From 84064d11a40a6d6b55de8a97049042fc6d67dbb3 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Thu, 12 Nov 2015 17:01:53 +0100 Subject: [PATCH] x86/traps: honor EXT bit in error codes The specification does not explicitly limit the use of this bit to exceptions that can have selector style error codes, so to be on the safe side we should deal with it being set even on error codes formally documented to be always zero (if they're indeed always zero, the change is simply dead code in those cases). Introduce and use (where suitable) X86_XEC_* constants to make the code easier to read. To match the placement of the "hardware_trap" label, the "hardware_gp" one gets moved slightly too. Signed-off-by: Jan Beulich Reviewed-by: Andrew Cooper --- xen/arch/x86/traps.c | 18 ++++++++++++------ xen/arch/x86/x86_64/entry.S | 2 +- xen/include/asm-x86/processor.h | 5 +++++ 3 files changed, 18 insertions(+), 7 deletions(-) diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c index b32f6960a2..e21fb784f2 100644 --- a/xen/arch/x86/traps.c +++ b/xen/arch/x86/traps.c @@ -615,6 +615,9 @@ static void do_trap(struct cpu_user_regs *regs, int use_error_code) unsigned int trapnr = regs->entry_vector; unsigned long fixup; + if ( regs->error_code & X86_XEC_EXT ) + goto hardware_trap; + DEBUGGER_trap_entry(trapnr, regs); if ( guest_mode(regs) ) @@ -641,6 +644,7 @@ static void do_trap(struct cpu_user_regs *regs, int use_error_code) return; } + hardware_trap: DEBUGGER_trap_fatal(trapnr, regs); show_execution_state(regs); @@ -1262,13 +1266,14 @@ static int handle_gdt_ldt_mapping_fault( tb = propagate_page_fault(curr->arch.pv_vcpu.ldt_base + offset, regs->error_code); if ( tb ) - tb->error_code = ((u16)offset & ~3) | 4; + tb->error_code = (offset & ~(X86_XEC_EXT | X86_XEC_IDT)) | + X86_XEC_TI; } } else { /* GDT fault: handle the fault as #GP(selector). */ - regs->error_code = (u16)offset & ~7; + regs->error_code = offset & ~(X86_XEC_EXT | X86_XEC_IDT | X86_XEC_TI); (void)do_general_protection(regs); } @@ -3221,7 +3226,7 @@ void do_general_protection(struct cpu_user_regs *regs) DEBUGGER_trap_entry(TRAP_gp_fault, regs); - if ( regs->error_code & 1 ) + if ( regs->error_code & X86_XEC_EXT ) goto hardware_gp; if ( !guest_mode(regs) ) @@ -3240,14 +3245,15 @@ void do_general_protection(struct cpu_user_regs *regs) * * Instead, a GPF occurs with the faulting IDT vector in the error code. * Bit 1 is set to indicate that an IDT entry caused the fault. Bit 0 is - * clear to indicate that it's a software fault, not hardware. + * clear (which got already checked above) to indicate that it's a software + * fault, not a hardware one. * * NOTE: Vectors 3 and 4 are dealt with from their own handler. This is * okay because they can only be triggered by an explicit DPL-checked * instruction. The DPL specified by the guest OS for these vectors is NOT * CHECKED!! */ - if ( (regs->error_code & 3) == 2 ) + if ( regs->error_code & X86_XEC_IDT ) { /* This fault must be due to instruction. */ const struct trap_info *ti; @@ -3289,9 +3295,9 @@ void do_general_protection(struct cpu_user_regs *regs) return; } + hardware_gp: DEBUGGER_trap_fatal(TRAP_gp_fault, regs); - hardware_gp: show_execution_state(regs); panic("GENERAL PROTECTION FAULT\n[error_code=%04x]", regs->error_code); } diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S index d4dd8e8114..94a54aa7f2 100644 --- a/xen/arch/x86/x86_64/entry.S +++ b/xen/arch/x86/x86_64/entry.S @@ -338,7 +338,7 @@ int80_slow_path: * Setup entry vector and error code as if this was a GPF caused by an * IDT entry with DPL==0. */ - movl $((0x80 << 3) | 0x2),UREGS_error_code(%rsp) + movl $((0x80 << 3) | X86_XEC_IDT),UREGS_error_code(%rsp) SAVE_PRESERVED movl $TRAP_gp_fault,UREGS_entry_vector(%rsp) /* A GPF wouldn't have incremented the instruction pointer. */ diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h index fcfa7ddc5d..a40c18ee0a 100644 --- a/xen/include/asm-x86/processor.h +++ b/xen/include/asm-x86/processor.h @@ -143,6 +143,11 @@ #define PFEC_page_paged (1U<<5) #define PFEC_page_shared (1U<<6) +/* Other exception error code values. */ +#define X86_XEC_EXT (_AC(1,U) << 0) +#define X86_XEC_IDT (_AC(1,U) << 1) +#define X86_XEC_TI (_AC(1,U) << 2) + #define XEN_MINIMAL_CR4 (X86_CR4_PGE | X86_CR4_PAE) #define XEN_SYSCALL_MASK (X86_EFLAGS_AC|X86_EFLAGS_VM|X86_EFLAGS_RF| \ -- 2.39.5