[uclibc-ng-devel] Re: [PATCH v3] Static PIE support for mips

Hello, This is a slight update to the v2 patch. I realized that I left some extraneous comments in crt1.S. This patch removes those comments. -------- From f5a4f77a396631bfceea2967b6a9100b09802f6c Mon Sep 17 00:00:00 2001 From: linted &lt;linted(a)users.noreply.github.com&gt; Date: Sat, 20 Aug 2022 16:41:38 -0400 Subject: [PATCH] Added support for creation of Static Position-Independent  Executables (PIE) on mips Updated config to allow compilation of rcrt1.o for mips and modified it's crt1.S to perform relocates in __start. The mips architecture performs relocations differently then most other architectures. reloc_static_pie was rewritten, taking code from dl-startup.c, in order to perfrom the additional relocations. Modifications were made to mips' dl-startup.h to allow for the use of contained macros without including _start definition. Signed-off-by: linted &lt;linted(a)users.noreply.github.com&gt; ---  extra/Configs/Config.in                |  2 +-  ldso/ldso/mips/dl-startup.h            |  3 +-  libc/misc/internals/Makefile.in        |  2 +-  libc/misc/internals/reloc_static_pie.c | 93 +++++++++++++++++++++-----  libc/sysdeps/linux/mips/crt1.S         | 23 +++++++  5 files changed, 105 insertions(+), 18 deletions(-) diff --git a/extra/Configs/Config.in b/extra/Configs/Config.in index e0905e956..43c04fd0a 100644 --- a/extra/Configs/Config.in +++ b/extra/Configs/Config.in @@ -324,7 +324,7 @@ 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 || TARGET_aarch64) + depends on DOPIC && !UCLIBC_FORMAT_FDPIC_ELF && (TARGET_arm || TARGET_i386 || TARGET_x86_64 || TARGET_aarch64 || TARGET_mips)    config ARCH_HAS_NO_SHARED   bool diff --git a/ldso/ldso/mips/dl-startup.h b/ldso/ldso/mips/dl-startup.h index 8026f1702..c2168d774 100644 --- a/ldso/ldso/mips/dl-startup.h +++ b/ldso/ldso/mips/dl-startup.h @@ -7,6 +7,7 @@      #include <sgidefs.h> +#ifndef L_rcrt1  __asm__(""      " .text\n"      " .globl _start\n" @@ -114,6 +115,7 @@ __asm__(""      "\n\n"      ".previous\n"  ); +#endif    /*   * Get a pointer to the argv array.  On many platforms this can be just @@ -191,6 +193,5 @@ do { \   case R_MIPS_NONE: \   break; \   default: \ - SEND_STDERR("Aiieeee!"); \   _dl_exit(1); \   } diff --git a/libc/misc/internals/Makefile.in b/libc/misc/internals/Makefile.in index 69af8b76e..908b18321 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) +CFLAGS-reloc_static_pie.c := $(SSP_DISABLE_FLAGS) -DL_rcrt1    libc-y += $(MISC_INTERNALS_OBJ)  ifneq ($(UCLIBC_FORMAT_SHARED_FLAT),y) diff --git a/libc/misc/internals/reloc_static_pie.c b/libc/misc/internals/ reloc_static_pie.c index 578202d23..c0027de6f 100644 --- a/libc/misc/internals/reloc_static_pie.c +++ b/libc/misc/internals/reloc_static_pie.c @@ -15,33 +15,96 @@     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/>.  */ - +#define IS_IN_rtld      // force inline function calls  #include <link.h>  #include <elf.h>  #include <dl-elf.h>   +#include <ldso.h> +#ifdef __mips__ +#include <dl-startup.h> +#endif +  ElfW(Addr) _dl_load_base = NULL;    void  reloc_static_pie (ElfW(Addr) load_addr);    void -reloc_static_pie (ElfW(Addr) load_addr) +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}; +    int indx; +    ElfW(Addr) got; +    ElfW(Dyn) *dpnt; +    struct elf_resolve tpnt_tmp; + struct elf_resolve *tpnt = &tpnt_tmp; + +    DL_BOOT_COMPUTE_GOT(got); +    DL_BOOT_COMPUTE_DYN(dpnt, got, (DL_LOADADDR_TYPE)load_addr); + +    _dl_memset(tpnt, 0, sizeof(struct elf_resolve)); +    