[PPC64V2] Emit _savegpr0_*, _restgpr0_*, _savegpr1_* and _restgpr1_* …

…symbols Fixes #1203
rui314 · Feb 27, 2024 · d4ff48a · d4ff48a
1 parent 21f2554
commit d4ff48a
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diff --git a/elf/arch-ppc64v2.cc b/elf/arch-ppc64v2.cc
@@ -568,6 +568,106 @@ void Thunk<E>::copy_buf(Context<E> &ctx) {
   }
 }
 
+// GCC may emit references to the following functions in function prologue
+// and epiilogue if -Os is specified. For some reason, these functions are
+// not in libgcc.a and expected to be synthesized by the linker.
+const std::vector<std::pair<std::string_view, u32>>
+ppc64_save_restore_insns = {
+  { "_savegpr0_14", 0xf9c1ff70 }, // std r14,-144(r1)
+  { "_savegpr0_15", 0xf9e1ff78 }, // std r15,-136(r1)
+  { "_savegpr0_16", 0xfa01ff80 }, // std r16,-128(r1)
+  { "_savegpr0_17", 0xfa21ff88 }, // std r17,-120(r1)
+  { "_savegpr0_18", 0xfa41ff90 }, // std r18,-112(r1)
+  { "_savegpr0_19", 0xfa61ff98 }, // std r19,-104(r1)
+  { "_savegpr0_20", 0xfa81ffa0 }, // std r20,-96(r1)
+  { "_savegpr0_21", 0xfaa1ffa8 }, // std r21,-88(r1)
+  { "_savegpr0_22", 0xfac1ffb0 }, // std r22,-80(r1)
+  { "_savegpr0_23", 0xfae1ffb8 }, // std r23,-72(r1)
+  { "_savegpr0_24", 0xfb01ffc0 }, // std r24,-64(r1)
+  { "_savegpr0_25", 0xfb21ffc8 }, // std r25,-56(r1)
+  { "_savegpr0_26", 0xfb41ffd0 }, // std r26,-48(r1)
+  { "_savegpr0_27", 0xfb61ffd8 }, // std r27,-40(r1)
+  { "_savegpr0_28", 0xfb81ffe0 }, // std r28,-32(r1)
+  { "_savegpr0_29", 0xfba1ffe8 }, // std r29,-24(r1)
+  { "_savegpr0_30", 0xfbc1fff0 }, // std r30,-16(r1)
+  { "_savegpr0_31", 0xfbe1fff8 }, // std r31,-8(r1)
+  { "",             0xf8010010 }, // std r0,16(r1)
+  { "",             0x4e800020 }, // blr
+
+  { "_restgpr0_14", 0xe9c1ff70 }, // ld r14,-144(r1)
+  { "_restgpr0_15", 0xe9e1ff78 }, // ld r15,-136(r1)
+  { "_restgpr0_16", 0xea01ff80 }, // ld r16,-128(r1)
+  { "_restgpr0_17", 0xea21ff88 }, // ld r17,-120(r1)
+  { "_restgpr0_18", 0xea41ff90 }, // ld r18,-112(r1)
+  { "_restgpr0_19", 0xea61ff98 }, // ld r19,-104(r1)
+  { "_restgpr0_20", 0xea81ffa0 }, // ld r20,-96(r1)
+  { "_restgpr0_21", 0xeaa1ffa8 }, // ld r21,-88(r1)
+  { "_restgpr0_22", 0xeac1ffb0 }, // ld r22,-80(r1)
+  { "_restgpr0_23", 0xeae1ffb8 }, // ld r23,-72(r1)
+  { "_restgpr0_24", 0xeb01ffc0 }, // ld r24,-64(r1)
+  { "_restgpr0_25", 0xeb21ffc8 }, // ld r25,-56(r1)
+  { "_restgpr0_26", 0xeb41ffd0 }, // ld r26,-48(r1)
+  { "_restgpr0_27", 0xeb61ffd8 }, // ld r27,-40(r1)
+  { "_restgpr0_28", 0xeb81ffe0 }, // ld r28,-32(r1)
+  { "_restgpr0_29", 0xe8010010 }, // ld r0,16(r1)
+  { "",             0xeba1ffe8 }, // ld r29,-24(r1)
+  { "",             0x7c0803a6 }, // mtlr r0
