Messages in this thread | | | Date | Wed, 15 Jan 2014 14:31:10 -0500 | From | David Long <> | Subject | Re: [PATCH v4 13/16] ARM: Add an emulate flag to the kprobes/uprobes instruction decode functions |
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On 12/20/13 09:58, Jon Medhurst (Tixy) wrote: > On Sun, 2013-12-15 at 23:08 -0500, David Long wrote: >> From: "David A. Long" <dave.long@linaro.org> >> >> Add an emulate flag into the instruction interpreter, primarily for uprobes >> support. >> >> Signed-off-by: David A. Long <dave.long@linaro.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?
I undid the that change.
>> 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.
Fixed.
>> { >> #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.
Fixed.
>> { >> #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. :-) >
The conditional modification of the instruction was part of Rabin's original work for uprobes, but I messed up the merge from an earlier working version of my patches. My intention was/is to delete the old unconditional code. Sounds like maybe you disagree though. The intent is to only modify the instruction in the kprobes case.
>> } >> >> - *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.
Fixed.
> [Rest of patch cut] >
-dl
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