Do not emit bad dynamic relocations when sections are shrunk

Author: rui314

src/output-chunks.cc

@@ -923,6 +923,12 @@ void OutputSection<E>::copy_buf(Context<E> &ctx) {
     u64 addr = this->shdr.sh_addr + r.isec->offset + r.offset;
     Symbol<E> &sym = *r.sym;
 
+    if constexpr (is_riscv<E> || is_loongarch<E>) {
+      i64 delta = get_r_delta(*r.isec, r.offset);
+      loc = (Word<E> *)(buf + r.isec->offset + r.offset - delta);
+      addr -= delta;
+    }
+
     switch (r.kind) {
     case ABS_REL_NONE:
     case ABS_REL_RELR:
@@ -1103,6 +1109,7 @@ void OutputSection<E>::scan_abs_relocations(Context<E> &ctx) {
   if (ctx.arg.pack_dyn_relocs_relr)
     for (AbsRel<E> &r : abs_rels)
       if (r.kind == ABS_REL_BASEREL &&
+          !(r.isec->shdr().sh_flags & SHF_EXECINSTR) &&
           r.isec->shdr().sh_addralign % sizeof(Word<E>) == 0 &&
           r.offset % sizeof(Word<E>) == 0)
         r.kind = ABS_REL_RELR;

test/textrel.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+. $(dirname $0)/common.inc
+
+cat <<EOF | $CC -o $t/a.o -c -xc - -fno-PIE
+void hello();
+int main() { hello(); }
+EOF
+
+cat <<EOF | $CC -o $t/b.o -c -xc - -fno-PIE
+#include <stdio.h>
+
+__attribute__((section(".text")))
+int (*fn)(const char *s) = puts;
+
+void hello() {
+  puts("Hello world");
+}
+EOF
+
+$CC -B. -o $t/exe $t/a.o $t/b.o -no-pie
+$QEMU $t/exe | grep -q 'Hello world'

test/textrel2.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+. $(dirname $0)/common.inc
+
+cat <<EOF | $CC -o $t/a.o -c -xc - -fPIE
+#include <stdio.h>
+
+void hello() {
+  puts("Hello world");
+}
+
+__attribute__((section(".text")))
+void (*p)() = hello;
+
+int main() {
+  p();
+}
+EOF
+
+$CC -B. -o $t/exe1 $t/a.o -pie
+$QEMU $t/exe1 | grep -q 'Hello world'
+
+$CC -B. -o $t/exe2 $t/a.o -pie -Wl,-z,pack-relative-relocs
+$QEMU $t/exe2 | grep -q 'Hello world'