Date: Tue, 30 Oct 2018 14:32:10 -0700 From: Mark Millard <marklmi26-fbsd@yahoo.com> To: Alexander Richardson <arichardson@freebsd.org> Cc: svn-src-head@freebsd.org Subject: Re: svn commit: r339876 - head/libexec/rtld-elf Message-ID: <A392133D-3E02-422C-81FF-5BAD4D15665D@yahoo.com> In-Reply-To: <CA%2BZ_v8oZDqfrO0EsJjQXAat287TeDAO7C5omSaDaUNEj6q0oCw@mail.gmail.com> References: <7DC6D9C4-C153-4BCE-851C-22C890AB0D73@yahoo.com> <CA%2BZ_v8oZDqfrO0EsJjQXAat287TeDAO7C5omSaDaUNEj6q0oCw@mail.gmail.com>
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On 2018-Oct-30, at 2:23 PM, Alexander Richardson <arichardson at = freebsd.org> wrote: > On Tue, 30 Oct 2018 at 18:19, Mark Millard <marklmi26-fbsd at = yahoo.com> wrote: >>=20 >> Alexander Richardson arichardson at freebsd.org wrote on >> Tue Oct 30 15:33:00 UTC 2018 : >>=20 >>> On Tue, 30 Oct 2018 at 10:17, Michael Tuexen >>> <Michael.Tuexen at macmic.franken.de> wrote: >>>>=20 >>>>> On 29. Oct 2018, at 22:08, Alex Richardson <arichardson at = FreeBSD.org> wrote: >>>>>=20 >>>>> Author: arichardson >>>>> Date: Mon Oct 29 21:08:02 2018 >>>>> New Revision: 339876 >>>>> URL: https://svnweb.freebsd.org/changeset/base/339876 >>>>>=20 >>>>> Log: >>>>> rtld: set obj->textsize correctly >>>>>=20 >>>>> With lld-generated binaries the first PT_LOAD will usually be a = read-only >>>>> segment unless you pass --no-rosegment. For those binaries the = textsize is >>>>> determined by the next PT_LOAD. To allow both LLD and bfd 2.17 = binaries to >>>>> be parsed correctly use the end of the last PT_LOAD that is marked = as >>>>> executable instead. >>>>>=20 >>>>> I noticed that the value was wrong while adding some debug prints = for some rtld >>>>> changes for CHERI binaries. `obj->textsize` only seems to be used = by PPC so the >>>>> effect is untested. However, the value before was definitely wrong = and the new >>>>> result matches the phdrs. >>>> I build kernel and world with a revision later than this on a PPC. = Buildword >>>> ends up with a world where almost all binaries are segfaulting.... = Especially gdb >>>> (but svn, ls or so all segfault). >>>>=20 >>>> Best regards >>>> Michael >>>=20 >>> This is rather surprising since if anything the range of the icache >>> flush should increase rather than decrease after this change. >>>=20 >>> I can only see this causing a behaviour change if we actually need = to >>> flush more than just the executable segments. >>> Is it possible that some binary/library contains a non-executable >>> segment as the first PT_LOAD? >>> Or is there some linker script that adds custom PHDRS? >>=20 >> The following is based on using devel/powerpc64-xtoolchain-gcc >> to buildworld buildkernel on/for powerpc64. (I experiment with >> using fairly modern tools to target powerpc64 and powerpc.) >> The build context is head -r339076 based, both for what >> did the build and for what it was building. >>=20 >> I report from both elfdump and objdump output >> because each seems to have some