+++ John Stultz [30/03/20 23:25 -0700]:
On Mon, Mar 30, 2020 at 10:49 PM John Stultz john.stultz@linaro.org wrote:
On Wed, Mar 11, 2020 at 10:03 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)
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).Despite the documentation here claiming the namespace field can be empty, I'm seeing some trouble with this patch when building external modules: FATAL: parse error in symbol dump file
I've confirmed reverting it make things work again, but its not clear to me quite yet why.
The only difference I can find is that the Module.symvers in the external module project doesn't seem to have a tab at the end of each line (where as Module.symvers for the kernel - which doesn't seem to have any namespace names - does).
Is there something I need to tweak on the external Kbuild to get Module.symvers to be generated properly (with the empty tab at the end) for this new change? Or does the parser need to be a bit more flexible?
One extra clue on this: I noticed the external module Makefile had KBUILD_EXTRA_SYMBOLS="$(EXTRA_SYMBOLS)" in the $(MAKE) string, where EXTRA_SYMBOLS pointed to some files that no longer exist. I removed the KBUILD_EXTRA_SYMBOLS= argument, and magically, the generated Module.symvers now had tabs at the end of each line.
I wonder if there some path in the KBUILD_EXTRA_SYMBOLS= handling that isn't generating the output in the same way?
I'm afraid we're going to need some specifics on reproducing this issue. Could you provide a reproducer or steps on how to reproduce? I have not been able to trigger this problem even with KBUILD_EXTRA_SYMBOLS pointing to an invalid path (I also tested with valid paths).
I tested with a skeleton external module that exports two functions, one with a namespace and one without. I built this module against the latest v5.6 kernel. The generated Module.symvers was correct - the namespaced function had the namespace at the end and the other function without a namespace had a tab at the end.
I also tested with two external modules, one with a symbol dependency on the other, so KBUILD_EXTRA_SYMBOLS usage is required here. The generated Module.symvers was also correct here.
The only advice I can offer at this time is that all external modules must be built against the new kernel to generate a correctly formated Module.symvers file. If you have any KBUILD_EXTRA_SYMBOLS pointing to an outdated Module.symvers file for example, you will see the "FATAL: parse error in symbol dump file" error.
Hope this helps,
Jessica