From: Brijesh Singh <brijesh.singh@amd.com>
To: <x86@kernel.org>, <linux-kernel@vger.kernel.org>,
<kvm@vger.kernel.org>, <linux-efi@vger.kernel.org>,
<platform-driver-x86@vger.kernel.org>,
<linux-coco@lists.linux.dev>, <linux-mm@kvack.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
Tom Lendacky <thomas.lendacky@amd.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Ard Biesheuvel <ardb@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
"Vitaly Kuznetsov" <vkuznets@redhat.com>,
Jim Mattson <jmattson@google.com>,
"Andy Lutomirski" <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
"Peter Zijlstra" <peterz@infradead.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
David Rientjes <rientjes@google.com>,
Dov Murik <dovmurik@linux.ibm.com>,
Tobin Feldman-Fitzthum <tobin@ibm.com>,
Borislav Petkov <bp@alien8.de>,
Michael Roth <michael.roth@amd.com>,
Vlastimil Babka <vbabka@suse.cz>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Andi Kleen <ak@linux.intel.com>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
<tony.luck@intel.com>, <marcorr@google.com>,
<sathyanarayanan.kuppuswamy@linux.intel.com>,
Brijesh Singh <brijesh.singh@amd.com>
Subject: [PATCH v6 25/42] x86/head: re-enable stack protection for 32/64-bit builds
Date: Fri, 8 Oct 2021 13:04:36 -0500 [thread overview]
Message-ID: <20211008180453.462291-26-brijesh.singh@amd.com> (raw)
In-Reply-To: <20211008180453.462291-1-brijesh.singh@amd.com>
From: Michael Roth <michael.roth@amd.com>
As of commit 103a4908ad4d ("x86/head/64: Disable stack protection for
head$(BITS).o") kernel/head64.c is compiled with -fno-stack-protector
to allow a call to set_bringup_idt_handler(), which would otherwise
have stack protection enabled with CONFIG_STACKPROTECTOR_STRONG. While
sufficient for that case, there may still be issues with calls to any
external functions that were compiled with stack protection enabled that
in-turn make stack-protected calls, or if the exception handlers set up
by set_bringup_idt_handler() make calls to stack-protected functions.
As part of 103a4908ad4d, stack protection was also disabled for
kernel/head32.c as a precaution.
Subsequent patches for SEV-SNP CPUID validation support will introduce
both such cases. Attempting to disable stack protection for everything
in scope to address that is prohibitive since much of the code, like
SEV-ES #VC handler, is shared code that remains in use after boot and
could benefit from having stack protection enabled. Attempting to inline
calls is brittle and can quickly balloon out to library/helper code
where that's not really an option.
Instead, re-enable stack protection for head32.c/head64.c and make the
appropriate changes to ensure the segment used for the stack canary is
initialized in advance of any stack-protected C calls.
for head64.c:
- The BSP will enter from startup_64 and call into C code
(startup_64_setup_env) shortly after setting up the stack, which may
result in calls to stack-protected code. Set up %gs early to allow
for this safely.
- APs will enter from secondary_startup_64*, and %gs will be set up
soon after. There is one call to C code prior to this
(__startup_secondary_64), but it is only to fetch sme_me_mask, and
unlikely to be stack-protected, so leave things as they are, but add
a note about this in case things change in the future.
for head32.c:
- BSPs/APs will set %fs to __BOOT_DS prior to any C calls. In recent
kernels, the compiler is configured to access the stack canary at
%fs:__stack_chk_guard, which overlaps with the initial per-cpu
__stack_chk_guard variable in the initial/'master' .data..percpu
area. This is sufficient to allow access to the canary for use
during initial startup, so no changes are needed there.
