Re: [PATCH v2] modpost: move the namespace field in Module.symvers last

On Wed, Mar 11, 2020 at 10:02 AM Jessica Yu jeyu@kernel.org wrote:

In order to preserve backwards compatability with kmod tools, we have to move the namespace field in Module.symvers last, as the depmod -e -E option looks at the first three fields in Module.symvers to check symbol versions (and it's expected they stay in the original order of crc, symbol, module).

In addition, update an ancient comment above read_dump() in modpost that suggested that the export type field in Module.symvers was optional. I suspect that there were historical reasons behind that comment that are no longer accurate. We have been unconditionally printing the export type since 2.6.18 (commit bd5cbcedf44), which is over a decade ago now.

Fix up read_dump() to treat each field as non-optional. I suspect the original read_dump() code treated the export field as optional in order to support pre <= 2.6.18 Module.symvers (which did not have the export type field). Note that although symbol namespaces are optional, the field will not be omitted from Module.symvers if a symbol does not have a namespace. In this case, the field will simply be empty and the next delimiter or end of line will follow.

Cc: stable@vger.kernel.org Fixes: cb9b55d21fe0 ("modpost: add support for symbol namespaces") Tested-by: Matthias Maennich maennich@google.com Reviewed-by: Matthias Maennich maennich@google.com Reviewed-by: Lucas De Marchi lucas.demarchi@intel.com Signed-off-by: Jessica Yu jeyu@kernel.org

---

v2:

• Explain the changes to read_dump() and the comment (and provide historical context) in the commit message. (Lucas De Marchi)

Great, thanks for fixing this.

Lucas De Marchi

Documentation/kbuild/modules.rst | 4 ++-- scripts/export_report.pl | 2 +- scripts/mod/modpost.c | 24 ++++++++++++------------ 3 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/Documentation/kbuild/modules.rst b/Documentation/kbuild/modules.rst index 69fa48ee93d6..e0b45a257f21 100644 --- a/Documentation/kbuild/modules.rst +++ b/Documentation/kbuild/modules.rst @@ -470,9 +470,9 @@ build.

    The syntax of the Module.symvers file is::

•   <CRC>       <Symbol>          <Namespace>  <Module>                         <Export Type>
  

•   <CRC>       <Symbol>         <Module>                         <Export Type>     <Namespace>
  
  

•   0xe1cc2a05  usb_stor_suspend  USB_STORAGE  drivers/usb/storage/usb-storage  EXPORT_SYMBOL_GPL
  

•   0xe1cc2a05  usb_stor_suspend drivers/usb/storage/usb-storage  EXPORT_SYMBOL_GPL USB_STORAGE
  
    The fields are separated by tabs and values may be empty (e.g.
    if no namespace is defined for an exported symbol).
  

diff --git a/scripts/export_report.pl b/scripts/export_report.pl index 548330e8c4e7..feb3d5542a62 100755 --- a/scripts/export_report.pl +++ b/scripts/export_report.pl @@ -94,7 +94,7 @@ if (defined $opt{'o'}) { # while ( <$module_symvers> ) { chomp;

•   my (undef, $symbol, $namespace, $module, $gpl) = split('\t');
  

•   my (undef, $symbol, $module, $gpl, $namespace) = split('\t');
    $SYMBOL { $symbol } =  [ $module , "0" , $symbol, $gpl];
  

} close($module_symvers); diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index a3d8370f9544..e1963ef8c07c 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -2421,7 +2421,7 @@ static void write_if_changed(struct buffer *b, const char *fname) }

/* parse Module.symvers file. line format:

• • 0x12345678<tab>symbol<tab>module[[<tab>export]<tab>something]

• • 0x12345678<tab>symbol<tab>module<tab>export<tab>namespace
  **/

static void read_dump(const char *fname, unsigned int kernel) { @@ -2434,7 +2434,7 @@ static void read_dump(const char *fname, unsigned int kernel) return;

    while ((line = get_next_line(&pos, file, size))) {

•           char *symname, *namespace, *modname, *d, *export, *end;
  

•           char *symname, *namespace, *modname, *d, *export;
            unsigned int crc;
            struct module *mod;
            struct symbol *s;
  

@@ -2442,16 +2442,16 @@ static void read_dump(const char *fname, unsigned int kernel) if (!(symname = strchr(line, '\t'))) goto fail; *symname++ = '\0';

•           if (!(namespace = strchr(symname, '\t')))
  

•                   goto fail;
  

•           *namespace++ = '\0';
  

•           if (!(modname = strchr(namespace, '\t')))
  

•           if (!(modname = strchr(symname, '\t')))
                    goto fail;
            *modname++ = '\0';
  

•           if ((export = strchr(modname, '\t')) != NULL)
  

•                   *export++ = '\0';
  

•           if (export && ((end = strchr(export, '\t')) != NULL))
  

•                   *end = '\0';
  

•           if (!(export = strchr(modname, '\t')))
  

•                   goto fail;
  

•           *export++ = '\0';
  

•           if (!(namespace = strchr(export, '\t')))
  

•                   goto fail;
  

•           *namespace++ = '\0';
  

•           crc = strtoul(line, &d, 16);
            if (*symname == '\0' || *modname == '\0' || *d != '\0')
                    goto fail;
  

@@ -2502,9 +2502,9 @@ static void write_dump(const char *fname) namespace = symbol->namespace; buf_printf(&buf, "0x%08x\t%s\t%s\t%s\t%s\n", symbol->crc, symbol->name,

•                                      namespace ? namespace : "",
                                       symbol->module->name,
  

•                                      export_str(symbol->export));
  

•                                      export_str(symbol->export),
  

•                                      namespace ? namespace : "");
                    }
                    symbol = symbol->next;
            }
  

-- 2.16.4