| Message ID | 20210711022824.29915-4-jrtc27@jrtc27.com |
|---|---|
| State | Accepted |
| Headers | show |
| Series | Fully support standalone Clang/LLVM toolchains | expand |
On Sun, Jul 11, 2021 at 10:29 AM Jessica Clarke <jrtc27@jrtc27.com> wrote: > > When using Clang with a bare-metal triple, -pie does not get passed to > the linker as it's not normally a thing that makes sense, unlike GCC > which will unconditionally forward it on and potentially result in a > linker error. However, LLD does support it, and manually forwarding it > on works as desired, so do so to fully support FW_PIC with Clang and > LLD. > > Signed-off-by: Jessica Clarke <jrtc27@jrtc27.com> > --- > firmware/objects.mk | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > Reviewed-by: Bin Meng <bmeng.cn@gmail.com> Tested-by: Bin Meng <bmeng.cn@gmail.com>
On Sun, Jul 11, 2021 at 10:29 AM Jessica Clarke <jrtc27@jrtc27.com> wrote: > > When using Clang with a bare-metal triple, -pie does not get passed to > the linker as it's not normally a thing that makes sense, unlike GCC > which will unconditionally forward it on and potentially result in a It seems GCC driver does not unconditionally forward it to the linker, see: $ riscv64-unknown-elf-gcc -fPIE -nostdlib -x c /dev/null -o /dev/null 2>&1 && echo y /opt/riscv-unknown-elf/lib/gcc/riscv64-unknown-elf/10.1.0/../../../../riscv64-unknown-elf/bin/ld: warning: cannot find entry symbol _start; defaulting to 0000000000010040 y But $ riscv64-unknown-elf-gcc -fPIE -nostdlib -Wl,-pie -x c /dev/null -o /dev/null 2>&1 && echo y /opt/riscv-unknown-elf/lib/gcc/riscv64-unknown-elf/10.1.0/../../../../riscv64-unknown-elf/bin/ld: -pie not supported collect2: error: ld returned 1 exit status So regarding bare-metal triple, GCC driver and clang driver behave the same way. It's just GNU bare-metal ld does not support PIE, while LLD supports. So we need to revise the above commit message. > linker error. However, LLD does support it, and manually forwarding it > on works as desired, so do so to fully support FW_PIC with Clang and > LLD. > > Signed-off-by: Jessica Clarke <jrtc27@jrtc27.com> > --- > firmware/objects.mk | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > Regards, Bin
On 11 Jul 2021, at 14:05, Bin Meng <bmeng.cn@gmail.com> wrote: > > On Sun, Jul 11, 2021 at 10:29 AM Jessica Clarke <jrtc27@jrtc27.com> wrote: >> >> When using Clang with a bare-metal triple, -pie does not get passed to >> the linker as it's not normally a thing that makes sense, unlike GCC >> which will unconditionally forward it on and potentially result in a > > It seems GCC driver does not unconditionally forward it to the linker, see: > > $ riscv64-unknown-elf-gcc -fPIE -nostdlib -x c /dev/null -o /dev/null > 2>&1 && echo y > /opt/riscv-unknown-elf/lib/gcc/riscv64-unknown-elf/10.1.0/../../../../riscv64-unknown-elf/bin/ld: > warning: cannot find entry symbol _start; defaulting to > 0000000000010040 > y > > But > > $ riscv64-unknown-elf-gcc -fPIE -nostdlib -Wl,-pie -x c /dev/null -o > /dev/null 2>&1 && echo y > /opt/riscv-unknown-elf/lib/gcc/riscv64-unknown-elf/10.1.0/../../../../riscv64-unknown-elf/bin/ld: > -pie not supported > collect2: error: ld returned 1 exit status > > So regarding bare-metal triple, GCC driver and clang driver behave > the same way. It's just GNU bare-metal ld does not support PIE, while > LLD supports. > > So we need to revise the above commit message. You didn’t pass -pie, only -fPIE. Jess >> linker error. However, LLD does support it, and manually forwarding it >> on works as desired, so do so to fully support FW_PIC with Clang and >> LLD. >> >> Signed-off-by: Jessica Clarke <jrtc27@jrtc27.com> >> --- >> firmware/objects.mk | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> > > Regards, > Bin
