[PATCH v8 11/14] x86/vsyscall/64: Fixup shadow stack and branch tracking for vsyscall
From: Yu-cheng Yu <hidden>
Date: 2019-08-13 21:04:19
Also in:
linux-arch, linux-doc, linux-mm, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit), x86 entry code · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski
When emulating a RET, also unwind the task's shadow stack and cancel the current branch tracking status. Signed-off-by: Yu-cheng Yu <redacted> --- arch/x86/entry/vsyscall/vsyscall_64.c | 29 ++++++++++++++++++++++++ arch/x86/entry/vsyscall/vsyscall_trace.h | 1 + 2 files changed, 30 insertions(+)
diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index e7c596dea947..27ff81f75c82 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c@@ -38,6 +38,9 @@ #include <asm/fixmap.h> #include <asm/traps.h> #include <asm/paravirt.h> +#include <asm/fpu/xstate.h> +#include <asm/fpu/types.h> +#include <asm/fpu/internal.h> #define CREATE_TRACE_POINTS #include "vsyscall_trace.h"
@@ -286,6 +289,32 @@ bool emulate_vsyscall(unsigned long error_code, /* Emulate a ret instruction. */ regs->ip = caller; regs->sp += 8; + + /* Unwind shadow stack. */ + +#ifdef CONFIG_X86_INTEL_SHADOW_STACK_USER + if (current->thread.cet.shstk_enabled) { + u64 r; + + modify_fpu_regs_begin(); + rdmsrl(MSR_IA32_PL3_SSP, r); + wrmsrl(MSR_IA32_PL3_SSP, r + 8); + modify_fpu_regs_end(); + } +#endif + + /* Fixup branch tracking */ +#ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER + if (current->thread.cet.ibt_enabled) { + u64 r; + + modify_fpu_regs_begin(); + rdmsrl(MSR_IA32_U_CET, r); + wrmsrl(MSR_IA32_U_CET, r & ~MSR_IA32_CET_WAIT_ENDBR); + modify_fpu_regs_end(); + } +#endif + return true; sigsegv:
diff --git a/arch/x86/entry/vsyscall/vsyscall_trace.h b/arch/x86/entry/vsyscall/vsyscall_trace.h
index 3c3f9765a85c..7aa2101ada44 100644
--- a/arch/x86/entry/vsyscall/vsyscall_trace.h
+++ b/arch/x86/entry/vsyscall/vsyscall_trace.h@@ -25,6 +25,7 @@ TRACE_EVENT(emulate_vsyscall, #endif #undef TRACE_INCLUDE_PATH +#undef TRACE_INCLUDE_FILE #define TRACE_INCLUDE_PATH ../../arch/x86/entry/vsyscall/ #define TRACE_INCLUDE_FILE vsyscall_trace #include <trace/define_trace.h>
--
2.17.1