On arm64 and x86 the kernel can control if there is write access to the shadow stack via specific instructions defined for the purpose, useful for things like userspace threading at the expense of some security. Add a flag to allow this to be selected when changing the shadow stack status.
On arm64 the kernel can separately control if userspace is able to pop and push values directly onto the shadow stack via GCS push and pop instructions, supporting many scenarios where userspace needs to write to the stack with less security exposure than full write access. Add a flag to allow this to be selected when changing the shadow stack status.
Signed-off-by: Mark Brown broonie@kernel.org --- include/uapi/linux/prctl.h | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 9fdc77fa2bfe..e88d2ddcdb2d 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -321,5 +321,7 @@ struct prctl_mm_map { #define PR_SET_SHADOW_STACK_STATUS 72 # define PR_SHADOW_STACK_LOCK (1UL << 0) # define PR_SHADOW_STACK_ENABLE (1UL << 1) +# define PR_SHADOW_STACK_WRITE (1UL << 2) +# define PR_SHADOW_STACK_PUSH (1UL << 3)
#endif /* _LINUX_PRCTL_H */