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authorSami Tolvanen <samitolvanen@google.com>2023-09-27 22:48:02 +0000
committerPalmer Dabbelt <palmer@rivosinc.com>2023-10-27 14:43:08 -0700
commitd1584d791a297aa8ed93503382a682a6ecfc4218 (patch)
tree371b56adbd1d77f436e143555ab9fb47b4ad50c0 /arch/riscv/kernel/head.S
parente609b4f4252a2ad2454736078693571b9fbff019 (diff)
downloadlwn-d1584d791a297aa8ed93503382a682a6ecfc4218.tar.gz
lwn-d1584d791a297aa8ed93503382a682a6ecfc4218.zip
riscv: Implement Shadow Call Stack
Implement CONFIG_SHADOW_CALL_STACK for RISC-V. When enabled, the compiler injects instructions to all non-leaf C functions to store the return address to the shadow stack and unconditionally load it again before returning, which makes it harder to corrupt the return address through a stack overflow, for example. The active shadow call stack pointer is stored in the gp register, which makes SCS incompatible with gp relaxation. Use --no-relax-gp to ensure gp relaxation is disabled and disable global pointer loading. Add SCS pointers to struct thread_info, implement SCS initialization, and task switching Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Tested-by: Nathan Chancellor <nathan@kernel.org> Link: https://lore.kernel.org/r/20230927224757.1154247-12-samitolvanen@google.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv/kernel/head.S')
-rw-r--r--arch/riscv/kernel/head.S4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index a0484d95d8fb..18f97ec0f7ed 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -14,6 +14,7 @@
#include <asm/cpu_ops_sbi.h>
#include <asm/hwcap.h>
#include <asm/image.h>
+#include <asm/scs.h>
#include <asm/xip_fixup.h>
#include "efi-header.S"
@@ -153,6 +154,7 @@ secondary_start_sbi:
XIP_FIXUP_OFFSET a3
add a3, a3, a1
REG_L sp, (a3)
+ scs_load_current
.Lsecondary_start_common:
@@ -289,6 +291,7 @@ clear_bss_done:
la sp, init_thread_union + THREAD_SIZE
XIP_FIXUP_OFFSET sp
addi sp, sp, -PT_SIZE_ON_STACK
+ scs_load_init_stack
#ifdef CONFIG_BUILTIN_DTB
la a0, __dtb_start
XIP_FIXUP_OFFSET a0
@@ -307,6 +310,7 @@ clear_bss_done:
la tp, init_task
la sp, init_thread_union + THREAD_SIZE
addi sp, sp, -PT_SIZE_ON_STACK
+ scs_load_current
#ifdef CONFIG_KASAN
call kasan_early_init