Messages in this thread | | | Subject | Re: [PATCH] powerpc:Don't print raw EIP/LR hex values in dump_stack() and show_regs() | From | Xiaoming Ni <> | Date | Tue, 22 Dec 2020 21:45:03 +0800 |
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On 2020/12/22 1:12, Segher Boessenkool wrote: > On Mon, Dec 21, 2020 at 04:42:23PM +0000, David Laight wrote: >> From: Segher Boessenkool >>> Sent: 21 December 2020 16:32 >>> >>> On Mon, Dec 21, 2020 at 04:17:21PM +0100, Christophe Leroy wrote: >>>> Le 21/12/2020 à 04:27, Xiaoming Ni a écrit : >>>>> Since the commit 2b0e86cc5de6 ("powerpc/fsl_booke/32: implement KASLR >>>>> infrastructure"), the powerpc system is ready to support KASLR. >>>>> To reduces the risk of invalidating address randomization, don't print the >>>>> EIP/LR hex values in dump_stack() and show_regs(). >>> >>>> I think your change is not enough to hide EIP address, see below a dump >>>> with you patch, you get "Faulting instruction address: 0xc03a0c14" >>> >>> As far as I can see the patch does nothing to the GPR printout. Often >>> GPRs contain code addresses. As one example, the LR is moved via a GPR >>> (often GPR0, but not always) for storing on the stack. >>> >>> So this needs more work. >> >> If the dump_stack() is from an oops you need the real EIP value >> on order to stand any chance of making headway. > > Or at least the function name + offset, yes. > When the system is healthy, only symbols and offsets are printed, Output address and symbol + offset when the system is dying Does this meet both debugging and security requirements? For example:
+static void __show_regs_ip_lr(const char *flag, unsigned long addr) +{ + if (system_going_down()) { /* panic oops reboot */ + pr_cont("%s["REG"] %pS", flag, addr, (void *)addr); + } else { + pr_cont("%s%pS", flag, (void *)addr); + } +} + static void __show_regs(struct pt_regs *regs) { int i, trap;
- printk("NIP: "REG" LR: "REG" CTR: "REG"\n", - regs->nip, regs->link, regs->ctr); + __show_regs_ip_lr("NIP: ", regs->nip); + __show_regs_ip_lr(" LR: ", regs->link); + pr_cont(" CTR: "REG"\n", regs->ctr); printk("REGS: %px TRAP: %04lx %s (%s)\n", regs, regs->trap, print_tainted(), init_utsname()->release); printk("MSR: "REG" ", regs->msr);
>> Otherwise you might just as well just print 'borked - tough luck'. > > Yes. ASLR is a house of cards. But that isn't constructive wrt this > patch :-) > > > Segher > . >
Thanks Xiaoming Ni
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