Bug 225775
| Summary: | btxld does not handle input with other than 2 PT_LOAD segments | ||
|---|---|---|---|
| Product: | Base System | Reporter: | Ed Maste <emaste> |
| Component: | bin | Assignee: | Ed Maste <emaste> |
| Status: | Closed FIXED | ||
| Severity: | Affects Only Me | CC: | imp |
| Priority: | --- | Flags: | koobs:
mfc-stable11+
|
| Version: | CURRENT | ||
| Hardware: | Any | ||
| OS: | Any | ||
Just curious, why the boot code may need more than two segments. It would be interesting to see readelf or objdump output for zfsloader.bin. It is because lld collects read-only contents into a separate segment, for example: % readelf -l zfsloader.sym Elf file type is EXEC (Executable file) Entry point 0x0 There are 5 program headers, starting at offset 52 Program Headers: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align LOAD 0x001000 0x00000000 0x00000000 0x58694 0x58694 R E 0x1000 LOAD 0x05a000 0x00059000 0x00059000 0x0afcc 0x0afcc R 0x1000 LOAD 0x065000 0x00064000 0x00064000 0x07854 0x14c9c RW 0x1000 GNU_RELRO 0x06c000 0x0006b000 0x0006b000 0x00854 0x01000 R 0x1 GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0 Section to Segment mapping: Segment Sections... 00 .text .gnu_debuglink .comment .debug_str .debug_loc .debug_abbrev .debug_info .debug_ranges .debug_macinfo .debug_pubnames .debug_pubtypes .debug_frame .debug_line .debug_aranges .symtab .shstrtab .strtab 01 .rodata set_Xcommand_set 02 .data set_Xficl_compile_set .data.rel.ro .got .bss 03 .data.rel.ro .got 04 Linking with -z norelro leaves the three PT_LOADs, just the PT_GNU_RELRO is not emitted. From the output above btxld should coalesce two PT_LOADs, and discarding a PT_LOAD should be an error not a warning. See https://reviews.freebsd.org/D14956, which stops lld from generating > 2 PT_LOADs. The underlying issue in btxld will still exist. IMO we should upgrade the warning btxld: zfsloader.bin: Warning: Ignoring extra elf PT_LOAD segments to an error to ensure we won't silently ignore segments in the future, and such a change is sufficient to resolve this. A commit references this bug: Author: emaste Date: Fri Apr 6 02:57:59 UTC 2018 New revision: 332090 URL: https://svnweb.freebsd.org/changeset/base/332090 Log: stand: pass --no-rosegment for i386 bits when linking with lld btxld does not correctly handle input with other than 2 PT_LOAD segments. Passing --no-rosegment lets lld produce output eqivalent to ld.bfd: 2 PT_LOAD segments and no PT_GNU_RELRO. PR: 225775 MFC after: 3 weeks Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D14956 Changes: head/stand/i386/Makefile.inc A commit references this bug: Author: emaste Date: Fri Apr 27 01:21:52 UTC 2018 New revision: 333048 URL: https://svnweb.freebsd.org/changeset/base/333048 Log: MFC r332090: stand: pass --no-rosegment for i386 bits when linking with lld btxld does not correctly handle input with other than 2 PT_LOAD segments. Passing --no-rosegment lets lld produce output eqivalent to ld.bfd: 2 PT_LOAD segments and no PT_GNU_RELRO. PR: 225775 Sponsored by: The FreeBSD Foundation Changes: _U stable/11/ stable/11/stand/i386/Makefile.inc Fix commited, closing |
