| Message ID | 20140617155658.30560.578.stgit@nimbus (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
Hi Laurent, > The commit 71ec7c55ed91 introduced the magic symbol ".TOC." for ELFv2 > ABI. This symbol is built manually and has no CRC value computed. A > zero value is put in the CRC section to avoid modpost complaining > about a missing CRC. Unfortunately, this breaks the kernel module > loading when the kernel is relocated (kdump case for instance) > because of the relocation applied to the kcrctab values. > > This patch compute a CRC value for the TOC symbol which will match > the one compute by the kernel when it is relocated - aka '0 - > relocate_start' done in maybe_relocated called by check_version > (module.c). Adding Rusty since he maintains the module loader code. Anton > Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com> > Cc: Anton Blanchard <anton@samba.org> > --- > arch/powerpc/kernel/module_64.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/module_64.c > b/arch/powerpc/kernel/module_64.c index 077d2ce..a80c933 100644 > --- a/arch/powerpc/kernel/module_64.c > +++ b/arch/powerpc/kernel/module_64.c > @@ -315,8 +315,15 @@ static void dedotify_versions(struct > modversion_info *vers, struct modversion_info *end; > > for (end = (void *)vers + size; vers < end; vers++) > - if (vers->name[0] == '.') > + if (vers->name[0] == '.') { > memmove(vers->name, vers->name+1, strlen(vers->name)); > + /* The TOC symbol has no CRC computed. To avoid CRC > + * check failing, we must force it to the expected > + * value (see CRC check in module.c). > + */ > + if (!strcmp(vers->name, "TOC.")) > + vers->crc = -(unsigned long)reloc_start; > + } > } > > /* Undefined symbols which refer to .funcname, hack to funcname > (or .TOC.) */
On Thu, 2014-06-19 at 09:44 +1000, Anton Blanchard wrote: > Hi Laurent, > > > The commit 71ec7c55ed91 introduced the magic symbol ".TOC." for ELFv2 > > ABI. This symbol is built manually and has no CRC value computed. A > > zero value is put in the CRC section to avoid modpost complaining > > about a missing CRC. Unfortunately, this breaks the kernel module > > loading when the kernel is relocated (kdump case for instance) > > because of the relocation applied to the kcrctab values. > > > > This patch compute a CRC value for the TOC symbol which will match > > the one compute by the kernel when it is relocated - aka '0 - > > relocate_start' done in maybe_relocated called by check_version > > (module.c). > > Adding Rusty since he maintains the module loader code. This patch gives me: arch/powerpc/kernel/module_64.c: In function 'dedotify_versions': arch/powerpc/kernel/module_64.c:325:33: error: 'reloc_start' undeclared (first use in this function) arch/powerpc/kernel/module_64.c:325:33: note: each undeclared identifier is reported only once for each function it appears in Cheers, Ben.
On 24/06/2014 06:06, Benjamin Herrenschmidt wrote: > On Thu, 2014-06-19 at 09:44 +1000, Anton Blanchard wrote: >> Hi Laurent, >> >>> The commit 71ec7c55ed91 introduced the magic symbol ".TOC." for ELFv2 >>> ABI. This symbol is built manually and has no CRC value computed. A >>> zero value is put in the CRC section to avoid modpost complaining >>> about a missing CRC. Unfortunately, this breaks the kernel module >>> loading when the kernel is relocated (kdump case for instance) >>> because of the relocation applied to the kcrctab values. >>> >>> This patch compute a CRC value for the TOC symbol which will match >>> the one compute by the kernel when it is relocated - aka '0 - >>> relocate_start' done in maybe_relocated called by check_version >>> (module.c). >> >> Adding Rusty since he maintains the module loader code. > > This patch gives me: > > arch/powerpc/kernel/module_64.c: In function 'dedotify_versions': > arch/powerpc/kernel/module_64.c:325:33: error: 'reloc_start' undeclared (first use in this function) > arch/powerpc/kernel/module_64.c:325:33: note: each undeclared identifier is reported only once for each function it appears in Hi Ben, My mistake, I forgot to check building the kernel when module version checking is disabled. I'll send a v2 asap. Cheers, Laurent. > Cheers, > Ben. > >
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c index 077d2ce..a80c933 100644 --- a/arch/powerpc/kernel/module_64.c +++ b/arch/powerpc/kernel/module_64.c @@ -315,8 +315,15 @@ static void dedotify_versions(struct modversion_info *vers, struct modversion_info *end; for (end = (void *)vers + size; vers < end; vers++) - if (vers->name[0] == '.') + if (vers->name[0] == '.') { memmove(vers->name, vers->name+1, strlen(vers->name)); + /* The TOC symbol has no CRC computed. To avoid CRC + * check failing, we must force it to the expected + * value (see CRC check in module.c). + */ + if (!strcmp(vers->name, "TOC.")) + vers->crc = -(unsigned long)reloc_start; + } } /* Undefined symbols which refer to .funcname, hack to funcname (or .TOC.) */
The commit 71ec7c55ed91 introduced the magic symbol ".TOC." for ELFv2 ABI. This symbol is built manually and has no CRC value computed. A zero value is put in the CRC section to avoid modpost complaining about a missing CRC. Unfortunately, this breaks the kernel module loading when the kernel is relocated (kdump case for instance) because of the relocation applied to the kcrctab values. This patch compute a CRC value for the TOC symbol which will match the one compute by the kernel when it is relocated - aka '0 - relocate_start' done in maybe_relocated called by check_version (module.c). Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com> Cc: Anton Blanchard <anton@samba.org> --- arch/powerpc/kernel/module_64.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)