On Sun, Jul 11, 2021 at 9:06 PM Jessica Clarke <jrtc27@jrtc27.com> wrote: > > On 11 Jul 2021, at 14:05, Bin Meng <bmeng.cn@gmail.com> wrote: > > > > On Sun, Jul 11, 2021 at 10:29 AM Jessica Clarke <jrtc27@jrtc27.com> wrote: > >> > >> When using Clang with a bare-metal triple, -pie does not get passed to > >> the linker as it's not normally a thing that makes sense, unlike GCC > >> which will unconditionally forward it on and potentially result in a > > > > It seems GCC driver does not unconditionally forward it to the linker, see: > > > > $ riscv64-unknown-elf-gcc -fPIE -nostdlib -x c /dev/null -o /dev/null > > 2>&1 && echo y > > /opt/riscv-unknown-elf/lib/gcc/riscv64-unknown-elf/10.1.0/../../../../riscv64-unknown-elf/bin/ld: > > warning: cannot find entry symbol _start; defaulting to > > 0000000000010040 > > y > > > > But > > > > $ riscv64-unknown-elf-gcc -fPIE -nostdlib -Wl,-pie -x c /dev/null -o > > /dev/null 2>&1 && echo y > > /opt/riscv-unknown-elf/lib/gcc/riscv64-unknown-elf/10.1.0/../../../../riscv64-unknown-elf/bin/ld: > > -pie not supported > > collect2: error: ld returned 1 exit status > > > > So regarding bare-metal triple, GCC driver and clang driver behave > > the same way. It's just GNU bare-metal ld does not support PIE, while > > LLD supports. > > > > So we need to revise the above commit message. > > You didn’t pass -pie, only -fPIE. Ah, yes. Indeed -pie is the linker option. Then we are good. Regards, Bin
On Sun, Jul 11, 2021 at 5:45 PM Bin Meng <bmeng.cn@gmail.com> wrote: > > On Sun, Jul 11, 2021 at 10:29 AM Jessica Clarke <jrtc27@jrtc27.com> wrote: > > > > When using Clang with a bare-metal triple, -pie does not get passed to > > the linker as it's not normally a thing that makes sense, unlike GCC > > which will unconditionally forward it on and potentially result in a > > linker error. However, LLD does support it, and manually forwarding it > > on works as desired, so do so to fully support FW_PIC with Clang and > > LLD. > > > > Signed-off-by: Jessica Clarke <jrtc27@jrtc27.com> > > --- > > firmware/objects.mk | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > Reviewed-by: Bin Meng <bmeng.cn@gmail.com> > Tested-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Anup Patel <anup.patel@wdc.com> Applied this patch to the riscv/opensbi repo. Thanks, Anup > > -- > opensbi mailing list > opensbi@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/opensbi
diff --git a/firmware/objects.mk b/firmware/objects.mk index ce91c2f..3bc83cd 100644 --- a/firmware/objects.mk +++ b/firmware/objects.mk @@ -21,7 +21,7 @@ ifeq ($(FW_PIC),y) firmware-genflags-y += -DFW_PIC firmware-asflags-y += -fpic firmware-cflags-y += -fPIE -pie -firmware-ldflags-y += -Wl,--no-dynamic-linker +firmware-ldflags-y += -Wl,--no-dynamic-linker -Wl,-pie endif ifdef FW_TEXT_START
When using Clang with a bare-metal triple, -pie does not get passed to the linker as it's not normally a thing that makes sense, unlike GCC which will unconditionally forward it on and potentially result in a linker error. However, LLD does support it, and manually forwarding it on works as desired, so do so to fully support FW_PIC with Clang and LLD. Signed-off-by: Jessica Clarke <jrtc27@jrtc27.com> --- firmware/objects.mk | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)