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>,
<brijesh.ksingh@gmail.com>, <tony.luck@intel.com>,
<marcorr@google.com>,
<sathyanarayanan.kuppuswamy@linux.intel.com>,
Brijesh Singh <brijesh.singh@amd.com>
Subject: [PATCH v10 23/45] x86/head/64: Re-enable stack protection
Date: Wed, 9 Feb 2022 12:10:17 -0600 [thread overview]
Message-ID: <20220209181039.1262882-24-brijesh.singh@amd.com> (raw)
In-Reply-To: <20220209181039.1262882-1-brijesh.singh@amd.com>
From: Michael Roth <michael.roth@amd.com>
Due to commit 103a4908ad4d ("x86/head/64: Disable stack protection for
head$(BITS).o"), kernel/head{32,64}.c are 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.
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 %gs being setup
(__startup_secondary_64()), but it is only to fetch 'sme_me_mask'
global, so just load 'sme_me_mask' directly instead, and remove the
now-unused __startup_secondary_64() function.
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 [1], 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.
[1] commit 3fb0fdb3bbe7 ("x86/stackprotector/32: Make the canary into a regular percpu variable")
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/include/asm/setup.h | 1 -
arch/x86/kernel/Makefile | 1 -
arch/x86/kernel/head64.c | 9 ---------
arch/x86/kernel/head_64.S | 24 +++++++++++++++++++++---
4 files changed, 21 insertions(+), 14 deletions(-)
diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index a12458a7a8d4..72ede9159951 100644
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -49,7 +49,6 @@ extern unsigned long saved_video_mode;
extern void reserve_standard_io_resources(void);
extern void i386_reserve_resources(void);
extern unsigned long __startup_64(unsigned long physaddr, struct boot_params *bp);
-extern unsigned long __startup_secondary_64(void);
extern void startup_64_setup_env(unsigned long physbase);
extern void early_setup_idt(void);
extern void __init do_early_exception(struct pt_regs *regs, int trapnr);
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 6aef9ee28a39..bd45e5ee6fe3 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/head64.c b/arch/x86/kernel/head64.c
index 4a24b121a2ba..e94e32ba9636 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -318,15 +318,6 @@ unsigned long __head __startup_64(unsigned long physaddr,
return sme_postprocess_startup(bp, pmd);
}
-unsigned long __startup_secondary_64(void)
-{
- /*
- * Return the SME encryption mask (if SME is active) to be used as a
- * modifier for the initial pgdir entry programmed into CR3.
- */
- return sme_get_me_mask();
-}
-
/* Wipe all early page tables except for the kernel symbol map */
static void __init reset_early_page_tables(void)
{
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 9c2c3aff5ee4..9e84263bcb94 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_percpu_data 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
@@ -145,9 +161,11 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
* Retrieve the modifier (SME encryption mask if SME is active) to be
* added to the initial pgdir entry that will be programmed into CR3.