tpnt->loadaddr = load_addr; +    tpnt->dynamic_addr = dpnt; + +    __dl_parse_dynamic_info(dpnt, tpnt->dynamic_info, NULL, load_addr); + +#if defined(PERFORM_BOOTSTRAP_GOT) + /* some arches (like MIPS) we have to tweak the GOT before relocations */ + PERFORM_BOOTSTRAP_GOT(tpnt); +#endif + + +#if defined(ELF_MACHINE_PLTREL_OVERLAP) +# define INDX_MAX 1 +#else +# define INDX_MAX 2 +#endif + +    for (indx = 0; indx < INDX_MAX; indx++) { +        unsigned long rel_addr, rel_size; +        ElfW(Word) relative_count = tpnt->dynamic_info[DT_RELCONT_IDX]; + +        rel_addr = (indx ? tpnt->dynamic_info[DT_JMPREL] : +                           tpnt->dynamic_info[DT_RELOC_TABLE_ADDR]); +        rel_size = (indx ? tpnt->dynamic_info[DT_PLTRELSZ] : +               tpnt->dynamic_info[DT_RELOC_TABLE_SIZE]); + +        if (!rel_addr) +            continue;   -    /* Read our own dynamic section and fill in the info array.  */ -    dyn_addr = ((void *) load_addr + elf_machine_dynamic ()); +        if((0 == indx) && relative_count) { + rel_size -= relative_count * sizeof(ELF_RELOC); +            elf_machine_relative(load_addr, rel_addr, relative_count); + rel_addr += relative_count * sizeof(ELF_RELOC); +        }   -    /* Use the underlying function to avoid TLS access before initialization * / -    __dl_parse_dynamic_info(dyn_addr, dynamic_info, NULL, load_addr); +#ifdef ARCH_NEEDS_BOOTSTRAP_RELOCS + { + ELF_RELOC *rpnt; + unsigned int i; + ElfW(Sym) *sym; + unsigned long symbol_addr; + int symtab_index; + unsigned long *reloc_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); + /* Now parse the relocation information */ + rpnt = (ELF_RELOC *) rel_addr; + for (i = 0; i < rel_size; i += sizeof(ELF_RELOC), rpnt++) { + reloc_addr = (unsigned long *) DL_RELOC_ADDR(load_addr, (unsigned long)rpnt-> r_offset); + symtab_index = ELF_R_SYM(rpnt->r_info); + symbol_addr = 0; + sym = NULL; + if (symtab_index) { + ElfW(Sym) *symtab; + symtab = (ElfW(Sym) *) tpnt->dynamic_info[DT_SYMTAB]; + sym = &symtab[symtab_index]; + symbol_addr = (unsigned long) DL_RELOC_ADDR(load_addr, sym->st_value); + } + /* Use this machine-specific macro to perform the actual relocation.  */ + PERFORM_BOOTSTRAP_RELOC(rpnt, reloc_addr, symbol_addr, load_addr, sym); + } + } +#endif +    }      _dl_load_base = load_addr; -} +} \ No newline at end of file diff --git a/libc/sysdeps/linux/mips/crt1.S b/libc/sysdeps/linux/mips/crt1.S index 083615515..7c4db447c 100644 --- a/libc/sysdeps/linux/mips/crt1.S +++ b/libc/sysdeps/linux/mips/crt1.S @@ -77,6 +77,10 @@  #ifndef __UCLIBC_CTOR_DTOR__   .weak _init   .weak _fini +#endif +#ifdef L_rcrt1 + .type reloc_static_pie,@function + .hidden .L0  #endif   .type    main,@function   .type    __uClibc_main,@function @@ -89,6 +93,25 @@ __start:  #else   PTR_LA $28, _gp             /* Setup GP correctly if we're non-PIC.  */   move $31, $0 +#endif +#ifdef L_rcrt1 + PTR_LA $4, _DYNAMIC           /* Place _DYNAMIC into the GOT */ + REG_S $4, -0x7ff0($28)        /* offset to GOT stolen from dl-startup */ + jal .L0                       /* Get the current $pc address */ +.L0: + PTR_SUBU $4, $31, $25         /* Calculate load addr */ + move $31, $0                  /* Clear ra */ + and $29, -2 * SZREG           /* Ensure stack is aligned */ + PTR_ADDIU $29, (-2 * SZREG)   /* Allocate 2 register spaces on stack */ + REG_S $2, SZREG($29)          /* Store atexit in case it exists */ + PTR_LA $5, reloc_static_pie   /* function calls before relocation +                                 don't work unless we set $t9 manually */ + PTR_ADDU $25, $4, $5          /* store reloc_static_pie in $t9 */ + jalr $25                      /* call reloc_static_pie */ + nop  /* delay slot, just in case */ + REG_L $2, SZREG($29)          /* cleanup stack */ + PTR_ADDIU $29, $29, (2 * SZREG) +  #endif     PTR_LA $4, main /* main */ -- 2.34.1

