Old TDX modules can clobber RBP in the TDH.VP.ENTER SEAMCALL. However RBP is used as frame pointer in the x86_64 calling convention, and clobbering RBP could result in bad things like being unable to unwind the stack if any non-maskable exceptions (NMI, #MC etc) happens in that gap. A new "NO_RBP_MOD" feature was introduced to more recent TDX modules to not clobber RBP. This feature is reported in the TDX_FEATURES0 global metadata field via bit 18. Don't initialize the TDX module if this feature is not supported [1]. Link: https://lore.kernel.org/all/c0067319-2653-4cbd-8fee-1ccf21b1e646@xxxxxxxx/T/#mef98469c51e2382ead2c537ea189752360bd2bef [1] Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx> Reviewed-by: Nikolay Borisov <nik.borisov@xxxxxxxx> --- v2 -> v3: - check_module_compatibility() -> check_features(). - Improve error message. https://lore.kernel.org/kvm/cover.1721186590.git.kai.huang@xxxxxxxxx/T/#md9e2eeef927838cbf20d7b361cdbea518b8aec50 --- arch/x86/virt/vmx/tdx/tdx.c | 17 +++++++++++++++++ arch/x86/virt/vmx/tdx/tdx.h | 3 +++ 2 files changed, 20 insertions(+) diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c index fa335ab1ae92..032a53ddf5bc 100644 --- a/arch/x86/virt/vmx/tdx/tdx.c +++ b/arch/x86/virt/vmx/tdx/tdx.c @@ -454,6 +454,18 @@ static int get_tdx_sys_info(struct tdx_sys_info *sysinfo) return get_tdx_sys_info_tdmr(&sysinfo->tdmr); } +static int check_features(struct tdx_sys_info *sysinfo) +{ + u64 tdx_features0 = sysinfo->features.tdx_features0; + + if (!(tdx_features0 & TDX_FEATURES0_NO_RBP_MOD)) { + pr_err("frame pointer (RBP) clobber bug present, upgrade TDX module\n"); + return -EINVAL; + } + + return 0; +} + /* Calculate the actual TDMR size */ static int tdmr_size_single(u16 max_reserved_per_tdmr) { @@ -1235,6 +1247,11 @@ static int init_tdx_module(void) print_basic_sys_info(&sysinfo); + /* Check whether the kernel can support this module */ + ret = check_features(&sysinfo); + if (ret) + return ret; + /* * To keep things simple, assume that all TDX-protected memory * will come from the page allocator. Make sure all pages in the diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h index e7bed9e717c7..831361e6d0fb 100644 --- a/arch/x86/virt/vmx/tdx/tdx.h +++ b/arch/x86/virt/vmx/tdx/tdx.h @@ -154,6 +154,9 @@ struct tdx_sys_info_features { u64 tdx_features0; }; +/* Architectural bit definitions of TDX_FEATURES0 metadata field */ +#define TDX_FEATURES0_NO_RBP_MOD _BITULL(18) + /* Class "TDX Module Version" */ struct tdx_sys_info_version { u16 major; -- 2.46.0
