Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

2014-05-06 Thread Oleg Nesterov
Firstly, let me remind that my understanding of low lovel hardware details is very limited. On 05/06, Denys Vlasenko wrote: > > Oleg, can you clear for me the following - > > If the probed instruction triggers an "illegal insn" or "privileged insn" > CPU exception - are we completely fine? Yes I

Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

2014-05-06 Thread Denys Vlasenko
On 05/05/2014 09:41 PM, Oleg Nesterov wrote: > On 05/05, Denys Vlasenko wrote: >> >> + * Opcodes we'll probably never support: >> + * 6c-6f - ins,outs. SEGVs if used in userspace >> + * e4-e7 - in,out imm. SEGVs if used in userspace >> + * ec-ef - in,out acc. SEGVs if used in userspace > > Well.

Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

2014-05-06 Thread Denys Vlasenko
On 05/06/2014 12:32 AM, Jim Keniston wrote: > All of the following is FYI. > > The good-instruction tables date back 2006-2007. Back then, the > philosophy was to disallow any questionable opcodes, and add them back > into the "good" tables only when a need was demonstrated (i.e., somebody >

Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

2014-05-06 Thread Denys Vlasenko
On 05/06/2014 12:32 AM, Jim Keniston wrote: All of the following is FYI. The good-instruction tables date back 2006-2007. Back then, the philosophy was to disallow any questionable opcodes, and add them back into the good tables only when a need was demonstrated (i.e., somebody needed to

Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

2014-05-06 Thread Denys Vlasenko
On 05/05/2014 09:41 PM, Oleg Nesterov wrote: On 05/05, Denys Vlasenko wrote: + * Opcodes we'll probably never support: + * 6c-6f - ins,outs. SEGVs if used in userspace + * e4-e7 - in,out imm. SEGVs if used in userspace + * ec-ef - in,out acc. SEGVs if used in userspace Well. I have no

Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

2014-05-06 Thread Oleg Nesterov
Firstly, let me remind that my understanding of low lovel hardware details is very limited. On 05/06, Denys Vlasenko wrote: Oleg, can you clear for me the following - If the probed instruction triggers an illegal insn or privileged insn CPU exception - are we completely fine? Yes I think we

Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

2014-05-05 Thread Jim Keniston
On Mon, 2014-05-05 at 20:24 +0200, Denys Vlasenko wrote: > After adding these, it's clear we have some awkward choices there. > Some valid instructions are prohibited from uprobing while > several invalid ones are allowed. > > Hopefully future edits to the good-opcode tables will fix wrong bits >

Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

2014-05-05 Thread Oleg Nesterov
On 05/05, Denys Vlasenko wrote: > > + * Opcodes we'll probably never support: > + * 6c-6f - ins,outs. SEGVs if used in userspace > + * e4-e7 - in,out imm. SEGVs if used in userspace > + * ec-ef - in,out acc. SEGVs if used in userspace Well. I have no idea why they are nacked, but this is not the

[PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

2014-05-05 Thread Denys Vlasenko
After adding these, it's clear we have some awkward choices there. Some valid instructions are prohibited from uprobing while several invalid ones are allowed. Hopefully future edits to the good-opcode tables will fix wrong bits or explain why those bits are not wrong. No actual code changes.

[PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

2014-05-05 Thread Denys Vlasenko
After adding these, it's clear we have some awkward choices there. Some valid instructions are prohibited from uprobing while several invalid ones are allowed. Hopefully future edits to the good-opcode tables will fix wrong bits or explain why those bits are not wrong. No actual code changes.

Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

2014-05-05 Thread Oleg Nesterov
On 05/05, Denys Vlasenko wrote: + * Opcodes we'll probably never support: + * 6c-6f - ins,outs. SEGVs if used in userspace + * e4-e7 - in,out imm. SEGVs if used in userspace + * ec-ef - in,out acc. SEGVs if used in userspace Well. I have no idea why they are nacked, but this is not the

Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

2014-05-05 Thread Jim Keniston
On Mon, 2014-05-05 at 20:24 +0200, Denys Vlasenko wrote: After adding these, it's clear we have some awkward choices there. Some valid instructions are prohibited from uprobing while several invalid ones are allowed. Hopefully future edits to the good-opcode tables will fix wrong bits or