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Message-ID: <1387551482.3404.63.camel@linaro1.home>
Date: Fri, 20 Dec 2013 14:58:02 +0000
From: "Jon Medhurst (Tixy)" <tixy@...aro.org>
To: David Long <dave.long@...aro.org>
Cc: linux-arm-kernel@...ts.infradead.org,
Russell King <linux@....linux.org.uk>,
Rabin Vincent <rabin@....in>, Oleg Nesterov <oleg@...hat.com>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
Ingo Molnar <mingo@...hat.com>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Ananth N Mavinakayanahalli <ananth@...ibm.com>,
Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
davem@...emloft.net, Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Paul Mackerras <paulus@...ba.org>,
Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 13/16] ARM: Add an emulate flag to the
kprobes/uprobes instruction decode functions
On Sun, 2013-12-15 at 23:08 -0500, David Long wrote:
> From: "David A. Long" <dave.long@...aro.org>
>
> Add an emulate flag into the instruction interpreter, primarily for uprobes
> support.
>
> Signed-off-by: David A. Long <dave.long@...aro.org>
> ---
> arch/arm/kernel/kprobes.c | 3 ++-
> arch/arm/kernel/kprobes.h | 1 +
> arch/arm/kernel/probes-arm.c | 4 ++--
> arch/arm/kernel/probes-arm.h | 2 +-
> arch/arm/kernel/probes-thumb.c | 8 ++++----
> arch/arm/kernel/probes-thumb.h | 4 ++--
> arch/arm/kernel/probes.c | 32 +++++++++++++++++++++++---------
> arch/arm/kernel/probes.h | 2 +-
> 8 files changed, 36 insertions(+), 20 deletions(-)
>
> diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c
> index 0d9d49b..04690f9 100644
> --- a/arch/arm/kernel/kprobes.c
> +++ b/arch/arm/kernel/kprobes.c
> @@ -87,7 +87,8 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
> p->opcode = insn;
> p->ainsn.insn = tmp_insn;
>
> - switch ((*decode_insn)(insn, &p->ainsn, actions)) {
> + switch ((*decode_insn)(insn, &p->ainsn,
> + true, actions)) {
Any reason why the function args need splitting over two lines?
> case INSN_REJECTED: /* not supported */
> return -EINVAL;
>
[...]
> --- a/arch/arm/kernel/probes.c
> +++ b/arch/arm/kernel/probes.c
> @@ -193,7 +193,7 @@ void __kprobes probes_emulate_none(probes_opcode_t opcode,
> */
> static probes_opcode_t __kprobes
> prepare_emulated_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
> - bool thumb)
> + bool thumb)
Seems like a spurious indentation change.
> {
> #ifdef CONFIG_THUMB2_KERNEL
> if (thumb) {
> @@ -218,7 +218,7 @@ prepare_emulated_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
> */
> static void __kprobes
> set_emulated_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
> - bool thumb)
> + bool thumb)
Another spurious whitespace change.
> {
> #ifdef CONFIG_THUMB2_KERNEL
> if (thumb) {
> @@ -253,7 +253,7 @@ set_emulated_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
> * non-zero value, the corresponding nibble in pinsn is validated and modified
> * according to the type.
> */
> -static bool __kprobes decode_regs(probes_opcode_t *pinsn, u32 regs)
> +static bool __kprobes decode_regs(probes_opcode_t *pinsn, u32 regs, bool modify)
> {
> probes_opcode_t insn = *pinsn;
> probes_opcode_t mask = 0xf; /* Start at least significant nibble */
> @@ -317,9 +317,16 @@ static bool __kprobes decode_regs(probes_opcode_t *pinsn, u32 regs)
> /* Replace value of nibble with new register number... */
> insn &= ~mask;
> insn |= new_bits & mask;
> + if (modify) {
> + /* Replace value of nibble with new register number */
> + insn &= ~mask;
> + insn |= new_bits & mask;
> + }
Huh? As is, the above addition doesn't do anything because insn has
already been modified. I guess you played with the idea that you needed
to avoid changing insn (you don't) and then didn't undo the experiment
quite right. :-)
> }
>
> - *pinsn = insn;
> + if (modify)
> + *pinsn = insn;
> +
> return true;
>
> reject:
> @@ -380,14 +387,15 @@ static const int decode_struct_sizes[NUM_DECODE_TYPES] = {
> */
> int __kprobes
> probes_decode_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
> - const union decode_item *table, bool thumb,
> - const union decode_item *actions)
> + const union decode_item *table, bool thumb,
> + bool emulate, const union decode_item *actions)
> {
> struct decode_header *h = (struct decode_header *)table;
> struct decode_header *next;
> bool matched = false;
>
> - insn = prepare_emulated_insn(insn, asi, thumb);
> + if (emulate)
> + insn = prepare_emulated_insn(insn, asi, thumb);
>
> for (;; h = next) {
> enum decode_type type = h->type_regs.bits & DECODE_TYPE_MASK;
> @@ -402,7 +410,7 @@ probes_decode_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
> if (!matched && (insn & h->mask.bits) != h->value.bits)
> continue;
>
> - if (!decode_regs(&insn, regs))
> + if (!decode_regs(&insn, regs, emulate))
> return INSN_REJECTED;
>
> switch (type) {
> @@ -415,7 +423,8 @@ probes_decode_insn(probes_opcode_t insn, struct arch_specific_insn *asi,
>
> case DECODE_TYPE_CUSTOM: {
> struct decode_custom *d = (struct decode_custom *)h;
> - return actions[d->decoder.bits].decoder(insn, asi, h);
> + return actions[d->decoder.bits].decoder(insn,
> + asi, h);
No need to split the above line, you haven't changed it and it doesn't
exceed 80 characters anyway.
[Rest of patch cut]
--
Tixy
--
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