July 2022 - devel - example.com

Odd thing in aarch64 support
by Thomas Petazzoni 11 Aug '22

11 Aug '22

Hello, While looking at some uClibc code, I stumbled across the following snippet in Rules.mak: UCLIBC_LDSO_NAME := ld-uClibc ARCH_NATIVE_BIT := 32 ifneq ($(findstring $(TARGET_ARCH) , hppa64 ia64 powerpc64 s390x sparc64 x86_64 kvx ),) UCLIBC_LDSO_NAME := ld64-uClibc ARCH_NATIVE_BIT := 64 else ifeq ($(CONFIG_MIPS_N64_ABI),y) UCLIBC_LDSO_NAME := ld64-uClibc ARCH_NATIVE_BIT := 64 endif endif I was surprised not to see aarch64 in the list of 64-bit architectures here. Turns out that the situation is not that simple in fact. Indeed, gcc does not expect all 64-bit architecture to have their dynamic loader called ld64-uClibc. For aarch64 specifically, it indeed assumes the dynamic loader is called ld-uClibc, which explains why it is working today. However, it means that ARCH_NATIVE_BIT is defined to 32 on aarch64, which is obviously (?) wrong. But turns out that ARCH_NATIVE_BIT is only used in utils/porting.h to define __WORDSIZE and __WORDSIZE is only used in utils/ldd.c. So to me, it seems like this would gain in being clarified. Something like (completely untested): diff --git a/Rules.mak b/Rules.mak index 3fb64c728..a0b012d7f 100644 --- a/Rules.mak +++ b/Rules.mak @@ -142,17 +142,8 @@ export MAJOR_VERSION MINOR_VERSION SUBLEVEL VERSION ABI_VERSION LC_ALL LIBC := libc SHARED_LIBNAME := $(LIBC).so.$(ABI_VERSION) -UCLIBC_LDSO_NAME := ld-uClibc -ARCH_NATIVE_BIT := 32 -ifneq ($(findstring $(TARGET_ARCH) , hppa64 ia64 powerpc64 s390x sparc64 x86_64 kvx ),) -UCLIBC_LDSO_NAME := ld64-uClibc -ARCH_NATIVE_BIT := 64 -else -ifeq ($(CONFIG_MIPS_N64_ABI),y) -UCLIBC_LDSO_NAME := ld64-uClibc -ARCH_NATIVE_BIT := 64 -endif -endif +UCLIBC_LDSO_NAME := $(call qstrip,$(TARGET_LDSO_NAME)) +ARCH_NATIVE_BIT := $(call qstrip,$(TARGET_ARCH_BITS)) UCLIBC_LDSO := $(UCLIBC_LDSO_NAME).so.$(ABI_VERSION) NONSHARED_LIBNAME := uclibc_nonshared.a diff --git a/extra/Configs/Config.in b/extra/Configs/Config.in index a49278b30..e6369bd82 100644 --- a/extra/Configs/Config.in +++ b/extra/Configs/Config.in @@ -145,6 +145,26 @@ config TARGET_xtensa endchoice +config TARGET_LDSO_NAME + string + default "ld64-uClibc" if TARGET_ia64 + default "ld64-uClibc" if TARGET_powerpc64 + default "ld64-uClibc" if TARGET_sparc64 + default "ld64-uClibc" if TARGET_x86_64 + default "ld64-uClibc" if TARGET_kvx + default "ld64-uClibc" if CONFIG_MIPS_N64_ABI + default "ld-uClibc" + +config TARGET_ARCH_BITS + int + default 64 if TARGET_aarch64 + default 64 if TARGET_ia64 + default 64 if TARGET_powerpc64 + default 64 if TARGET_sparc64 + default 64 if TARGET_x86_64 + default 64 if TARGET_kvx + default 64 if CONFIG_MIPS_N64_ABI + default 32 menu "Target Architecture Features and Options" Best regards, Thomas Petazzoni -- Thomas Petazzoni, co-owner and CEO, Bootlin Embedded Linux and Kernel engineering and training https://bootlin.com

2 1

[PATCH] Added support for creation of Static Position-Independent Executable (PIE) on aarch64
by linted 28 Jul '22