oddities in what >> it outputs. >>=20 >> I start with elfdump (which leaves sh_flags blank >> and shows a section header with sh_name empty >> that objdump does not list at all): >>=20 >> # elfdump -pc /bin/ls | less >>=20 >> . . . >>=20 >> As for objdump on the same file (section >> one less than elfdump listed, no empty sh_name >> section listed): >>=20 >> # objdump -ph /bin/ls | less >>=20 >> /bin/ls: file format elf64-powerpc-freebsd >>=20 >> Program Header: >> PHDR off 0x0000000000000040 vaddr 0x0000000010000040 paddr = 0x0000000010000040 align 2**3 >> filesz 0x0000000000000188 memsz 0x0000000000000188 flags r-- >> INTERP off 0x00000000000001c8 vaddr 0x00000000100001c8 paddr = 0x00000000100001c8 align 2**0 >> filesz 0x0000000000000015 memsz 0x0000000000000015 flags r-- >> LOAD off 0x0000000000000000 vaddr 0x0000000010000000 paddr = 0x0000000010000000 align 2**16 >> filesz 0x000000000000910c memsz 0x000000000000910c flags r-x >> LOAD off 0x0000000000009110 vaddr 0x0000000010019110 paddr = 0x0000000010019110 align 2**16 >> filesz 0x0000000000000ee0 memsz 0x00000000000010e8 flags rw- >> DYNAMIC off 0x0000000000009138 vaddr 0x0000000010019138 paddr = 0x0000000010019138 align 2**3 >> filesz 0x00000000000001c0 memsz 0x00000000000001c0 flags rw- >> NOTE off 0x00000000000001e0 vaddr 0x00000000100001e0 paddr = 0x00000000100001e0 align 2**2 >> filesz 0x0000000000000030 memsz 0x0000000000000030 flags r-- >> STACK off 0x0000000000000000 vaddr 0x0000000000000000 paddr = 0x0000000000000000 align 2**4 >> filesz 0x0000000000000000 memsz 0x0000000000000000 flags rw- >>=20 >> Dynamic Section: >> NEEDED libutil.so.9 >> NEEDED libncursesw.so.8 >> NEEDED libc.so.7 >> INIT 0x0000000010019328 >> FINI 0x0000000010019340 >> HASH 0x0000000010000210 >> STRTAB 0x0000000010000d00 >> SYMTAB 0x0000000010000490 >> STRSZ 0x000000000000035a >> SYMENT 0x0000000000000018 >> DEBUG 0x0000000000000000 >> PLTGOT 0x0000000010019898 >> PLTRELSZ 0x00000000000006f0 >> PLTREL 0x0000000000000007 >> JMPREL 0x00000000100012f8 >> 0x70000000 0x00000000100089b4 >> RELA 0x0000000010001160 >> RELASZ 0x0000000000000198 >> RELAENT 0x0000000000000018 >> VERNEED 0x0000000010001110 >> VERNEEDNUM 0x0000000000000001 >> VERSYM 0x000000001000105a >>=20 >> Version References: >> required from libc.so.7: >> 0x077a28b3 0x00 05 FBSD_1.3 >> 0x077a28b1 0x00 04 FBSD_1.1 >> 0x077a28b5 0x00 03 FBSD_1.5 >> 0x077a28b0 0x00 02 FBSD_1.0 >> private flags =3D 0x1: [abiv1] >>=20 >> Sections: >> Idx Name Size VMA LMA File = off Algn >> 0 .interp 00000015 00000000100001c8 00000000100001c8 = 000001c8 2**0 >> CONTENTS, ALLOC, LOAD, READONLY, DATA >> 1 .note.tag 00000030 00000000100001e0 00000000100001e0 = 000001e0 2**2 >> CONTENTS, ALLOC, LOAD, READONLY, DATA >> 2 .hash 0000027c 0000000010000210 0000000010000210 = 00000210 2**3 >> CONTENTS, ALLOC, LOAD, READONLY, DATA >> 3 .dynsym 00000870 0000000010000490 0000000010000490 = 00000490 2**3 >> CONTENTS, ALLOC, LOAD, READONLY, DATA >> 4 .dynstr 0000035a 0000000010000d00 