From 2e85579c34047c305caf15fb0ebe02bf3d001d0e Mon Sep 17 00:00:00 2001 From: Dima Zavin Date: Wed, 20 May 2009 18:28:09 -0700 Subject: [PATCH] linker: Make the errors reported by dlopen/dlsym be more useful. Changed it so that when the linker generates error messages, they are scribbled away into a buffer that dlfcn and friends can read from. Since the error messages are generetad with snprintf, and snprintf MAY call malloc during some code paths, we now link against a version of libc that does not contain malloc/free/realloc/calloc. We then define malloc and friends in the dynamic loader, and make them abort() if they are ever called. Signed-off-by: Dima Zavin --- linker/Android.mk | 2 +- linker/dlfcn.c | 43 +++++++++++-------- linker/linker.c | 113 +++++++++++++++++++++++++++++++------------------- linker/linker.h | 1 + linker/linker_debug.h | 14 +++---- 5 files changed, 106 insertions(+), 67 deletions(-) diff --git a/linker/Android.mk b/linker/Android.mk index 48141bef5..3d3ad920b 100644 --- a/linker/Android.mk +++ b/linker/Android.mk @@ -37,7 +37,7 @@ endif LOCAL_MODULE:= linker -LOCAL_STATIC_LIBRARIES := libcutils libc +LOCAL_STATIC_LIBRARIES := libcutils libc_nomalloc #LOCAL_FORCE_STATIC_EXECUTABLE := true # not necessary when not including BUILD_EXECUTABLE diff --git a/linker/dlfcn.c b/linker/dlfcn.c index cd73d11dc..b54674f2f 100644 --- a/linker/dlfcn.c +++ b/linker/dlfcn.c @@ -15,41 +15,49 @@ */ #include #include +#include #include "linker.h" /* This file hijacks the symbols stubbed out in libdl.so. */ #define DL_SUCCESS 0 -#define DL_ERR_CANNOT_FIND_LIBRARY 1 +#define DL_ERR_CANNOT_LOAD_LIBRARY 1 #define DL_ERR_INVALID_LIBRARY_HANDLE 2 #define DL_ERR_BAD_SYMBOL_NAME 3 #define DL_ERR_SYMBOL_NOT_FOUND 4 #define DL_ERR_SYMBOL_NOT_GLOBAL 5 +static char dl_err_buf[1024]; +static const char *dl_err_str; + static const char *dl_errors[] = { - [DL_SUCCESS] = NULL, - [DL_ERR_CANNOT_FIND_LIBRARY] = "Cannot find library", + [DL_ERR_CANNOT_LOAD_LIBRARY] = "Cannot load library", [DL_ERR_INVALID_LIBRARY_HANDLE] = "Invalid library handle", [DL_ERR_BAD_SYMBOL_NAME] = "Invalid symbol name", [DL_ERR_SYMBOL_NOT_FOUND] = "Symbol not found", [DL_ERR_SYMBOL_NOT_GLOBAL] = "Symbol is not global", }; -static int dl_last_err = DL_SUCCESS; - #define likely(expr) __builtin_expect (expr, 1) #define unlikely(expr) __builtin_expect (expr, 0) static pthread_mutex_t dl_lock = PTHREAD_MUTEX_INITIALIZER; -void *dlopen(const char *filename, int flag) +static void set_dlerror(int err) +{ + snprintf(dl_err_buf, sizeof(dl_err_buf), "%s: %s", dl_errors[err], + linker_get_error()); + dl_err_str = (const char *)&dl_err_buf[0]; +}; + +void *dlopen(const char *filename, int flag) { soinfo *ret; pthread_mutex_lock(&dl_lock); ret = find_library(filename); if (unlikely(ret == NULL)) { - dl_last_err = DL_ERR_CANNOT_FIND_LIBRARY; + set_dlerror(DL_ERR_CANNOT_LOAD_LIBRARY); } else { ret->refcount++; } @@ -59,9 +67,9 @@ void *dlopen(const char *filename, int flag) const char *dlerror(void) { - const char *err = dl_errors[dl_last_err]; - dl_last_err = DL_SUCCESS; - return err; + const char *tmp = dl_err_str; + dl_err_str = NULL; + return (const char *)tmp; } void *dlsym(void *handle, const char *symbol) @@ -71,16 +79,16 @@ void *dlsym(void *handle, const char *symbol) unsigned bind; pthread_mutex_lock(&dl_lock); - + if(unlikely(handle == 0)) { - dl_last_err = DL_ERR_INVALID_LIBRARY_HANDLE; + set_dlerror(DL_ERR_INVALID_LIBRARY_HANDLE); goto err; } if(unlikely(symbol == 0)) { - dl_last_err = DL_ERR_BAD_SYMBOL_NAME; + set_dlerror(DL_ERR_BAD_SYMBOL_NAME); goto err; } - + if(handle == RTLD_DEFAULT) { sym = lookup(symbol, &base); } else if(handle == RTLD_NEXT) { @@ -92,16 +100,17 @@ void *dlsym(void *handle, const char *symbol) if(likely(sym != 0)) { bind = ELF32_ST_BIND(sym->st_info); - + if(likely((bind == STB_GLOBAL) && (sym->st_shndx != 0))) { unsigned ret = sym->st_value + base; pthread_mutex_unlock(&dl_lock); return (void*)ret; } - dl_last_err = DL_ERR_SYMBOL_NOT_GLOBAL; + set_dlerror(DL_ERR_SYMBOL_NOT_GLOBAL); } - else dl_last_err = DL_ERR_SYMBOL_NOT_FOUND; + else + set_dlerror(DL_ERR_SYMBOL_NOT_FOUND); err: pthread_mutex_unlock(&dl_lock); diff --git a/linker/linker.c b/linker/linker.c index 5180ae020..08a591a21 100644 --- a/linker/linker.c +++ b/linker/linker.c @@ -104,6 +104,31 @@ unsigned bitmask[4096]; #define PT_ARM_EXIDX 0x70000001 /* .ARM.exidx segment */ #endif +#define HOODLUM(name, ret, ...) \ + ret name __VA_ARGS__ \ + { \ + char errstr[] = "ERROR: " #name " called from the dynamic linker!\n"; \ + write(2, errstr, sizeof(errstr)); \ + abort(); \ + } +HOODLUM(malloc, void *, (size_t size)); +HOODLUM(free, void, (void *ptr)); +HOODLUM(realloc, void *, (void *ptr, size_t size)); +HOODLUM(calloc, void *, (size_t cnt, size_t size)); + +static char __linker_dl_err_buf[768]; +#define DL_ERR(fmt, x...) \ + do { \ + snprintf(__linker_dl_err_buf, sizeof(__linker_dl_err_buf), \ + "%s[%d]: " fmt, __func__, __LINE__, ##x); \ + ERROR(fmt, ##x); \ + } while(0) + +const char *linker_get_error(void) +{ + return (const char *)&__linker_dl_err_buf[0]; +} + /* * This function is an empty stub where GDB locates a breakpoint to get notified * about linker activity. @@ -207,7 +232,7 @@ static soinfo *alloc_info(const char *name) soinfo *si; if(strlen(name) >= SOINFO_NAME_LEN) { - ERROR("%5d library name %s too long\n", pid, name); + DL_ERR("%5d library name %s too long\n", pid, name); return 0; } @@ -216,7 +241,7 @@ static soinfo *alloc_info(const char *name) */ if (!freelist) { if(socount == SO_MAX) { - ERROR("%5d too many libraries when loading %s\n", pid, name); + DL_ERR("%5d too many libraries when loading %s\n", pid, name); return NULL; } freelist = sopool + socount++; @@ -252,7 +277,7 @@ static void free_info(soinfo *si) } if (trav == NULL) { /* si was not ni solist */ - ERROR("%5d name %s is not in solist!\n", pid, si->name); + DL_ERR("%5d name %s is not in solist!\n", pid, si->name); return; } @@ -521,7 +546,7 @@ is_prelinked(int fd, const char *name) sz = lseek(fd, -sizeof(prelink_info_t), SEEK_END); if (sz < 0) { - ERROR("lseek() failed!\n"); + DL_ERR("lseek() failed!\n"); return 0; } @@ -597,7 +622,7 @@ get_lib_extents(int fd, const char *name, void *__hdr, unsigned *total_sz) TRACE("[ %5d Computing extents for '%s'. ]\n", pid, name); if (verify_elf_object(_hdr, name) < 0) { - ERROR("%5d - %s is not a valid ELF object\n", pid, name); + DL_ERR("%5d - %s is not a valid ELF object\n", pid, name); return (unsigned)-1; } @@ -625,7 +650,7 @@ get_lib_extents(int fd, const char *name, void *__hdr, unsigned *total_sz) } if ((min_vaddr == 0xffffffff) && (max_vaddr == 0)) { - ERROR("%5d - No loadable segments found in %s.\n", pid, name); + DL_ERR("%5d - No loadable segments found in %s.\n", pid, name); return (unsigned)-1; } @@ -661,13 +686,13 @@ static int reserve_mem_region(soinfo *si) void *base = mmap((void *)si->base, si->size, PROT_READ | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (base == MAP_FAILED) { - ERROR("%5d can NOT map (%sprelinked) library '%s' at 0x%08x " + DL_ERR("%5d can NOT map (%sprelinked) library '%s' at 0x%08x " "as requested, will try general pool: %d (%s)\n", pid, (si->base ? "" : "non-"), si->name, si->base, errno, strerror(errno)); return -1; } else if (base != (void *)si->base) { - ERROR("OOPS: %5d %sprelinked library '%s' mapped at 0x%08x, " + DL_ERR("OOPS: %5d %sprelinked library '%s' mapped at 0x%08x, " "not at 0x%08x\n", pid, (si->base ? "" : "non-"), si->name, (unsigned)base, si->base); munmap(base, si->size); @@ -705,7 +730,7 @@ alloc_mem_region(soinfo *si) } err: - ERROR("OOPS: %5d cannot map library '%s'. no vspace available.\n", + DL_ERR("OOPS: %5d cannot map library '%s'. no vspace available.\n", pid, si->name); return -1; } @@ -764,7 +789,7 @@ load_segments(int fd, void *header, soinfo *si) MAP_PRIVATE | MAP_FIXED, fd, phdr->p_offset & (~PAGE_MASK)); if (pbase == MAP_FAILED) { - ERROR("%d failed to map segment from '%s' @ 0x%08x (0x%08x). " + DL_ERR("%d failed to map segment from '%s' @ 0x%08x (0x%08x). " "p_vaddr=0x%08x p_offset=0x%08x\n", pid, si->name, (unsigned)tmp, len, phdr->p_vaddr, phdr->p_offset); goto fail; @@ -820,8 +845,8 @@ load_segments(int fd, void *header, soinfo *si) MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS, -1, 0); if (extra_base == MAP_FAILED) { - ERROR("[ %5d - failed to extend segment from '%s' @ 0x%08x " - "(0x%08x) ]\n", pid, si->name, (unsigned)tmp, + DL_ERR("[ %5d - failed to extend segment from '%s' @ 0x%08x" + " (0x%08x) ]\n", pid, si->name, (unsigned)tmp, extra_len); goto fail; } @@ -873,7 +898,7 @@ load_segments(int fd, void *header, soinfo *si) /* Sanity check */ if (total_sz > si->size) { - ERROR("%5d - Total length (0x%08x) of mapped segments from '%s' is " + DL_ERR("%5d - Total length (0x%08x) of mapped segments from '%s' is " "greater than what was allocated (0x%08x). THIS IS BAD!\n", pid, total_sz, si->name, si->size); goto fail; @@ -940,18 +965,20 @@ load_library(const char *name) soinfo *si = NULL; Elf32_Ehdr *hdr; - if(fd == -1) + if(fd == -1) { + DL_ERR("Library '%s' not found\n", name); return NULL; + } /* We have to read the ELF header to figure out what to do with this image */ if (lseek(fd, 0, SEEK_SET) < 0) { - ERROR("lseek() failed!\n"); + DL_ERR("lseek() failed!\n"); goto fail; } if ((cnt = read(fd, &__header[0], PAGE_SIZE)) < 0) { - ERROR("read() failed!\n"); + DL_ERR("read() failed!\n"); goto fail; } @@ -1042,8 +1069,8 @@ soinfo *find_library(const char *name) if(!strcmp(name, si->name)) { if(si->flags & FLAG_ERROR) return 0; if(si->flags & FLAG_LINKED) return si; - ERROR("OOPS: %5d recursive link to '%s'\n", pid, si->name); - return 0; + DL_ERR("OOPS: %5d recursive link to '%s'\n", pid, si->name); + return NULL; } } @@ -1074,7 +1101,7 @@ unsigned unload_library(soinfo *si) if(lsi) unload_library(lsi); else - ERROR("%5d could not unload '%s'\n", + DL_ERR("%5d could not unload '%s'\n", pid, si->strtab + d[1]); } } @@ -1124,19 +1151,19 @@ static int reloc_library(soinfo *si, Elf32_Rel *rel, unsigned count) sym_name = (char *)(strtab + symtab[sym].st_name); s = _do_lookup(si, sym_name, &base); if(s == 0) { - ERROR("%5d cannot locate '%s'...\n", pid, sym_name); + DL_ERR("%5d cannot locate '%s'...