28 Jul '22

Hello, Here is the next installment of static-pie support. This time it is for aarch64 (arm64). It uses the same relocation methods as i386, x86_64, and arm. The only other major difference is the disabling of stack protectors in reloc_static_pie.c since it can lead to access of dynamic memory prior to relocation. --- From b55075957b6a95e120095fb5d5dcc96bd500749e Mon Sep 17 00:00:00 2001 From: linted <linted(a)users.noreply.github.com> Date: Sat, 16 Jul 2022 16:23:45 -0400 Subject: [PATCH] Added support for creation of Static Position-Independent Executables (PIE) on aarch64 Updated config to allow compilation of rcrt1.o for aarch64 and modified it's crt1.S to relocate dynamic section prior to __uClibc_main. Disabled stack protector when compiling reloc_static_pie.c to avoid TLS access prior to it being setup. Signed-off-by: linted <linted(a)users.noreply.github.com> --- extra/Configs/Config.in | 2 +- libc/misc/internals/Makefile.in | 2 +- libc/sysdeps/linux/aarch64/crt1.S | 14 ++++++++++++++ 3 files changed, 16 insertions(+), 2 deletions(-) diff --git a/extra/Configs/Config.in b/extra/Configs/Config.in index a49278b30..7d7d374c3 100644 --- a/extra/Configs/Config.in +++ b/extra/Configs/Config.in @@ -304,7 +304,7 @@ config DOPIC config STATIC_PIE bool "Add support for Static Position Independent Executables (PIE)" default n - depends on DOPIC && !UCLIBC_FORMAT_FDPIC_ELF && (TARGET_arm || TARGET_i386 || TARGET_x86_64) + depends on DOPIC && !UCLIBC_FORMAT_FDPIC_ELF && (TARGET_arm || TARGET_i386 || TARGET_x86_64 || TARGET_aarch64) config ARCH_HAS_NO_SHARED bool diff --git a/libc/misc/internals/Makefile.in b/libc/misc/internals/Makefile.in index 4a6e73d2d..69af8b76e 100644 --- a/libc/misc/internals/Makefile.in +++ b/libc/misc/internals/Makefile.in @@ -17,7 +17,7 @@ MISC_INTERNALS_SRC := $(patsubst %.c,$(MISC_INTERNALS_DIR)/%.c,$(CSRC-y)) MISC_INTERNALS_OBJ := $(patsubst %.c,$(MISC_INTERNALS_OUT)/%.o,$(CSRC-y)) CFLAGS-__uClibc_main.c := $(SSP_DISABLE_FLAGS) - +CFLAGS-reloc_static_pie.c := $(SSP_DISABLE_FLAGS) libc-y += $(MISC_INTERNALS_OBJ) ifneq ($(UCLIBC_FORMAT_SHARED_FLAT),y) diff --git a/libc/sysdeps/linux/aarch64/crt1.S b/libc/sysdeps/linux/aarch64/crt1.S index 09d0327ac..e9f946894 100644 --- a/libc/sysdeps/linux/aarch64/crt1.S +++ b/libc/sysdeps/linux/aarch64/crt1.S @@ -48,6 +48,20 @@ _start: mov x29, #0 mov x30, #0 +#ifdef L_rcrt1 + /* Save off the atexit pointer */ + mov x19, x0 + + /* Calculate load address... idk how this works, but it does */ + adrp x0, _start + + /* Do relocations */ + bl reloc_static_pie + + /* restore atexit pointer */ + mov x0, x19 +#endif + /* Setup _fini in argument register */ mov x5, x0 -- 2.34.1

1 0

[PATCH 1/2] linuxthreads/arm: fix ldrex/strex loop when built with O0
by Vladimir Murzin 26 Jul '22

