[ELF] Fix .debug_rnglists reader

Fixes https://github.com/rui314/mold/issues/453

elf/dwarf.cc

@@ -368,10 +368,15 @@ read_address_areas(Context<E> &ctx, ObjectFile<E> &file, i64 offset) {
 
   DebugInfoReader<E> reader{ctx, file, cu};
 
-  std::pair<u64, u64> low_pc;
-  std::pair<u64, u64> high_pc;
-  std::optional<u64> ranges;
-  u64 rnglists_base = 0;
+  struct Record {
+    u64 form = 0;
+    u64 value = 0;
+  };
+
+  Record low_pc;
+  Record high_pc;
+  Record ranges;
+  std::optional<u64> rnglists_base;
   typename E::WordTy *addrx = nullptr;
 
   // Read all interesting debug records.
@@ -397,61 +402,68 @@ read_address_areas(Context<E> &ctx, ObjectFile<E> &file, i64 offset) {
       addrx = (typename E::WordTy *)(get_buffer(ctx, ctx.debug_addr) + val);
       break;
     case DW_AT_ranges:
-      ranges = val;
+      ranges = {form, val};
       break;
     }
   }
 
   // Handle non-contiguous address ranges.
-  if (ranges) {
+  if (ranges.form) {
     if (dwarf_version <= 4) {
       typename E::WordTy *range_begin =
-        (typename E::WordTy *)(get_buffer(ctx, ctx.debug_ranges) + *ranges);
+        (typename E::WordTy *)(get_buffer(ctx, ctx.debug_ranges) + ranges.value);
       return read_debug_range(ctx, file, range_begin);
     }
 
     assert(dwarf_version == 5);
 
-    u8 *buf = get_buffer(ctx, ctx.debug_rnglists) + rnglists_base;
-    u64 offset = *(u32 *)(buf + *ranges * 4);
-    return read_rnglist_range(ctx, file, buf + offset, addrx);
+    u8 *buf = get_buffer(ctx, ctx.debug_rnglists);
+    if (ranges.form == DW_FORM_sec_offset)
+      return read_rnglist_range(ctx, file, buf + ranges.value, addrx);
+
+    if (!rnglists_base)
+      Fatal(ctx) << file << ": --gdb-index: missing DW_AT_rnglists_base";
+
+    u8 *base = buf + *rnglists_base;
+    return read_rnglist_range(ctx, file, base + *(u32 *)base, addrx);
   }
 
   // Handle a contiguous address range.
-  if (low_pc.first && high_pc.first) {
+  if (low_pc.form && high_pc.form) {
     u64 lo;
 
-    switch (low_pc.first) {
+    switch (low_pc.form) {
     case DW_FORM_addr:
-      lo = low_pc.second;
+      lo = low_pc.value;
       break;
     case DW_FORM_addrx:
     case DW_FORM_addrx1:
     case DW_FORM_addrx2:
     case DW_FORM_addrx4:
-      lo = addrx[low_pc.second];
+      lo = addrx[low_pc.value];
       break;
     default:
       Fatal(ctx) << file << ": --gdb-index: unhandled form for DW_AT_low_pc: 0x"
-                 << std::hex << high_pc.first;
+                 << std::hex << high_pc.form;
     }
 
-    switch (high_pc.first) {
+    switch (high_pc.form) {
     case DW_FORM_addr:
-      return {lo, high_pc.second};
+      return {lo, high_pc.value};
     case DW_FORM_addrx:
     case DW_FORM_addrx1:
     case DW_FORM_addrx2:
     case DW_FORM_addrx4:
-      return {lo, addrx[high_pc.second]};
+      return {lo, addrx[high_pc.value]};
+    case DW_FORM_udata:
     case DW_FORM_data1:
     case DW_FORM_data2:
     case DW_FORM_data4:
     case DW_FORM_data8:
-      return {lo, lo + high_pc.second};
+      return {lo, lo + high_pc.value};
     default:
       Fatal(ctx) << file << ": --gdb-index: unhandled form for DW_AT_high_pc: 0x"
-                 << std::hex << high_pc.first;
+                 << std::hex << high_pc.form;
     }
   }
 

test/elf/gdb-index-dwarf5.sh

@@ -21,41 +21,73 @@ which gdb >& /dev/null || { echo skipped; exit; }
 echo 'int main() {}' | $CC -o /dev/null -xc -gdwarf-5 -g - >& /dev/null ||
   { echo skipped; exit; }
 