Suggested-by: Joerg Roedel <jroedel@suse.de> #for 64-bit %gs set up
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/kernel/Makefile | 1 -
arch/x86/kernel/head_64.S | 24 ++++++++++++++++++++++++
2 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 2ff3e600f426..4df8c8f7d2ac 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -48,7 +48,6 @@ endif
# non-deterministic coverage.
KCOV_INSTRUMENT := n
-CFLAGS_head$(BITS).o += -fno-stack-protector
CFLAGS_cc_platform.o += -fno-stack-protector
CFLAGS_irq.o := -I $(srctree)/$(src)/../include/asm/trace
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index d8b3ebd2bb85..7074ebf2b47b 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -65,6 +65,22 @@ SYM_CODE_START_NOALIGN(startup_64)
leaq (__end_init_task - FRAME_SIZE)(%rip), %rsp
leaq _text(%rip), %rdi
+
+ /*
+ * initial_gs points to initial fixed_per_cpu struct with storage for
+ * the stack protector canary. Global pointer fixups are needed at this
+ * stage, so apply them as is done in fixup_pointer(), and initialize %gs
+ * such that the canary can be accessed at %gs:40 for subsequent C calls.
+ */
+ movl $MSR_GS_BASE, %ecx
+ movq initial_gs(%rip), %rax
+ movq $_text, %rdx
+ subq %rdx, %rax
+ addq %rdi, %rax
+ movq %rax, %rdx
+ shrq $32, %rdx
+ wrmsr
+
pushq %rsi
call startup_64_setup_env
popq %rsi
@@ -133,6 +149,14 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
* added to the initial pgdir entry that will be programmed into CR3.
*/
pushq %rsi
+ /*
+ * NOTE: %gs at this point is a stale data segment left over from the
+ * real-mode trampoline, so the default stack protector canary location
+ * at %gs:40 does not yet coincide with the expected fixed_per_cpu struct
+ * that contains storage for the stack canary. So take care not to add
+ * anything to the C functions in this path that would result in stack
+ * protected C code being generated.
+ */
call __startup_secondary_64
popq %rsi
--
2.25.1
next prev parent reply other threads:[~2021-10-08 18:06 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-08 18:04 [PATCH v6 00/42] Add AMD Secure Nested Paging (SEV-SNP) Guest Support Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 01/42] x86/mm: Extend cc_attr to include AMD SEV-SNP Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 02/42] x86/sev: Shorten GHCB terminate macro names Brijesh Singh
2021-10-11 13:15 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 03/42] x86/sev: Get rid of excessive use of defines Brijesh Singh
2021-10-11 8:48 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 04/42] x86/head64: Carve out the guest encryption postprocessing into a helper Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 05/42] x86/sev: Define the Linux specific guest termination reasons Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 06/42] x86/sev: Save the negotiated GHCB version Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 07/42] x86/sev: Add support for hypervisor feature VMGEXIT Brijesh Singh
2021-10-13 14:02 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 08/42] x86/sev-es: initialize sev_status/features within #VC handler Brijesh Singh
2021-10-18 14:29 ` Borislav Petkov
2021-10-18 18:40 ` Michael Roth
2021-10-18 19:18 ` Borislav Petkov
2021-10-20 16:10 ` Michael Roth
2021-10-20 18:01 ` Borislav Petkov
2021-10-21 0:35 ` Michael Roth
2021-10-21 14:28 ` Borislav Petkov
2021-10-20 18:08 ` Borislav Petkov
2021-10-21 2:05 ` Michael Roth
2021-10-21 14:39 ` Borislav Petkov
2021-10-21 23:00 ` Michael Roth
2021-10-21 14:48 ` Borislav Petkov
2021-10-21 15:56 ` Dr. David Alan Gilbert
2021-10-21 16:55 ` Borislav Petkov
2021-10-21 17:12 ` Dr. David Alan Gilbert
2021-10-21 17:37 ` Borislav Petkov
2021-10-21 17:47 ` Dr. David Alan Gilbert
2021-10-21 18:46 ` Borislav Petkov
2021-10-21 21:34 ` Michael Roth
2021-10-21 14:51 ` Borislav Petkov
2021-10-21 20:41 ` Michael Roth
2021-10-25 11:04 ` Borislav Petkov
2021-10-25 16:35 ` Michael Roth
2021-10-27 11:17 ` Borislav Petkov
2021-10-27 15:13 ` Michael Roth
2021-10-08 18:04 ` [PATCH v6 09/42] x86/sev: Check SEV-SNP features support Brijesh Singh
2021-10-19 14:47 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 10/42] x86/sev: Add a helper for the PVALIDATE instruction Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 11/42] x86/sev: Check the vmpl level Brijesh Singh