*/
- pushq %rsi
- call __startup_secondary_64
- popq %rsi
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+ movq sme_me_mask, %rax
+#else
+ xorq %rax, %rax
+#endif
/* Form the CR3 value being sure to include the CR3 modifier */
addq $(init_top_pgt - __START_KERNEL_map), %rax
--
2.25.1
next prev parent reply other threads:[~2022-02-09 18:12 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-09 18:09 [PATCH v10 00/45] Add AMD Secure Nested Paging (SEV-SNP) Guest Support Brijesh Singh
2022-02-09 18:09 ` [PATCH v10 01/45] KVM: SVM: Define sev_features and vmpl field in the VMSA Brijesh Singh
2022-02-09 18:09 ` [PATCH v10 02/45] KVM: SVM: Create a separate mapping for the SEV-ES save area Brijesh Singh
2022-02-09 18:09 ` [PATCH v10 03/45] KVM: SVM: Create a separate mapping for the GHCB " Brijesh Singh
2022-02-09 18:09 ` [PATCH v10 04/45] KVM: SVM: Update the SEV-ES save area mapping Brijesh Singh
2022-02-09 18:09 ` [PATCH v10 05/45] x86/boot: Introduce helpers for MSR reads/writes Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 06/45] x86/boot: Use MSR read/write helpers instead of inline assembly Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 07/45] x86/compressed/64: Detect/setup SEV/SME features earlier in boot Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 08/45] x86/sev: " Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 09/45] x86/mm: Extend cc_attr to include AMD SEV-SNP Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 10/45] x86/sev: Define the Linux specific guest termination reasons Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 11/45] x86/sev: Save the negotiated GHCB version Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 12/45] x86/sev: Check SEV-SNP features support Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 13/45] x86/sev: Add a helper for the PVALIDATE instruction Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 14/45] x86/sev: Check the vmpl level Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 15/45] x86/compressed: Add helper for validating pages in the decompression stage Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 16/45] x86/compressed: Register GHCB memory when SEV-SNP is active Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 17/45] x86/sev: " Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 18/45] x86/sev: Add helper for validating pages in early enc attribute changes Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 19/45] x86/kernel: Make the .bss..decrypted section shared in RMP table Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 20/45] x86/kernel: Validate ROM memory before accessing when SEV-SNP is active Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 21/45] x86/mm: Add support to validate memory when changing C-bit Brijesh Singh
2022-02-10 16:48 ` Borislav Petkov
2022-02-11 14:55 ` Borislav Petkov
2022-02-11 17:27 ` Brijesh Singh
2022-02-13 12:15 ` Borislav Petkov
2022-02-13 14:50 ` Tom Lendacky
2022-02-13 17:21 ` Borislav Petkov
2022-02-15 12:43 ` Kirill A. Shutemov
2022-02-15 12:54 ` Borislav Petkov
2022-02-15 13:15 ` Kirill A. Shutemov
2022-02-15 14:41 ` Borislav Petkov
2022-02-16 13:32 ` Borislav Petkov
2022-02-09 18:10 ` [PATCH v10 22/45] x86/sev: Use SEV-SNP AP creation to start secondary CPUs Brijesh Singh
2022-02-09 18:10 ` Brijesh Singh [this message]
2022-02-09 18:10 ` [PATCH v10 24/45] x86/compressed/acpi: Move EFI detection to helper Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 25/45] x86/compressed/acpi: Move EFI system table lookup " Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 26/45] x86/compressed/acpi: Move EFI config " Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 27/45] x86/compressed/acpi: Move EFI vendor " Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 28/45] x86/compressed/acpi: Move EFI kexec handling into common code Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 29/45] x86/boot: Add Confidential Computing type to setup_data Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 30/45] KVM: x86: Move lookup of indexed CPUID leafs to helper Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 31/45] x86/sev: Move MSR-based VMGEXITs for CPUID " Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 32/45] x86/compressed/64: Add support for SEV-SNP CPUID table in #VC handlers Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 33/45] x86/boot: Add a pointer to Confidential Computing blob in bootparams Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 34/45] x86/compressed: Add SEV-SNP feature detection/setup Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 35/45] x86/compressed: Use firmware-validated CPUID leaves for SEV-SNP guests Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 36/45] x86/compressed: Export and rename add_identity_map() Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 37/45] x86/compressed/64: Add identity mapping for Confidential Computing blob Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 38/45] x86/sev: Add SEV-SNP feature detection/setup Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 39/45] x86/sev: Use firmware-validated CPUID for SEV-SNP guests Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 40/45] x86/sev: Provide support for SNP guest request NAEs Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 41/45] x86/sev: Register SEV-SNP guest request platform device Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 42/45] virt: Add SEV-SNP guest driver Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 43/45] virt: sevguest: Add support to derive key Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 44/45] virt: sevguest: Add support to get extended report Brijesh Singh
2022-02-09 18:10 ` [PATCH v10 45/45] virt: sevguest: Add documentation for SEV-SNP CPUID Enforcement Brijesh Singh
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