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Message-ID: <CAKi4VAKgeKDq9uiBKfXRjgMV9TTDHrRX8dT42N1zyqwCgkw35A@mail.gmail.com>
Date: Thu, 12 Mar 2020 00:17:39 -0700
From: Lucas De Marchi <lucas.de.marchi@...il.com>
To: Jessica Yu <jeyu@...nel.org>
Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>,
Matthias Maennich <maennich@...gle.com>,
stable@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] modpost: move the namespace field in Module.symvers last
On Wed, Mar 11, 2020 at 10:02 AM Jessica Yu <jeyu@...nel.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@...r.kernel.org
> Fixes: cb9b55d21fe0 ("modpost: add support for symbol namespaces")
> Tested-by: Matthias Maennich <maennich@...gle.com>
> Reviewed-by: Matthias Maennich <maennich@...gle.com>
> Reviewed-by: Lucas De Marchi <lucas.demarchi@...el.com>
> Signed-off-by: Jessica Yu <jeyu@...nel.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
>
--
Lucas De Marchi
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