile with -fPIC

9
ld/testsuite/ld-loongarch-elf/bad_pcala_hi20_weak.s Normal file
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@ -0,0 +1,9 @@
.hidden global_a
.weak global_b
.text
.align 2
main:
# Symbols defined .hidden are bound local and
# the linker should differenciate them.
la.pcrel $a0, global_a
la.pcrel $a0, global_b

5
ld/testsuite/ld-loongarch-elf/bad_pcrel20_s2_global.d Normal file
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@ -0,0 +1,5 @@
#name: PC-relative relocation making shared
#source: bad_pcrel20_s2_global.s
#target: [check_shared_lib_support]
#ld: -shared --defsym global_a=0x10 --defsym global_b=0x20
#error: .*: relocation R_LARCH_PCREL20_S2 against `global_b` can not be used when making a shared object; recompile with -fPIC

8
ld/testsuite/ld-loongarch-elf/bad_pcrel20_s2_global.s Normal file
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@ -0,0 +1,8 @@
.hidden global_a
.text
.align 2
main:
# Symbols defined .hidden are bound local and
# the linker should differenciate them.
pcaddi $a0, %pcrel_20(global_a)
pcaddi $a0, %pcrel_20(global_b)

5
ld/testsuite/ld-loongarch-elf/bad_pcrel20_s2_weak.d Normal file
View File

@ -0,0 +1,5 @@
#name: PC-relative relocation making shared
#source: bad_pcrel20_s2_weak.s
#target: [check_shared_lib_support]
#ld: -shared --defsym global_a=0x10 --defsym global_b=0x20
#error: .*: relocation R_LARCH_PCREL20_S2 against `global_b` can not be used when making a shared object; recompile with -fPIC

9
ld/testsuite/ld-loongarch-elf/bad_pcrel20_s2_weak.s Normal file
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@ -0,0 +1,9 @@
.hidden global_a
.weak global_b
.text
.align 2
main:
# Symbols defined .hidden are bound local and
# the linker should differenciate them.
pcaddi $a0, %pcrel_20(global_a)
pcaddi $a0, %pcrel_20(global_b)

1
ld/testsuite/ld-loongarch-elf/data-plt.s
View File

@ -2,6 +2,7 @@
# R_LARCH_PCALA_HI20 only need to generate PLT entry for function symbols.
.text
.globl a
.hidden a
.data
.align 2

4
ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
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@ -166,6 +166,10 @@ if [istarget "loongarch64-*-*"] {
run_dump_test "relr-got-shared"
run_dump_test "relr-text-shared"
run_dump_test "abssym_shared"
run_dump_test "bad_pcala_hi20_global"
run_dump_test "bad_pcala_hi20_weak"
run_dump_test "bad_pcrel20_s2_global"
run_dump_test "bad_pcrel20_s2_weak"
}
if [check_pie_support] {