I have tried to rebuild osv with `-mcmodel=large`. A strang error happened:
... LINK loader.elf ld.bfd: dynamic STT_GNU_IFUNC symbol `memcpy' with pointer equality in ` build/release.x64/arch/x64/string.o' can not be used when making an executable; recompile with -fPIE and relink with -pie But when I see the original osv kernel image. file build/release.x64/loader-stripped.elf build/release.x64/loader-stripped.elf: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked, stripped readelf -ls build/release.x64/loader-stripped.elf | grep IFUNC 1859: 0000000000388120 76 IFUNC GLOBAL DEFAULT 2 memcpy 5685: 00000000003f48f0 32 IFUNC GLOBAL DEFAULT 2 _ZN5sched10set_fsbaseEm 5768: 0000000000396ce0 32 IFUNC GLOBAL DEFAULT 2 _ZN5sched17fpu_state_rest 10518: 0000000000388360 32 IFUNC GLOBAL DEFAULT 2 memset 11790: 0000000000396ca0 32 IFUNC GLOBAL DEFAULT 2 _ZN5sched14fpu_state_init 13365: 0000000000396cc0 32 IFUNC GLOBAL DEFAULT 2 _ZN5sched14fpu_state_save It certainly is an executable with dynamic STT_GNU_IFUNC symbols. I don't know the reason of the error, I just changed code model from small to large. 在 2018年12月24日星期一 UTC+8下午5:30:30，Nadav Har'El写道： > > > On Mon, Dec 24, 2018 at 10:40 AM <[email protected] <javascript:>> wrote: > >> OSv can run unmodified Linux applications which are complied with `-fPIC` >> or `-pie`. However, position dependent executables are not support. >> >> Currently, OSv kernel image is mapped at low address space (0x 20 0000). >> Many position dependent executable executables also start at a low address, >> such as 0x 40 0040. >> > > The ability to run one position-dependent executable was proposed in > https://github.com/cloudius-systems/osv/issues/190 > But so far nobody has done this, because it's usually quite easy to > recompile as shared object, and because running a regular executable will > come with strings attached: you can only run one of them (so you can't > expect completely normal Linux packages, including shell scripts and other > stuff, to just work out of the box), and you'll also have all the regular > problems of PIE - see https://github.com/cloudius-systems/osv/issues/352 > and https://github.com/cloudius-systems/osv/issues/689 (shared objects > have more complete support). > > >> >> OSv Linear Address Space: >> >> >> --------- 0x 0000 0000 0000 0000 >> >> | | >> >> --------- 0x 0000 0000 0020 0000 kernel_base --\ >> >> | | |- Kernel (Core ELF) >> - 22M >> >> --------- 0x 0000 0000 0180 0000 lzkernel_base --/ >> >> | | >> >> |-------- 0x 0000 1000 0000 0000 program_base --\ >> >> | | |- s_program - 8G >> >> |-------| 0x 0000 1002 0000 0000 --\ --X >> >> | | |- Program | >> >> |-------| 0x 0000 1004 0000 0000 --/ | >> >> | | |- ELF Namespaces(max >> : 32) - 256G >> >> | | ...................... | >> >> | | | >> >> |-------| 0x 0000 1042 0000 0000 --/ >> >> | | >> >> --------- 0x ffff 8000 0000 0000 phys_mem --\ >> >> | | |- Main Area - 16T >> >> --------- 0x ffff 9000 0000 0000 --X >> >> | | |- Page Area - 16T >> >> --------- 0x ffff a000 0000 0000 --X >> >> | | |- Mempool Area - 16T >> >> --------- 0x ffff b000 0000 0000 --X >> >> | | |- Debug Area - 80T >> >> --------- 0x ffff ffff ffff ffff --/ >> >> >> >> Linux Linear Address Space: >> >> --------- 0x 0000 0000 0000 0000 --\ >> >> | | |- Reserved (Catch Exceptions of >> NULL/Little Pointers) >> >> --------- --X >> >> | | |- Text Segment >> >> --------- --X >> >> | | |- Data Segment >> >> --------- --X >> >> | | |- [Random] >> >> --------- --X >> >> | | |- Heap >> >> --------- --/ \/ >> >> | | >> >> --------- --\ >> >> | | |- Memory Mapping Segment >> >> --------- --/ >> >> | | |- [Random] >> >> --------- --/ >> >> | | >> >> --------- --\ /\ >> >> | | |- Stack >> >> --------- --X >> >> | | |- [Random] >> >> --------- --X >> >> | | |- Command-line Arguments >> >> --------- --X >> >> | | |- Environment Variables >> >> | | --/ >> >> --------- >> >> | | >> >> --------- 0x 0000 7fff ffff ffff >> >> | | >> >> | | -- Unused Space >> >> | | >> >> --------- 0x ffff 8000 0000 0000 --\ >> >> | | | >> >> | | |- Kernel Space - 128T >> >> | | | >> >> --------- 0x ffff ffff ffff ffff --/ >> >> >> >> If OSv kernel image can be mapped to high address space like Linux ( 0x >> ffff 8000 0000 0000 ?), then low address space can be used for applications. >> So, single position dependent executable can be supported like shared >> objects and PIE. >> >> I have tried to do this, but it seems difficult for me. Can you give some >> advice? >> >> > I haven't tried to do this, or thought it through, but it should be > possible. Right now in 0xfff.... we map the entire physical memory > linearly, to return through malloc(). We can start this mapping in a > slightly higher address, i.e., increase "phys_mem" and leave a lower range > in 0xfff... for the other stuff - kernel, mmap(), and shared objects. We'll > also need to change the loader to load the kernel to a different address. > > Nadav. > -- You received this message because you are subscribed to the Google Groups "OSv Development" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
