Re: [PATCH 3/7] ppc64: detect zImage files and load the uncompressed vmlinux

[Laurent Dufour <ldufour@linux.vnet.ibm.com>]

On 18/04/2014 16:08, Cédric Le Goater wrote:
> The zImage* executable files on ppc64 use a special section called
> ".kernel:vmlinux.strip" which contains a compressed vmlinux executable
> file.
> 
> This patch adds a service to detect and unzip such a section in a
> malloc'ed buffer. The buffer is then used in elf_ppc64_load() to
> load the new vmlinux.
> 
> Signed-off-by: Cédric Le Goater <clg@fr.ibm.com>
> ---
>  kexec/arch/ppc64/kexec-elf-ppc64.c    |   15 ++++
>  kexec/arch/ppc64/kexec-ppc64.h        |    2 +
>  kexec/arch/ppc64/kexec-zImage-ppc64.c |  123 +++++++++++++++++++++++++++++++++
>  3 files changed, 140 insertions(+)
> 
> diff --git a/kexec/arch/ppc64/kexec-elf-ppc64.c b/kexec/arch/ppc64/kexec-elf-ppc64.c
> index ce1036762582..069d8ba6e690 100644
> --- a/kexec/arch/ppc64/kexec-elf-ppc64.c
> +++ b/kexec/arch/ppc64/kexec-elf-ppc64.c
> @@ -116,6 +116,8 @@ int elf_ppc64_load(int argc, char **argv, const char *buf, off_t len,
>  	uint64_t toc_addr;
>  	uint32_t my_run_at_load;
>  	unsigned int slave_code[256/sizeof (unsigned int)], master_entry;
> +	void *vmlinux_addr;
> +	int vmlinux_size;
>  
>  	/* See options.h -- add any more there, too. */
>  	static const struct option options[] = {
> @@ -184,6 +186,7 @@ int elf_ppc64_load(int argc, char **argv, const char *buf, off_t len,
>  		modified_cmdline_len = strlen(modified_cmdline);
>  	}
>  
> +retry:
>  	/* Parse the Elf file */
>  	result = build_elf_exec_info(buf, len, &ehdr, 0);
>  	if (result < 0) {
> @@ -191,6 +194,18 @@ int elf_ppc64_load(int argc, char **argv, const char *buf, off_t len,
>  		return result;
>  	}
>  
> +	/* If this is a zimage boot wrapper, rebuild the elf info on
> +	 * the new vmlinux which has been unzipped and go on with the
> +	 * kernel load.
> +	 */
> +	if (!zImage_ppc64_unzip(&ehdr, &vmlinux_addr, &vmlinux_size)) {
> +		free_elf_info(&ehdr);
> +		free((void *) buf);
> +		buf = vmlinux_addr;
> +		len = vmlinux_size;
> +		goto retry;
> +	}
> +
>  	/* Load the Elf data. Physical load addresses in elf64 header do not
>  	 * show up correctly. Use user supplied address for now to patch the
>  	 * elf header
> diff --git a/kexec/arch/ppc64/kexec-ppc64.h b/kexec/arch/ppc64/kexec-ppc64.h
> index 9a0aecff7b33..e546d4737bfa 100644
> --- a/kexec/arch/ppc64/kexec-ppc64.h
> +++ b/kexec/arch/ppc64/kexec-ppc64.h
> @@ -37,4 +37,6 @@ typedef struct mem_rgns {
>  
>  extern mem_rgns_t usablemem_rgns;
>  
> +int zImage_ppc64_unzip(struct mem_ehdr *ehdr, void **buf, int *len);
> +
>  #endif /* KEXEC_PPC64_H */
> diff --git a/kexec/arch/ppc64/kexec-zImage-ppc64.c b/kexec/arch/ppc64/kexec-zImage-ppc64.c
> index d084ee587be5..67d751f19d7d 100644
> --- a/kexec/arch/ppc64/kexec-zImage-ppc64.c
> +++ b/kexec/arch/ppc64/kexec-zImage-ppc64.c
> @@ -30,6 +30,9 @@
>  #include <getopt.h>
>  #include <linux/elf.h>
>  #include "../../kexec.h"
> +#include "kexec-ppc64.h"
> +
> +#include <zlib.h>
>  
>  #define MAX_HEADERS 32
>  
> @@ -175,3 +178,123 @@ void zImage_ppc64_usage(void)
>  {