26 Jul '22

O0 build result in the following codegen 00000000 <ldrex>: 0: b480 push {r7} 2: b085 sub sp, #20 4: af00 add r7, sp, #0 6: 6078 str r0, [r7, #4] 8: 687b ldr r3, [r7, #4] a: e853 3f00 ldrex r3, [r3] e: 60fb str r3, [r7, #12] 10: 68fb ldr r3, [r7, #12] 12: 4618 mov r0, r3 14: 3714 adds r7, #20 16: 46bd mov sp, r7 18: f85d 7b04 ldr.w r7, [sp], #4 1c: 4770 bx lr 0000001e <strex>: 1e: b480 push {r7} 20: b085 sub sp, #20 22: af00 add r7, sp, #0 24: 6078 str r0, [r7, #4] 26: 6039 str r1, [r7, #0] 28: 687b ldr r3, [r7, #4] 2a: 683a ldr r2, [r7, #0] 2c: e842 3300 strex r3, r3, [r2] 30: 60fb str r3, [r7, #12] 32: 68fb ldr r3, [r7, #12] 34: 4618 mov r0, r3 36: 3714 adds r7, #20 38: 46bd mov sp, r7 3a: f85d 7b04 ldr.w r7, [sp], #4 3e: 4770 bx lr 00000040 <testandset>: 40: b590 push {r4, r7, lr} 42: b083 sub sp, #12 44: af00 add r7, sp, #0 46: 6078 str r0, [r7, #4] 48: 6878 ldr r0, [r7, #4] 4a: f7ff fffe bl 0 <ldrex> 4e: 4603 mov r3, r0 50: 461c mov r4, r3 52: 6879 ldr r1, [r7, #4] 54: 2001 movs r0, #1 56: f7ff fffe bl 1e <strex> 5a: 4603 mov r3, r0 5c: 2b00 cmp r3, #0 5e: d1f3 bne.n 48 <testandset+0x8> 60: 4623 mov r3, r4 62: 4618 mov r0, r3 64: 370c adds r7, #12 66: 46bd mov sp, r7 68: bd90 pop {r4, r7, pc} ARM ARM suggests that LoadExcl/StoreExcl loops are guaranteed to make forward progress only if, for any LoadExcl/StoreExcl loop within a single thread of execution, the software meets all of the following conditions: 1 Between the Load-Exclusive and the Store-Exclusive, there are no explicit memory accesses, preloads, direct or indirect System register writes, address translation instructions, cache or TLB maintenance instructions, exception generating instructions, exception returns, or indirect branches. ... Obviously condition is not met for O0 builds. O2 build (which is highly likely the most common setting) able to do the right thing resulting in 00000000 <ldrex>: 0: e850 0f00 ldrex r0, [r0] 4: 4770 bx lr 6: bf00 nop 00000008 <strex>: 8: e841 0000 strex r0, r0, [r1] c: 4770 bx lr e: bf00 nop 00000010 <testandset>: 10: 2101 movs r1, #1 12: 4603 mov r3, r0 14: e853 0f00 ldrex r0, [r3] 18: e843 1200 strex r2, r1, [r3] 1c: 2a00 cmp r2, #0 1e: d1f9 bne.n 14 <testandset+0x4> 20: 4770 bx lr 22: bf00 nop Rather than depending on level of optimisation implement whole ldrex/strex loop in inline assembly. Signed-off-by: Vladimir Murzin <vladimir.murzin(a)arm.com> --- .../linuxthreads/sysdeps/arm/pt-machine.h | 34 +++++-------------- 1 file changed, 9 insertions(+), 25 deletions(-) diff --git a/libpthread/linuxthreads/sysdeps/arm/pt-machine.h b/libpthread/linuxthreads/sysdeps/arm/pt-machine.h index fc17e9bc7..b00b10495 100644 --- a/libpthread/linuxthreads/sysdeps/arm/pt-machine.h +++ b/libpthread/linuxthreads/sysdeps/arm/pt-machine.h @@ -29,35 +29,19 @@ #endif #if defined(__thumb2__) -PT_EI long int ldrex(int *spinlock) -{ - long int ret; - __asm__ __volatile__( - "ldrex %0, [%1]\n" - : "=r"(ret) - : "r"(spinlock) : "memory"); - return ret; -} - -PT_EI long int strex(int val, int *spinlock) -{ - long int ret; - __asm__ __volatile__( - "strex %0, %1, [%2]\n" - : "=r"(ret) - : "r" (val), "r"(spinlock) : "memory"); - return ret; -} - /* Spinlock implementation; required. */ PT_EI long int testandset (int *spinlock) { - register unsigned int ret; - - do { - ret = ldrex(spinlock); - } while (strex(1, spinlock)); + unsigned int ret, tmp, val = 1; + + __asm__ __volatile__ ( +"0: ldrex %0, [%2] \n" +" strex %1, %3, [%2] \n" +" cmp %1, #0 \n" +" bne 0b" + : "=&r" (ret), "=&r" (tmp) + : "r" (spinlock), "r" (val) : "memory", "cc"); return ret; } -- 2.25.1

