| Message ID | 20250326224506.27165-2-palmer@rivosinc.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | bb58e1579f431d42469b6aed0f03eff383ba6db5 |
| Headers | show |
| Series | RISC-V: errata: Use medany for relocatable builds | expand |
| Context | Check | Description |
|---|---|---|
| bjorn/pre-ci_am | success | Success |
| bjorn/build-rv32-defconfig | success | build-rv32-defconfig |
| bjorn/build-rv64-clang-allmodconfig | success | build-rv64-clang-allmodconfig |
| bjorn/build-rv64-gcc-allmodconfig | success | build-rv64-gcc-allmodconfig |
| bjorn/build-rv64-nommu-k210-defconfig | success | build-rv64-nommu-k210-defconfig |
| bjorn/build-rv64-nommu-k210-virt | success | build-rv64-nommu-k210-virt |
| bjorn/checkpatch | success | checkpatch |
| bjorn/dtb-warn-rv64 | success | dtb-warn-rv64 |
| bjorn/header-inline | success | header-inline |
| bjorn/kdoc | success | kdoc |
| bjorn/module-param | success | module-param |
| bjorn/verify-fixes | success | verify-fixes |
| bjorn/verify-signedoff | success | verify-signedoff |
On 26/03/2025 23:45, Palmer Dabbelt wrote: > We're trying to mix non-PIC/PIE objects into the otherwise-PIE > relocatable kernels, to avoid GOT/PLT references during early boot > alternative resolution (which happens before the GOT/PLT are set up). > > riscv64-unknown-linux-gnu-ld: arch/riscv/errata/sifive/errata.o: relocation R_RISCV_HI20 against `tlb_flush_all_threshold' can not be used when making a shared object; recompile with -fPIC > riscv64-unknown-linux-gnu-ld: arch/riscv/errata/thead/errata.o: relocation R_RISCV_HI20 against `riscv_cbom_block_size' can not be used when making a shared object; recompile with -fPIC thead erratas are already compiled with medany if CONFIG_RISCV_ALTERNATIVE_EARLY is set (https://elixir.bootlin.com/linux/v6.14-rc6/source/arch/riscv/errata/thead/Makefile#L2) so why isn't it enough? > > Fixes: 8dc2a7e8027f ("riscv: Fix relocatable kernels with early alternatives using -fno-pie") > Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> > --- > I'm not 100% sure it's possible to expose this without Samuel's NOMMU > relocatable builds, see > <https://lore.kernel.org/all/mhng-517c0318-c8fb-4c4a-aa0e-0d08f8d34d78@palmer-ri-x1c9/> > --- > arch/riscv/errata/Makefile | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile > index f0da9d7b39c3..bc6c77ba837d 100644 > --- a/arch/riscv/errata/Makefile > +++ b/arch/riscv/errata/Makefile > @@ -1,5 +1,9 @@ > ifdef CONFIG_RELOCATABLE > -KBUILD_CFLAGS += -fno-pie > +# We can't use PIC/PIE when handling early-boot errata parsing, as the kernel > +# doesn't have a GOT setup at that point. So instead just use medany: it's > +# usually position-independent, so it should be good enough for the errata > +# handling. > +KBUILD_CFLAGS += -fno-pie -mcmodel=medany > endif > > ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
On 28/03/2025 09:18, Alexandre Ghiti wrote: > On 26/03/2025 23:45, Palmer Dabbelt wrote: >> We're trying to mix non-PIC/PIE objects into the otherwise-PIE >> relocatable kernels, to avoid GOT/PLT references during early boot >> alternative resolution (which happens before the GOT/PLT are set up). >> >> riscv64-unknown-linux-gnu-ld: arch/riscv/errata/sifive/errata.o: >> relocation R_RISCV_HI20 against `tlb_flush_all_threshold' can not be >> used when making a shared object; recompile with -fPIC >> riscv64-unknown-linux-gnu-ld: arch/riscv/errata/thead/errata.o: >> relocation R_RISCV_HI20 against `riscv_cbom_block_size' can not be >> used when making a shared object; recompile with -fPIC > > > thead erratas are already compiled with medany if > CONFIG_RISCV_ALTERNATIVE_EARLY is set > (https://elixir.bootlin.com/linux/v6.14-rc6/source/arch/riscv/errata/thead/Makefile#L2) > so why isn't it enough? > FYI, this config without early boot alternatives trigger the same relocation issue with thead erratas: https://download.01.org/0day-ci/archive/20250328/202503281836.8pntHm6I-lkp@intel.com/config > >> >> Fixes: 8dc2a7e8027f ("riscv: Fix relocatable kernels with early >> alternatives using -fno-pie") >> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> >> --- >> I'm not 100% sure it's possible to expose this without Samuel's NOMMU >> relocatable builds, see >> <https://lore.kernel.org/all/mhng-517c0318-c8fb-4c4a-aa0e-0d08f8d34d78@palmer-ri-x1c9/> >> >> --- >> arch/riscv/errata/Makefile | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile >> index f0da9d7b39c3..bc6c77ba837d 100644 >> --- a/arch/riscv/errata/Makefile >> +++ b/arch/riscv/errata/Makefile >> @@ -1,5 +1,9 @@ >> ifdef CONFIG_RELOCATABLE >> -KBUILD_CFLAGS += -fno-pie >> +# We can't use PIC/PIE when handling early-boot errata parsing, as >> the kernel >> +# doesn't have a GOT setup at that point. So instead just use >> medany: it's >> +# usually position-independent, so it should be good enough for the >> errata >> +# handling. >> +KBUILD_CFLAGS += -fno-pie -mcmodel=medany >> endif >> ifdef CONFIG_RISCV_ALTERNATIVE_EARLY > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv
On Fri, 28 Mar 2025 01:18:01 PDT (-0700), Alexandre Ghiti wrote: > On 26/03/2025 23:45, Palmer Dabbelt wrote: >> We're trying to mix non-PIC/PIE objects into the otherwise-PIE >> relocatable kernels, to avoid GOT/PLT references during early boot >> alternative resolution (which happens before the GOT/PLT are set up). >> >> riscv64-unknown-linux-gnu-ld: arch/riscv/errata/sifive/errata.o: relocation R_RISCV_HI20 against `tlb_flush_all_threshold' can not be used when making a shared object; recompile with -fPIC >> riscv64-unknown-linux-gnu-ld: arch/riscv/errata/thead/errata.o: relocation R_RISCV_HI20 against `riscv_cbom_block_size' can not be used when making a shared object; recompile with -fPIC > > > thead erratas are already compiled with medany if > CONFIG_RISCV_ALTERNATIVE_EARLY is set > (https://elixir.bootlin.com/linux/v6.14-rc6/source/arch/riscv/errata/thead/Makefile#L2) > so why isn't it enough? Those are linker errors, we can't pull the medlow code into PIC objects. So any objects in relocatable kernels need to either be PIC/PIE or be medany (which can't reference any absolute symbols). >> Fixes: 8dc2a7e8027f ("riscv: Fix relocatable kernels with early alternatives using -fno-pie") >> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> >> --- >> I'm not 100% sure it's possible to expose this without Samuel's NOMMU >> relocatable builds, see >> <https://lore.kernel.org/all/mhng-517c0318-c8fb-4c4a-aa0e-0d08f8d34d78@palmer-ri-x1c9/> >> --- >> arch/riscv/errata/Makefile | 6 +++++- >> 1 file changed, 5 insertions(+), 1 deletion(-) >> >> diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile >> index f0da9d7b39c3..bc6c77ba837d 100644 >> --- a/arch/riscv/errata/Makefile >> +++ b/arch/riscv/errata/Makefile >> @@ -1,5 +1,9 @@ >> ifdef CONFIG_RELOCATABLE >> -KBUILD_CFLAGS += -fno-pie >> +# We can't use PIC/PIE when handling early-boot errata parsing, as the kernel >> +# doesn't have a GOT setup at that point. So instead just use medany: it's >> +# usually position-independent, so it should be good enough for the errata >> +# handling. >> +KBUILD_CFLAGS += -fno-pie -mcmodel=medany >> endif >> >> ifdef CONFIG_RISCV_ALTERNATIVE_EARLY > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv
Hello: This patch was applied to riscv/linux.git (for-next) by Palmer Dabbelt <palmer@rivosinc.com>: On Wed, 26 Mar 2025 15:45:07 -0700 you wrote: > We're trying to mix non-PIC/PIE objects into the otherwise-PIE > relocatable kernels, to avoid GOT/PLT references during early boot > alternative resolution (which happens before the GOT/PLT are set up). > > riscv64-unknown-linux-gnu-ld: arch/riscv/errata/sifive/errata.o: relocation R_RISCV_HI20 against `tlb_flush_all_threshold' can not be used when making a shared object; recompile with -fPIC > riscv64-unknown-linux-gnu-ld: arch/riscv/errata/thead/errata.o: relocation R_RISCV_HI20 against `riscv_cbom_block_size' can not be used when making a shared object; recompile with -fPIC > > [...] Here is the summary with links: - RISC-V: errata: Use medany for relocatable builds https://git.kernel.org/riscv/c/bb58e1579f43 You are awesome, thank you!
diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile index f0da9d7b39c3..bc6c77ba837d 100644 --- a/arch/riscv/errata/Makefile +++ b/arch/riscv/errata/Makefile @@ -1,5 +1,9 @@ ifdef CONFIG_RELOCATABLE -KBUILD_CFLAGS += -fno-pie +# We can't use PIC/PIE when handling early-boot errata parsing, as the kernel +# doesn't have a GOT setup at that point. So instead just use medany: it's +# usually position-independent, so it should be good enough for the errata +# handling. +KBUILD_CFLAGS += -fno-pie -mcmodel=medany endif ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
We're trying to mix non-PIC/PIE objects into the otherwise-PIE relocatable kernels, to avoid GOT/PLT references during early boot alternative resolution (which happens before the GOT/PLT are set up). riscv64-unknown-linux-gnu-ld: arch/riscv/errata/sifive/errata.o: relocation R_RISCV_HI20 against `tlb_flush_all_threshold' can not be used when making a shared object; recompile with -fPIC riscv64-unknown-linux-gnu-ld: arch/riscv/errata/thead/errata.o: relocation R_RISCV_HI20 against `riscv_cbom_block_size' can not be used when making a shared object; recompile with -fPIC Fixes: 8dc2a7e8027f ("riscv: Fix relocatable kernels with early alternatives using -fno-pie") Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> --- I'm not 100% sure it's possible to expose this without Samuel's NOMMU relocatable builds, see <https://lore.kernel.org/all/mhng-517c0318-c8fb-4c4a-aa0e-0d08f8d34d78@palmer-ri-x1c9/> --- arch/riscv/errata/Makefile | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)