From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1muaWc-008hbS-4S for kexec@lists.infradead.org; Tue, 07 Dec 2021 13:28:56 +0000 Date: Tue, 7 Dec 2021 14:28:43 +0100 From: Philipp Rudo Subject: Re: [PATCH] kernel/crash_core: suppress unknown crashkernel parameter warning Message-ID: <20211207142843.0a27d71b@rhtmp> In-Reply-To: <20211207033446.GC5604@MiWiFi-R3L-srv> References: <20211206111733.4602-1-prudo@redhat.com> <20211207033446.GC5604@MiWiFi-R3L-srv> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Baoquan He Cc: kexec@lists.infradead.org, ahalaney@redhat.com, akpm@linux-foundation.org Hi Baoquan, On Tue, 7 Dec 2021 11:34:46 +0800 Baoquan He wrote: > On 12/06/21 at 12:17pm, Philipp Rudo wrote: > > When booting with crashkernel= on the kernel command line a warning > > similar to > > > > [ 0.038294] Kernel command line: ro console=ttyS0 crashkernel=256M > > [ 0.038353] Unknown kernel command line parameters "crashkernel=256M", will be passed to user space. > > > > is printed. This originates from crashkernel= being parsed independent from > > the early_param() mechanism. So the code in init/main.c doesn't know > > Not only the early_param(), __setup() also takes the same mechanism. > It's just handled in different stage. You might need to call it kernel > param handling mechanism, not sure if it's accurate. you are right, "kernel param handling" is better. I used early_param as that's where we would need to hook into if we wanted to use the common kernel param handling. But I don't think it is worth it. @akpm: do you update the commit message before sending the patch to Linus or shall I send a v2? > > that crashkernel= is a valid kernel parameter and prints this incorrect > > warning. Suppress the warning by adding a dummy early_param handler for > > crashkernel=. > > The fix looks good to me, thanks. > > Acked-by: Baoquan He Thanks > By the way, on which arch did you find this issue? Ask because I am > wondering whether there's any other similiar independent kernel cmdline > handling from __setup_param(). If have, is there a chance to take a > common method to handle them, e.g a generic function or a place to > identify them. Just wild thought, I have no idea yet. Otherwise, we may > need several this kind of dummy handler for each one. The issue was first reported on s390 but I used x86 to test the fix. The only other reported parameter I encountered was BOOT_IMAGE= which is not a kernel parameter and thus correct. But in the corresponding bugzilla Andrew (on cc) said "Gah! I thought I had squashed all of these interesting uses of the kernel command line, it is like playing whack-a-mole." So I believe there were multiple other parameters that had the same problem. Thanks Philipp > > Fixes: 86d1919a4fb0 ("init: print out unknown kernel parameters") > > Signed-off-by: Philipp Rudo > > --- > > kernel/crash_core.c | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/kernel/crash_core.c b/kernel/crash_core.c > > index eb53f5ec62c9..256cf6db573c 100644 > > --- a/kernel/crash_core.c > > +++ b/kernel/crash_core.c > > @@ -6,6 +6,7 @@ > > > > #include > > #include > > +#include > > #include > > #include > > > > @@ -295,6 +296,16 @@ int __init parse_crashkernel_low(char *cmdline, > > "crashkernel=", suffix_tbl[SUFFIX_LOW]); > > } > > > > +/* > > + * Add a dummy early_param handler to mark crashkernel= as a known command line > > + * parameter and suppress incorrect warnings in init/main.c. > > + */ > > +static int __init parse_crashkernel_dummy(char *arg) > > +{ > > + return 0; > > +} > > +early_param("crashkernel", parse_crashkernel_dummy); > > + > > Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type, > > void *data, size_t data_len) > > { > > -- > > 2.31.1 > > > > > > _______________________________________________ > > kexec mailing list > > kexec@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/kexec > > > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec