From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.8 required=5.0 tests=DKIM_INVALID,DKIM_SIGNED, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL,RDNS_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.2 Received: (qmail 22246 invoked from network); 29 Mar 2020 00:31:42 -0000 Received-SPF: pass (mother.openwall.net: domain of lists.openwall.com designates 195.42.179.200 as permitted sender) receiver=inbox.vuxu.org; client-ip=195.42.179.200 envelope-from= Received: from unknown (HELO mother.openwall.net) (195.42.179.200) by inbox.vuxu.org with ESMTP; 29 Mar 2020 00:31:42 -0000 Received: (qmail 18372 invoked by uid 550); 29 Mar 2020 00:31:31 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 9726 invoked from network); 29 Mar 2020 00:20:13 -0000 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=rcombs.me; q=dns/txt; s=mx; t=1585441215; h=References: In-Reply-To: Message-Id: Date: Subject: To: From: Sender; bh=CMi7Y0Icfei6lGxghEhqZ+vnRpSJajyjak2x79ms6dU=; b=Lu2vDxOLJho68dfR8rNF2EGZsTckExcpcxXF8DVqu/29m0UM4lj1skgPhjUGMlmgxcfeOg9d diORhTTmylybaFZ4LvupSLk3uFuBiWU6Rkwob9eT5d+ESk5y651sNFI2qRUJDpsqlY3SE1C1 fgYkZFcr2o6wafMiPnTeSMseBqE= X-Mailgun-Sending-Ip: 198.61.254.54 X-Mailgun-Sid: WyI4ZjMyMiIsICJtdXNsQGxpc3RzLm9wZW53YWxsLmNvbSIsICJiMGJhIl0= Sender: rcombs@rcombs.me From: rcombs To: musl@lists.openwall.com Date: Sat, 28 Mar 2020 19:19:28 -0500 Message-Id: <1585441168-23444-4-git-send-email-rcombs@rcombs.me> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1585441168-23444-1-git-send-email-rcombs@rcombs.me> References: <1585441168-23444-1-git-send-email-rcombs@rcombs.me> Subject: [musl] [PATCH 4/4] crt: add dcrt1, with support for locating the dynamic loader at runtime --- Makefile | 10 +- crt/dcrt1.c | 372 ++++++++++++++++++++++++++++++++++++++++++++++++ ldso/dlstart.c | 59 +++++--- ldso/dynlink.c | 13 ++ ldso/map_library.h | 59 ++++---- tools/ld.musl-clang.in | 17 ++- tools/musl-clang.in | 8 ++ tools/musl-gcc.specs.sh | 4 +- 8 files changed, 490 insertions(+), 52 deletions(-) create mode 100644 crt/dcrt1.c diff --git a/Makefile b/Makefile index bd8f5c3..348ffd0 100644 --- a/Makefile +++ b/Makefile @@ -106,13 +106,15 @@ obj/src/internal/version.h: $(wildcard $(srcdir)/VERSION $(srcdir)/.git) obj/src/internal/version.o obj/src/internal/version.lo: obj/src/internal/version.h -obj/crt/rcrt1.o obj/ldso/dlstart.lo obj/ldso/dynlink.lo: $(srcdir)/src/internal/dynlink.h $(srcdir)/arch/$(ARCH)/reloc.h +obj/crt/rcrt1.o obj/crt/dcrt1.o obj/ldso/dlstart.lo obj/ldso/dynlink.lo: $(srcdir)/src/internal/dynlink.h $(srcdir)/arch/$(ARCH)/reloc.h -obj/crt/crt1.o obj/crt/scrt1.o obj/crt/rcrt1.o obj/ldso/dlstart.lo: $(srcdir)/arch/$(ARCH)/crt_arch.h +obj/crt/crt1.o obj/crt/scrt1.o obj/crt/rcrt1.o obj/crt/dcrt1.o obj/ldso/dlstart.lo: $(srcdir)/arch/$(ARCH)/crt_arch.h -obj/crt/rcrt1.o: $(srcdir)/ldso/dlstart.c +obj/crt/rcrt1.o obj/crt/dcrt1.o: $(srcdir)/ldso/dlstart.c -obj/crt/Scrt1.o obj/crt/rcrt1.o: CFLAGS_ALL += -fPIC +obj/crt/Scrt1.o obj/crt/rcrt1.o obj/crt/dcrt1.o: CFLAGS_ALL += -fPIC + +obj/crt/dcrt1.o: CFLAGS_ALL += -DLDSO_PATHNAME=\"$(LDSO_PATHNAME)\" OPTIMIZE_SRCS = $(wildcard $(OPTIMIZE_GLOBS:%=$(srcdir)/src/%)) $(OPTIMIZE_SRCS:$(srcdir)/%.c=obj/%.o) $(OPTIMIZE_SRCS:$(srcdir)/%.c=obj/%.lo): CFLAGS += -O3 diff --git a/crt/dcrt1.c b/crt/dcrt1.c new file mode 100644 index 0000000..d58a606 --- /dev/null +++ b/crt/dcrt1.c @@ -0,0 +1,372 @@ +#define SYSCALL_NO_TLS 1 + +#include +#include +#include +#include +#include +#include +#include +#include +#include "atomic.h" +#include "dynlink.h" +#include "syscall.h" + +extern weak hidden const size_t _DYNAMIC[]; + +int main(); +weak void _init(); +weak void _fini(); +weak _Noreturn int __libc_start_main(int (*)(), int, char **, + void (*)(), void(*)(), void(*)()); + +#define START "_start" +#define _dlstart_c _start_c +#define DL_DNI +#include "../ldso/dlstart.c" + +struct dso { + unsigned char *base; + struct fdpic_loadmap *loadmap; + size_t *dynv; + Phdr *phdr; + int phnum; + size_t phentsize; + unsigned char *map; + size_t map_len; +}; + +#ifndef PAGESIZE +#ifdef PAGE_SIZE +#undef PAGE_SIZE // We don't want to use libc.page_size here +#endif +static size_t page_size; +#define PAGE_SIZE page_size +#endif + +#ifdef SYS_mmap2 +#define mmap(start, len, prot, flags, fd, off) (void*)__syscall(SYS_mmap2, start, len, prot, flags, fd, off/SYSCALL_MMAP2_UNIT) +#else +#define mmap(start, len, prot, flags, fd, off) (void*)__syscall(SYS_mmap, start, len, prot, flags, fd, off) +#endif + +#define munmap(ptr, len) __syscall(SYS_munmap, ptr, len) + +static inline int crt_mprotect(void *addr, size_t len, int prot) +{ + size_t start, end; + start = (size_t)addr & -PAGE_SIZE; + end = (size_t)((char *)addr + len + PAGE_SIZE-1) & -PAGE_SIZE; + return __syscall(SYS_mprotect, start, end-start, prot); +} +#define mprotect crt_mprotect + +#define read(fd, buf, size) __syscall(SYS_read, fd, buf, size) +#define pread(fd, buf, size, ofs) __syscall(SYS_pread, fd, buf, size, __SYSCALL_LL_PRW(ofs)) + +static inline off_t crt_lseek(int fd, off_t offset, int whence) +{ +#ifdef SYS__llseek + off_t result; + return __syscall(SYS__llseek, fd, offset>>32, offset, &result, whence) ? -1 : result; +#else + return __syscall(SYS_lseek, fd, offset, whence); +#endif +} +#define lseek crt_lseek + +static inline void *map_library_allocz(size_t *size) +{ + void *ret; + *size = (*size + SYSCALL_MMAP2_UNIT - 1) & -SYSCALL_MMAP2_UNIT; + ret = mmap(0, *size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (ret == MAP_FAILED) + return NULL; + return ret; +} + +static inline void map_library_free(void *ptr, size_t size) +{ + if (ptr) + munmap(ptr, size); +} + +#define map_library_failed(val) ((unsigned long)val > -4096UL) +#define map_library_error(ret) (-(long)ret) + +#ifdef SYS_readlink +#define readlink(path, buf, bufsize) __syscall(SYS_readlink, path, buf, bufsize) +#else +#define readlink(path, buf, bufsize) __syscall(SYS_readlinkat, AT_FDCWD, path, buf, bufsize) +#endif + +#ifdef SYS_access +#define access(filename, amode) __syscall(SYS_access, filename, amode) +#else +#define access(filename, amode) __syscall(SYS_faccessat, AT_FDCWD, filename, amode, 0) +#endif + +static void *crt_memcpy(void *restrict dest, const void *restrict src, size_t n) +{ + unsigned char *d = dest; + const unsigned char *s = src; + for (; n; n--) *d++ = *s++; + return dest; +} + +static void *crt_memset(void *dest, int c, size_t n) +{ + unsigned char *s = dest; + for (; n; n--, s++) *s = c; + return dest; +} +#define memset crt_memset + +static size_t crt_strlen(const char *s) +{ + const char *a = s; + for (; *s; s++); + return s-a; +} + +static char *crt_strchrnul(const char *s, int c) +{ + c = (unsigned char)c; + if (!c) return (char *)s + crt_strlen(s); + for (; *s && *(unsigned char *)s != c; s++); + return (char *)s; +} + +static int crt_strncmp(const char *_l, const char *_r, size_t n) +{ + const unsigned char *l=(void *)_l, *r=(void *)_r; + if (!n--) return 0; + for (; *l && *r && n && *l == *r ; l++, r++, n--); + return *l - *r; +} + +static char *crt_getenv(const char *name, char **environ) +{ + size_t l = crt_strchrnul(name, '=') - name; + if (l && !name[l] && environ) + for (char **e = environ; *e; e++) + if (!crt_strncmp(name, *e, l) && l[*e] == '=') + return *e + l+1; + return 0; +} + +#define LD_CRT +#include "../ldso/map_library.h" + +static void decode_vec(const size_t *v, size_t *a, size_t cnt) +{ + size_t i; + for (i=0; i 1 && this_path[thisl] == '/') + thisl--; + while (thisl > 0 && this_path[thisl] != '/') + thisl--; + + const char *envpath = crt_getenv("LD_LOADER_PATH", environ); + if (envpath) { + size_t envlen = crt_strlen(envpath); + if (envlen < bufsize) { + crt_memcpy(outbuf, envpath, envlen + 1); + return envlen + 1; + } + } + + get_rpath(&paths[1], dyn, base); + + paths[0] = crt_getenv("LD_LIBRARY_PATH", environ); + + for (i = 0; i < 2; i++) { + const char *p = paths[i]; + char *o = outbuf; + if (!p) + continue; + for (;;) { + if (!crt_strncmp(p, "$ORIGIN", 7) || + !crt_strncmp(p, "${ORIGIN}", 9)) { + if (o + thisl + 1 < outbuf + bufsize) { + crt_memcpy(o, this_path, thisl); + o += thisl; + } else { + o = outbuf + bufsize - 1; + } + p += (p[1] == '{' ? 9 : 7); + } else if (*p == ':' || !*p) { +#define LDSO_FILENAME "ld-musl-" LDSO_ARCH ".so.1" + if (o + sizeof(LDSO_FILENAME) + 1 < outbuf + bufsize) { + *o++ = '/'; + crt_memcpy(o, LDSO_FILENAME, sizeof(LDSO_FILENAME)); + if (!access(outbuf, R_OK | X_OK)) + return (o + sizeof(LDSO_FILENAME)) - outbuf; + } + if (!