[PATCH V6 09/11] riscv: Add support for STACKLEAK gcc plugin

[guoren]

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.

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
 
 	/* 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