From: Jordan Niethe <jniethe5@gmail.com>
To: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: Alistair Popple <alistair@popple.id.au>,
Balamuruhan S <bala24@linux.ibm.com>,
Nicholas Piggin <npiggin@gmail.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Daniel Axtens <dja@axtens.net>
Subject: Re: [PATCH v8 27/30] powerpc/kprobes: Don't allow breakpoints on suffixes
Date: Thu, 20 May 2021 13:45:42 +1000 [thread overview]
Message-ID: <CACzsE9oUHycpJbFU0ppcWv3M4b97Ys_GtAZCrNpv52LTbLn+xg@mail.gmail.com> (raw)
In-Reply-To: <1621411610.rhqg7trx2p.naveen@linux.ibm.com>
On Wed, May 19, 2021 at 6:11 PM Naveen N. Rao
<naveen.n.rao@linux.vnet.ibm.com> wrote:
>
> Christophe Leroy wrote:
> >
> >
> > Le 06/05/2020 à 05:40, Jordan Niethe a écrit :
> >> Do not allow inserting breakpoints on the suffix of a prefix instruction
> >> in kprobes.
> >>
> >> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> >> ---
> >> v8: Add this back from v3
> >> ---
> >> arch/powerpc/kernel/kprobes.c | 13 +++++++++++++
> >> 1 file changed, 13 insertions(+)
> >>
> >> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> >> index 33d54b091c70..227510df8c55 100644
> >> --- a/arch/powerpc/kernel/kprobes.c
> >> +++ b/arch/powerpc/kernel/kprobes.c
> >> @@ -106,7 +106,9 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
> >> int arch_prepare_kprobe(struct kprobe *p)
> >> {
> >> int ret = 0;
> >> + struct kprobe *prev;
> >> struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->addr);
> >> + struct ppc_inst prefix = ppc_inst_read((struct ppc_inst *)(p->addr - 1));
> >
> > What if p->addr is the first word of a page and the previous page is
> > not mapped ?
>
> Good catch!
> I think we can just skip validation if the instruction is at the
> beginning of a page. I have a few cleanups in this area - I will post a
> patchset soon.
Yeah thanks Christophe for noticing that. And thanks Naveen that
sounds like it should fix it.
>
> >
> >>
> >> if ((unsigned long)p->addr & 0x03) {
> >> printk("Attempt to register kprobe at an unaligned address\n");
> >> @@ -114,6 +116,17 @@ int arch_prepare_kprobe(struct kprobe *p)
> >> } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) {
> >> printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n");
> >> ret = -EINVAL;
> >> + } else if (ppc_inst_prefixed(prefix)) {
> >
> > If p->addr - 2 contains a valid prefixed instruction, then p->addr - 1 contains the suffix of that
> > prefixed instruction. Are we sure a suffix can never ever be misinterpreted as the prefix of a
> > prefixed instruction ?
>
> Yes. Per the ISA:
> Bits 0:5 of all prefixes are assigned the primary opcode
> value 0b000001. 0b000001 is not available for use as a
> primary opcode for either word instructions or suffixes
> of prefixed instructions.
Yep, a prefix will never be a valid word instruction or suffix.
>
>
> - Naveen
>
next prev parent reply other threads:[~2021-05-20 3:46 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-06 3:40 [PATCH v8 00/30] Initial Prefixed Instruction support Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 01/30] powerpc/xmon: Remove store_inst() for patch_instruction() Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 02/30] powerpc/xmon: Move breakpoint instructions to own array Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 03/30] powerpc/xmon: Move breakpoints to text section Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 04/30] powerpc/xmon: Use bitwise calculations in_breakpoint_table() Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 05/30] powerpc: Change calling convention for create_branch() et. al Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 06/30] powerpc: Use a macro for creating instructions from u32s Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 07/30] powerpc: Use an accessor for instructions Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 08/30] powerpc: Use a function for getting the instruction op code Jordan Niethe
2020-05-15 7:48 ` Jordan Niethe
2020-05-16 11:08 ` Michael Ellerman
2020-05-17 7:41 ` Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 09/30] powerpc: Use a function for byte swapping instructions Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 10/30] powerpc: Introduce functions for instruction equality Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 11/30] powerpc: Use a datatype for instructions Jordan Niethe
2020-05-08 1:51 ` Jordan Niethe
2020-05-08 7:17 ` Christophe Leroy
2020-05-11 1:19 ` Jordan Niethe
2020-05-08 2:15 ` Jordan Niethe
2020-05-17 10:48 ` Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 12/30] powerpc: Use a function for reading instructions Jordan Niethe
2020-05-16 18:39 ` Christophe Leroy
2020-05-17 10:44 ` Jordan Niethe
2020-05-19 4:05 ` Michael Ellerman
2020-05-19 5:03 ` Christophe Leroy
2020-05-20 4:16 ` Michael Ellerman
2020-05-06 3:40 ` [PATCH v8 13/30] powerpc: Add a probe_user_read_inst() function Jordan Niethe
2020-05-13 12:52 ` Michael Ellerman
2020-05-13 23:51 ` Jordan Niethe
2020-05-14 5:46 ` Christophe Leroy
2020-05-15 3:46 ` Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 14/30] powerpc: Add a probe_kernel_read_inst() function Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 15/30] powerpc/kprobes: Use patch_instruction() Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 16/30] powerpc: Define and use __get_user_instr{, inatomic}() Jordan Niethe
2020-05-13 14:18 ` Michael Ellerman
2020-05-13 23:54 ` Jordan Niethe
2020-05-14 1:43 ` Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 17/30] powerpc: Introduce a function for reporting instruction length Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 18/30] powerpc/xmon: Use a function for reading instructions Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 19/30] powerpc/xmon: Move insertion of breakpoint for xol'ing Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 20/30] powerpc: Make test_translate_branch() independent of instruction length Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 21/30] powerpc: Enable Prefixed Instructions Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 22/30] powerpc: Define new SRR1 bits for a future ISA version Jordan Niethe
2020-05-08 2:26 ` Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 23/30] powerpc: Add prefixed instructions to instruction data type Jordan Niethe
2020-05-14 1:40 ` Jordan Niethe
2020-05-14 6:11 ` Christophe Leroy
2020-05-14 12:06 ` Alistair Popple
2020-05-14 12:29 ` Jordan Niethe
2020-05-14 12:57 ` Christophe Leroy
2020-05-14 12:28 ` Jordan Niethe
2020-05-15 1:33 ` Michael Ellerman
2020-05-15 7:52 ` Jordan Niethe
2020-05-16 11:54 ` [PATCH v8 22.5/30] powerpc/optprobes: Add register argument to patch_imm64_load_insns() Michael Ellerman
2020-06-09 5:51 ` Michael Ellerman
2020-05-06 3:40 ` [PATCH v8 24/30] powerpc: Test prefixed code patching Jordan Niethe
2020-05-15 7:54 ` Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 25/30] powerpc: Test prefixed instructions in feature fixups Jordan Niethe
2020-05-15 7:57 ` Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 26/30] powerpc/xmon: Don't allow breakpoints on suffixes Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 27/30] powerpc/kprobes: " Jordan Niethe
2021-05-18 18:43 ` Christophe Leroy
2021-05-18 19:52 ` Gabriel Paubert
2021-05-19 8:11 ` Naveen N. Rao
2021-05-20 3:45 ` Jordan Niethe [this message]
2020-05-06 3:40 ` [PATCH v8 28/30] powerpc: Support prefixed instructions in alignment handler Jordan Niethe
2020-05-14 6:14 ` Christophe Leroy
2020-05-14 12:15 ` Alistair Popple
2020-05-14 12:59 ` Christophe Leroy
2020-05-06 3:40 ` [PATCH v8 29/30] powerpc sstep: Add support for prefixed load/stores Jordan Niethe
2020-05-14 6:15 ` Christophe Leroy
2020-05-14 12:19 ` Alistair Popple
2020-05-14 13:00 ` Christophe Leroy
2020-05-15 7:59 ` Jordan Niethe
2020-05-06 3:40 ` [PATCH v8 30/30] powerpc sstep: Add support for prefixed fixed-point arithmetic Jordan Niethe
2020-05-14 6:15 ` Christophe Leroy
2020-05-15 8:02 ` Jordan Niethe
2020-05-14 5:31 ` [PATCH v8 00/30] Initial Prefixed Instruction support Christophe Leroy
2020-05-14 10:33 ` Jordan Niethe
2020-05-20 10:59 ` Michael Ellerman
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