Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH v2] powerpc/kprobes: Fix Oops by passing ppc_inst as a pointer to emulate_step() on ppc32 | Date | Fri, 25 Jun 2021 14:48:50 +1000 |
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Christophe Leroy <christophe.leroy@csgroup.eu> writes: > Le 24/06/2021 à 12:59, Naveen N. Rao a écrit : >> Christophe Leroy wrote: >>> From: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> >>> >>> Trying to use a kprobe on ppc32 results in the below splat: >>> BUG: Unable to handle kernel data access on read at 0x7c0802a6 >>> Faulting instruction address: 0xc002e9f0 >>> Oops: Kernel access of bad area, sig: 11 [#1] >>> BE PAGE_SIZE=4K PowerPC 44x Platform >>> Modules linked in: >>> CPU: 0 PID: 89 Comm: sh Not tainted 5.13.0-rc1-01824-g3a81c0495fdb #7 >>> NIP: c002e9f0 LR: c0011858 CTR: 00008a47 >>> REGS: c292fd50 TRAP: 0300 Not tainted (5.13.0-rc1-01824-g3a81c0495fdb) >>> MSR: 00009000 <EE,ME> CR: 24002002 XER: 20000000 >>> DEAR: 7c0802a6 ESR: 00000000 >>> <snip> >>> NIP [c002e9f0] emulate_step+0x28/0x324 >>> LR [c0011858] optinsn_slot+0x128/0x10000 >>> Call Trace: >>> opt_pre_handler+0x7c/0xb4 (unreliable) >>> optinsn_slot+0x128/0x10000 >>> ret_from_syscall+0x0/0x28 >>> >>> The offending instruction is: >>> 81 24 00 00 lwz r9,0(r4) >>> >>> Here, we are trying to load the second argument to emulate_step(): >>> struct ppc_inst, which is the instruction to be emulated. On ppc64, >>> structures are passed in registers when passed by value. However, per >>> the ppc32 ABI, structures are always passed to functions as pointers. >>> This isn't being adhered to when setting up the call to emulate_step() >>> in the optprobe trampoline. Fix the same. >>> >>> Fixes: eacf4c0202654a ("powerpc: Enable OPTPROBES on PPC32") >>> Cc: stable@vger.kernel.org >>> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> >>> --- >>> v2: Rebased on powerpc/merge 7f030e9d57b8 >>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> >> >> Thanks for rebasing this! >> >> I think git am drops everything after three dashes, so applying this patch will drop your SOB. The >> recommended style (*) for adding a changelog is to include it within [] before the second SOB. > > Yes, I saw that after sending the mail. Usually I add a signed-off-by with 'git --amend -s' when I > add the history, so it goes before the '---' I'm adding. > > This time I must have forgotten the '-s' so it was added by the 'git format-patch -s' which is in my > submit script, and so it was added at the end. > > It's not really a big deal, up to Michael to either move it at the right place or discard it, I > don't really mind. Do the easiest for you.
I just added Christophe's SoB.
cheers
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