*p) + break; + o = outbuf; + p++; + } else { + if (o < outbuf + bufsize) + *o++ = *p; + p++; + } + } + } + + default_path: + // Didn't find a usable loader anywhere (or in secure mode), so try the default + crt_memcpy(outbuf, LDSO_PATHNAME, sizeof(LDSO_PATHNAME)); + return sizeof(LDSO_PATHNAME); +} + +hidden _Noreturn void __dls2(unsigned char *base, size_t *p) +{ + int argc = p[0]; + char **argv = (void *)(p+1); + int fd; + int secure; + int prot = PROT_READ; + struct dso loader; + Ehdr *loader_hdr; + Phdr *new_hdr; + void *entry; + char this_path[PATH_MAX]; + size_t thisl; + char linker_path[PATH_MAX]; + size_t linker_len; + size_t i; + size_t aux[AUX_CNT]; + size_t *auxv; + size_t dyn[DYN_CNT]; + char **environ = argv + argc + 1; + + // We're already finished here; just run main. + if (__libc_start_main) + __libc_start_main(main, argc, argv, _init, _fini, 0); + + /* Find aux vector just past environ[] and use it to initialize + * global data that may be needed before we can make syscalls. */ + for (i = argc + 1; argv[i]; i++); + auxv = (void *)(argv + i + 1); + decode_vec(auxv, aux, AUX_CNT); + secure = ((aux[0] & 0x7800) != 0x7800 || aux[AT_UID] != aux[AT_EUID] + || aux[AT_GID] != aux[AT_EGID] || aux[AT_SECURE]); + +#ifndef PAGESIZE + page_size = aux[AT_PAGESZ]; +#endif + + decode_vec(_DYNAMIC, dyn, DYN_CNT); + + thisl = readlink("/proc/self/exe", this_path, sizeof this_path); + linker_len = find_linker(linker_path, sizeof linker_path, this_path, thisl, dyn, base, environ, secure); + + fd = __sys_open2(, linker_path, O_RDONLY); + if (fd < 0) + goto error; + + loader_hdr = map_library(fd, &loader); + if (!loader_hdr) + goto error; + + __syscall(SYS_close, fd); + + // Copy the program headers into an anonymous mapping + new_hdr = mmap(0, (aux[AT_PHENT] * (aux[AT_PHNUM] + 2) + linker_len + PAGE_SIZE - 1) & -PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (map_library_failed(new_hdr)) + goto error; + + // Point it back at the original kernel-provided base + new_hdr->p_type = PT_PHDR; + new_hdr->p_vaddr = (size_t)new_hdr - (size_t)base; + + ((Phdr*)((char*)new_hdr + aux[AT_PHENT]))->p_type = PT_INTERP; + ((Phdr*)((char*)new_hdr + aux[AT_PHENT]))->p_vaddr = new_hdr->p_vaddr + aux[AT_PHENT] * (aux[AT_PHNUM] + 2); + + crt_memcpy((char*)new_hdr + aux[AT_PHENT] * (aux[AT_PHNUM] + 2), linker_path, linker_len); + + for (i = 0; i < aux[AT_PHNUM]; i++) { + Phdr *hdr = (void*)((char*)aux[AT_PHDR] + aux[AT_PHENT] * i); + Phdr *dst = (void*)((char*)new_hdr + aux[AT_PHENT] * (i + 2)); + if (hdr->p_type == PT_PHDR || hdr->p_type == PT_INTERP) { + // Can't have a duplicate + dst->p_type = PT_NULL; + } else { + crt_memcpy(dst, hdr, aux[AT_PHENT]); + } + } + + if (mprotect(new_hdr, aux[AT_PHENT] * (aux[AT_PHNUM] + 2) + linker_len, PROT_READ)) + goto error; + + for (i=0; auxv[i]; i+=2) { + if (auxv[i] == AT_BASE) + auxv[i + 1] = (size_t)loader_hdr; + if (auxv[i] == AT_PHDR) + auxv[i + 1] = (size_t)new_hdr; + if (auxv[i] == AT_PHNUM) + auxv[i + 1] += 2; + } + + entry = laddr(&loader, loader_hdr->e_entry); + +#ifndef LD_FDPIC + /* Undo the relocations performed by dlstart */ + + if (NEED_MIPS_GOT_RELOCS) { + const size_t *dynv = _DYNAMIC; + size_t local_cnt = 0; + size_t *got = (void *)(base + dyn[DT_PLTGOT]); + for (i=0; dynv[i]; i+=2) if (dynv[i]==DT_MIPS_LOCAL_GOTNO) + local_cnt = dynv[i+1]; + for (i=0; i