This patch does a lot of cleanup in comments and formatting, but it does not change any code.
Rename save_paranoid to paranoid_entry: this makes naming similar to its "non-paranoid" sibling, error_entry, and to its counterpart, paranoid_exit. Use the same CFI annotation atop paranoid_entry and error_entry. Fix irregular indentation of assembler operands. Add/fix comments on top of paranoid_entry and error_entry. Remove stale comment about "oldrax". Make comments about "no swapgs" flag in ebx more prominent. Deindent wrongly indented top-level comment atop paranoid_exit. Indent wrongly deindented comment inside error_entry. Signed-off-by: Denys Vlasenko <[email protected]> CC: Linus Torvalds <[email protected]> CC: Oleg Nesterov <[email protected]> CC: Borislav Petkov <[email protected]> CC: "H. Peter Anvin" <[email protected]> CC: Andy Lutomirski <[email protected]> CC: Frederic Weisbecker <[email protected]> CC: X86 ML <[email protected]> CC: Alexei Starovoitov <[email protected]> CC: Will Drewry <[email protected]> CC: Kees Cook <[email protected]> CC: [email protected] --- arch/x86/kernel/entry_64.S | 68 ++++++++++++++++++++++++---------------------- 1 file changed, 36 insertions(+), 32 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 71b549a..03498d0 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -981,10 +981,11 @@ ENTRY(\sym) testl $3, CS(%rsp) /* If coming from userspace, switch */ jnz 1f /* stacks. */ .endif - call save_paranoid + call paranoid_entry .else call error_entry .endif + /* returned flag: ebx=0: need swapgs on exit, ebx=1: don't need it */ DEFAULT_FRAME 0 @@ -1015,10 +1016,11 @@ ENTRY(\sym) addq $EXCEPTION_STKSZ, INIT_TSS_IST(\shift_ist) .endif + /* these procedures expect "no swapgs" flag in ebx */ .if \paranoid - jmp paranoid_exit /* %ebx: no swapgs flag */ + jmp paranoid_exit .else - jmp error_exit /* %ebx: no swapgs flag */ + jmp error_exit .endif .if \paranoid == 1 @@ -1253,8 +1255,13 @@ idtentry async_page_fault do_async_page_fault has_error_code=1 idtentry machine_check has_error_code=0 paranoid=1 do_sym=*machine_check_vector(%rip) #endif -ENTRY(save_paranoid) - XCPT_FRAME 1 RDI+8 +/* + * Save all registers in pt_regs, and switch gs if needed. + * Use slow, but surefire "are we in kernel?" check. + * Return: ebx=0: need swapgs on exit, ebx=1: otherwise + */ +ENTRY(paranoid_entry) + XCPT_FRAME 1 15*8 cld SAVE_C_REGS 8 SAVE_EXTRA_REGS 8 @@ -1267,20 +1274,19 @@ ENTRY(save_paranoid) xorl %ebx,%ebx 1: ret CFI_ENDPROC -END(save_paranoid) - - /* - * "Paranoid" exit path from exception stack. This is invoked - * only on return from non-NMI IST interrupts that came - * from kernel space. - * - * We may be returning to very strange contexts (e.g. very early - * in syscall entry), so checking for preemption here would - * be complicated. Fortunately, we there's no good reason - * to try to handle preemption here. - */ +END(paranoid_entry) - /* ebx: no swapgs flag */ +/* + * "Paranoid" exit path from exception stack. This is invoked + * only on return from non-NMI IST interrupts that came + * from kernel space. + * + * We may be returning to very strange contexts (e.g. very early + * in syscall entry), so checking for preemption here would + * be complicated. Fortunately, we there's no good reason + * to try to handle preemption here. + */ +/* On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it) */ ENTRY(paranoid_exit) DEFAULT_FRAME DISABLE_INTERRUPTS(CLBR_NONE) @@ -1301,13 +1307,11 @@ paranoid_exit_restore: END(paranoid_exit) /* - * Exception entry point. This expects an error code/orig_rax on the stack. - * returns in "no swapgs flag" in %ebx. + * Save all registers in pt_regs, and switch gs if needed. + * Return: ebx=0: need swapgs on exit, ebx=1: otherwise */ ENTRY(error_entry) - XCPT_FRAME - CFI_ADJUST_CFA_OFFSET 15*8 - /* oldrax contains error code */ + XCPT_FRAME 1 15*8 cld SAVE_C_REGS 8 SAVE_EXTRA_REGS 8 @@ -1320,12 +1324,12 @@ error_sti: TRACE_IRQS_OFF ret -/* - * There are two places in the kernel that can potentially fault with - * usergs. Handle them here. B stepping K8s sometimes report a - * truncated RIP for IRET exceptions returning to compat mode. Check - * for these here too. - */ + /* + * There are two places in the kernel that can potentially fault with + * usergs. Handle them here. B stepping K8s sometimes report a + * truncated RIP for IRET exceptions returning to compat mode. Check + * for these here too. + */ error_kernelspace: CFI_REL_OFFSET rcx, RCX+8 incl %ebx @@ -1355,7 +1359,7 @@ error_bad_iret: END(error_entry) -/* ebx: no swapgs flag (1: don't need swapgs, 0: need it) */ +/* On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it) */ ENTRY(error_exit) DEFAULT_FRAME movl %ebx,%eax @@ -1581,13 +1585,13 @@ end_repeat_nmi: ALLOC_PT_GPREGS_ON_STACK /* - * Use save_paranoid to handle SWAPGS, but no need to use paranoid_exit + * Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit * as we should not be calling schedule in NMI context. * Even with normal interrupts enabled. An NMI should not be * setting NEED_RESCHED or anything that normal interrupts and * exceptions might do. */ - call save_paranoid + call paranoid_entry DEFAULT_FRAME 0 /* -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