\n", pid, sym_name); return -1; } #if 0 if((base == 0) && (si->base != 0)){ /* linking from libraries to main image is bad */ - ERROR("%5d cannot locate '%s'...\n", + DL_ERR("%5d cannot locate '%s'...\n", pid, strtab + symtab[sym].st_name); return -1; } #endif if ((s->st_shndx == SHN_UNDEF) && (s->st_value != 0)) { - ERROR("%5d In '%s', shndx=%d && value=0x%08x. We do not " + DL_ERR("%5d In '%s', shndx=%d && value=0x%08x. We do not " "handle this yet\n", pid, si->name, s->st_shndx, s->st_value); return -1; @@ -1198,7 +1225,7 @@ static int reloc_library(soinfo *si, Elf32_Rel *rel, unsigned count) COUNT_RELOC(RELOC_RELATIVE); MARK(rel->r_offset); if(sym){ - ERROR("%5d odd RELATIVE form...\n", pid); + DL_ERR("%5d odd RELATIVE form...\n", pid); return -1; } TRACE_TYPE(RELO, "%5d RELO RELATIVE %08x <- +%08x\n", pid, @@ -1239,7 +1266,7 @@ static int reloc_library(soinfo *si, Elf32_Rel *rel, unsigned count) #endif /* ANDROID_ARM_LINKER */ default: - ERROR("%5d unknown reloc type %d @ %p (%d)\n", + DL_ERR("%5d unknown reloc type %d @ %p (%d)\n", pid, type, rel, (int) (rel - start)); return -1; } @@ -1296,9 +1323,9 @@ static void call_constructors(soinfo *si) TRACE("[ %5d Done calling preinit_array for '%s' ]\n", pid, si->name); } else { if (si->preinit_array) { - ERROR("%5d Shared library '%s' has a preinit_array table @ 0x%08x." - " This is INVALID.\n", pid, si->name, - (unsigned)si->preinit_array); + DL_ERR("%5d Shared library '%s' has a preinit_array table @ 0x%08x." + " This is INVALID.\n", pid, si->name, + (unsigned)si->preinit_array); } } @@ -1344,7 +1371,7 @@ static int nullify_closed_stdio (void) dev_null = open("/dev/null", O_RDWR); if (dev_null < 0) { - ERROR("Cannot open /dev/null.\n"); + DL_ERR("Cannot open /dev/null.\n"); return -1; } TRACE("[ %5d Opened /dev/null file-descriptor=%d]\n", pid, dev_null); @@ -1370,7 +1397,7 @@ static int nullify_closed_stdio (void) /* The only error we allow is that the file descriptor does not exist, in which case we dup /dev/null to it. */ if (errno != EBADF) { - ERROR("nullify_stdio: unhandled error %s\n", strerror(errno)); + DL_ERR("nullify_stdio: unhandled error %s\n", strerror(errno)); return_value = -1; continue; } @@ -1381,9 +1408,9 @@ static int nullify_closed_stdio (void) do { status = dup2(dev_null, i); } while (status < 0 && errno == EINTR); - + if (status < 0) { - ERROR("nullify_stdio: dup2 error %s\n", strerror(errno)); + DL_ERR("nullify_stdio: dup2 error %s\n", strerror(errno)); return_value = -1; continue; } @@ -1392,12 +1419,12 @@ static int nullify_closed_stdio (void) /* If /dev/null is not one of the stdio file descriptors, close it. */ if (dev_null > 2) { TRACE("[ %5d Closing /dev/null file-descriptor=%d]\n", pid, dev_null); - do { + do { status = close(dev_null); } while (status < 0 && errno == EINTR); if (status < 0) { - ERROR("nullify_stdio: close error %s\n", strerror(errno)); + DL_ERR("nullify_stdio: close error %s\n", strerror(errno)); return_value = -1; } } @@ -1465,7 +1492,7 @@ static int link_image(soinfo *si, unsigned wr_offset) } } else if (phdr->p_type == PT_DYNAMIC) { if (si->dynamic != (unsigned *)-1) { - ERROR("%5d multiple PT_DYNAMIC segments found in '%s'. " + DL_ERR("%5d multiple PT_DYNAMIC segments found in '%s'. " "Segment at 0x%08x, previously one found at 0x%08x\n", pid, si->name, si->base + phdr->p_vaddr, (unsigned)si->dynamic); @@ -1478,7 +1505,7 @@ static int link_image(soinfo *si, unsigned wr_offset) } if (si->dynamic == (unsigned *)-1) { - ERROR("%5d missing PT_DYNAMIC?!