On 15/05/2019 13:39, Christophe Lyon wrote:
> In FDPIC mode, we set -fPIE unless the user provides -fno-PIE, -fpie,
> -fPIC or -fpic: indeed FDPIC code is PIC, but we want to generate code
> for executables rather than shared libraries by default.
>
> We also make sure to use the --fdpic assembler option, and select the
> appropriate linker emulation.
>
> At link time, we also default to -pie, unless we are generating a
> shared library or a relocatable file (-r). Note that even for static
> link, we must specify the dynamic linker because the executable still
> has to relocate itself at startup.
>
> We also force 'now' binding since lazy binding is not supported.
>
> We should also apply the same behavior for -Wl,-Ur as for -r, but I
> couldn't find how to describe that in the specs fragment.
...
> +/* Unless we generate a shared library or a relocatable object, we
> + force -pie. */
> +/* Even with -static, we have to define the dynamic-linker, as we
> + have some relocations to resolve at load time. */
> +#undef SUBTARGET_EXTRA_LINK_SPEC
> +#define SUBTARGET_EXTRA_LINK_SPEC \
> + "%{!mno-fdpic: -m " TARGET_FDPIC_LINKER_EMULATION \
> + "%{!shared:%{!r: -pie}} \
> + %{static:-dynamic-linker " GNU_USER_DYNAMIC_LINKER "}}" \
> + "%{mno-fdpic: -m " TARGET_LINKER_EMULATION "}" \
> + "%{!r:%{!mno-fdpic: -z now}}"
i think -dynamic-linker can be avoided for -static using
-static-pie linking with rcrt0.o
but more importantly: does the abi spec require the sysv dynamic
linker name? that sounds suboptimal (in principle the same os
can support both normal elf and fdpic elf so you can test/use
an fdpic toolchain on a system with mmu, but this requires
different dynamic linker name ..otherwise one has to run
executables in a chroot or separate mount namespace to change
the dynamic linker)
> +
> +#undef STARTFILE_SPEC
> +#define STARTFILE_SPEC "%{!mno-fdpic:%{!shared:crtreloc.o%s}} " \
> + LINUX_OR_ANDROID_LD (GNU_USER_TARGET_STARTFILE_SPEC,
> ANDROID_STARTFILE_SPEC)
> diff --git a/libsanitizer/configure.tgt b/libsanitizer/configure.tgt
> index b241ddb..c38b3f4 100644
> --- a/libsanitizer/configure.tgt
> +++ b/libsanitizer/configure.tgt
> @@ -45,6 +45,9 @@ case "${target}" in
> ;;
> sparc*-*-solaris2.11*)
> ;;
> + arm*-*-uclinuxfdpiceabi)
> + UNSUPPORTED=1
> + ;;
musl libc has fdpic support on sh (e.g. with sh2eb-linux-muslfdpic
target and --enable-fdpic), it can probably support fdpic on arm
too with minimal changes, i assume the target name for that would
be arm-linux-muslfdpiceabi.
so i think it is better to check arm*-*fdpiceabi where the libc
does not matter (so we dont have to patch the same files when
*-muslfdpiceabi support is added).
