From d12d80cdcafd2f84321d311d6ce3e291f0e7b9a9 Mon Sep 17 00:00:00 2001 From: XingLi 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 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