Commit 74f8295c authored by Tiezhu Yang's avatar Tiezhu Yang Committed by Huacai Chen
Browse files

LoongArch: Handle jump tables options for RUST 



When compiling with LLVM and CONFIG_RUST is set, there exist objtool
warnings in rust/core.o and rust/kernel.o, like this:

    rust/core.o: warning: objtool:
_RNvXs1_NtNtCs5QSdWC790r4_4core5ascii10ascii_charNtB5_9AsciiCharNtNtB9_3fmt5Debug3fmt+0x54:
sibling call from callable instruction with modified stack frame

For this special case, the related object file shows that there is no
generated relocation section '.rela.discard.tablejump_annotate' for the
table jump instruction jirl, thus objtool can not know that what is the
actual destination address.

If rustc has the option "-Cllvm-args=--loongarch-annotate-tablejump",
pass the option to enable jump tables for objtool, otherwise it should
pass "-Zno-jump-tables" to keep compatibility with older rustc.

How to test:

  $ rustup component add rust-src
  $ make LLVM=1 rustavailable
  $ make ARCH=loongarch LLVM=1 clean defconfig
  $ scripts/config -d MODVERSIONS \
    -e RUST -e SAMPLES -e SAMPLES_RUST \
    -e SAMPLE_RUST_CONFIGFS -e SAMPLE_RUST_MINIMAL \
    -e SAMPLE_RUST_MISC_DEVICE -e SAMPLE_RUST_PRINT \
    -e SAMPLE_RUST_DMA -e SAMPLE_RUST_DRIVER_PCI \
    -e SAMPLE_RUST_DRIVER_PLATFORM -e SAMPLE_RUST_DRIVER_FAUX \
    -e SAMPLE_RUST_DRIVER_AUXILIARY -e SAMPLE_RUST_HOSTPROGS
  $ make ARCH=loongarch LLVM=1 olddefconfig all

Cc: stable@vger.kernel.org
Acked-by: default avatarMiguel Ojeda <ojeda@kernel.org>
Reported-by: default avatarMiguel Ojeda <ojeda@kernel.org>
Closes: https://lore.kernel.org/rust-for-linux/CANiq72mNeCuPkCDrG2db3w=AX+O-zYrfprisDPmRac_qh65Dmg@mail.gmail.com/


Suggested-by: default avatarWANG Rui <wangrui@loongson.cn>
Signed-off-by: default avatarTiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent b1521282

arch/loongarch/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -298,6 +298,10 @@ config AS_HAS_LVZ_EXTENSION 
config CC_HAS_ANNOTATE_TABLEJUMP

	def_bool $(cc-option,-mannotate-tablejump)



config RUSTC_HAS_ANNOTATE_TABLEJUMP

	depends on RUST

	def_bool $(rustc-option,-Cllvm-args=--loongarch-annotate-tablejump)



menu "Kernel type and options"



source "kernel/Kconfig.hz"

arch/loongarch/Makefile

+5 −0
Original line number Diff line number Diff line
@@ -106,6 +106,11 @@ KBUILD_CFLAGS += -mannotate-tablejump 
else

KBUILD_CFLAGS			+= -fno-jump-tables # keep compatibility with older compilers

endif

ifdef CONFIG_RUSTC_HAS_ANNOTATE_TABLEJUMP

KBUILD_RUSTFLAGS		+= -Cllvm-args=--loongarch-annotate-tablejump

else

KBUILD_RUSTFLAGS		+= -Zno-jump-tables # keep compatibility with older compilers

endif

ifdef CONFIG_LTO_CLANG

# The annotate-tablejump option can not be passed to LLVM backend when LTO is enabled.

# Ensure it is aware of linker with LTO, '--loongarch-annotate-tablejump' also needs to