0000000010000d00 = 00000d00 2**0 >> CONTENTS, ALLOC, LOAD, READONLY, DATA >> 5 .gnu.version 000000b4 000000001000105a 000000001000105a = 0000105a 2**1 >> CONTENTS, ALLOC, LOAD, READONLY, DATA >> 6 .gnu.version_r 00000050 0000000010001110 0000000010001110 = 00001110 2**3 >> CONTENTS, ALLOC, LOAD, READONLY, DATA >> 7 .rela.dyn 00000198 0000000010001160 0000000010001160 = 00001160 2**3 >> CONTENTS, ALLOC, LOAD, READONLY, DATA >> 8 .rela.plt 000006f0 00000000100012f8 00000000100012f8 = 000012f8 2**3 >> CONTENTS, ALLOC, LOAD, READONLY, DATA >> 9 .init 0000002c 00000000100019f0 00000000100019f0 = 000019f0 2**4 >> CONTENTS, ALLOC, LOAD, READONLY, CODE >> 10 .text 00007204 0000000010001a20 0000000010001a20 = 00001a20 2**5 >> CONTENTS, ALLOC, LOAD, READONLY, CODE >> 11 .fini 00000024 0000000010008c30 0000000010008c30 = 00008c30 2**4 >> CONTENTS, ALLOC, LOAD, READONLY, CODE >> 12 .rodata 000004b0 0000000010008c58 0000000010008c58 = 00008c58 2**3 >> CONTENTS, ALLOC, LOAD, READONLY, DATA >> 13 .eh_frame 00000004 0000000010009108 0000000010009108 = 00009108 2**2 >> CONTENTS, ALLOC, LOAD, READONLY, DATA >> 14 .ctors 00000010 0000000010019110 0000000010019110 = 00009110 2**3 >> CONTENTS, ALLOC, LOAD, DATA >> 15 .dtors 00000010 0000000010019120 0000000010019120 = 00009120 2**3 >> CONTENTS, ALLOC, LOAD, DATA >> 16 .jcr 00000008 0000000010019130 0000000010019130 = 00009130 2**3 >> CONTENTS, ALLOC, LOAD, DATA >> 17 .dynamic 000001c0 0000000010019138 0000000010019138 = 00009138 2**3 >> CONTENTS, ALLOC, LOAD, DATA >> 18 .opd 00000468 00000000100192f8 00000000100192f8 = 000092f8 2**3 >> CONTENTS, ALLOC, LOAD, DATA >> 19 .got 00000098 0000000010019800 0000000010019800 = 00009800 2**8 >> CONTENTS, ALLOC, LOAD, DATA >> 20 .plt 00000708 0000000010019898 0000000010019898 = 00009898 2**3 >> ALLOC >> 21 .data 00000050 0000000010019fa0 0000000010019fa0 = 00009fa0 2**3 >> CONTENTS, ALLOC, LOAD, DATA >> 22 .bss 00000208 0000000010019ff0 0000000010019ff0 = 00009ff0 2**3 >> ALLOC >> 23 .comment 000002b5 0000000000000000 0000000000000000 = 00009ff0 2**0 >> CONTENTS, READONLY >> 24 .gnu_debuglink 00000010 0000000000000000 0000000000000000 = 0000a2a8 2**2 >> CONTENTS, READONLY >>=20 >>=20 >=20 > The first PT_LOAD is also executable so there will be no be behaviour > change. It must be one of the library dependencies that is different. > The difference in section headers output doesn't matter here since all > that RTLD looks at is the PHDRS. >=20 I think you missed the fact that the .got and .plt are in the material from the 2nd PT_LOAD: there are writeable code areas involved for powerpc64. So both PT_LOAD's contribute code areas and there is a space between the two contributions. The first PT_LOAD loads most code (the readonly code, to be specific). The 2nd contributes a writable-code area. But may be i've misunderstood the assumptions that your change is based on. =3D=3D=3D Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
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