\n", pid); + DL_ERR("%5d missing PT_DYNAMIC?!\n", pid); goto fail; } @@ -1502,7 +1529,7 @@ static int link_image(soinfo *si, unsigned wr_offset) break; case DT_PLTREL: if(*d != DT_REL) { - ERROR("DT_RELA not supported\n"); + DL_ERR("DT_RELA not supported\n"); goto fail; } break; @@ -1527,7 +1554,7 @@ static int link_image(soinfo *si, unsigned wr_offset) *d = (int) &_r_debug; break; case DT_RELA: - ERROR("%5d DT_RELA not supported\n", pid); + DL_ERR("%5d DT_RELA not supported\n", pid); goto fail; case DT_INIT: si->init_func = (void (*)(void))(si->base + *d); @@ -1579,16 +1606,16 @@ static int link_image(soinfo *si, unsigned wr_offset) pid, si->base, si->strtab, si->symtab); if((si->strtab == 0) || (si->symtab == 0)) { - ERROR("%5d missing essential tables\n", pid); + DL_ERR("%5d missing essential tables\n", pid); goto fail; } for(d = si->dynamic; *d; d += 2) { if(d[0] == DT_NEEDED){ DEBUG("%5d %s needs %s\n", pid, si->name, si->strtab + d[1]); - soinfo *lsi = find_library(si->strtab + d[1]); + soinfo *lsi = find_library(si->strtab + d[1]); if(lsi == 0) { - ERROR("%5d could not load '%s'\n", pid, si->strtab + d[1]); + DL_ERR("%5d could not load '%s'\n", pid, si->strtab + d[1]); goto fail; } lsi->refcount++; @@ -1747,8 +1774,10 @@ unsigned __linker_init(unsigned **elfdata) si->wrprotect_start = 0xffffffff; si->wrprotect_end = 0; - if(link_image(si, 0)){ - ERROR("CANNOT LINK EXECUTABLE '%s'\n", argv[0]); + if(link_image(si, 0)) { + char errmsg[] = "CANNOT LINK EXECUTABLE\n"; + write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf)); + write(2, errmsg, sizeof(errmsg)); exit(-1); } diff --git a/linker/linker.h b/linker/linker.h index d80c7614e..69042c05f 100644 --- a/linker/linker.h +++ b/linker/linker.h @@ -204,6 +204,7 @@ soinfo *find_library(const char *name); unsigned unload_library(soinfo *si); Elf32_Sym *lookup_in_library(soinfo *si, const char *name); Elf32_Sym *lookup(const char *name, unsigned *base); +const char *linker_get_error(void); #ifdef ANDROID_ARM_LINKER typedef long unsigned int *_Unwind_Ptr; diff --git a/linker/linker_debug.h b/linker/linker_debug.h index 3cc1343af..3f4fc4c70 100644 --- a/linker/linker_debug.h +++ b/linker/linker_debug.h @@ -55,17 +55,16 @@ #define TRUE 1 #define FALSE 0 - -#define __PRINTVF(v,f,x...) do { \ - (debug_verbosity > (v)) && (printf(x), ((f) && fflush(stdout))); \ - } while (0) /* Only use printf() during debugging. We have seen occasional memory * corruption when the linker uses printf(). */ #if LINKER_DEBUG extern int debug_verbosity; #warning "*** LINKER IS USING printf(); DO NOT CHECK THIS IN ***" -#define _PRINTVF(v,f,x...) __PRINTVF(v,f,x) +#define _PRINTVF(v,f,x...) \ + do { \ + (debug_verbosity > (v)) && (printf(x), ((f) && fflush(stdout))); \ + } while (0) #else /* !LINKER_DEBUG */ #define _PRINTVF(v,f,x...) do {} while(0) #endif /* LINKER_DEBUG */ @@ -75,8 +74,9 @@ extern int debug_verbosity; #define TRACE(x...) _PRINTVF(1, TRUE, x) #define WARN(fmt,args...) \ _PRINTVF(-1, TRUE, "%s:%d| WARNING: " fmt, __FILE__, __LINE__, ## args) -#define ERROR(fmt,args...) \ - __PRINTVF(-1, TRUE, "%s:%d| ERROR: " fmt, __FILE__, __LINE__, ## args) +#define ERROR(fmt,args...) \ + _PRINTVF(-1, TRUE, "%s:%d| ERROR: " fmt, __FILE__, __LINE__, ## args) + #if TRACE_DEBUG #define DEBUG(x...) _PRINTVF(2, TRUE, "DEBUG: " x) -- 2.11.0