2 2

[Patch v4] Static PIE support for i386, x86_64, and arm
by linted 26 Jul '22

26 Jul '22

Hello, I first want to apologize for so many patch versions. This version of the patch correctly adjusts the offset of the TLS initimage used by __libc_setup_tls when copying. I would love feedback on my modifications to libc-tls.c as I had to use a new global variable defined in reloc_static_pie.c containing the load address. Originally I attempted to copy how glibc pulls the load address from a memory map when initializing the TLS, however I could not find a similar structure available in __libc_setup_tls. I would love to know if there is a better method which I overlooked. From 30b435a0b7a7f2d4323eafea2bcebb087cc62462 Mon Sep 17 00:00:00 2001 From: linted <linted(a)users.noreply.github.com> Date: Sat, 23 Jul 2022 16:25:41 -0400 Subject: [PATCH] Added support for creation of Static Position-Independent Executables (PIE) on i386, x86_64, and arm. This patch adds the generation of rcrt1.o which is used by gcc when compiling with the --static-pie flag. rcrt1.o differs from crt1.o and Scrt1.o in that it the executable has a dynamic section but no relocations have been performed prior to _start being called. crt1.o assumes there to be no dynamic relocations, and Scrt1.o has all relocations performed prior to execution by lsdo. The new reloc_static_pie function handles parsing the dynamic section, and performing the relocations in a architecture agnostic method. It also sets _dl_load_base which is used when initalizing TLS to ensure loading from the proper location. This allows for easier porting of static-pie support to additional architectures as only modifications to crt1.S to find the load address are required. Signed-off-by: linted <linted(a)users.noreply.github.com> --- Makerules | 5 +++ extra/Configs/Config.in | 5 +++ libc/misc/internals/Makefile.in | 1 + libc/misc/internals/reloc_static_pie.c | 47 +++++++++++++++++++++ libc/sysdeps/linux/arm/crt1.S | 19 +++++++++ libc/sysdeps/linux/i386/crt1.S | 20 +++++++++ libc/sysdeps/linux/x86_64/crt1.S | 16 ++++++- libpthread/nptl/sysdeps/generic/Makefile.in | 4 ++ libpthread/nptl/sysdeps/generic/libc-tls.c | 4 ++ 9 files changed, 120 insertions(+), 1 deletion(-) create mode 100644 libc/misc/internals/reloc_static_pie.c diff --git a/Makerules b/Makerules index fd40e6c7b..845d81897 100644 --- a/Makerules +++ b/Makerules @@ -405,8 +405,13 @@ else CRTS=$(top_builddir)lib/$(CRT).o endif +ifeq ($(STATIC_PIE),y) +CRTS+=$(top_builddir)lib/r$(CRT).o +endif + ASFLAGS-$(CRT).o := -DL_$(CRT) ASFLAGS-S$(CRT).o := $(PIEFLAG) -DL_S$(CRT) +ASFLAGS-r$(CRT).o := $(PIEFLAG) -DL_r$(CRT) $(CRTS): $(top_srcdir)libc/sysdeps/linux/$(TARGET_ARCH)/$(CRT).S $(compile.S) $(Q)$(STRIPTOOL) -x -R .note -R .comment $@ diff --git a/extra/Configs/Config.in b/extra/Configs/Config.in index a58ceb265..a49278b30 100644 --- a/extra/Configs/Config.in +++ b/extra/Configs/Config.in @@ -301,6 +301,11 @@ config DOPIC If you wish to build all of uClibc as PIC objects, then answer Y here. If you are unsure, then you should answer N. +config STATIC_PIE + bool "Add support for Static Position Independent Executables (PIE)" + default n + depends on DOPIC && !UCLIBC_FORMAT_FDPIC_ELF && (TARGET_arm || TARGET_i386 || TARGET_x86_64) + config ARCH_HAS_NO_SHARED bool diff --git a/libc/misc/internals/Makefile.in b/libc/misc/internals/Makefile.in index a8e4e36f9..4a6e73d2d 100644 --- a/libc/misc/internals/Makefile.in +++ b/libc/misc/internals/Makefile.in @@ -34,6 +34,7 @@ libc-static-$(UCLIBC_FORMAT_FLAT_SEP_DATA) += \ libc-static-$(UCLIBC_FORMAT_SHARED_FLAT) += \ $(MISC_INTERNALS_OUT)/shared_flat_initfini.o \ $(MISC_INTERNALS_OUT)/shared_flat_add_library.o +libc-static-$(STATIC_PIE) += $(MISC_INTERNALS_OUT)/reloc_static_pie.o libc-shared-$(UCLIBC_FORMAT_SHARED_FLAT) += \ $(MISC_INTERNALS_OUT)/shared_flat_initfini.os \ $(MISC_INTERNALS_OUT)/shared_flat_add_library.os diff --git a/libc/misc/internals/reloc_static_pie.c b/libc/misc/internals/reloc_static_pie.c new file mode 100644 index 000000000..578202d23 --- /dev/null +++ b/libc/misc/internals/reloc_static_pie.c @@ -0,0 +1,47 @@ +/* Support for relocating static PIE. + Copyright (C) 2017-2022 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +#include <link.h> +#include <elf.h> +#include <dl-elf.h> + +ElfW(Addr) _dl_load_base = NULL; + +void +reloc_static_pie (ElfW(Addr) load_addr); + +void +reloc_static_pie (ElfW(Addr) load_addr) +{ + ElfW(Word) relative_count = 0; + ElfW(Addr) rel_addr = 0; + ElfW(Dyn) * dyn_addr = NULL; + unsigned long dynamic_info[DYNAMIC_SIZE] = {0}; + + /* Read our own dynamic section and fill in the info array. */ + dyn_addr = ((void *) load_addr + elf_machine_dynamic ()); + + /* Use the underlying function to avoid TLS access before initialization */ + __dl_parse_dynamic_info(dyn_addr, dynamic_info, NULL, load_addr); + + /* Perform relocations */ + relative_count = dynamic_info[DT_RELCONT_IDX]; + rel_addr = dynamic_info[DT_RELOC_TABLE_ADDR]; + elf_machine_relative(load_addr, rel_addr, relative_count); + _dl_load_base = load_addr; +} diff --git a/libc/sysdeps/linux/arm/crt1.S b/libc/sysdeps/linux/arm/crt1.S index a1d7f0f23..fade1d25c 100644 --- a/libc/sysdeps/linux/arm/crt1.S +++ b/libc/sysdeps/linux/arm/crt1.S @@ -246,6 +246,22 @@ _start: mov lr, #0 #ifdef __ARCH_USE_MMU__ +#ifdef L_rcrt1 + /* We don't need to save a1 since no dynamic linker should have run */ + ldr a1, .L_GOT /* Get value at .L_GOT + 0 (offset to GOT)*/ + adr a2, .L_GOT /* Get address of .L_GOT */ + ldr a3, .L_GOT+16 /* Get value of _start(GOT) stored in .L_GOT */ + adr a4, _start /* Get address of _start after relocation (changes to pc - ~30 or so) */ + add a1, a1, a2 /* Calculate where the GOT is */ + ldr a2, [a1, a3] /* GOT + _start(GOT) = offset of _start from begin of file */ + sub a1, a4, a2 /* Current addr of _start - offset from beginning of file = load addr */ + bl reloc_static_pie + mov a1, #0 /* Clean up a1 so that a random address won't get called at the end of program */ + + /* Clear the frame pointer and link register again since it might be modified by previous call */ + mov fp, #0 + mov lr, #0 +#endif /* Pop argc off the stack and save a pointer to argv */ ldr a2, [sp], #4 mov a3, sp @@ -309,6 +325,9 @@ _start: .word _fini(GOT) .word _init(GOT) .word main(GOT) +#ifdef L_rcrt1 + .word _start(GOT) +#endif #endif #endif diff --git a/libc/sysdeps/linux/i386/crt1.S b/libc/sysdeps/linux/i386/crt1.S index 35a6552e8..decc68967 100644 --- a/libc/sysdeps/linux/i386/crt1.S +++ b/libc/sysdeps/linux/i386/crt1.S @@ -67,6 +67,9 @@ #endif .type main,%function .type __uClibc_main,%function +#ifdef L_rcrt1 +.type reloc_static_pie,%function +#endif _start: /* Clear the frame pointer. The ABI suggests this be done, to mark the outermost frame obviously. */ @@ -100,6 +103,23 @@ _start: pop %ebx addl $_GLOBAL_OFFSET_TABLE_+[.-.L0],%ebx +#ifdef L_rcrt1 + /* We cannot rely on _DYNAMIC being usable here due to RELRO. + Instead we calculate the load address based off a symbol + that we know will exist, _start. */ + pushl %ecx /* Save ecx so it won't get clobbered */ + pushl %ebx /* Save ebx so it won't get clobbered */ + xorl %ecx, %ecx /* Clear ecx */ + addl _start@GOT(%ebx), %ecx /* Get the offset of _start */ + movl _start@GOT(%ebx), %eax /* Get the run time address of _start */ + subl %ecx, %eax /* Subtract to find the load address */ + pushl %eax /* Pass the load address */ + call reloc_static_pie@PLT + popl %eax /* Clean up from function call */ + popl %ebx /* Restore the GOT address */ + popl %ecx /* restore ecx */ +#endif + /* Push address of our own entry points to .fini and .init. */ pushl _fini@GOT(%ebx) pushl _init@GOT(%ebx) diff --git a/libc/sysdeps/linux/x86_64/crt1.S b/libc/sysdeps/linux/x86_64/crt1.S index 87777dd5d..701cbf2f6 100644 --- a/libc/sysdeps/linux/x86_64/crt1.S +++ b/libc/sysdeps/linux/x86_64/crt1.S @@ -80,6 +80,20 @@ _start: the outermost frame obviously. */ xorl %ebp, %ebp +#ifdef L_rcrt1 + pushq %rdi /* save rdi (but should be 0...) */ + pushq %rdx /* store rdx (rtld_fini) */ + xorq %rcx, %rcx /* ensure rcx is 0 */ + addq _start@GOTPCREL(%rip), %rcx /* get offset of _start from beginning of file */ + movq _start@GOTPCREL(%rip), %rax /* get run time address of _start */ + subq %rcx, %rax /* calculate run time load offset */ + movq %rax, %rdi /* load offset -> param 1 */ + call reloc_static_pie /* relocate dynamic addrs */ + xorq %rax, %rax /* cleanup */ + popq %rdx + popq %rdi +#endif + /* Extract the arguments as encoded on the stack and set up the arguments for __libc_start_main (int (*main) (int, char **, char **), int argc, char *argv, @@ -107,7 +121,7 @@ _start: which grow downwards). */ pushq %rsp -#if defined(L_Scrt1) +#if defined(L_Scrt1) || defined(L_rcrt1) /* Give address for main() */ movq main@GOTPCREL(%rip), %rdi diff --git a/libpthread/nptl/sysdeps/generic/Makefile.in b/libpthread/nptl/sysdeps/generic/Makefile.in index eb656ee17..a5ba9bbe8 100644 --- a/libpthread/nptl/sysdeps/generic/Makefile.in +++ b/libpthread/nptl/sysdeps/generic/Makefile.in @@ -13,6 +13,10 @@ subdirs += libpthread/nptl/sysdeps/generic libpthread_generic_DIR := $(top_srcdir)libpthread/nptl/sysdeps/generic libpthread_generic_OUT := $(top_builddir)libpthread/nptl/sysdeps/generic +ifeq ($(STATIC_PIE),y) +CFLAGS-libc-tls.c := -DSTATIC_PIE +endif + libpthread_generic_libc_a_CSRC = libc-tls.c libpthread_generic_libc_a_COBJ = $(patsubst %.c,$(libpthread_generic_OUT)/%.o,$(libpthread_generic_libc_a_CSRC)) libpthread_generic_libc_a_OBJS = $(libpthread_generic_libc_a_COBJ) diff --git a/libpthread/nptl/sysdeps/generic/libc-tls.c b/libpthread/nptl/sysdeps/generic/libc-tls.c index d746c9a38..0c8c558d0 100644 --- a/libpthread/nptl/sysdeps/generic/libc-tls.c +++ b/libpthread/nptl/sysdeps/generic/libc-tls.c @@ -142,6 +142,10 @@ __libc_setup_tls (size_t tcbsize, size_t tcbalign) initimage = (void *) &__tdata_start; #else initimage = (void *) phdr->p_vaddr; +#if !defined(SHARED) && defined(STATIC_PIE) + extern ElfW(Addr) _dl_load_base; + initimage += _dl_load_base; +#endif #endif align = phdr->p_align; if (phdr->p_align > max_align) -- 2.34.1

