Re: [PATCH 2/5] filetype: add GPT support

From: Sascha Hauer <s.hauer@pengutronix.de>
To: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: barebox@lists.infradead.org, Rob Herring <rob.herring@calxeda.com>
Subject: Re: [PATCH 2/5] filetype: add GPT support
Date: Fri, 15 Feb 2013 18:48:24 +0100	[thread overview]
Message-ID: <20130215174824.GB1906@pengutronix.de> (raw)
In-Reply-To: <20130215173655.GC19322@game.jcrosoft.org>

On Fri, Feb 15, 2013 at 06:36:55PM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 18:32 Fri 15 Feb     , Sascha Hauer wrote:
> > On Fri, Feb 15, 2013 at 02:35:14PM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> > > GPT need to be check before MBR
> > > 
> > > Cc: Rob Herring <rob.herring@calxeda.com>
> > > Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
> > > ---
> > >  common/filetype.c  |   47 +++++++++++++++++++++++++++++++++++++++++++++++
> > >  include/filetype.h |    1 +
> > >  2 files changed, 48 insertions(+)
> > > 
> > > diff --git a/common/filetype.c b/common/filetype.c
> > > index 22fc621..06fa803 100644
> > > --- a/common/filetype.c
> > > +++ b/common/filetype.c
> > > @@ -48,6 +48,7 @@ static const struct filetype_str filetype_str[] = {
> > >  	[filetype_bmp] = { "BMP image", "bmp" },
> > >  	[filetype_png] = { "PNG image", "png" },
> > >  	[filetype_ext] = { "ext filesystem", "ext" },
> > > +	[filetype_gpt] = { "GUID Partition Table", "gpt" },
> > >  };
> > >  
> > >  const char *file_type_to_string(enum filetype f)
> > > @@ -69,9 +70,52 @@ const char *file_type_to_short_string(enum filetype f)
> > >  #define MBR_StartSector		8	/* MBR: Offset of Starting Sector in Partition Table Entry */
> > >  #define BS_55AA			510	/* Boot sector signature (2) */
> > >  #define MBR_Table		446	/* MBR: Partition table offset (2) */
> > > +#define MBR_partition_size	16	/* MBR: Partition table offset (2) */
> > >  #define BS_FilSysType32		82	/* File system type (1) */
> > >  #define BS_FilSysType		54	/* File system type (1) */
> > >  
> > > +#define MBR_PART_sys_ind	4
> > > +#define MBR_PART_start_sect	8
> > > +#define MBR_OSTYPE_EFI_GPT	0xee
> > > +
> > > +static inline int pmbr_part_valid(const uint8_t *buf)
> > > +{
> > > +	if (buf[MBR_PART_sys_ind] == MBR_OSTYPE_EFI_GPT &&
> > > +		get_unaligned_le32(&buf[MBR_PART_start_sect]) == 1UL) {
> > > +		return 1;
> > > +	}
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +/**
> > > + * is_gpt_valid(): test Protective MBR for validity and EFI PART
> > > + * @mbr: pointer to a legacy mbr structure
> > > + *
> > > + * Description: Returns 1 if PMBR is valid, 0 otherwise.
> > > + * Validity depends on two things:
> > > + *  1) MSDOS signature is in the last two bytes of the MBR
> > > + *  2) One partition of type 0xEE is found
> > 
> > Still wrong. This describes is_pmbr_valid, but the function is named and
> > implements is_gpt_valid. I suggest implemting a real is_pmbr_valid
> > function and call it from is_gpt_valid which additionally checks for the
> > gpt header.
> 
> we test both pmr and EFI PART fo this is right
> 
> test Protective MBR for validity and EFI PART
> 
> so the comment is correct

The comment says: "Returns 1 if PMBR is valid, 0 otherwise", but the
function implements "Returns 1 if PBMR is valid *and* an EFI header is
found, 0 otherwise"

Sascha

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