Hi,
Xing-Hao Chen <ericxh@xxxxxxxxxxx> writes:
> Dear GCC experts
>
> Please forgive me if it’s bothering you.
>
> I have a question about LD and dynamic library, which I have been struggling with for a while
> it will be great if you can help me out,
>
> in my program, two "so" - libcpss.so and libhelper.so have to be loaded into a fixed virtual address, it’s done by the ld script,
>
> SECTIONS
> {
> /* Code section, access rights RX */
> . = 0x14600000;
> …
> }
>
> readelf -l libhelper.so | less
>
> Elf file type is DYN (Shared object file) Entry point 0x14607ad8 There are 8 program headers, starting at offset 64
>
> Program Headers:
> Type Offset VirtAddr PhysAddr
> FileSiz MemSiz Flags Align
> LOAD 0x0000000000010000 0x0000000014600000 0x0000000014600000
> 0x000000000001aaec 0x000000000001aaec R E 0x10000
>
> an elf program(appDemo) linked with these two ".so", we can see the two so indeed were loaded into the expected fixed address,
I might be wrong, but I don't think there's any supported way of
forcing the DSO to be loaded at this address. The dynamic linker
can load DSOs at whichever address is convenient, and it expects
to be able to relocate DSOs as necessary.
That's probably not very useful to you, sorry.
Richard
>
> ldd ./appDemo
>
> linux-vdso.so.1 => (0x0000ffff917ec000)
> libcpss.so => ./libcpss.so (0x0000000010000000)
> libhelper.so => ./libhelper.so (0x0000000014600000)
> libpthread.so.0 => /lib/aarch64-linux-gnu/libpthread.so.0 (0x0000ffff917b5000)
> librt.so.1 => /lib/aarch64-linux-gnu/librt.so.1 (0x0000ffff9179d000)
> libdl.so.2 => /lib/aarch64-linux-gnu/libdl.so.2 (0x0000ffff91789000)
> libm.so.6 => /lib/aarch64-linux-gnu/libm.so.6 (0x0000ffff916d7000)
> libc.so.6 => /lib/aarch64-linux-gnu/libc.so.6 (0x0000ffff91583000)
> /lib/ld-linux-aarch64.so.1 (0x0000aaaadd94f000)
>
> however, i built another "so" – libtestScript.so that linking(depending on) these two so, seems not able to load these two so into proper fixed address, see below -
>
> ldd ./libtestScript.so
>
> linux-vdso.so.1 => (0x0000ffff8d87c000)
> libcpss.so => ./libcpss.so (0x0000ffff89d50000)
> libhelper.so => ./libhelper.so (0x0000ffff5e350000)
> libpthread.so.0 => /lib/aarch64-linux-gnu/libpthread.so.0 (0x0000ffff5e31c000)
> librt.so.1 => /lib/aarch64-linux-gnu/librt.so.1 (0x0000ffff5e304000)
> libdl.so.2 => /lib/aarch64-linux-gnu/libdl.so.2 (0x0000ffff5e2f0000)
> libm.so.6 => /lib/aarch64-linux-gnu/libm.so.6 (0x0000ffff5e23e000)
> libc.so.6 => /lib/aarch64-linux-gnu/libc.so.6 (0x0000ffff5e0ea000)
> /lib/ld-linux-aarch64.so.1 (0x0000aaaae0958000)
>
> do i missed any LD flags during building of the “joint .so" ? i saw the only difference between elf main program and “joint” so is the flag of “-shared”, so why “joint .so" missed the info of the two dependent so’s loading address? seems when the ld.so load "joint .so" and try to resolve and load the dependency two ".so", but it doesn't load them into the fixed address(0x10000000 / 0x14600000)
>
> NOK: LD_DEBUG=all ldd ./libtestScript.so
>
> 2349: file=libhelper.so [0]; generating link map
> 2349: dynamic: 0x0000ffff5d581ba0 base: 0x0000ffff48f57000 size: 0x000000002b9ff004
> 2349: entry: 0x0000ffff5d55ead8 phdr: 0x0000ffff8ca6fcc0 phnum: 8
>
> OK: LD_DEBUG=all ldd ./appDemo
>
> 2289: trying file=./libhelper.so
> 2289:
> 2289: file=libhelper.so [0]; generating link map
> 2289: dynamic: 0x000000001462aba0 base: 0x0000000000000000 size: 0x000000002b9ff004
> 2289: entry: 0x0000000014607ad8 phdr: 0x0000ffffb2e24cc0 phnum: 8
>
> readelf -h ./libhelper.so
>
> ELF Header:
> Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
> Class: ELF64
> Data: 2's complement, little endian
> Version: 1 (current)
> OS/ABI: UNIX - System V
> ABI Version: 0
> Type: DYN (Shared object file)
> Machine: AArch64
> Version: 0x1
> Entry point address: 0x14607ad8
> Start of program headers: 64 (bytes into file)
> Start of section headers: 228680 (bytes into file)
> Flags: 0x0
> Size of this header: 64 (bytes)
> Size of program headers: 56 (bytes)
> Number of program headers: 8
> Size of section headers: 64 (bytes)
> Number of section headers: 34
> Section header string table index: 31
>
> i appreciate if you can help me out.
>
> For your reference on how I built the elf executable program and shared lib.
> /home/ericxh/work/toolchain/marvell-gcc-5.2.1-16.02.0-armv8/armv8/le/aarch64v8-
> marvell-linux-gnu-5.2.1_i686_20151110/bin/aarch64-marvell-linux-gnu-gcc -shared
> -Xlinker --whole-archive
> compilation_root/cpss_4.2/armv8_DX_SHARED/cpssEnabler/libs/TESTSCRIPT.a -Xlinker
> --no-whole-archive \ compilation_root/cpss_4.2/armv8_DX_SHARED/libcpss.so
> compilation_root/cpss_4.2/armv8_DX_SHARED/libhelper.so -Xlinker -z -Xlinker
> nocopyreloc -rdynamic -lpthread -lrt -ldl -lm -Xlinker -Map -Xlinker
> compilation_root/cpss_4.2/armv8_DX_SHARED/libtestScript.map \ -Xlinker -soname -
> Xlinker libtestScript.so -o
> compilation_root/cpss_4.2/armv8_DX_SHARED/libtestScript.so
>
>
> /home/ericxh/work/toolchain/marvell-gcc-5.2.1-16.02.0-armv8/armv8/le/aarch64v8-
> marvell-linux-gnu-5.2.1_i686_20151110/bin/aarch64-marvell-linux-gnu-gcc -Xlinker
> --whole-archive
> compilation_root/cpss_4.2/armv8_DX_SHARED/referenceCode/libs/REFERENCECODE.a
> …
> …
> compilation_root/cpss_4.2/armv8_DX_SHARED/cpssEnabler/libs/CPSSAPPREF.a
> compilation_root/cpss_4.2/armv8_DX_SHARED/version_info.o -Xlinker --no-whole-
> archive \ compilation_root/cpss_4.2/armv8_DX_SHARED/libcpss.so
> compilation_root/cpss_4.2/armv8_DX_SHARED/libhelper.so -Xlinker -z -Xlinker
> nocopyreloc -rdynamic -lpthread -lrt -ldl -lm -Xlinker -Map -Xlinker
> compilation_root/cpss_4.2/armv8_DX_SHARED/appDemo.map -o
> compilation_root/cpss_4.2/armv8_DX_SHARED/appDemo
>
>
>
>
>
> Best regards
>
> Xinghao Chen （陈行浩）
