From a352fde45ef58ed4766c074d772c3cf9f4410fd7 Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Wed, 1 May 2013 22:00:51 +0100 Subject: [PATCH] [smbios] Allow access to unreferenced SMBIOS strings iPXE allows access to general SMBIOS settings using the syntax: smbios/.. This provides access to any fixed-offset field within an SMBIOS structure. This syntax is currently overloaded to interpret a zero as meaning that the byte at contains a string index; this provides access to SMBIOS strings (which are not located at fixed offsets). The "OEM Strings" SMBIOS structure contains strings which are not referenced by any fixed string index field within the structure. iPXE currently provides no way to access these strings. Fix by overloading the syntax for numerical SMBIOS settings to interpret an of zero as implying that contains a literal string index. The OEM Strings can then be accessed using: smbios/11.0.1 smbios/11.0.2 smbios/11.0.3 ... The actual byte at offset zero will always contain the structure type, which is already known since it must be specified in order to access the structure. There is thus no plausible existing use case for an offset of zero; overloading the syntax in this way should therefore not break compatibility with any existing scripts. The corner case where both and are zero is undefined (and, for now, will simply return a "not found" error). Signed-off-by: Michael Brown --- src/interface/smbios/smbios_settings.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/src/interface/smbios/smbios_settings.c b/src/interface/smbios/smbios_settings.c index 7b2efcd7..17f9a48e 100644 --- a/src/interface/smbios/smbios_settings.c +++ b/src/interface/smbios/smbios_settings.c @@ -99,16 +99,22 @@ static int smbios_fetch ( struct settings *settings __unused, uint8_t buf[structure.header.len]; const void *raw; union uuid uuid; + unsigned int index; /* Read SMBIOS structure */ if ( ( rc = read_smbios_structure ( &structure, buf, sizeof ( buf ) ) ) != 0 ) return rc; - /* A tag length of zero indicates a string */ - if ( tag_len == 0 ) { - if ( ( rc = read_smbios_string ( &structure, - buf[tag_offset], + /* A of zero indicates that the byte at + * contains a string index. An of + * zero indicates that the contains a literal + * string index. + */ + if ( ( tag_len == 0 ) || ( tag_offset == 0 ) ) { + index = ( ( tag_offset == 0 ) ? + tag_len : buf[tag_offset] ); + if ( ( rc = read_smbios_string ( &structure, index, data, len ) ) < 0 ) { return rc; }