linux-kernel - Re: [PATCH 2/2] x86: Add support for uncompressed kernel images

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Date:	Thu, 14 Nov 2013 09:45:12 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Christian Ruppert <christian.ruppert@...lis.com>,
	Pavel Roskin <proski@....org>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-kernel@...r.kernel.org,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	Noam Camus <noamc@...hip.com>
Subject: Re: [PATCH 2/2] x86: Add support for uncompressed kernel images

On 11/14/2013 12:38 AM, Christian Ruppert wrote:
> diff --git a/lib/decompress_copy.c b/lib/decompress_copy.c
> new file mode 100644
> index 0000000..8a41090
> --- /dev/null
> +++ b/lib/decompress_copy.c
> @@ -0,0 +1,47 @@
> +#include <linux/decompress/mm.h>
> +
> +#define NOZIP_BUFSZ (16 * 1024)
> +STATIC int INIT nozip(unsigned char *buf, int len,
> +			int(*fill)(void*, unsigned int),
> +			int(*flush)(void*, unsigned int),
> +			unsigned char *outbuf,
> +			int *pos,
> +			void(*error)(char *x))
> +{
> +	char *b;
> +
> +	if (buf)
> +		b = buf;
> +	else
> +		b = malloc(NOZIP_BUFSZ);
> +
> +	if (!b) {
> +		error("Out of memory while allocating buffer");
> +		return -1;
> +	}
> +
> +	if (flush) {
> +		if (!len)
> +			len = fill(b, NOZIP_BUFSZ);
> +
> +		len = flush(b, len);
> +	} else {
> +		if (!len)
> +			len = fill(outbuf, NOZIP_BUFSZ);
> +		else {
> +			int i;
> +			for (i = 0; i < len; i++)
> +				outbuf[i] = b[i];

Clever way of doing memcpy().  I know some other compression
implementations open-code memmove(), but using it for the entire data
set in the most common case is atrocious.  If we need to get a default
implementation of memmove() we should just do that.

	-hpa

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