+  { "",             0xebc1fff0 }, // ld r30,-16(r1)
+  { "",             0xebe1fff8 }, // ld r31,-8(r1)
+  { "",             0x4e800020 }, // blr
+  { "_restgpr0_30", 0xebc1fff0 }, // ld r30,-16(r1)
+  { "_restgpr0_31", 0xe8010010 }, // ld r0,16(r1)
+  { "",             0xebe1fff8 }, // ld r31,-8(r1)
+  { "",             0x7c0803a6 }, // mtlr r0
+  { "",             0x4e800020 }, // blr
+
+  { "_savegpr1_14", 0xf9ccff70 }, // std r14,-144(r12)
+  { "_savegpr1_15", 0xf9ecff78 }, // std r15,-136(r12)
+  { "_savegpr1_16", 0xfa0cff80 }, // std r16,-128(r12)
+  { "_savegpr1_17", 0xfa2cff88 }, // std r17,-120(r12)
+  { "_savegpr1_18", 0xfa4cff90 }, // std r18,-112(r12)
+  { "_savegpr1_19", 0xfa6cff98 }, // std r19,-104(r12)
+  { "_savegpr1_20", 0xfa8cffa0 }, // std r20,-96(r12)
+  { "_savegpr1_21", 0xfaacffa8 }, // std r21,-88(r12)
+  { "_savegpr1_22", 0xfaccffb0 }, // std r22,-80(r12)
+  { "_savegpr1_23", 0xfaecffb8 }, // std r23,-72(r12)
+  { "_savegpr1_24", 0xfb0cffc0 }, // std r24,-64(r12)
+  { "_savegpr1_25", 0xfb2cffc8 }, // std r25,-56(r12)
+  { "_savegpr1_26", 0xfb4cffd0 }, // std r26,-48(r12)
+  { "_savegpr1_27", 0xfb6cffd8 }, // std r27,-40(r12)
+  { "_savegpr1_28", 0xfb8cffe0 }, // std r28,-32(r12)
+  { "_savegpr1_29", 0xfbacffe8 }, // std r29,-24(r12)
+  { "_savegpr1_30", 0xfbccfff0 }, // std r30,-16(r12)
+  { "_savegpr1_31", 0xfbecfff8 }, // std r31,-8(r12)
+  { "",             0x4e800020 }, // blr
+
+  { "_restgpr1_14", 0xe9ccff70 }, // ld r14,-144(r12)
+  { "_restgpr1_15", 0xe9ecff78 }, // ld r15,-136(r12)
+  { "_restgpr1_16", 0xea0cff80 }, // ld r16,-128(r12)
+  { "_restgpr1_17", 0xea2cff88 }, // ld r17,-120(r12)
+  { "_restgpr1_18", 0xea4cff90 }, // ld r18,-112(r12)
+  { "_restgpr1_19", 0xea6cff98 }, // ld r19,-104(r12)
+  { "_restgpr1_20", 0xea8cffa0 }, // ld r20,-96(r12)
+  { "_restgpr1_21", 0xeaacffa8 }, // ld r21,-88(r12)
+  { "_restgpr1_22", 0xeaccffb0 }, // ld r22,-80(r12)
+  { "_restgpr1_23", 0xeaecffb8 }, // ld r23,-72(r12)
+  { "_restgpr1_24", 0xeb0cffc0 }, // ld r24,-64(r12)
+  { "_restgpr1_25", 0xeb2cffc8 }, // ld r25,-56(r12)
+  { "_restgpr1_26", 0xeb4cffd0 }, // ld r26,-48(r12)
+  { "_restgpr1_27", 0xeb6cffd8 }, // ld r27,-40(r12)
+  { "_restgpr1_28", 0xeb8cffe0 }, // ld r28,-32(r12)
+  { "_restgpr1_29", 0xebacffe8 }, // ld r29,-24(r12)
+  { "_restgpr1_30", 0xebccfff0 }, // ld r30,-16(r12)
+  { "_restgpr1_31", 0xebecfff8 }, // ld r31,-8(r12)
+  { "",             0x4e800020 }, // blr
+};
+
+void PPC64SaveRestoreSection::copy_buf(Context<E> &ctx) {
+  ul32 *buf = (ul32 *)(ctx.buf + this->shdr.sh_offset);
+  for (auto [label, insn] : ppc64_save_restore_insns)
+    *buf++ = insn;
+}
+
 template <>
 u64 get_eflags(Context<E> &ctx) {
   return 2;

