The following commit has been merged into the x86/seves branch of tip: Commit-ID: 1ac0dc494a9796d6f94ff392f16e0c9a8cea7021 Gitweb: https://git.kernel.org/tip/1ac0dc494a9796d6f94ff392f16e0c9a8cea7021 Author: Martin Radev <martin.b.radev@xxxxxxxxx> AuthorDate: Mon, 07 Sep 2020 15:16:13 +02:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Wed, 09 Sep 2020 18:03:48 +02:00 x86/sev-es: Check required CPU features for SEV-ES Make sure the machine supports RDRAND, otherwise there is no trusted source of randomness in the system. To also check this in the pre-decompression stage, make has_cpuflag() not depend on CONFIG_RANDOMIZE_BASE anymore. Signed-off-by: Martin Radev <martin.b.radev@xxxxxxxxx> Signed-off-by: Joerg Roedel <jroedel@xxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20200907131613.12703-73-joro@xxxxxxxxxx --- arch/x86/boot/compressed/cpuflags.c | 4 ---- arch/x86/boot/compressed/misc.h | 5 +++-- arch/x86/boot/compressed/sev-es.c | 3 +++ arch/x86/kernel/sev-es-shared.c | 15 +++++++++++++++ arch/x86/kernel/sev-es.c | 3 +++ 5 files changed, 24 insertions(+), 6 deletions(-) diff --git a/arch/x86/boot/compressed/cpuflags.c b/arch/x86/boot/compressed/cpuflags.c index 6448a81..0cc1323 100644 --- a/arch/x86/boot/compressed/cpuflags.c +++ b/arch/x86/boot/compressed/cpuflags.c @@ -1,6 +1,4 @@ // SPDX-License-Identifier: GPL-2.0 -#ifdef CONFIG_RANDOMIZE_BASE - #include "../cpuflags.c" bool has_cpuflag(int flag) @@ -9,5 +7,3 @@ bool has_cpuflag(int flag) return test_bit(flag, cpu.flags); } - -#endif diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h index c0e0ffe..6d31f1b 100644 --- a/arch/x86/boot/compressed/misc.h +++ b/arch/x86/boot/compressed/misc.h @@ -85,8 +85,6 @@ void choose_random_location(unsigned long input, unsigned long *output, unsigned long output_size, unsigned long *virt_addr); -/* cpuflags.c */ -bool has_cpuflag(int flag); #else static inline void choose_random_location(unsigned long input, unsigned long input_size, @@ -97,6 +95,9 @@ static inline void choose_random_location(unsigned long input, } #endif +/* cpuflags.c */ +bool has_cpuflag(int flag); + #ifdef CONFIG_X86_64 extern int set_page_decrypted(unsigned long address); extern int set_page_encrypted(unsigned long address); diff --git a/arch/x86/boot/compressed/sev-es.c b/arch/x86/boot/compressed/sev-es.c index 2a6c7c3..954cb27 100644 --- a/arch/x86/boot/compressed/sev-es.c +++ b/arch/x86/boot/compressed/sev-es.c @@ -145,6 +145,9 @@ void sev_es_shutdown_ghcb(void) if (!boot_ghcb) return; + if (!sev_es_check_cpu_features()) + error("SEV-ES CPU Features missing."); + /* * GHCB Page must be flushed from the cache and mapped encrypted again. * Otherwise the running kernel will see strange cache effects when diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c index 4be8af2..5f83cca 100644 --- a/arch/x86/kernel/sev-es-shared.c +++ b/arch/x86/kernel/sev-es-shared.c @@ -9,6 +9,21 @@ * and is included directly into both code-bases. */ +#ifndef __BOOT_COMPRESSED +#define error(v) pr_err(v) +#define has_cpuflag(f) boot_cpu_has(f) +#endif + +static bool __init sev_es_check_cpu_features(void) +{ + if (!has_cpuflag(X86_FEATURE_RDRAND)) { + error("RDRAND instruction not supported - no trusted source of randomness available\n"); + return false; + } + + return true; +} + static void sev_es_terminate(unsigned int reason) { u64 val = GHCB_SEV_TERMINATE; diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c index 8cac9f8..6fcfdd3 100644 --- a/arch/x86/kernel/sev-es.c +++ b/arch/x86/kernel/sev-es.c @@ -665,6 +665,9 @@ void __init sev_es_init_vc_handling(void) if (!sev_es_active()) return; + if (!sev_es_check_cpu_features()) + panic("SEV-ES CPU Features missing"); + /* Enable SEV-ES special handling */ static_branch_enable(&sev_es_enable_key);
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