Hi Mark, Here is the test result with stackleak_erase_on_task_stack. # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT [ 53.110405] lkdtm: Performing direct entry STACKLEAK_ERASING [ 53.111630] lkdtm: stackleak stack usage: [ 53.111630] high offset: 288 bytes [ 53.111630] current: 592 bytes [ 53.111630] lowest: 1136 bytes [ 53.111630] tracked: 1136 bytes [ 53.111630] untracked: 576 bytes [ 53.111630] poisoned: 14376 bytes [ 53.111630] low offset: 8 bytes [ 53.115078] lkdtm: OK: the rest of the thread stack is properly erased On Sat, Oct 8, 2022 at 11:26 AM Guo Ren <guoren@xxxxxxxxxx> wrote: > > On Mon, Oct 3, 2022 at 7:34 PM Mark Rutland <mark.rutland@xxxxxxx> wrote: > > > > On Sat, Oct 01, 2022 at 09:24:49PM -0400, guoren@xxxxxxxxxx wrote: > > > From: Dao Lu <daolu@xxxxxxxxxxxx> > > > > > > Add support for STACKLEAK gcc plugin to riscv by implementing > > > stackleak_check_alloca, based heavily on the arm64 version, and > > > modifying the entry.S. Additionally, this disables the plugin for EFI > > > stub code for riscv. All modifications base on generic_entry. > > > > I think this commit message is stale; `stackleak_check_alloca` doesn't exist > > any more. > > > > > Link: https://lore.kernel.org/linux-riscv/20220615213834.3116135-1-daolu@xxxxxxxxxxxx/ > > > Signed-off-by: Dao Lu <daolu@xxxxxxxxxxxx> > > > Co-developed-by: Xianting Tian <xianting.tian@xxxxxxxxxxxxxxxxx> > > > Signed-off-by: Xianting Tian <xianting.tian@xxxxxxxxxxxxxxxxx> > > > Co-developed-by: Guo Ren <guoren@xxxxxxxxxx> > > > Signed-off-by: Guo Ren <guoren@xxxxxxxxxx> > > > Cc: Conor Dooley <Conor.Dooley@xxxxxxxxxxxxx> > > > Cc: Mark Rutland <mark.rutland@xxxxxxx> > > > --- > > > arch/riscv/Kconfig | 1 + > > > arch/riscv/kernel/entry.S | 8 +++++++- > > > drivers/firmware/efi/libstub/Makefile | 2 +- > > > 3 files changed, 9 insertions(+), 2 deletions(-) > > > > > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > > > index dfe600f3526c..76bde12d9f8c 100644 > > > --- a/arch/riscv/Kconfig > > > +++ b/arch/riscv/Kconfig > > > @@ -81,6 +81,7 @@ config RISCV > > > select HAVE_ARCH_MMAP_RND_BITS if MMU > > > select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT > > > select HAVE_ARCH_SECCOMP_FILTER > > > + select HAVE_ARCH_STACKLEAK > > > select HAVE_ARCH_TRACEHOOK > > > select HAVE_ARCH_TRANSPARENT_HUGEPAGE if 64BIT && MMU > > > select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE > > > diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S > > > index 5f49517cd3a2..39097c1474a0 100644 > > > --- a/arch/riscv/kernel/entry.S > > > +++ b/arch/riscv/kernel/entry.S > > > @@ -130,7 +130,6 @@ END(handle_exception) > > > ENTRY(ret_from_exception) > > > REG_L s0, PT_STATUS(sp) > > > > > > - csrc CSR_STATUS, SR_IE > > > #ifdef CONFIG_RISCV_M_MODE > > > /* the MPP value is too large to be used as an immediate arg for addi */ > > > li t0, SR_MPP > > > @@ -139,6 +138,9 @@ ENTRY(ret_from_exception) > > > andi s0, s0, SR_SPP > > > #endif > > > bnez s0, 1f > > > +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK > > > + call stackleak_erase > > > +#endif > > > > I assume this can happen on an arbitrary stack, and so you can't use the > > stackleak_erase_{on,off}_task_stack variants? > I misunderstood before. > > Yes, riscv could use stackleak_erase_on_task_stack. Because the sp has > changed to task_stack, even when irq/soft_irq. > > > > > Just to check, have you given this a spin with LKDTM and the STACKLEAK_ERASING > > test? If not, it'd be good to test that (and ideally, put some sample output > > from that into the commit message). > > > > For example, as per: > > > > https://lore.kernel.org/all/20220427173128.2603085-1-mark.rutland@xxxxxxx/ > > > > ... on arm64 this looks something like: > > > > | # uname -a > > | Linux buildroot 5.18.0-rc1-00013-g26f638ab0d7c #3 SMP PREEMPT Wed Apr 27 16:21:37 BST 2022 aarch64 GNU/Linux > > | # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT > > | lkdtm: Performing direct entry STACKLEAK_ERASING > > | lkdtm: stackleak stack usage: > > | high offset: 336 bytes > > | current: 688 bytes > > | lowest: 1232 bytes > > | tracked: 1232 bytes > > | untracked: 672 bytes > > | poisoned: 14136 bytes > > | low offset: 8 bytes > > | lkdtm: OK: the rest of the thread stack is properly erased > > > > Thanks, > > Mark. > > > > > > > > /* Save unwound kernel stack pointer in thread_info */ > > > addi s0, sp, PT_SIZE_ON_STACK > > > @@ -148,8 +150,12 @@ ENTRY(ret_from_exception) > > > * Save TP into the scratch register , so we can find the kernel data > > > * structures again. > > > */ > > > + csrc CSR_STATUS, SR_IE > > > csrw CSR_SCRATCH, tp > > > + j 2f > > > 1: > > > + csrc CSR_STATUS, SR_IE > > > +2: > > > /* > > > * The current load reservation is effectively part of the processor's > > > * state, in the sense that load reservations cannot be shared between > > > diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile > > > index d0537573501e..5e1fc4f82883 100644 > > > --- a/drivers/firmware/efi/libstub/Makefile > > > +++ b/drivers/firmware/efi/libstub/Makefile > > > @@ -25,7 +25,7 @@ cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ > > > -fno-builtin -fpic \ > > > $(call cc-option,-mno-single-pic-base) > > > cflags-$(CONFIG_RISCV) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ > > > - -fpic > > > + -fpic $(DISABLE_STACKLEAK_PLUGIN) > > > > > > cflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt > > > > > > -- > > > 2.36.1 > > > > > > > -- > Best Regards > Guo Ren -- Best Regards Guo Ren