2021-10-28 15:07 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 12/42] x86/compressed: Add helper for validating pages in the decompression stage Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 13/42] x86/compressed: Register GHCB memory when SEV-SNP is active Brijesh Singh
2021-11-02 16:33 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 14/42] x86/sev: " Brijesh Singh
2021-11-02 16:53 ` Borislav Petkov
2021-11-02 18:24 ` Brijesh Singh
2021-11-02 18:44 ` Borislav Petkov
2021-11-03 20:10 ` Brijesh Singh
2021-11-04 13:58 ` Borislav Petkov
2021-11-04 15:26 ` Brijesh Singh
2021-11-04 16:03 ` Boris Petkov
2021-10-08 18:04 ` [PATCH v6 15/42] x86/sev: Remove do_early_exception() forward declarations Brijesh Singh
2021-11-02 16:54 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 16/42] x86/sev: Add helper for validating pages in early enc attribute changes Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 17/42] x86/kernel: Make the bss.decrypted section shared in RMP table Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 18/42] x86/kernel: Validate rom memory before accessing when SEV-SNP is active Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 19/42] x86/mm: Add support to validate memory when changing C-bit Brijesh Singh
2021-11-09 19:34 ` Borislav Petkov
2021-11-10 14:21 ` Brijesh Singh
2021-11-10 18:43 ` Borislav Petkov
2021-11-11 14:49 ` Tom Lendacky
2021-11-11 16:01 ` Borislav Petkov
2021-10-08 18:04 ` [PATCH v6 20/42] KVM: SVM: Define sev_features and vmpl field in the VMSA Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 21/42] KVM: SVM: Create a separate mapping for the SEV-ES save area Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 22/42] KVM: SVM: Create a separate mapping for the GHCB " Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 23/42] KVM: SVM: Update the SEV-ES save area mapping Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 24/42] x86/sev: Use SEV-SNP AP creation to start secondary CPUs Brijesh Singh
2021-10-08 18:04 ` Brijesh Singh [this message]
2021-10-08 18:04 ` [PATCH v6 26/42] x86/sev: move MSR-based VMGEXITs for CPUID to helper Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 27/42] KVM: x86: move lookup of indexed CPUID leafs " Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 28/42] x86/compressed/acpi: move EFI system table lookup " Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 29/42] x86/compressed/acpi: move EFI config " Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 30/42] x86/compressed/acpi: move EFI vendor " Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 31/42] x86/boot: Add Confidential Computing type to setup_data Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 32/42] x86/compressed/64: add support for SEV-SNP CPUID table in #VC handlers Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 33/42] boot/compressed/64: use firmware-validated CPUID for SEV-SNP guests Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 34/42] x86/boot: add a pointer to Confidential Computing blob in bootparams Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 35/42] x86/compressed/64: store Confidential Computing blob address " Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 36/42] x86/compressed/64: add identity mapping for Confidential Computing blob Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 37/42] x86/sev: use firmware-validated CPUID for SEV-SNP guests Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 38/42] x86/sev: Provide support for SNP guest request NAEs Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 39/42] x86/sev: Register SNP guest request platform device Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 40/42] virt: Add SEV-SNP guest driver Brijesh Singh
2021-10-10 17:51 ` Dov Murik
2021-10-13 11:37 ` Brijesh Singh
2021-10-20 21:33 ` Peter Gonda
2021-10-27 16:07 ` Brijesh Singh
2021-10-27 20:10 ` Peter Gonda
2021-10-27 20:47 ` Brijesh Singh
2021-10-27 21:05 ` Peter Gonda
2021-10-27 21:12 ` Brijesh Singh
2021-10-27 21:15 ` Peter Gonda
2021-10-08 18:04 ` [PATCH v6 41/42] virt: sevguest: Add support to derive key Brijesh Singh
2021-10-08 18:04 ` [PATCH v6 42/42] virt: sevguest: Add support to get extended report Brijesh Singh
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