On Thu, Jun 5, 2025 at 1:17 AM Deepak Gupta <debug@xxxxxxxxxxxx> wrote: > > From: Jim Shu <jim.shu@xxxxxxxxxx> > > user mode tasks compiled with zicfilp may call indirectly into vdso (like > hwprobe indirect calls). Add landing pad compile support in vdso. vdso > with landing pad in it will be nop for tasks which have not enabled > landing pad. > This patch allows to run user mode tasks with cfi eanbled and do no harm. > > Future work can be done on this to do below > - labeled landing pad on vdso functions (whenever labeling support shows > up in gnu-toolchain) > - emit shadow stack instructions only in vdso compiled objects as part of > kernel compile. > > Signed-off-by: Jim Shu <jim.shu@xxxxxxxxxx> > Reviewed-by: Zong Li <zong.li@xxxxxxxxxx> > Signed-off-by: Deepak Gupta <debug@xxxxxxxxxxxx> > --- > arch/riscv/Makefile | 5 +++- > arch/riscv/include/asm/assembler.h | 44 +++++++++++++++++++++++++++++++++++ > arch/riscv/kernel/vdso/Makefile | 6 +++++ > arch/riscv/kernel/vdso/flush_icache.S | 4 ++++ > arch/riscv/kernel/vdso/getcpu.S | 4 ++++ > arch/riscv/kernel/vdso/rt_sigreturn.S | 4 ++++ > arch/riscv/kernel/vdso/sys_hwprobe.S | 4 ++++ > 7 files changed, 70 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile > index 539d2aef5cab..c2dd09bb9db3 100644 > --- a/arch/riscv/Makefile > +++ b/arch/riscv/Makefile > @@ -88,9 +88,12 @@ riscv-march-$(CONFIG_TOOLCHAIN_HAS_ZACAS) := $(riscv-march-y)_zacas > # Check if the toolchain supports Zabha > riscv-march-$(CONFIG_TOOLCHAIN_HAS_ZABHA) := $(riscv-march-y)_zabha > > +KBUILD_BASE_ISA = -march=$(shell echo $(riscv-march-y) | sed -E 's/(rv32ima|rv64ima)fd([^v_]*)v?/\1\2/') > +export KBUILD_BASE_ISA > + > # Remove F,D,V from isa string for all. Keep extensions between "fd" and "v" by > # matching non-v and non-multi-letter extensions out with the filter ([^v_]*) > -KBUILD_CFLAGS += -march=$(shell echo $(riscv-march-y) | sed -E 's/(rv32ima|rv64ima)fd([^v_]*)v?/\1\2/') > +KBUILD_CFLAGS += $(KBUILD_BASE_ISA) > > KBUILD_AFLAGS += -march=$(riscv-march-y) > > diff --git a/arch/riscv/include/asm/assembler.h b/arch/riscv/include/asm/assembler.h > index 44b1457d3e95..a058ea5e9c58 100644 > --- a/arch/riscv/include/asm/assembler.h > +++ b/arch/riscv/include/asm/assembler.h > @@ -80,3 +80,47 @@ > .endm > > #endif /* __ASM_ASSEMBLER_H */ > + > +#if defined(CONFIG_RISCV_USER_CFI) && (__riscv_xlen == 64) > +.macro vdso_lpad > +lpad 0 > +.endm > +#else > +.macro vdso_lpad > +.endm > +#endif > + > +/* > + * This macro emits a program property note section identifying > + * architecture features which require special handling, mainly for > + * use in assembly files included in the VDSO. > + */ > +#define NT_GNU_PROPERTY_TYPE_0 5 > +#define GNU_PROPERTY_RISCV_FEATURE_1_AND 0xc0000000 > + > +#define GNU_PROPERTY_RISCV_FEATURE_1_ZICFILP (1U << 0) > +#define GNU_PROPERTY_RISCV_FEATURE_1_ZICFISS (1U << 1) > + > +#if defined(CONFIG_RISCV_USER_CFI) && (__riscv_xlen == 64) > +#define GNU_PROPERTY_RISCV_FEATURE_1_DEFAULT \ > + (GNU_PROPERTY_RISCV_FEATURE_1_ZICFILP) > +#endif > + > +#ifdef GNU_PROPERTY_RISCV_FEATURE_1_DEFAULT > +.macro emit_riscv_feature_1_and, feat = GNU_PROPERTY_RISCV_FEATURE_1_DEFAULT > + .pushsection .note.gnu.property, "a" > + .p2align 3 > + .word 4 > + .word 16 > + .word NT_GNU_PROPERTY_TYPE_0 > + .asciz "GNU" > + .word GNU_PROPERTY_RISCV_FEATURE_1_AND > + .word 4 > + .word \feat > + .word 0 > + .popsection > +.endm > +#else > +.macro emit_riscv_feature_1_and, feat = 0 > +.endm > +#endif > diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile > index ad73607abc28..441c5431d27e 100644 > --- a/arch/riscv/kernel/vdso/Makefile > +++ b/arch/riscv/kernel/vdso/Makefile > @@ -13,12 +13,18 @@ vdso-syms += flush_icache > vdso-syms += hwprobe > vdso-syms += sys_hwprobe > > +ifdef CONFIG_RISCV_USER_CFI > +LPAD_MARCH = _zicfilp_zicfiss -fcf-protection=full Hi Deepak, I guess we only want to generate landing pad instructions in vdso, if so, the -fcf-protection should be set to branch instead of full. (i.e., -fcf-protection=branch). > +endif > + > # Files to link into the vdso > obj-vdso = $(patsubst %, %.o, $(vdso-syms)) note.o > > ccflags-y := -fno-stack-protector > ccflags-y += -DDISABLE_BRANCH_PROFILING > ccflags-y += -fno-builtin > +ccflags-y += $(KBUILD_BASE_ISA)$(LPAD_MARCH) > +asflags-y += $(KBUILD_BASE_ISA)$(LPAD_MARCH) > > ifneq ($(c-gettimeofday-y),) > CFLAGS_vgettimeofday.o += -fPIC -include $(c-gettimeofday-y) > diff --git a/arch/riscv/kernel/vdso/flush_icache.S b/arch/riscv/kernel/vdso/flush_icache.S > index 8f884227e8bc..e4c56970905e 100644 > --- a/arch/riscv/kernel/vdso/flush_icache.S > +++ b/arch/riscv/kernel/vdso/flush_icache.S > @@ -5,11 +5,13 @@ > > #include <linux/linkage.h> > #include <asm/unistd.h> > +#include <asm/assembler.h> > > .text > /* int __vdso_flush_icache(void *start, void *end, unsigned long flags); */ > SYM_FUNC_START(__vdso_flush_icache) > .cfi_startproc > + vdso_lpad > #ifdef CONFIG_SMP > li a7, __NR_riscv_flush_icache > ecall > @@ -20,3 +22,5 @@ SYM_FUNC_START(__vdso_flush_icache) > ret > .cfi_endproc > SYM_FUNC_END(__vdso_flush_icache) > + > +emit_riscv_feature_1_and > diff --git a/arch/riscv/kernel/vdso/getcpu.S b/arch/riscv/kernel/vdso/getcpu.S > index 9c1bd531907f..5c1ecc4e1465 100644 > --- a/arch/riscv/kernel/vdso/getcpu.S > +++ b/arch/riscv/kernel/vdso/getcpu.S > @@ -5,14 +5,18 @@ > > #include <linux/linkage.h> > #include <asm/unistd.h> > +#include <asm/assembler.h> > > .text > /* int __vdso_getcpu(unsigned *cpu, unsigned *node, void *unused); */ > SYM_FUNC_START(__vdso_getcpu) > .cfi_startproc > + vdso_lpad > /* For now, just do the syscall. */ > li a7, __NR_getcpu > ecall > ret > .cfi_endproc > SYM_FUNC_END(__vdso_getcpu) > + > +emit_riscv_feature_1_and > diff --git a/arch/riscv/kernel/vdso/rt_sigreturn.S b/arch/riscv/kernel/vdso/rt_sigreturn.S > index 3dc022aa8931..e82987dc3739 100644 > --- a/arch/riscv/kernel/vdso/rt_sigreturn.S > +++ b/arch/riscv/kernel/vdso/rt_sigreturn.S > @@ -5,12 +5,16 @@ > > #include <linux/linkage.h> > #include <asm/unistd.h> > +#include <asm/assembler.h> > > .text > SYM_FUNC_START(__vdso_rt_sigreturn) > .cfi_startproc > .cfi_signal_frame > + vdso_lpad > li a7, __NR_rt_sigreturn > ecall > .cfi_endproc > SYM_FUNC_END(__vdso_rt_sigreturn) > + > +emit_riscv_feature_1_and > diff --git a/arch/riscv/kernel/vdso/sys_hwprobe.S b/arch/riscv/kernel/vdso/sys_hwprobe.S > index 77e57f830521..f1694451a60c 100644 > --- a/arch/riscv/kernel/vdso/sys_hwprobe.S > +++ b/arch/riscv/kernel/vdso/sys_hwprobe.S > @@ -3,13 +3,17 @@ > > #include <linux/linkage.h> > #include <asm/unistd.h> > +#include <asm/assembler.h> > > .text > SYM_FUNC_START(riscv_hwprobe) > .cfi_startproc > + vdso_lpad > li a7, __NR_riscv_hwprobe > ecall > ret > > .cfi_endproc > SYM_FUNC_END(riscv_hwprobe) > + > +emit_riscv_feature_1_and > > -- > 2.43.0 >
