From 511eea5e2ccdfdbf3d626bde0314e551f247dd18 Mon Sep 17 00:00:00 2001 From: "Naveen N. Rao" Date: Wed, 23 Jun 2021 05:23:30 +0000 Subject: [PATCH] powerpc/kprobes: Fix Oops by passing ppc_inst as a pointer to emulate_step() on ppc32 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 CR: 24002002 XER: 20000000 DEAR: 7c0802a6 ESR: 00000000 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 Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/5bdc8cbc9a95d0779e27c9ddbf42b40f51f883c0.1624425798.git.christophe.leroy@csgroup.eu --- arch/powerpc/kernel/optprobes.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c index 8b9f82dc6ece..c79899abcec8 100644 --- a/arch/powerpc/kernel/optprobes.c +++ b/arch/powerpc/kernel/optprobes.c @@ -228,8 +228,12 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p) /* * 3. load instruction to be emulated into relevant register, and */ - temp = ppc_inst_read(p->ainsn.insn); - patch_imm_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX); + if (IS_ENABLED(CONFIG_PPC64)) { + temp = ppc_inst_read(p->ainsn.insn); + patch_imm_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX); + } else { + patch_imm_load_insns((unsigned long)p->ainsn.insn, 4, buff + TMPL_INSN_IDX); + } /* * 4. branch back from trampoline -- 2.20.1