From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Young Date: Mon, 29 Apr 2019 05:04:10 +0000 Subject: Re: [PATCHv2] kernel/crash: make parse_crashkernel()'s return value more indicant Message-Id: <20190429050410.GA7982@dhcp-128-65.nay.redhat.com> List-Id: References: <1556087581-14513-1-git-send-email-kernelfans@gmail.com> <10dc5468-6cd9-85c7-ba66-1dfa5aa922b7@suse.com> <20190428083710.GA11981@dhcp-128-65.nay.redhat.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Pingfan Liu Cc: Rich Felker , linux-ia64@vger.kernel.org, Julien Thierry , Yangtao Li , Benjamin Herrenschmidt , Palmer Dabbelt , Heiko Carstens , Stefan Agner , linux-mips@vger.kernel.org, Paul Mackerras , "H. Peter Anvin" , Thomas Gleixner , Logan Gunthorpe , linux-s390@vger.kernel.org, Florian Fainelli , Yoshinori Sato , linux-sh@vger.kernel.org, Michael Ellerman , x86@kernel.org, Russell King , Ingo Molnar , Hari Bathini , Catalin Marinas , James Hogan , Fenghua Yu , Tony Luck , Will Deacon , Johannes Weiner , Ananth N Mavinakayanahalli , Borislav Petkov , David Hildenbrand , linux-arm-kernel@lists.infradead.org, Jens Axboe , Matthias Brugger , Baoquan He , Ard Biesheuvel , Robin Murphy , kexec@lists.infradead.org, LKML , Ralf Baechle , Thomas Bogendoerfer , Paul Burton , Greg Kroah-Hartman , Martin Schwidefsky , Andrew Morton , linuxppc-dev@lists.ozlabs.org, Greg Hackmann On 04/29/19 at 12:48pm, Pingfan Liu wrote: > On Mon, Apr 29, 2019 at 11:04 AM Pingfan Liu wrote: > > > > On Sun, Apr 28, 2019 at 4:37 PM Dave Young wrote: > > > > > > On 04/25/19 at 04:20pm, Pingfan Liu wrote: > > > > On Wed, Apr 24, 2019 at 4:31 PM Matthias Brugger wrote: > > > > > > > > > > > > > > [...] > > > > > > @@ -139,6 +141,8 @@ static int __init parse_crashkernel_simple(char *cmdline, > > > > > > pr_warn("crashkernel: unrecognized char: %c\n", *cur); > > > > > > return -EINVAL; > > > > > > } > > > > > > + if (*crash_size = 0) > > > > > > + return -EINVAL; > > > > > > > > > > This covers the case where I pass an argument like "crashkernel=0M" ? > > > > > Can't we fix that by using kstrtoull() in memparse and check if the return value > > > > > is < 0? In that case we could return without updating the retptr and we will be > > > > > fine. > > > > > > > > > It seems that kstrtoull() treats 0M as invalid parameter, while > > > > simple_strtoull() does not. > > > > > > > > If changed like your suggestion, then all the callers of memparse() > > > > will treats 0M as invalid parameter. This affects many components > > > > besides kexec. Not sure this can be done or not. > > > > > > simple_strtoull is obsolete, move to kstrtoull is the right way. > > > > > > $ git grep memparse|wc > > > 158 950 10479 > > > > > > Except some documentation/tools etc there are still a log of callers > > > which directly use the return value as the ull number without error > > > checking. > > > > > > So it would be good to mark memparse as obsolete as well in > > > lib/cmdline.c, and introduce a new function eg. kmemparse() to use > > > kstrtoull, and return a real error code, and save the size in an > > > argument like &size. Then update X86 crashkernel code to use it. > > > > > Thank for your good suggestion. > > > Go through the v5.0 kernel code, I think it will be a huge job. > > The difference between unsigned long long simple_strtoull(const char > *cp, char **endp, unsigned int base) and int _kstrtoull(const char *s, > unsigned int base, unsigned long long *res) is bigger than expected, > especially the output parameter @res. Many references to > memparse(const char *ptr, char **retptr) rely on @retptr to work. A > typical example from arch/x86/kernel/e820.c > mem_size = memparse(p, &p); > if (p = oldp) > return -EINVAL; > > userdef = 1; > if (*p = '@') { <----------- here > start_at = memparse(p+1, &p); > e820__range_add(start_at, mem_size, E820_TYPE_RAM); > } else if (*p = '#') { > start_at = memparse(p+1, &p); > e820__range_add(start_at, mem_size, E820_TYPE_ACPI); > } else if (*p = '$') { > start_at = memparse(p+1, &p); > e820__range_add(start_at, mem_size, E820_TYPE_RESERVED); > } > > So we need to resolve the prototype of kstrtoull() firstly, and maybe > kstrtouint() etc too. All of them have lots of references in kernel. > > Any idea about this? Not only this place, a lot of other places, I think no hurry to fix them all at one time. As we talked just do it according to previous reply, mark memparse as obsolete, and create a new function to use kstrtoull, and make it used in crashkernel code first. Thanks Dave