From: Andrew Cooper <andrew.cooper3@citrix.com>
To: "Wei Liu" <wei.liu2@citrix.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Cc: Jan Beulich <JBeulich@suse.com>, Xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH 2/7] x86/alt: Clean up struct alt_instr and its users
Date: Mon, 12 Feb 2018 17:53:41 +0000 [thread overview]
Message-ID: <57842b04-07e3-3393-0589-2e677bfdc6ad@citrix.com> (raw)
In-Reply-To: <20180212171837.hyhm5ngl7bx4doui@citrix.com>
On 12/02/18 17:18, Wei Liu wrote:
> On Mon, Feb 12, 2018 at 04:52:21PM +0000, Roger Pau Monné wrote:
>> On Mon, Feb 12, 2018 at 11:23:02AM +0000, Andrew Cooper wrote:
>>> * Rename some fields for consistency and clarity, and use standard types.
>>> * Don't opencode the use of ALT_{ORIG,REPL}_PTR().
>>>
>>> No functional change.
>>>
>>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
>>
>>> ---
>>> CC: Jan Beulich <JBeulich@suse.com>
>>> CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>>> CC: Roger Pau Monné <roger.pau@citrix.com>
>>> CC: Wei Liu <wei.liu2@citrix.com>
>>> ---
>>> xen/arch/x86/alternative.c | 24 ++++++++++++------------
>>> xen/include/asm-x86/alternative.h | 12 ++++++------
>>> 2 files changed, 18 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/xen/arch/x86/alternative.c b/xen/arch/x86/alternative.c
>>> index 5c8b6f6..f8ddab5 100644
>>> --- a/xen/arch/x86/alternative.c
>>> +++ b/xen/arch/x86/alternative.c
>>> @@ -163,8 +163,6 @@ void init_or_livepatch apply_alternatives(const struct alt_instr *start,
>>> const struct alt_instr *end)
>>> {
>>> const struct alt_instr *a;
>>> - u8 *instr, *replacement;
>>> - u8 insnbuf[MAX_PATCH_LEN];
>>>
>>> printk(KERN_INFO "alt table %p -> %p\n", start, end);
>>>
>>> @@ -179,23 +177,25 @@ void init_or_livepatch apply_alternatives(const struct alt_instr *start,
>>> */
>>> for ( a = start; a < end; a++ )
>>> {
>>> - instr = (u8 *)&a->instr_offset + a->instr_offset;
>>> - replacement = (u8 *)&a->repl_offset + a->repl_offset;
>>> - BUG_ON(a->replacementlen > a->instrlen);
>>> - BUG_ON(a->instrlen > sizeof(insnbuf));
>>> + uint8_t *orig = ALT_ORIG_PTR(a);
>>> + uint8_t *repl = ALT_REPL_PTR(a);
>>> + uint8_t buf[MAX_PATCH_LEN];
>>> +
>>> + BUG_ON(a->repl_len > a->orig_len);
>>> + BUG_ON(a->orig_len > sizeof(buf));
>> Would be nice to have an assembly BUILD_BUG_ON equivalent so that this
>> could be turned into a compile time check and added to ALTINSTR_ENTRY.
> This function is also used to livepatch the hypervisor.
>
> I would actually suggest not use BUG_ON here instead but I didn't want
> to add noise to the problem at hand. :-)
We've got some assembler time checks already, and I've introduced more
in patch 5 which include this sizeof(buf) one.
As for BUG_ON()s, I considered dropping them as well, but the only thing
which will happen if these are skipped is that we will crash in less
obvious ways in the patch points.
~Andrew
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next prev parent reply other threads:[~2018-02-12 17:53 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-12 11:23 [PATCH 0/7] x86/alternatives: Support for automatic padding calculations Andrew Cooper
2018-02-12 11:23 ` [PATCH 1/7] x86/alt: Drop unused alternative infrastructure Andrew Cooper
2018-02-12 12:30 ` Wei Liu
2018-02-12 15:56 ` Roger Pau Monné
2018-02-12 15:58 ` Andrew Cooper
2018-02-13 14:22 ` Jan Beulich
2018-02-13 14:41 ` Andrew Cooper
2018-02-13 15:33 ` Jan Beulich
2018-02-14 10:02 ` Jan Beulich
2018-02-12 11:23 ` [PATCH 2/7] x86/alt: Clean up struct alt_instr and its users Andrew Cooper
2018-02-12 12:30 ` Wei Liu
2018-02-12 16:52 ` Roger Pau Monné
2018-02-12 17:18 ` Wei Liu
2018-02-12 17:53 ` Andrew Cooper [this message]
2018-02-13 14:26 ` Jan Beulich
2018-02-21 21:22 ` Konrad Rzeszutek Wilk
2018-02-12 11:23 ` [PATCH 3/7] x86/alt: Clean up the assembly used to generate alternatives Andrew Cooper
2018-02-12 12:30 ` Wei Liu
2018-02-12 17:26 ` Roger Pau Monné
2018-02-12 17:54 ` Andrew Cooper
2018-02-13 14:37 ` Jan Beulich
2018-02-23 14:03 ` Andrew Cooper
2018-02-23 15:12 ` Jan Beulich
2018-02-23 16:24 ` Andrew Cooper
2018-02-23 17:28 ` Jan Beulich
2018-02-12 11:23 ` [PATCH 4/7] x86/asm: Remove opencoded uses of altinstruction_entry Andrew Cooper
2018-02-12 12:30 ` Wei Liu
2018-02-12 12:34 ` Andrew Cooper
2018-02-13 9:56 ` Jan Beulich
2018-02-13 10:07 ` Andrew Cooper
2018-02-13 11:10 ` Jan Beulich
2018-02-12 12:52 ` Wei Liu
2018-02-12 17:46 ` Roger Pau Monné
2018-02-12 17:59 ` Andrew Cooper
2018-02-14 9:53 ` Jan Beulich
2018-02-12 11:23 ` [PATCH 5/7] x86/alt: Support for automatic padding calculations Andrew Cooper
2018-02-12 14:39 ` Wei Liu
2018-02-12 15:04 ` Andrew Cooper
2018-02-12 18:41 ` Roger Pau Monné
2018-02-12 18:45 ` Andrew Cooper
2018-02-12 18:09 ` Roger Pau Monné
2018-02-13 9:45 ` Roger Pau Monné
2018-02-13 10:09 ` Andrew Cooper
2018-02-13 10:26 ` Roger Pau Monné
2018-02-14 9:46 ` Jan Beulich
2018-02-12 11:23 ` [PATCH 6/7] x86/alt: Drop explicit padding of origin sites Andrew Cooper
2018-02-12 14:39 ` Wei Liu
2018-02-12 18:12 ` Roger Pau Monné
2018-02-14 9:53 ` Jan Beulich
2018-02-12 11:23 ` [PATCH 7/7] x86/build: Use new .nop directive when available Andrew Cooper
2018-02-12 14:40 ` Wei Liu
2018-02-13 11:08 ` Roger Pau Monné
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