Date: Tue, 4 Nov 2025 19:22:41 GMT From: Justin Hibbits <jhibbits@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: a935c2a63f92 - main - kexec: Add basic kexec_load man page Message-ID: <202511041922.5A4JMfwo050791@gitrepo.freebsd.org>
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The branch main has been updated by jhibbits: URL: https://cgit.FreeBSD.org/src/commit/?id=a935c2a63f9270500cddab1d9868c6183c25d5a8 commit a935c2a63f9270500cddab1d9868c6183c25d5a8 Author: Justin Hibbits <jhibbits@FreeBSD.org> AuthorDate: 2025-10-06 21:11:02 +0000 Commit: Justin Hibbits <jhibbits@FreeBSD.org> CommitDate: 2025-11-04 19:23:20 +0000 kexec: Add basic kexec_load man page Also add kexec reboot flag to the reboot man page. --- lib/libsys/Makefile.sys | 1 + lib/libsys/kexec_load.2 | 119 ++++++++++++++++++++++++++++++++++++++++++++++++ lib/libsys/reboot.2 | 7 ++- 3 files changed, 126 insertions(+), 1 deletion(-) diff --git a/lib/libsys/Makefile.sys b/lib/libsys/Makefile.sys index bd65b58083c2..1d1a4f1136ce 100644 --- a/lib/libsys/Makefile.sys +++ b/lib/libsys/Makefile.sys @@ -243,6 +243,7 @@ MAN+= abort2.2 \ jail.2 \ kcmp.2 \ kenv.2 \ + kexec_load.2 \ kill.2 \ kldfind.2 \ kldfirstmod.2 \ diff --git a/lib/libsys/kexec_load.2 b/lib/libsys/kexec_load.2 new file mode 100644 index 000000000000..c3d458f34100 --- /dev/null +++ b/lib/libsys/kexec_load.2 @@ -0,0 +1,119 @@ +.\" +.\" SPDX-License-Identifier: BSD-3-Clause +.\" +.\" Copyright (c) 2025 Juniper Networks, Inc. +.\" +.Dd October 29, 2025 +.Dt KEXEC_LOAD 2 +.Os +.Sh NAME +.Nm kexec_load +.Nd prepare new kernel to reboot into +.Sh SYNOPSIS +.Lb libc +.In sys/kexec.h +.Ft int +.Fn kexec_load "uint64_t entry" "unsigned long count" \ + "struct kexec_segment *segments" "unsigned long flags" +.Sh DESCRIPTION +The +.Fn kexec_load +system call loads a new kernel that can be executed later by +.Xr reboot 2 . +Subsequent calls will replace previously loaded images. +.Pp +The +.Fa flags +argument is a bitmask of flags that control the operation of the call. +This argument is present for compatibility with Linux, although it is currently +unused and must be 0. +.Pp +The +.Fa entry +argument is the physical address of the entry point of the new kernel image. +.Pp +The +.Fa count +argument is the number of segments in the image, currently limited to 16. +A value of 0 will unload the currently staged image, if one exists, without +staging a new image. +.Pp +The +.Fa segments +argument is an array of +.Fa count +members of the following structure: +.Bd -literal -offset indent +struct kexec_segment { + void *buf; + size_t bufsz; + vm_paddr_t mem; + vm_size_t memsz; +}; +.Ed +.Pp +The +.Va buf +and +.Va bufsz +members specify a memory region in the caller's address space containing the +source of the segment. +The +.Va mem +and +.Va memsz +members specify the target physical region of the segment. +.Va bufsz +must be less than or equal to +.Va memsz , +and +.Va mem +and +.Va memsz +must be page aligned. +The region covered by +.Va mem +must be in the list covered by the +.Va vm.phys_segs +sysctl. +.Pp +The +.Fn kexec_load +system call stages the kernel image in safe memory along with all +machine-dependent image data until +.Xr reboot 2 +is called with the +.Va RB_KEXEC +flag to load the image and execute the new kernel. +.Sh RETURN VALUES +The +.Fn kexec_load +system call returns 0 on success. +On failure, -1 is returned, and +.Va errno +is set to indicate the error. +On success any previously loaded image is unloaded and replaced with the new +image. +On failure, the previously loaded image is unchanged. +.Sh ERRORS +The following errors may be returned: +.Bl -tag -width Er +.It Bq Er EINVAL +Too many segments in image. +.It Bq Er EINVAL +The value of +.Va bufsz +is larger than +.Va memsz +in one or more segments. +.It Bq Er EINVAL +Machine-dependent load error. +.It Bq Er EBUSY +Another +.Fn kexec_load +call is in progress. +.Sh HISTORY +The +.Nm +system call appeared in +.Fx 16.0 . diff --git a/lib/libsys/reboot.2 b/lib/libsys/reboot.2 index f6c7bf6c83cc..54fa8b599cd5 100644 --- a/lib/libsys/reboot.2 +++ b/lib/libsys/reboot.2 @@ -25,7 +25,7 @@ .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" -.Dd July 10, 2018 +.Dd October 29, 2025 .Dt REBOOT 2 .Os .Sh NAME @@ -126,6 +126,10 @@ on the console. is actually interpreted by the .Xr init 8 program in the newly booted system. +.It Dv RB_KEXEC +Execute a new kernel loaded via +.Fn kexec_load 2 . +If no kernel was loaded, reboot as normal. .El .Pp When no options are given (i.e., @@ -149,6 +153,7 @@ variable The caller is not the super-user. .El .Sh SEE ALSO +.Xr kexec_load 2 , .Xr crash 8 , .Xr halt 8 , .Xr init 8 ,help
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