On Fri, Aug 20, 2021 at 11:11:52AM -0700, Yu-cheng Yu wrote:
quoted hunk ↗ jump to hunk
diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h
new file mode 100644
index 000000000000..6432baf4de1f
--- /dev/null
+++ b/arch/x86/include/asm/cet.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_CET_H
+#define _ASM_X86_CET_H
+
+#ifndef __ASSEMBLY__
+#include <linux/types.h>
+
+struct task_struct;
+
+/*
+ * Per-thread CET status
+ */
That comment is superfluous and wrong now. The struct name says exactly
what that thing is.
quoted hunk ↗ jump to hunk
+static unsigned long alloc_shstk(unsigned long size)
+{
+ int flags = MAP_ANONYMOUS | MAP_PRIVATE;
+ struct mm_struct *mm = current->mm;
+ unsigned long addr, populate;
s/populate/unused/
quoted hunk ↗ jump to hunk
+
+ mmap_write_lock(mm);
+ addr = do_mmap(NULL, 0, size, PROT_READ, flags, VM_SHADOW_STACK, 0,
+ &populate, NULL);
+ mmap_write_unlock(mm);
+
+ return addr;
+}
+
+int shstk_setup(void)
+{
+ struct thread_shstk *shstk = ¤t->thread.shstk;
+ unsigned long addr, size;
+ int err;
+
+ if (!cpu_feature_enabled(X86_FEATURE_SHSTK))
+ return 0;
+
+ size = round_up(min_t(unsigned long long, rlimit(RLIMIT_STACK), SZ_4G), PAGE_SIZE);
+ addr = alloc_shstk(size);
+ if (IS_ERR_VALUE(addr))
+ return PTR_ERR((void *)addr);
+
+ start_update_msrs();
You're setting CET_U with the MSR writes below. Why do you need to do
XRSTOR here? To zero out PL[012]_SSP?
If so, you can WRMSR those too - no need for a full XRSTOR...
quoted hunk ↗ jump to hunk
+ err = wrmsrl_safe(MSR_IA32_PL3_SSP, addr + size);
+ if (!err)
+ wrmsrl_safe(MSR_IA32_U_CET, CET_SHSTK_EN);
+ end_update_msrs();
+
+ if (!err) {
+ shstk->base = addr;
+ shstk->size = size;
+ }
+
+ return err;
+}
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette