[PATCH] LoongArch: Disallow TLS transition when a section contains TLS_IE64 or TLS_DESC64 reloc
Xi Ruoyao
xry111@xry111.site
Thu Jan 25 13:36:26 GMT 2024
We cannot do TLS transition for them without a psABI revision marking
some "key" instructions with reloc. Disallow the transition when we see
such a reloc in a section to prevent an invalid "partial" transition.
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
---
To Nick:
Sorry for another late update, but we need this for 2.42 or anything
compiled with -mcmodel=extreme and using errno will just blow up :(.
bfd/elfnn-loongarch.c | 53 +++++++++++++++++--
.../ld-loongarch-elf/ld-loongarch-elf.exp | 14 +++++
.../ld-loongarch-elf/tls-ie64-notrans.d | 3 ++
.../ld-loongarch-elf/tls-ie64-notrans.s | 7 +++
4 files changed, 73 insertions(+), 4 deletions(-)
create mode 100644 ld/testsuite/ld-loongarch-elf/tls-ie64-notrans.d
create mode 100644 ld/testsuite/ld-loongarch-elf/tls-ie64-notrans.s
diff --git a/bfd/elfnn-loongarch.c b/bfd/elfnn-loongarch.c
index b62bb424644..b9709401f56 100644
--- a/bfd/elfnn-loongarch.c
+++ b/bfd/elfnn-loongarch.c
@@ -717,6 +717,40 @@ loongarch_tls_transition (struct bfd_link_info *info, unsigned int r_type,
return loongarch_tls_transition_without_check (info, r_type, h);
}
+/* For TLS IE in extreme code model:
+ pcalau12i t0, %ie_pc_hi20(x)
+ li.d t1, %ie_pc_lo12(x)
+ lu32i.d t1, %ie64_pc_lo20(x)
+ lu52i.d t1, t1, %ie64_pc_hi12(x)
+ ldx.d t0, t0, t1
+ We've no idea how to remove the ldx.d instruction or turn it into a
+ nop because there is no reloc on it. But we have to stop turning this
+ into LE or we'll end up
+ lu12i.w t0, %le_hi20(x)
+ ori t1, t1, %le_lo12(x)
+ lu32i.d t1, %ie64_pc_lo20(x)
+ lu52i.d t1, t1, %ie64_pc_hi12(x)
+ ldx.d t0, t0, t1
+ which is completely wrong. For TLS DESC it's similar: we cannot remove
+ the add.d instruction but we have to stop the transition. */
+static bool
+loongarch_elf_allow_tls_transition_p (const Elf_Internal_Rela *r_begin,
+ const Elf_Internal_Rela *r_end)
+{
+ for (; r_begin != r_end; r_begin++)
+ switch (ELFNN_R_TYPE (r_begin->r_info))
+ {
+ case R_LARCH_TLS_IE64_PC_HI12:
+ case R_LARCH_TLS_IE64_PC_LO20:
+ case R_LARCH_TLS_DESC64_PC_HI12:
+ case R_LARCH_TLS_DESC64_PC_LO20:
+ return false;
+ }
+
+ return true;
+}
+
+
/* Look through the relocs for a section during the first phase, and
allocate space in the global offset table or procedure linkage
table. */
@@ -730,6 +764,7 @@ loongarch_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
struct elf_link_hash_entry **sym_hashes;
const Elf_Internal_Rela *rel;
asection *sreloc = NULL;
+ bool allow_tls_transition;
if (bfd_link_relocatable (info))
return true;
@@ -741,6 +776,9 @@ loongarch_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
if (htab->elf.dynobj == NULL)
htab->elf.dynobj = abfd;
+ allow_tls_transition = loongarch_elf_allow_tls_transition_p (
+ relocs, relocs + sec->reloc_count);
+
for (rel = relocs; rel < relocs + sec->reloc_count; rel++)
{
unsigned int r_type;
@@ -818,7 +856,8 @@ loongarch_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
int need_dynreloc = 0;
int only_need_pcrel = 0;
- r_type = loongarch_tls_transition (info, r_type, h, abfd, r_symndx);
+ if (allow_tls_transition)
+ r_type = loongarch_tls_transition (info, r_type, h, abfd, r_symndx);
switch (r_type)
{
case R_LARCH_GOT_PC_HI20:
@@ -2632,7 +2671,6 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
asection **local_sections)
{
Elf_Internal_Rela *rel;
- Elf_Internal_Rela *relend;
bool fatal = false;
asection *sreloc = elf_section_data (input_section)->sreloc;
struct loongarch_elf_link_hash_table *htab = loongarch_elf_hash_table (info);
@@ -2643,8 +2681,10 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
bool is_dyn = elf_hash_table (info)->dynamic_sections_created;
asection *plt = htab->elf.splt ? htab->elf.splt : htab->elf.iplt;
asection *got = htab->elf.sgot;
+ Elf_Internal_Rela *relend = relocs + input_section->reloc_count;
+ bool allow_tls_transition =
+ loongarch_elf_allow_tls_transition_p (relocs, relend);
- relend = relocs + input_section->reloc_count;
for (rel = relocs; rel < relend; rel++)
{
unsigned int r_type = ELFNN_R_TYPE (rel->r_info);
@@ -2789,7 +2829,12 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
BFD_ASSERT (!resolved_local || defined_local);
- relaxed_r_type = loongarch_tls_transition (info, r_type, h, input_bfd, r_symndx);
+ relaxed_r_type =
+ (allow_tls_transition ? loongarch_tls_transition (info, r_type,
+ h, input_bfd,
+ r_symndx)
+ : r_type);
+
if (relaxed_r_type != r_type)
{
howto = loongarch_elf_rtype_to_howto (input_bfd, relaxed_r_type);
diff --git a/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp b/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
index 2ff06d62236..9e35940f5d6 100644
--- a/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
+++ b/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
@@ -88,6 +88,20 @@ if [istarget "loongarch64-*-*"] {
"medium-call" \
] \
]
+
+ run_ld_link_tests \
+ [list \
+ [list \
+ "disable TLS IE transition with TLS_IE64_PC reloc" \
+ "-e 0x0" "" \
+ "" \
+ {tls-ie64-notrans.s} \
+ [list \
+ [list objdump -D tls-ie64-notrans.d] \
+ ] \
+ "tls-ie64-notrans" \
+ ] \
+ ]
}
if [istarget "loongarch64-*-*"] {
diff --git a/ld/testsuite/ld-loongarch-elf/tls-ie64-notrans.d b/ld/testsuite/ld-loongarch-elf/tls-ie64-notrans.d
new file mode 100644
index 00000000000..47d507a0538
--- /dev/null
+++ b/ld/testsuite/ld-loongarch-elf/tls-ie64-notrans.d
@@ -0,0 +1,3 @@
+#...
+.*pcalau12i.*
+#pass
diff --git a/ld/testsuite/ld-loongarch-elf/tls-ie64-notrans.s b/ld/testsuite/ld-loongarch-elf/tls-ie64-notrans.s
new file mode 100644
index 00000000000..cd8c65ff9d3
--- /dev/null
+++ b/ld/testsuite/ld-loongarch-elf/tls-ie64-notrans.s
@@ -0,0 +1,7 @@
+# it had segfaulted the linker due to invalid IE->LE transition
+.globl _start
+_start:
+ la.tls.ie $a0, $a1, foo
+
+.section .tdata
+foo: .word 114514
--
2.43.0
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