>  	fprintf(stderr, "zImage support is still broken\n");
>  }
> +
> +#define HEAD_CRC	2
> +#define EXTRA_FIELD	4
> +#define ORIG_NAME	8
> +#define COMMENT		0x10
> +#define RESERVED	0xe0
> +
> +static int get_header_len(const char *header)
> +{
> +	int len = 10;
> +	int flags = header[3];
> +
> +	/* check for gzip header */
> +	if ((header[0] != 0x1f) || (header[1] != 0x8b) ||
> +	    (header[2] != Z_DEFLATED) || (flags & RESERVED) != 0) {
> +		fprintf(stderr, "bad gzip header\n");
> +		return -1;
> +	}
> +
> +	if ((flags & EXTRA_FIELD) != 0)
> +		len = 12 + header[10] + (header[11] << 8);
> +
> +	if ((flags & ORIG_NAME) != 0)
> +		while (header[len++] != 0)
> +				;
> +	if ((flags & COMMENT) != 0)
> +		while (header[len++] != 0)
> +			;
> +	if ((flags & HEAD_CRC) != 0)
> +		len += 2;
> +
> +	return len;
> +}
> +
> +static int gunzip(void *src, int srclen, void *dst, int dstlen)
> +{
> +	z_stream strm;
> +	int hdrlen;
> +	int len;
> +	int ret;
> +
> +	strm.zalloc = Z_NULL;
> +	strm.zfree = Z_NULL;
> +	strm.opaque = Z_NULL;
> +	strm.avail_in = 0;
> +	strm.next_in = Z_NULL;
> +
> +	hdrlen = get_header_len(src);
> +	if (hdrlen == -1)
> +		return -1;
> +
> +	if (hdrlen >= srclen) {
> +		fprintf(stderr, "gzip header too large : %d\n", hdrlen);
> +		return -1;
> +	}
> +
> +	ret = inflateInit2(&strm, -MAX_WBITS);
> +	if (ret != Z_OK) {
> +		fprintf(stderr, "inflateInit2 failed : %d\n", ret);
> +		return -1;
> +	}
> +
> +	/* skip gzip header */
> +	strm.total_in = hdrlen;
> +	strm.next_in = src + hdrlen;
> +	strm.avail_in = srclen - hdrlen;
> +
> +	strm.next_out = dst;
> +	strm.avail_out = dstlen;
> +
> +	ret = inflate(&strm, Z_FULL_FLUSH);
> +	if (ret != Z_OK && ret != Z_STREAM_END) {
> +		fprintf(stderr, "inflate failed: %d %s\n", ret, strm.msg);
> +		return -1;
> +	}
> +
> +	len = strm.next_out - (unsigned char *) dst;
> +
> +	inflateEnd(&strm);
> +
> +	return len;
> +}
> +
> +int zImage_ppc64_unzip(struct mem_ehdr *ehdr, void **buf, int *len)
> +{
> +	struct mem_shdr *shdr;
> +	void *vmlinuz_addr;
> +	unsigned long vmlinuz_size;
> +	unsigned int *vmlinux_sizep;
> +
> +	void *vmlinux_addr;
> +	int vmlinux_size;
> +
> +	shdr = elf_rel_find_section(ehdr, ".kernel:vmlinux.strip");
> +	if (!shdr)
> +		return -1;
> +
> +	vmlinuz_addr = (void *) shdr->sh_data;
> +	vmlinuz_size = shdr->sh_size;
> +
> +	 /* The size of the uncompressed file is stored in the last 4
> +	  * bytes. The vmlinux size should be less than 4G ... */
> +	vmlinux_sizep = (vmlinuz_addr + vmlinuz_size) - 4;
> +
> +	fprintf(stderr, "Found vmlinuz at %p, unzipping %d bytes\n",
> +		vmlinuz_addr, *vmlinux_sizep);

Hi Cédric,

I'd rather use dbgprintf instead of directly call fprintf here.

Laurent.

> +	vmlinux_addr = xmalloc(*vmlinux_sizep);
> +
> +	vmlinux_size = gunzip(vmlinuz_addr, vmlinuz_size,
> +			      vmlinux_addr, *vmlinux_sizep);
> +	if (vmlinux_size != *vmlinux_sizep) {
> +		fprintf(stderr, "gunzip failed : only got %d of %d bytes.\n",
> +				vmlinux_size, *vmlinux_sizep);
> +		return -1;
> +	}
> +
> +	*buf = vmlinux_addr;
> +	*len = vmlinux_size;
> +	return 0;
> +}
> 


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