From f5a4f77a396631bfceea2967b6a9100b09802f6c Mon Sep 17 00:00:00 2001 From: linted &lt;linted(a)users.noreply.github.com&gt; Date: Sat, 20 Aug 2022 16:41:38 -0400 Subject: [PATCH] Added support for creation of Static Position-Independent Executables (PIE) on mips Updated config to allow compilation of rcrt1.o for mips and modified it's crt1.S to perform relocates in __start. The mips architecture performs relocations differently then most other architectures. reloc_static_pie was rewritten, taking code from dl-startup.c, in order to perfrom the additional relocations. Modifications were made to mips' dl-startup.h to allow for the use of contained macros without including _start definition. Signed-off-by: linted &lt;linted(a)users.noreply.github.com&gt; --- extra/Configs/Config.in | 2 +- ldso/ldso/mips/dl-startup.h | 3 +- libc/misc/internals/Makefile.in | 2 +- libc/misc/internals/reloc_static_pie.c | 93 +++++++++++++++++++++----- libc/sysdeps/linux/mips/crt1.S | 23 +++++++ 5 files changed, 105 insertions(+), 18 deletions(-) diff --git a/extra/Configs/Config.in b/extra/Configs/Config.in index e0905e956..43c04fd0a 100644 --- a/extra/Configs/Config.in +++ b/extra/Configs/Config.in @@ -324,7 +324,7 @@ 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 || TARGET_aarch64) + depends on DOPIC && !UCLIBC_FORMAT_FDPIC_ELF && (TARGET_arm || TARGET_i386 || TARGET_x86_64 || TARGET_aarch64 || TARGET_mips) config ARCH_HAS_NO_SHARED bool diff --git a/ldso/ldso/mips/dl-startup.h b/ldso/ldso/mips/dl-startup.h index 8026f1702..c2168d774 100644 --- a/ldso/ldso/mips/dl-startup.h +++ b/ldso/ldso/mips/dl-startup.h @@ -7,6 +7,7 @@ #include <sgidefs.h> +#ifndef L_rcrt1 __asm__("" " .text\n" " .globl _start\n" @@ -114,6 +115,7 @@ __asm__("" "\n\n" ".previous\n" ); +#endif /* * Get a pointer to the argv array. On many platforms this can be just @@ -191,6 +193,5 @@ do { \ case R_MIPS_NONE: \ break; \ default: \ - SEND_STDERR("Aiieeee!"); \ _dl_exit(1); \ } diff --git a/libc/misc/internals/Makefile.in b/libc/misc/internals/Makefile.in index 69af8b76e..908b18321 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) +CFLAGS-reloc_static_pie.c := $(SSP_DISABLE_FLAGS) -DL_rcrt1 libc-y += $(MISC_INTERNALS_OBJ) ifneq ($(UCLIBC_FORMAT_SHARED_FLAT),y) diff --git a/libc/misc/internals/reloc_static_pie.c b/libc/misc/internals/reloc_static_pie.c index 578202d23..c0027de6f 100644 --- a/libc/misc/internals/reloc_static_pie.c +++ b/libc/misc/internals/reloc_static_pie.c @@ -15,33 +15,96 @@ 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/>. */ - +#define IS_IN_rtld // force inline function calls #include <link.h> #include <elf.h> #include <dl-elf.h> +#include <ldso.h> +#ifdef __mips__ +#include <dl-startup.h> +#endif + ElfW(Addr) _dl_load_base = NULL; void reloc_static_pie (ElfW(Addr) load_addr); void -reloc_static_pie (ElfW(Addr) load_addr) +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}; + int indx; + ElfW(Addr) got; + ElfW(Dyn) *dpnt; + struct elf_resolve tpnt_tmp; + struct elf_resolve *tpnt = &tpnt_tmp; + + DL_BOOT_COMPUTE_GOT(got); + DL_BOOT_COMPUTE_DYN(dpnt, got, (DL_LOADADDR_TYPE)load_addr); + + _dl_memset(tpnt, 0, sizeof(struct elf_resolve)); + tpnt->loadaddr = load_addr; + tpnt->dynamic_addr = dpnt; + + __dl_parse_dynamic_info(dpnt, tpnt->dynamic_info, NULL, load_addr); + +#if defined(PERFORM_BOOTSTRAP_GOT) + /* some arches (like MIPS) we have to tweak the GOT before relocations */ + PERFORM_BOOTSTRAP_GOT(tpnt); +#endif + + +#if defined(ELF_MACHINE_PLTREL_OVERLAP) +# define INDX_MAX 1 +#else +# define INDX_MAX 2 +#endif + + for (indx = 0; indx < INDX_MAX; indx++) { + unsigned long rel_addr, rel_size; + ElfW(Word) relative_count = tpnt->dynamic_info[DT_RELCONT_IDX]; + + rel_addr = (indx ? tpnt->dynamic_info[DT_JMPREL] : + tpnt->dynamic_info[DT_RELOC_TABLE_ADDR]); + rel_size = (indx ? tpnt->dynamic_info[DT_PLTRELSZ] : + tpnt->dynamic_info[DT_RELOC_TABLE_SIZE]); + + if (!rel_addr) + continue; - /* Read our own dynamic section and fill in the info array. */ - dyn_addr = ((void *) load_addr + elf_machine_dynamic ()); + if((0 == indx) && relative_count) { + rel_size -= relative_count * sizeof(ELF_RELOC); + elf_machine_relative(load_addr, rel_addr, relative_count); + rel_addr += relative_count * sizeof(ELF_RELOC); + } - /* Use the underlying function to avoid TLS access before initialization */ - __dl_parse_dynamic_info(dyn_addr, dynamic_info, NULL, load_addr); +#ifdef ARCH_NEEDS_BOOTSTRAP_RELOCS + { + ELF_RELOC *rpnt; + unsigned int i; + ElfW(Sym) *sym; + unsigned long symbol_addr; + int symtab_index; + unsigned long *reloc_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); + /* Now parse the relocation information */ + rpnt = (ELF_RELOC *) rel_addr; + for (i = 0; i < rel_size; i += sizeof(ELF_RELOC), rpnt++) { + reloc_addr = (unsigned long *) DL_RELOC_ADDR(load_addr, (unsigned long)rpnt->r_offset); + symtab_index = ELF_R_SYM(rpnt->r_info); + symbol_addr = 0; + sym = NULL; + if (symtab_index) { + ElfW(Sym) *symtab; + symtab = (ElfW(Sym) *) tpnt->dynamic_info[DT_SYMTAB]; + sym = &symtab[symtab_index]; + symbol_addr = (unsigned long) DL_RELOC_ADDR(load_addr, sym->st_value); + } + /* Use this machine-specific macro to perform the actual relocation. */ + PERFORM_BOOTSTRAP_RELOC(rpnt, reloc_addr, symbol_addr, load_addr, sym); + } + } +#endif + } _dl_load_base = load_addr; -} +} \ No newline at end of file diff --git a/libc/sysdeps/linux/mips/crt1.S b/libc/sysdeps/linux/mips/crt1.S index 083615515..7c4db447c 100644 --- a/libc/sysdeps/linux/mips/crt1.S +++ b/libc/sysdeps/linux/mips/crt1.S @@ -77,6 +77,10 @@ #ifndef __UCLIBC_CTOR_DTOR__ .weak _init .weak _fini +#endif +#ifdef L_rcrt1 + .type reloc_static_pie,@function + .hidden .L0 #endif .type main,@function .type __uClibc_main,@function @@ -89,6 +93,25 @@ __start: #else PTR_LA $28, _gp /* Setup GP correctly if we're non-PIC. */ move $31, $0 +#endif +#ifdef L_rcrt1 + PTR_LA $4, _DYNAMIC /* Place _DYNAMIC into the GOT */ + REG_S $4, -0x7ff0($28) /* offset to GOT stolen from dl-startup */ + jal .L0 /* Get the current $pc address */ +.L0: + PTR_SUBU $4, $31, $25 /* Calculate load addr */ + move $31, $0 /* Clear ra */ + and $29, -2 * SZREG /* Ensure stack is aligned */ + PTR_ADDIU $29, (-2 * SZREG) /* Allocate 2 register spaces on stack */ + REG_S $2, SZREG($29) /* Store atexit in case it exists */ + PTR_LA $5, reloc_static_pie /* function calls before relocation + don't work unless we set $t9 manually */ + PTR_ADDU $25, $4, $5 /* store reloc_static_pie in $t9 */ + jalr $25 /* call reloc_static_pie */ + nop /* delay slot, just in case */ + REG_L $2, SZREG($29) /* cleanup stack */ + PTR_ADDIU $29, $29, (2 * SZREG) + #endif PTR_LA $4, main /* main */ -- 2.34.1

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