diff --git a/elf/mold.h b/elf/mold.h
@@ -1470,6 +1470,22 @@ class PPC64OpdSection : public Chunk<PPC64V1> {
 // arch-ppc64v2.cc
 //
 
+extern const std::vector<std::pair<std::string_view, u32>>
+ppc64_save_restore_insns;
+
+class PPC64SaveRestoreSection : public Chunk<PPC64V2> {
+public:
+  PPC64SaveRestoreSection() {
+    this->name = ".save_restore_gprs";
+    this->shdr.sh_type = SHT_PROGBITS;
+    this->shdr.sh_flags = SHF_ALLOC | SHF_EXECINSTR;
+    this->shdr.sh_addralign = 16;
+    this->shdr.sh_size = ppc64_save_restore_insns.size() * 4;
+  }
+
+  void copy_buf(Context<PPC64V2> &ctx) override;
+};
+
 template <> u64 get_eflags(Context<PPC64V2> &ctx);
 
 //
@@ -1594,6 +1610,7 @@ struct ContextExtras<PPC64V1> {
 
 template <>
 struct ContextExtras<PPC64V2> {
+  PPC64SaveRestoreSection *save_restore = nullptr;
   Symbol<PPC64V2> *TOC = nullptr;
   Atomic<bool> is_power10 = false;
 };

diff --git a/elf/passes.cc b/elf/passes.cc
@@ -177,6 +177,9 @@ void create_synthetic_sections(Context<E> &ctx) {
   if constexpr (is_ppc64v1<E>)
     ctx.extra.opd = push(new PPC64OpdSection);
 
+  if constexpr (is_ppc64v2<E>)
+    ctx.extra.save_restore = push(new PPC64SaveRestoreSection);
+
   if constexpr (is_sparc<E>) {
     if (ctx.arg.is_static)
       ctx.extra.tls_get_addr_sec = push(new SparcTlsGetAddrSection);
@@ -824,6 +827,11 @@ void add_synthetic_symbols(Context<E> &ctx) {
     }
   }
 
+  if constexpr (is_ppc64v2<E>)
+    for (auto [label, insn] : ppc64_save_restore_insns)
+      if (!label.empty())
+        add(label);
+
   obj.elf_syms = ctx.internal_esyms;
   obj.has_symver.resize(ctx.internal_esyms.size() - 1);
 
@@ -2766,6 +2774,18 @@ void fix_synthetic_symbols(Context<E> &ctx) {
     }
   }
 
+  // PPC64's _{save,rest}gpr{0,1}_{14,15,16,...,31} symbols
+  if constexpr (is_ppc64v2<E>) {
+    i64 offset = 0;
+    for (auto [label, insn] : ppc64_save_restore_insns) {
+      if (!label.empty())
+        if (Symbol<E> *sym = get_symbol(ctx, label);
+            sym->file == ctx.internal_obj)
+          start(sym, ctx.extra.save_restore, offset);
+      offset += 4;
+    }
+  }
+
   // __start_ and __stop_ symbols
   for (Chunk<E> *chunk : sections) {
     if (std::optional<std::string> name = get_start_stop_name(ctx, *chunk)) {

diff --git a/test/elf/ppc64le_save_restore_gprs.sh b/test/elf/ppc64le_save_restore_gprs.sh
@@ -0,0 +1,12 @@
+#!/bin/bash
+. $(dirname $0)/common.inc
+
+cat <<EOF | $CC -o $t/a.o -c -xc -
+#include <stdio.h>
+int main() {
+  printf("Hello world\n");
+}
+EOF
+
+$CC -B. -o $t/exe $t/a.o
+$OBJDUMP -d $t/exe | grep -q '<_savegpr0_14>'