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]. Note the bit definitions of TDX_FEATURES0 are not auto-generated in tdx_global_metadata.h. Manually define a macro for it in "tdx.h". Link: https://lore.kernel.org/all/fc0e8ab7-86d4-4428-be31-82e1ece6dd21@xxxxxxxxx/ [1] Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx> Reviewed-by: Nikolay Borisov <nik.borisov@xxxxxxxx> Reviewed-by: Adrian Hunter <adrian.hunter@xxxxxxxxx> Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx> --- arch/x86/virt/vmx/tdx/tdx.c | 17 +++++++++++++++++ arch/x86/virt/vmx/tdx/tdx.h | 4 ++++ 2 files changed, 21 insertions(+) diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c index 9acb12c75e9b..9bc827a6cee8 100644 --- a/arch/x86/virt/vmx/tdx/tdx.c +++ b/arch/x86/virt/vmx/tdx/tdx.c @@ -326,6 +326,18 @@ static int init_tdx_sys_info(struct tdx_sys_info *sysinfo) return 0; } +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) { @@ -1109,6 +1121,11 @@ static int init_tdx_module(void) if (ret) return ret; + /* 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 0128b963b723..c8be00f6b15a 100644 --- a/arch/x86/virt/vmx/tdx/tdx.h +++ b/arch/x86/virt/vmx/tdx/tdx.h @@ -5,6 +5,7 @@ #include <linux/types.h> #include <linux/compiler_attributes.h> #include <linux/stddef.h> +#include <linux/bits.h> #include "tdx_global_metadata.h" /* @@ -54,6 +55,9 @@ struct tdmr_info { DECLARE_FLEX_ARRAY(struct tdmr_reserved_area, reserved_areas); } __packed __aligned(TDMR_INFO_ALIGNMENT); +/* Bit definitions of TDX_FEATURES0 metadata field */ +#define TDX_FEATURES0_NO_RBP_MOD BIT(18) + /* * Do not put any hardware-defined TDX structure representations below * this comment! -- 2.46.2
