Date: Thu, 14 Jan 2016 16:23:07 +0000 (UTC) From: Warner Losh <imp@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r294011 - head/share/man/man4 Message-ID: <201601141623.u0EGN7me063431@repo.freebsd.org>
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Author: imp Date: Thu Jan 14 16:23:07 2016 New Revision: 294011 URL: https://svnweb.freebsd.org/changeset/base/294011 Log: Document how to enter the debugger here. I'm sure there's some better canonical place, and the nit-pickers are welcome to move this information there with a cross reference. Differential Review: https://reviews.freebsd.org/D4860 Modified: head/share/man/man4/ddb.4 Modified: head/share/man/man4/ddb.4 ============================================================================== --- head/share/man/man4/ddb.4 Thu Jan 14 16:21:58 2016 (r294010) +++ head/share/man/man4/ddb.4 Thu Jan 14 16:23:07 2016 (r294011) @@ -1435,6 +1435,47 @@ The NMI allows one to break into the deb diagnose problems. Other bus' bridge chipsets may be able to generate NMI using bus specific methods. +There are many PCI and PCIe add-in cards which can generate NMI for +debugging. +Modern systems typically use IMPI to generate signals to enter the +debugger. +The +.Dv devel/ipmitool +port can be used to send the +.Cd chassis power diag +command which delivers an NMI to the processor. +.Pp +For serial consoles, you can break to the debugger by sending a BREAK +condition on the serial line if +.Cd options BREAK_TO_DEBUGGER +is specified in the kernel. +Most terminal emulation programs can send a break sequence with a +special key sequence or via a menu item. +However, in some setups, sending the break can be difficult to arrange +or happens spuriously, so if the kernel contains +.Cd options ALT_BREAK_TO_DEBUGGER +then the sequence of CR TILDE CTRL-B enters the debugger; +CR TILDE CTRL-P causes a panic instead of entering the +debugger; and +CR TILDE CTRL-R causes an immediate reboot. +In all the above sequences, CR is a Carriage Return and is usually +sent by hitting the Enter or Return key. +TILDE is the ASCII tilde character (~). +CTRL-x is Control x created by hitting the control key and then x +and then releasing both. +.Pp +The break to debugger behavior may also be enabled by setting the +.Xr sysctl 8 +.Dv debug.kdb.break_to_debugger +to 1. +The alt break to debugger behavior may also be enabled by setting the +.Xr sysctl 8 +.Dv debug.kdb.alt_break_to_debugger +to 1. +The debugger may be entered by setting the +.Xr sysctl 8 +.Dv debug.kdb.enter +to 1. .Sh FILES Header files mentioned in this manual page can be found below .Pa /usr/include
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