-cat <<EOF | $CC -c -o $t/a.o -fPIC -g -ggnu-pubnames -gdwarf-5 -xc - -ffunction-sections
-void hello2();
+cat <<EOF > $t/a.c
+void fn3();
 
-static void hello() {
-  hello2();
+static void fn2() {
+  fn3();
 }
 
-void greet() {
-  hello();
+void fn1() {
+  fn2();
 }
 EOF
 
-cat <<EOF | $CC -c -o $t/b.o -fPIC -g -ggnu-pubnames -gdwarf-4 -xc - -ffunction-sections
-#include <stdio.h>
+cat <<EOF > $t/b.c
+void fn5();
 
+static void fn4() {
+  fn5();
+}
+
+void fn3() {
+  fn4();
+}
+EOF
+
+cat <<EOF > $t/c.c
+void fn7();
+
+static void fn6() {
+  fn7();
+}
+
+void fn5() {
+  fn6();
+}
+EOF
+
+cat <<EOF > $t/d.c
+#include <stdio.h>
 void trap() {}
 
-void hello2() {
+static void fn8() {
   printf("Hello world\n");
   trap();
 }
-EOF
 
-$CC -B. -shared -o $t/c.so $t/a.o $t/b.o -Wl,--gdb-index
-readelf -WS $t/c.so 2> /dev/null | fgrep -q .gdb_index
-
-cat <<EOF | $CC -c -o $t/d.o -fPIC -g -ggnu-pubnames -gdwarf-5 -xc - -gz
-void greet();
-
-int main() {
-  greet();
+void fn7() {
+  fn8();
 }
 EOF
 
-$CC -B. -o $t/exe $t/c.so $t/d.o -Wl,--gdb-index
+$CC -c -o $t/a.o $t/a.c -fPIC -g -ggnu-pubnames -gdwarf-5 -ffunction-sections
+$CC -c -o $t/b.o $t/b.c -fPIC -g -ggnu-pubnames -gdwarf-4 -ffunction-sections
+$CC -c -o $t/c.o $t/c.c -fPIC -g -ggnu-pubnames -gdwarf-5
+$CC -c -o $t/d.o $t/d.c -fPIC -g -ggnu-pubnames -gdwarf-5 -ffunction-sections
+
+$CC -B. -shared -o $t/e.so $t/a.o $t/b.o $t/c.o $t/d.o -Wl,--gdb-index
+readelf -WS $t/e.so 2> /dev/null | fgrep -q .gdb_index
+
+cat <<EOF | $CC -c -o $t/f.o -fPIC -g -ggnu-pubnames -gdwarf-5 -xc - -gz
+void fn1();
+
+int main() {
+  fn1();
+}
+EOF
+
+$CC -B. -o $t/exe $t/e.so $t/f.o -Wl,--gdb-index
 readelf -WS $t/exe 2> /dev/null | fgrep -q .gdb_index
 
 $QEMU $t/exe | grep -q 'Hello world'
@@ -63,9 +95,13 @@ $QEMU $t/exe | grep -q 'Hello world'
 DEBUGINFOD_URLS= gdb $t/exe -batch -ex 'b main' -ex r -ex 'b trap' \
   -ex c -ex bt -ex quit >& $t/log
 
-grep -Pq 'hello2 \(\) at .*<stdin>:7' $t/log
-grep -Pq 'hello \(\) at .*<stdin>:4' $t/log
-grep -Pq 'greet \(\) at .*<stdin>:8' $t/log
-grep -Pq 'main \(\) at .*<stdin>:4' $t/log
+grep -Pq 'fn8 \(\) at .*/d.c:6' $t/log
+grep -Pq 'fn7 \(\) at .*/d.c:10' $t/log
+grep -Pq 'fn6 \(\) at .*/c.c:4' $t/log
+grep -Pq 'fn5 \(\) at .*/c.c:8' $t/log
+grep -Pq 'fn4 \(\) at .*/b.c:4' $t/log
+grep -Pq 'fn3 \(\) at .*/b.c:8' $t/log
+grep -Pq 'fn2 \(\) at .*/a.c:4' $t/log
+grep -Pq 'fn1 \(\) at .*/a.c:8' $t/log
 
 echo OK