3 2

[Patch v3] Static PIE support for i386, x86_64, and arm
by linted 22 Jul '22

22 Jul '22

Hello, This is an updated patch for static pie support. I have corrected formatting and code standard issues which appeared in my previous patches. I also updated the commit message to be clearer on what is occurring and why. -linted From 92056b7db87be00e6daea59a4f82d022bfc7f223 Mon Sep 17 00:00:00 2001 From: linted <linted(a)users.noreply.github.com> Date: Sun, 17 Jul 2022 13:38:49 -0400 Subject: [PATCH] Added support for creation of Static Position-Independent Executables (PIE) on i386, x86_64, and arm. This patch adds the generation of rcrt1.o which is used by gcc when compiling with the --static-pie flag. rcrt1.o differs from crt1.o and Scrt1.o in that it the executable has a dynamic section but no relocations have been performed prior to _start being called. crt1.o assumes there to be no dynamic relocations, and Scrt1.o has all relocations performed prior to execution by lsdo. The new reloc_static_pie function handles parsing the elf headers, locating the dynamic section, and performing the relocations in a architecture agnostic method. This allows for easier porting of static-pie support to additional architectures. Signed-off-by: linted <linted(a)users.noreply.github.com> --- Makerules | 5 ++++ extra/Configs/Config.in | 5 ++++ libc/misc/internals/Makefile.in | 1 + libc/misc/internals/reloc_static_pie.c | 41 ++++++++++++++++++++++++++ libc/sysdeps/linux/arm/crt1.S | 15 ++++++++++ libc/sysdeps/linux/i386/crt1.S | 20 +++++++++++++ libc/sysdeps/linux/x86_64/crt1.S | 16 +++++++++- 7 files changed, 102 insertions(+), 1 deletion(-) create mode 100644 libc/misc/internals/reloc_static_pie.c diff --git a/Makerules b/Makerules index fd40e6c7b..845d81897 100644 --- a/Makerules +++ b/Makerules @@ -405,8 +405,13 @@ else CRTS=$(top_builddir)lib/$(CRT).o endif +ifeq ($(STATIC_PIE),y) +CRTS+=$(top_builddir)lib/r$(CRT).o +endif + ASFLAGS-$(CRT).o := -DL_$(CRT) ASFLAGS-S$(CRT).o := $(PIEFLAG) -DL_S$(CRT) +ASFLAGS-r$(CRT).o := $(PIEFLAG) -DL_r$(CRT) $(CRTS): $(top_srcdir)libc/sysdeps/linux/$(TARGET_ARCH)/$(CRT).S $(compile.S) $(Q)$(STRIPTOOL) -x -R .note -R .comment $@ diff --git a/extra/Configs/Config.in b/extra/Configs/Config.in index a58ceb265..a49278b30 100644 --- a/extra/Configs/Config.in +++ b/extra/Configs/Config.in @@ -301,6 +301,11 @@ config DOPIC If you wish to build all of uClibc as PIC objects, then answer Y here. If you are unsure, then you should answer N. +config STATIC_PIE + bool "Add support for Static Position Independent Executables (PIE)" + default n + depends on DOPIC && !UCLIBC_FORMAT_FDPIC_ELF && (TARGET_arm || TARGET_i386 || TARGET_x86_64) + config ARCH_HAS_NO_SHARED bool diff --git a/libc/misc/internals/Makefile.in b/libc/misc/internals/Makefile.in index a8e4e36f9..4a6e73d2d 100644 --- a/libc/misc/internals/Makefile.in +++ b/libc/misc/internals/Makefile.in @@ -34,6 +34,7 @@ libc-static-$(UCLIBC_FORMAT_FLAT_SEP_DATA) += \ libc-static-$(UCLIBC_FORMAT_SHARED_FLAT) += \ $(MISC_INTERNALS_OUT)/shared_flat_initfini.o \ $(MISC_INTERNALS_OUT)/shared_flat_add_library.o +libc-static-$(STATIC_PIE) += $(MISC_INTERNALS_OUT)/reloc_static_pie.o libc-shared-$(UCLIBC_FORMAT_SHARED_FLAT) += \ $(MISC_INTERNALS_OUT)/shared_flat_initfini.os \ $(MISC_INTERNALS_OUT)/shared_flat_add_library.os diff --git a/libc/misc/internals/reloc_static_pie.c b/libc/misc/internals/reloc_static_pie.c new file mode 100644 index 000000000..9a8066b84 --- /dev/null +++ b/libc/misc/internals/reloc_static_pie.c @@ -0,0 +1,41 @@ +/* Support for relocating static PIE. + Copyright (C) 2017-2022 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +#include <link.h> +#include <elf.h> +#include <dl-elf.h> + +void +reloc_static_pie (ElfW(Addr) load_addr) +{ + ElfW(Word) relative_count = 0; + ElfW(Addr) rel_addr = NULL; + ElfW(Dyn) * dyn_addr = NULL; + unsigned long dynamic_info[DYNAMIC_SIZE] = {0}; + + /* Read our own dynamic section and fill in the info array. */ + dyn_addr = ((void *) load_addr + elf_machine_dynamic ()); + + /* Use the underlying function to avoid TLS access before initialization */ + __dl_parse_dynamic_info(dyn_addr, dynamic_info, NULL, load_addr); + + /* Perform relocations */ + relative_count = dynamic_info[DT_RELCONT_IDX]; + rel_addr = dynamic_info[DT_RELOC_TABLE_ADDR]; + elf_machine_relative(load_addr, rel_addr, relative_count); +} diff --git a/libc/sysdeps/linux/arm/crt1.S b/libc/sysdeps/linux/arm/crt1.S index a1d7f0f23..2aa2a5234 100644 --- a/libc/sysdeps/linux/arm/crt1.S +++ b/libc/sysdeps/linux/arm/crt1.S @@ -246,6 +246,18 @@ _start: mov lr, #0 #ifdef __ARCH_USE_MMU__ +#ifdef L_rcrt1 + /* We don't need to save a1 since no dynamic linker should have run */ + ldr a1, .L_GOT /* Get value at .L_GOT + 0 (offset to GOT)*/ + adr a2, .L_GOT /* Get address of .L_GOT */ + ldr a3, .L_GOT+16 /* get value of _start(GOT) stored in .L_GOT */ + adr a4, _start /* get address of _start after relocation (changes to pc - ~30 or so) */ + add a1, a1, a2 /* calculate where the GOT is */ + ldr a2, [a1, a3] /* GOT + _start(GOT) = offset of _start from begin of file */ + sub a1, a4, a2 /* current addr of _start - offset from beginning of file = load addr */ + bl reloc_static_pie + mov a1, #0 /* Clean up a1 so that a random address won't get called at the end of program */ +#endif /* Pop argc off the stack and save a pointer to argv */ ldr a2, [sp], #4 mov a3, sp @@ -309,6 +321,9 @@ _start: .word _fini(GOT) .word _init(GOT) .word main(GOT) +#ifdef L_rcrt1 + .word _start(GOT) +#endif #endif #endif diff --git a/libc/sysdeps/linux/i386/crt1.S b/libc/sysdeps/linux/i386/crt1.S index 35a6552e8..decc68967 100644 --- a/libc/sysdeps/linux/i386/crt1.S +++ b/libc/sysdeps/linux/i386/crt1.S @@ -67,6 +67,9 @@ #endif .type main,%function .type __uClibc_main,%function +#ifdef L_rcrt1 +.type reloc_static_pie,%function +#endif _start: /* Clear the frame pointer. The ABI suggests this be done, to mark the outermost frame obviously. */ @@ -100,6 +103,23 @@ _start: pop %ebx addl $_GLOBAL_OFFSET_TABLE_+[.-.L0],%ebx +#ifdef L_rcrt1 + /* We cannot rely on _DYNAMIC being usable here due to RELRO. + Instead we calculate the load address based off a symbol + that we know will exist, _start. */ + pushl %ecx /* Save ecx so it won't get clobbered */ + pushl %ebx /* Save ebx so it won't get clobbered */ + xorl %ecx, %ecx /* Clear ecx */ + addl _start@GOT(%ebx), %ecx /* Get the offset of _start */ + movl _start@GOT(%ebx), %eax /* Get the run time address of _start */ + subl %ecx, %eax /* Subtract to find the load address */ + pushl %eax /* Pass the load address */ + call reloc_static_pie@PLT + popl %eax /* Clean up from function call */ + popl %ebx /* Restore the GOT address */ + popl %ecx /* restore ecx */ +#endif + /* Push address of our own entry points to .fini and .init. */ pushl _fini@GOT(%ebx) pushl _init@GOT(%ebx) diff --git a/libc/sysdeps/linux/x86_64/crt1.S b/libc/sysdeps/linux/x86_64/crt1.S index 87777dd5d..701cbf2f6 100644 --- a/libc/sysdeps/linux/x86_64/crt1.S +++ b/libc/sysdeps/linux/x86_64/crt1.S @@ -80,6 +80,20 @@ _start: the outermost frame obviously. */ xorl %ebp, %ebp +#ifdef L_rcrt1 + pushq %rdi /* save rdi (but should be 0...) */ + pushq %rdx /* store rdx (rtld_fini) */ + xorq %rcx, %rcx /* ensure rcx is 0 */ + addq _start@GOTPCREL(%rip), %rcx /* get offset of _start from beginning of file */ + movq _start@GOTPCREL(%rip), %rax /* get run time address of _start */ + subq %rcx, %rax /* calculate run time load offset */ + movq %rax, %rdi /* load offset -> param 1 */ + call reloc_static_pie /* relocate dynamic addrs */ + xorq %rax, %rax /* cleanup */ + popq %rdx + popq %rdi +#endif + /* Extract the arguments as encoded on the stack and set up the arguments for __libc_start_main (int (*main) (int, char **, char **), int argc, char *argv, @@ -107,7 +121,7 @@ _start: which grow downwards). */ pushq %rsp -#if defined(L_Scrt1) +#if defined(L_Scrt1) || defined(L_rcrt1) /* Give address for main() */ movq main@GOTPCREL(%rip), %rdi -- 2.34.1

