Date: Fri, 17 Jul 2009 19:32:04 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r195743 - head/libexec/rtld-elf Message-ID: <200907171932.n6HJW4Pg079917@svn.freebsd.org>
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Author: kib Date: Fri Jul 17 19:32:04 2009 New Revision: 195743 URL: http://svn.freebsd.org/changeset/base/195743 Log: Only perform .bss mapping and cleaning operations when segment file size is not equal to its memory size. This eliminates unneeded clearing of the text segment that often happens due to text end not being page-aligned. For instance, $ readelf -l /lib/libedit.so.6 Program Headers: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align LOAD 0x000000 0x00000000 0x00000000 0x139e1 0x139e1 R E 0x1000 LOAD 0x014000 0x00014000 0x00014000 0x00f04 0x00f14 RW 0x1000 DYNAMIC 0x014cc4 0x00014cc4 0x00014cc4 0x000d0 0x000d0 RW 0x4 $ procstat -v $$ (for /bin/sh) 68585 0x28097000 0x280aa000 r-x 6 0 21 14 CN vn /lib/libedit.so.6 68585 0x280aa000 0x280ab000 r-x 1 0 1 0 CN vn /lib/libedit.so.6 <== 68585 0x280ab000 0x280ac000 rwx 1 0 1 0 CN vn /lib/libedit.so.6 Note the splitted map entry marked by '<=='. Reviewed by: kan Approved by: re (kensmith) MFC after: 1 month Modified: head/libexec/rtld-elf/map_object.c Modified: head/libexec/rtld-elf/map_object.c ============================================================================== --- head/libexec/rtld-elf/map_object.c Fri Jul 17 18:35:45 2009 (r195742) +++ head/libexec/rtld-elf/map_object.c Fri Jul 17 19:32:04 2009 (r195743) @@ -180,37 +180,43 @@ map_object(int fd, const char *path, con return NULL; } - /* Clear any BSS in the last page of the segment. */ - clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; - clear_addr = mapbase + (clear_vaddr - base_vaddr); - clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); - if ((nclear = data_vlimit - clear_vaddr) > 0) { - /* Make sure the end of the segment is writable */ - if ((data_prot & PROT_WRITE) == 0 && - -1 == mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) { + /* Do BSS setup */ + if (segs[i]->p_filesz != segs[i]->p_memsz) { + + /* Clear any BSS in the last page of the segment. */ + clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz; + clear_addr = mapbase + (clear_vaddr - base_vaddr); + clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr); + + if ((nclear = data_vlimit - clear_vaddr) > 0) { + /* Make sure the end of the segment is writable */ + if ((data_prot & PROT_WRITE) == 0 && -1 == + mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) { _rtld_error("%s: mprotect failed: %s", path, strerror(errno)); return NULL; - } + } - memset(clear_addr, 0, nclear); + memset(clear_addr, 0, nclear); - /* Reset the data protection back */ - if ((data_prot & PROT_WRITE) == 0) - mprotect(clear_page, PAGE_SIZE, data_prot); - } + /* Reset the data protection back */ + if ((data_prot & PROT_WRITE) == 0) + mprotect(clear_page, PAGE_SIZE, data_prot); + } - /* Overlay the BSS segment onto the proper region. */ - bss_vaddr = data_vlimit; - bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); - bss_addr = mapbase + (bss_vaddr - base_vaddr); - if (bss_vlimit > bss_vaddr) { /* There is something to do */ - if (mprotect(bss_addr, bss_vlimit - bss_vaddr, data_prot) == -1) { + /* Overlay the BSS segment onto the proper region. */ + bss_vaddr = data_vlimit; + bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz); + bss_addr = mapbase + (bss_vaddr - base_vaddr); + if (bss_vlimit > bss_vaddr) { /* There is something to do */ + if (mprotect(bss_addr, bss_vlimit - bss_vaddr, data_prot) == -1) { _rtld_error("%s: mprotect of bss failed: %s", path, strerror(errno)); - return NULL; + return NULL; + } } } + if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff && (data_vlimit - data_vaddr + data_offset) >= (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) {
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