Linking e.g. zfsloader reports (whitespace added for clarity): cc -O2 -pipe -I/usr/home/emaste/src/freebsd-wip/stand/i386/btx/lib -nostdinc -I/usr/obj/usr/home/emaste/src/freebsd-wip/amd64.amd64/stand/libsa32 -I/usr/home/emaste/src/freebsd-wip/stand/libsa -D_STANDALONE -I/usr/home/emaste/src/freebsd-wip/sys -DLOADER_GELI_SUPPORT -I/usr/home/emaste/src/freebsd-wip/stand/geli -DLOADER_DISK_SUPPORT -m32 -mcpu=i386 -ffreestanding -mno-mmx -mno-sse -mno-avx -mno-avx2 -msoft-float -march=i386 -I. -I/usr/home/emaste/src/freebsd-wip/stand/common -I/usr/home/emaste/src/freebsd-wip/stand/ficl -I/usr/home/emaste/src/freebsd-wip/stand/ficl/i386 -I/usr/home/emaste/src/freebsd-wip/stand/common -DBF_DICTSIZE=15000 -DLOADER_UFS_SUPPORT -DLOADER_GZIP_SUPPORT -DLOADER_BZIP2_SUPPORT -DLOADER_NET_SUPPORT -DLOADER_NFS_SUPPORT -DLOADER_TFTP_SUPPORT -DLOADER_GPT_SUPPORT -DLOADER_MBR_SUPPORT -DLOADER_ZFS_SUPPORT -I/usr/home/emaste/src/freebsd-wip/stand/zfs -I/usr/home/emaste/src/freebsd-wip/sys/cddl/boot/zfs -Wall -I/usr/home/emaste/src/freebsd-wip/stand/i386 -DLOADER_PREFER_AMD64 -std=gnu99 -Wsystem-headers -Werror -Wno-pointer-sign -Wno-empty-body -Wno-string-plus-int -Wno-unused-const-variable -Wno-tautological-compare -Wno-unused-value -Wno-parentheses-equality -Wno-unused-function -Wno-enum-conversion -Wno-unused-local-typedef -Wno-address-of-packed-member -Wno-switch -Wno-switch-enum -Wno-knr-promoted-parameter -Wno-parentheses -Qunused-arguments -nostdlib -Wl,-z,norelro -static -Ttext 0x0 -Wl,-z,norelro -o zfsloader.sym /usr/obj/usr/home/emaste/src/freebsd-wip/amd64.amd64/stand/i386/btx/lib/crt0.o main.o conf.o vers.o chain.o boot.o commands.o console.o devopen.o interp.o interp_backslash.o interp_parse.o ls.o misc.o module.o load_elf32.o load_elf32_obj.o reloc_elf32.o load_elf64.o load_elf64_obj.o reloc_elf64.o disk.o part.o dev_net.o bcache.o isapnp.o pnp.o interp_forth.o /usr/obj/usr/home/emaste/src/freebsd-wip/amd64.amd64/stand/ficl32/libficl.a /usr/obj/usr/home/emaste/src/freebsd-wip/amd64.amd64/stand/zfs32/libzfsboot.a /usr/obj/usr/home/emaste/src/freebsd-wip/amd64.amd64/stand/i386/libi386/libi386.a /usr/obj/usr/home/emaste/src/freebsd-wip/amd64.amd64/stand/geli/libgeliboot.a /usr/obj/usr/home/emaste/src/freebsd-wip/amd64.amd64/stand/libsa32/libsa32.a strip -R .comment -R .note -o zfsloader.bin zfsloader.sym btxld -v -f aout -e 0x200000 -o zfsloader -l /usr/obj/usr/home/emaste/src/freebsd-wip/amd64.amd64/stand/i386/btx/btxldr/btxldr -b /usr/obj/usr/home/emaste/src/freebsd-wip/amd64.amd64/stand/i386/btx/btx/btx zfsloader.bin btxld: zfsloader.bin: Warning: Ignoring extra elf PT_LOAD segments kernel: ver=1.02 size=690 load=9000 entry=9010 map=16M pgctl=0:59 client: fmt=elf size=6bcd0 text=58834 data=afec bss=0 entry=0 output: fmt=aout size=6f000 text=1000 data=6d000 org=200000 entry=200000 btxld has: case 2: Warn(fname, "Ignoring extra %s PT_LOAD segments", fmtlist[fmt]); i.e., it expects two PT_LOADs with a specific format, and just ignores the third or later ones.