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Building uClibc-ng for ARM32 targetting an ARMv8 core fails
by Thomas Petazzoni 18 Jul '22

18 Jul '22

Hello, Buildroot supports building ARM 32-bit systems for ARMv8 cores (even though those would more classically run an AArch64 system). Unfortunately, it seems like uClibc-ng doesn't support this situation, as it exhibits the following build failure: CC libpthread/linuxthreads/mutex.os /tmp/ccn8SFKU.s: Assembler messages: /tmp/ccn8SFKU.s:162: Error: swp{b} use is obsoleted for ARMv8 and later /tmp/ccn8SFKU.s:186: Error: swp{b} use is obsoleted for ARMv8 and later /tmp/ccn8SFKU.s:203: Error: swp{b} use is obsoleted for ARMv8 and later /tmp/ccn8SFKU.s:224: Error: swp{b} use is obsoleted for ARMv8 and later make[1]: *** [Makerules:369: libpthread/linuxthreads/mutex.os] Error 1 See http://autobuild.buildroot.net/results/1e2e5e6c752901a818630d0c0816f43874bf… for a more detailed log. This is due to libpthread/linuxthreads/sysdeps/arm/pt-machine.h which uses the swp instruction that is not allowed on ARMv8. Best regards, Thomas -- Thomas Petazzoni, co-owner and CEO, Bootlin Embedded Linux and Kernel engineering and training https://bootlin.com

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[Patch v2] Static PIE support for i386, x86_64, and arm
by linted 16 Jul '22

16 Jul '22

Hello, This is an updated patch for static pie support on i386, x86_64, and arm. I added dependency checks to ensure it only affects supported architectures. I also added a check to ensure an MMU is present on arm since there is no support for FDPIC yet.

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Static PIE support for i386, x86_64, and arm
by linted 15 Jul '22

15 Jul '22

Hello, I implemented support for static pie generation on i386, x86_64, and arm. This patch adds the generation of rcrt1.o which is used by gcc when compiling with the --static-pie flag. The main difference in rcrt1.o is that it is required to perform dynamic relocations which would normally occur in ldso. The new reloc_static_pie function handles parsing the elf headers, locating the dynamic section, and performing the relocations.

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