[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] x86/traps: Implement #CP handler and extend #PF for shadow stacks
commit 5ad05b9c249060fb0f8e8afb9215b08f04579f17 Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> AuthorDate: Fri Feb 21 17:56:57 2020 +0000 Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> CommitDate: Fri May 29 23:09:46 2020 +0100 x86/traps: Implement #CP handler and extend #PF for shadow stacks For now, any #CP exception or shadow stack #PF indicate a bug in Xen, but attempt to recover from #CP if taken in guest context. This will of course have to change as part of introducing CET-SS support for PV guests. Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx> --- xen/arch/x86/traps.c | 46 ++++++++++++++++++++++++++++++++++++++++- xen/arch/x86/x86_64/entry.S | 7 ++++++- xen/include/asm-x86/processor.h | 2 ++ 3 files changed, 53 insertions(+), 2 deletions(-) diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c index eeb3e146ef..7477bd93cc 100644 --- a/xen/arch/x86/traps.c +++ b/xen/arch/x86/traps.c @@ -156,7 +156,9 @@ void (* const exception_table[TRAP_nr])(struct cpu_user_regs *regs) = { [TRAP_alignment_check] = do_trap, [TRAP_machine_check] = (void *)do_machine_check, [TRAP_simd_error] = do_trap, - [TRAP_virtualisation ... + [TRAP_virtualisation] = do_reserved_trap, + [X86_EXC_CP] = do_entry_CP, + [X86_EXC_CP + 1 ... (ARRAY_SIZE(exception_table) - 1)] = do_reserved_trap, }; @@ -1431,6 +1433,10 @@ void do_page_fault(struct cpu_user_regs *regs) perfc_incr(page_faults); + /* Any shadow stack access fault is a bug in Xen. */ + if ( error_code & PFEC_shstk ) + goto fatal; + if ( unlikely(fixup_page_fault(addr, regs) != 0) ) return; @@ -1898,6 +1904,43 @@ void do_debug(struct cpu_user_regs *regs) pv_inject_hw_exception(TRAP_debug, X86_EVENT_NO_EC); } +void do_entry_CP(struct cpu_user_regs *regs) +{ + static const char errors[][10] = { + [1] = "near ret", + [2] = "far/iret", + [3] = "endbranch", + [4] = "rstorssp", + [5] = "setssbsy", + }; + const char *err = "??"; + unsigned int ec = regs->error_code; + + if ( debugger_trap_entry(TRAP_debug, regs) ) + return; + + /* Decode ec if possible */ + if ( ec < ARRAY_SIZE(errors) && errors[ec][0] ) + err = errors[ec]; + + /* + * For now, only supervisors shadow stacks should be active. A #CP from + * guest context is probably a Xen bug, but kill the guest in an attempt + * to recover. + */ + if ( guest_mode(regs) ) + { + gprintk(XENLOG_ERR, "Hit #CP[%04x] in guest context %04x:%p\n", + ec, regs->cs, _p(regs->rip)); + ASSERT_UNREACHABLE(); + domain_crash(current->domain); + return; + } + + show_execution_state(regs); + panic("CONTROL-FLOW PROTECTION FAULT: #CP[%04x] %s\n", ec, err); +} + static void __init noinline __set_intr_gate(unsigned int n, uint32_t dpl, void *addr) { @@ -1987,6 +2030,7 @@ void __init init_idt_traps(void) set_intr_gate(TRAP_alignment_check,&alignment_check); set_intr_gate(TRAP_machine_check,&machine_check); set_intr_gate(TRAP_simd_error,&simd_coprocessor_error); + set_intr_gate(X86_EXC_CP, entry_CP); /* Specify dedicated interrupt stacks for NMI, #DF, and #MC. */ enable_each_ist(idt_table); diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S index d55453f3f3..f7ee3dce91 100644 --- a/xen/arch/x86/x86_64/entry.S +++ b/xen/arch/x86/x86_64/entry.S @@ -795,6 +795,10 @@ ENTRY(alignment_check) movl $TRAP_alignment_check,4(%rsp) jmp handle_exception +ENTRY(entry_CP) + movl $X86_EXC_CP, 4(%rsp) + jmp handle_exception + ENTRY(double_fault) movl $TRAP_double_fault,4(%rsp) /* Set AC to reduce chance of further SMAP faults */ @@ -940,7 +944,8 @@ autogen_stubs: /* Automatically generated stubs. */ entrypoint 1b /* Reserved exceptions, heading towards do_reserved_trap(). */ - .elseif vec == TRAP_copro_seg || vec == TRAP_spurious_int || (vec > TRAP_simd_error && vec < TRAP_nr) + .elseif vec == X86_EXC_CSO || vec == X86_EXC_SPV || \ + vec == X86_EXC_VE || (vec > X86_EXC_CP && vec < TRAP_nr) 1: test $8,%spl /* 64bit exception frames are 16 byte aligned, but the word */ jz 2f /* size is 8 bytes. Check whether the processor gave us an */ diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h index a3d72b26ef..73354b10d2 100644 --- a/xen/include/asm-x86/processor.h +++ b/xen/include/asm-x86/processor.h @@ -68,6 +68,7 @@ #define PFEC_reserved_bit (_AC(1,U) << 3) #define PFEC_insn_fetch (_AC(1,U) << 4) #define PFEC_prot_key (_AC(1,U) << 5) +#define PFEC_shstk (_AC(1,U) << 6) #define PFEC_arch_mask (_AC(0xffff,U)) /* Architectural PFEC values. */ /* Internally used only flags. */ #define PFEC_page_paged (1U<<16) @@ -535,6 +536,7 @@ DECLARE_TRAP_HANDLER(coprocessor_error); DECLARE_TRAP_HANDLER(simd_coprocessor_error); DECLARE_TRAP_HANDLER_CONST(machine_check); DECLARE_TRAP_HANDLER(alignment_check); +DECLARE_TRAP_HANDLER(entry_CP); DECLARE_TRAP_HANDLER(entry_int82); -- generated by git-patchbot for /home/xen/git/xen.git#staging
|
![]() |
Lists.xenproject.org is hosted with RackSpace, monitoring our |