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Peter Anvin" , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Lorenzo Stoakes , Paul Walmsley , Palmer Dabbelt , Albert Ou , Conor Dooley , Rob Herring , Krzysztof Kozlowski , Arnd Bergmann , Christian Brauner , Peter Zijlstra , Oleg Nesterov , Eric Biederman , Kees Cook , Jonathan Corbet , Shuah Khan , Jann Horn , Conor Dooley , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, alistair.francis@wdc.com, richard.henderson@linaro.org, jim.shu@sifive.com, andybnac@gmail.com, kito.cheng@sifive.com, charlie@rivosinc.com, atishp@rivosinc.com, evan@rivosinc.com, cleger@rivosinc.com, alexghiti@rivosinc.com, samitolvanen@google.com, broonie@kernel.org, rick.p.edgecombe@intel.com, Zong Li Subject: Re: [PATCH v12 24/28] arch/riscv: compile vdso with landing pad Message-ID: References: <20250314-v5_user_cfi_series-v12-0-e51202b53138@rivosinc.com> <20250314-v5_user_cfi_series-v12-24-e51202b53138@rivosinc.com> <4f6a0c65-7c3a-4457-8b0b-cd39f40931c8@ghiti.fr> Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <4f6a0c65-7c3a-4457-8b0b-cd39f40931c8@ghiti.fr> On Tue, Apr 08, 2025 at 02:45:25PM +0200, Alexandre Ghiti wrote: > >On 14/03/2025 22:39, Deepak Gupta wrote: >>From: Jim Shu >> >>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 >>Reviewed-by: Zong Li >>Signed-off-by: Deepak Gupta >>--- >> arch/riscv/Makefile | 5 +++- >> arch/riscv/include/asm/assembler.h | 44 +++++++++++++++++++++++++++++++++++ >> arch/riscv/kernel/vdso/Makefile | 12 ++++++++++ >> 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, 76 insertions(+), 1 deletion(-) >> >>diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile >>index 13fbc0f94238..eca94246cda6 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 9a1b555e8733..daa10c2b0dd1 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 >>+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) >>@@ -40,6 +46,12 @@ endif >> CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) >> CFLAGS_REMOVE_hwprobe.o = $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS) >>+# Disable profiling and instrumentation for VDSO code >>+GCOV_PROFILE := n >>+KCOV_INSTRUMENT := n >>+KASAN_SANITIZE := n >>+UBSAN_SANITIZE := n > > >So I looked into this and it seems it is not needed. All the profilers >above only add their corresponding "clags" if the object >"is-kernel-object" (https://elixir.bootlin.com/linux/v6.14-rc6/source/scripts/Makefile.lib#L147) >which is not the case for hwprobe.c since it is not added to obj-y. Noted. Will remove it. > > >>+ >> # Force dependency >> $(obj)/vdso.o: $(obj)/vdso.so >>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 >> #include >>+#include >> .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 >> #include >>+#include >> .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 >> #include >>+#include >> .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 >> #include >>+#include >> .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 >>