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Re: [Qemu-devel] Re: [RFC][PATCH v5 09/21] virtagent: add va.getdmesg RP
From: |
Jes Sorensen |
Subject: |
Re: [Qemu-devel] Re: [RFC][PATCH v5 09/21] virtagent: add va.getdmesg RPC |
Date: |
Wed, 08 Dec 2010 20:22:59 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.12) Gecko/20101103 Fedora/1.0-0.33.b2pre.fc14 Lightning/1.0b3pre Thunderbird/3.1.6 |
On 12/07/10 18:32, Michael Roth wrote:
> On 12/07/2010 08:37 AM, Jes Sorensen wrote:
>> On 12/03/10 19:03, Michael Roth wrote:
>>> +static xmlrpc_value *va_getdmesg(xmlrpc_env *env,
>>> + xmlrpc_value *param,
>>> + void *user_data)
>>> +{
>>> + char *dmesg_buf = NULL, cmd[256];
>>> + int ret;
>>> + xmlrpc_value *result = NULL;
>>> + FILE *pipe;
>>> +
>>> + SLOG("va_getdmesg()");
>>> +
>>> + dmesg_buf = qemu_mallocz(VA_DMESG_LEN + 2048);
>>> + sprintf(cmd, "dmesg -s %d", VA_DMESG_LEN);
>>
>> What happens if the guest's dmesg buffer is larger than your hardcoded
>> value?
>
> It'll end up getting truncated by the fread() later:
>
> ret = fread(dmesg_buf, sizeof(char), VA_DMESG_LEN, pipe);
>
> That's where the dmesg -s VA_DMESG_LEN comes into play, it should size
> things such that we can buffer up till the end of the dmesg output.
>
> This param is kind of quirky though, size doesn't seem to have an affect
> for anything below 4KB, but if we stick with VA_DMESG_LEN >= 4KB this
> should cover us, unless it's a distro-specific. But it should blow
> anything up, at least.
I am wary of these hard coded constants. Isn't there a way to set the
kernel's dmesg buffer size, or is that only a compile time option?
Cheers,
Jes
- [Qemu-devel] Re: [RFC][PATCH v5 07/21] virtagent: add va.getfile RPC, (continued)
- [Qemu-devel] Re: [RFC][PATCH v5 07/21] virtagent: add va.getfile RPC, Jes Sorensen, 2010/12/07
- [Qemu-devel] Re: [RFC][PATCH v5 07/21] virtagent: add va.getfile RPC, Adam Litke, 2010/12/07
- [Qemu-devel] Re: [RFC][PATCH v5 07/21] virtagent: add va.getfile RPC, Jes Sorensen, 2010/12/08
- [Qemu-devel] Re: [RFC][PATCH v5 07/21] virtagent: add va.getfile RPC, Adam Litke, 2010/12/09
- [Qemu-devel] Re: [RFC][PATCH v5 07/21] virtagent: add va.getfile RPC, Michael Roth, 2010/12/09
- [Qemu-devel] Re: [RFC][PATCH v5 07/21] virtagent: add va.getfile RPC, Jes Sorensen, 2010/12/10
[Qemu-devel] [RFC][PATCH v5 09/21] virtagent: add va.getdmesg RPC, Michael Roth, 2010/12/03
[Qemu-devel] [RFC][PATCH v5 08/21] virtagent: add agent_viewfile qmp/hmp command, Michael Roth, 2010/12/03
[Qemu-devel] Re: [RFC][PATCH v5 08/21] virtagent: add agent_viewfile qmp/hmp command, Jes Sorensen, 2010/12/07