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Message-ID: <20171206013657.GA479@jagdpanzerIV>
Date: Wed, 6 Dec 2017 10:36:57 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Randy Dunlap <rdunlap@...radead.org>,
David Laight <David.Laight@...lab.com>,
Kees Cook <keescook@...omium.org>, "Tobin C. Harding" <me@...in.cc>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
"Jason A. Donenfeld" <Jason@...c4.com>,
Theodore Ts'o <tytso@....edu>, Paolo Bonzini <pbonzini@...hat.com>,
Tycho Andersen <tycho@...ho.ws>,
"Roberts, William C" <william.c.roberts@...el.com>,
Tejun Heo <tj@...nel.org>,
Jordan Glover <Golden_Miller83@...tonmail.ch>,
Greg KH <gregkh@...uxfoundation.org>,
Petr Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>,
Ian Campbell <ijc@...lion.org.uk>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
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Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
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Alexander Potapenko <glider@...gle.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH V11 4/5] vsprintf: add printk specifier %px
Hello,
On (12/05/17 13:22), Linus Torvalds wrote:
[..]
> It's not like those hex numbers were really helping people anyway.
> We've turned off most of them on x86 oops reports long ago (and
> entirely independently of the pointer hashing). Having stared at a lot
> of oopses in my time, the only hex numbers that tend to be really
> relevant are (a) the register contents (which aren't %p anyway), and
> things like the faulting address (which is not, and never has been, %p
> on x86, but might be on some other architecture).
I see some %p-s being used in _supposedly_ important output,
like arch/x86/mm/fault.c
show_fault_oops(struct pt_regs *regs, unsigned long error_code,
unsigned long address)
...
printk(KERN_CONT " at %p\n", (void *) address);
printk(KERN_ALERT "IP: %pS\n", (void *)regs->ip);
a quick %p grep gives me the following list:
arch/arm/mm/fault.c: pr_alert("pgd = %p\n", mm->pgd);
arch/arm64/mm/fault.c: pr_alert("%s pgtable: %luk pages, %u-bit VAs, pgd = %p\n",
arch/arm64/mm/fault.c: pr_info_ratelimited("%s[%d]: %s exception: pc=%p sp=%p\n",
arch/m68k/mm/fault.c: pr_debug("send_fault_sig: %p,%d,%d\n", siginfo.si_addr,
arch/m68k/mm/fault.c: pr_cont(" at virtual address %p\n", siginfo.si_addr);
arch/m68k/mm/fault.c: pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
arch/microblaze/mm/fault.c: pr_emerg("Page fault in user mode with faulthandler_disabled(), mm = %p\n",
arch/mn10300/mm/fault.c: printk(KERN_DEBUG "pgd entry %p: %016Lx\n",
arch/mn10300/mm/fault.c: printk(KERN_DEBUG "pmd entry %p: %016Lx\n",
arch/mn10300/mm/fault.c: printk(KERN_DEBUG "pte entry %p: %016Lx\n",
arch/mn10300/mm/fault.c: printk(KERN_DEBUG "--- do_page_fault(%p,%s:%04lx,%08lx)\n",
arch/powerpc/mm/fault.c: " mm=%p\n",
arch/sh/mm/fault.c: printk(KERN_ALERT "pgd = %p\n", pgd);
arch/unicore32/mm/fault.c: printk(KERN_ALERT "pgd = %p\n", mm->pgd);
arch/x86/mm/fault.c: printk(KERN_CONT " at %p\n", (void *) address);
arch/x86/mm/fault.c: printk(KERN_ALERT "IP: %pS\n", (void *)regs->ip);
arch/x86/mm/fault.c: printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
or is it OK to show hashes instead of pgd or pmd pointers?
-ss
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