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From d12d80cdcafd2f84321d311d6ce3e291f0e7b9a9 Mon Sep 17 00:00:00 2001
From: XingLi <lixing@loongson.cn>
Date: Thu, 27 Jul 2023 09:25:19 +0800
Subject: [PATCH 2/3] LoongArch: Add static PIE support
If the compiler is new enough, enable static PIE support. In the static
PIE version of _start (in rcrt1.o), use la.pcrel instead of la.got
because in a static PIE we cannot use GOT entries until the dynamic
relocations for GOT are resolved.
From: Xi Ruoyao <xry111@xry111.site>
Date: Sat, 24 Sep 2022 15:45:34 +0800
---
sysdeps/loongarch/configure | 51 ++++++++++++++++++++++++++++++++++
sysdeps/loongarch/configure.ac | 38 ++++++++++++++++++++++++-
sysdeps/loongarch/start.S | 16 +++++++----
3 files changed, 99 insertions(+), 6 deletions(-)
diff --git a/sysdeps/loongarch/configure b/sysdeps/loongarch/configure
index 1e5abf81..db6341e8 100644
--- a/sysdeps/loongarch/configure
+++ b/sysdeps/loongarch/configure
@@ -2,3 +2,54 @@
# Local configure fragment for sysdeps/loongarch/elf.
#AC_DEFINE(PI_STATIC_AND_HIDDEN)
+$as_echo "#define HIDDEN_VAR_NEEDS_DYNAMIC_RELOC 1" >>confdefs.h
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if the toolchain is sufficient to build static PIE on LoongArch" >&5
+$as_echo_n "checking if the toolchain is sufficient to build static PIE on LoongArch... " >&6; }
+if ${libc_cv_static_pie_on_loongarch+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+
+ cat > conftest.S << EOF
+.global _start
+.type _start, @function
+_start:
+ li.w \$a7, 93
+ /* This ensures the assembler supports explicit reloc. */
+ pcalau12i \$a0, %pc_hi20(x)
+ ld.w \$a0, \$a0, %pc_lo12(x)
+ syscall 0
+
+.data
+x:
+ .word 0
+ /* This should produce an R_LARCH_RELATIVE in the static PIE. */
+ .dword _start
+EOF
+ libc_cv_static_pie_on_loongarch=no
+ if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -static-pie -nostdlib -fPIE -o conftest conftest.S'
+ { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+ (eval $ac_try) 2>&5
+ ac_status=$?
+ $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+ test $ac_status = 0; }; } \
+ && { ac_try='LC_ALL=C $READELF -Wr conftest | grep -q R_LARCH_RELATIVE'
+ { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+ (eval $ac_try) 2>&5
+ ac_status=$?
+ $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+ test $ac_status = 0; }; }
+ then
+ libc_cv_static_pie_on_loongarch=yes
+ fi
+ rm -rf conftest.*
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_static_pie_on_loongarch" >&5
+$as_echo "$libc_cv_static_pie_on_loongarch" >&6; }
+
+if test "$libc_cv_static_pie_on_loongarch" = yes; then
+ $as_echo "#define SUPPORT_STATIC_PIE 1" >>confdefs.h
+
+fi
+
diff --git a/sysdeps/loongarch/configure.ac b/sysdeps/loongarch/configure.ac
index 67b46ce0..603085cd 100644
--- a/sysdeps/loongarch/configure.ac
+++ b/sysdeps/loongarch/configure.ac
@@ -3,4 +3,40 @@ GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
dnl It is always possible to access static and hidden symbols in an
dnl position independent way.
-#AC_DEFINE(PI_STATIC_AND_HIDDEN)
+ AC_DEFINE(HIDDEN_VAR_NEEDS_DYNAMIC_RELOC)
+
+dnl Test if the toolchain is new enough for static PIE.
+dnl We need a GAS supporting explicit reloc (older GAS produces stack-based
+dnl reloc and triggers an internal error in the linker). And, we need GCC to
+dnl pass the correct linker flags for static PIE. GCC >= 13 and GAS >= 2.40
+dnl satisify the requirement, but a distro may backport static PIE support into
+dnl earlier GCC or Binutils releases as well.
+AC_CACHE_CHECK([if the toolchain is sufficient to build static PIE on LoongArch],
+libc_cv_static_pie_on_loongarch, [
+ cat > conftest.S << EOF
+.global _start
+.type _start, @function
+_start:
+ li.w \$a7, 93
+ /* This ensures the assembler supports explicit reloc. */
+ pcalau12i \$a0, %pc_hi20(x)
+ ld.w \$a0, \$a0, %pc_lo12(x)
+ syscall 0
+
+.data
+x:
+ .word 0
+ /* This should produce an R_LARCH_RELATIVE in the static PIE. */
+ .dword _start
+EOF
+ libc_cv_static_pie_on_loongarch=no
+ if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -static-pie -nostdlib -fPIE -o conftest conftest.S]) \
+ && AC_TRY_COMMAND([LC_ALL=C $READELF -Wr conftest | grep -q R_LARCH_RELATIVE])
+ then
+ libc_cv_static_pie_on_loongarch=yes
+ fi
+ rm -rf conftest.*])
+
+if test "$libc_cv_static_pie_on_loongarch" = yes; then
+ AC_DEFINE(SUPPORT_STATIC_PIE)
+fi
diff --git a/sysdeps/loongarch/start.S b/sysdeps/loongarch/start.S
index 0deda78a..1b15fc9c 100644
--- a/sysdeps/loongarch/start.S
+++ b/sysdeps/loongarch/start.S
@@ -44,9 +44,15 @@ ENTRY (ENTRY_POINT)
cfi_undefined (1)
or a5, a0, zero /* rtld_fini */
-/* We must get symbol main through GOT table, since main may not be local.
- For instance: googletest defines main in dynamic library. */
- la.got a0, t0, main
+#if defined(PIC) && !defined(SHARED)
+/* For static PIE, the GOT cannot be used in _start because the GOT entries are
+ offsets instead of real addresses before __libc_start_main. */
+# define LA la.pcrel
+#else
+# define LA la.got
+#endif
+
+ LA a0, t0, main
#ifdef __loongarch_lp64
ld.d a1, sp, 0
addi.d a2, sp, SZREG
@@ -61,9 +67,9 @@ ENTRY (ENTRY_POINT)
move a4, zero /* used to be fini */
or a6, sp, zero /* stack_end */
- la.got ra, t0, __libc_start_main
+ LA ra, t0, __libc_start_main
jirl ra, ra, 0
- la.got ra, t0, abort
+ LA ra, t0, abort
jirl ra, ra, 0
END (ENTRY_POINT)
--
2.33.0
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