From: Roland McGrath Date: Wed, 6 Feb 2008 21:39:43 +0000 (+0100) Subject: x86: make traps on entry code be debuggable in user space, 64-bit X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=3aa4b37d3e899cfe7a9cbdcda2b277df4c1f210d;p=openwrt%2Fstaging%2Fblogic.git x86: make traps on entry code be debuggable in user space, 64-bit Unify the x86-64 behavior for 32-bit processes that set bogus %cs/%ss values (the only ones that can fault in iret) match what the native i386 behavior is. (do not kill the task via do_exit but generate a SIGSEGV signal) [ tglx@linutronix.de: build fix ] Signed-off-by: Roland McGrath Signed-off-by: Ingo Molnar --- diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index bea8474744ff..e518928114db 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -593,13 +593,22 @@ ENTRY(native_iret) .quad native_iret, bad_iret .previous .section .fixup,"ax" - /* force a signal here? this matches i386 behaviour */ - /* running with kernel gs */ bad_iret: - movq $11,%rdi /* SIGSEGV */ - TRACE_IRQS_ON - ENABLE_INTERRUPTS(CLBR_ANY | ~(CLBR_RDI)) - jmp do_exit + /* + * The iret traps when the %cs or %ss being restored is bogus. + * We've lost the original trap vector and error code. + * #GPF is the most likely one to get for an invalid selector. + * So pretend we completed the iret and took the #GPF in user mode. + * + * We are now running with the kernel GS after exception recovery. + * But error_entry expects us to have user GS to match the user %cs, + * so swap back. + */ + pushq $0 + + SWAPGS + jmp general_protection + .previous /* edi: workmask, edx: work */