| Message ID | 20180226121718.3432bbd6@ThinkPad (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Feb 26, 2018 at 12:17:18PM +0100, Philipp Rudo wrote: > Hi AKASHI > > On Thu, 22 Feb 2018 20:17:22 +0900 > AKASHI Takahiro <takahiro.akashi@linaro.org> wrote: > > [...] > > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > > index 990adae52151..a6d14a768b3e 100644 > > --- a/kernel/kexec_file.c > > +++ b/kernel/kexec_file.c > > @@ -26,34 +26,83 @@ > > #include <linux/vmalloc.h> > > #include "kexec_internal.h" > > > > +const __weak struct kexec_file_ops * const kexec_file_loaders[] = {NULL}; > > + > > Having a weak definition of kexec_file_loaders causes trouble on s390 with > gcc 4.8 (newer versions seem to work fine). For me it looks like that in this > version gcc doesn't recognize __weak but use the default value for > optimization. This leads to _kexec_kernel_image_probe to always return ENOEXEC > because the for-loop gets optimized out. I gave it a try to compile with gcc 4.9 (not 4.8) for arm64 and didn't see any errors or warnings, but > The problem can easily be worked around by declaring kexec_file_loaders in > include/linux/kexec.h and defining it in arch code. In particular doing this > > diff --git a/include/linux/kexec.h b/include/linux/kexec.h > index 37e9dce518aa..fc0788540d90 100644 > --- a/include/linux/kexec.h > +++ b/include/linux/kexec.h > @@ -139,6 +139,8 @@ struct kexec_file_ops { > #endif > }; > > +extern const struct kexec_file_ops * const kexec_file_loaders[]; > + > /** > * struct kexec_buf - parameters for finding a place for a buffer in memory > * @image: kexec image in which memory to search. > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > index 17ba407d0e79..4e3d1e4bc7f6 100644 > --- a/kernel/kexec_file.c > +++ b/kernel/kexec_file.c > @@ -31,8 +31,6 @@ > #include <linux/vmalloc.h> > #include "kexec_internal.h" > > -const __weak struct kexec_file_ops * const kexec_file_loaders[] = {NULL}; > - > #ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY > static int kexec_calculate_store_digests(struct kimage *image); > #else Your change is just fine with me, too. I will incorporate it in my next version. Thanks, -Takahiro AKASHI > A nice side effect of this solution is, that a developer who forgets to define > kexec_file_loaders gets a linker error. So he directly knows what's missing > instead of first having to find out where/why an error gets returned. > > Otherwise the series is fine for me. > > Thanks > Philipp > > > #ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY > > static int kexec_calculate_store_digests(struct kimage *image); > > #else > > static int kexec_calculate_store_digests(struct kimage *image) { return 0; }; > > #endif > > > > +int _kexec_kernel_image_probe(struct kimage *image, void *buf, > > + unsigned long buf_len) > > +{ > > + const struct kexec_file_ops * const *fops; > > + int ret = -ENOEXEC; > > + > > + for (fops = &kexec_file_loaders[0]; *fops && (*fops)->probe; ++fops) { > > + ret = (*fops)->probe(buf, buf_len); > > + if (!ret) { > > + image->fops = *fops; > > + return ret; > > + } > > + } > > + > > + return ret; > > +} > > + > > /* Architectures can provide this probe function */ > > int __weak arch_kexec_kernel_image_probe(struct kimage *image, void *buf, > > unsigned long buf_len) > > { > > - return -ENOEXEC; > > + return _kexec_kernel_image_probe(image, buf, buf_len); > > +} > > + > > +void *_kexec_kernel_image_load(struct kimage *image) > > +{ > > + if (!image->fops || !image->fops->load) > > + return ERR_PTR(-ENOEXEC); > > + > > + return image->fops->load(image, image->kernel_buf, > > + image->kernel_buf_len, image->initrd_buf, > > + image->initrd_buf_len, image->cmdline_buf, > > + image->cmdline_buf_len); > > } > > > > void * __weak arch_kexec_kernel_image_load(struct kimage *image) > > { > > - return ERR_PTR(-ENOEXEC); > > + return _kexec_kernel_image_load(image); > > +} > > + > > +int _kimage_file_post_load_cleanup(struct kimage *image) > > +{ > > + if (!image->fops || !image->fops->cleanup) > > + return 0; > > + > > + return image->fops->cleanup(image->image_loader_data); > > } > > > > int __weak arch_kimage_file_post_load_cleanup(struct kimage *image) > > { > > - return -EINVAL; > > + return _kimage_file_post_load_cleanup(image); > > } > > > > #ifdef CONFIG_KEXEC_VERIFY_SIG > > +int _kexec_kernel_verify_sig(struct kimage *image, void *buf, > > + unsigned long buf_len) > > +{ > > + if (!image->fops || !image->fops->verify_sig) { > > + pr_debug("kernel loader does not support signature verification.\n"); > > + return -EKEYREJECTED; > > + } > > + > > + return image->fops->verify_sig(buf, buf_len); > > +} > > + > > int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf, > > unsigned long buf_len) > > { > > - return -EKEYREJECTED; > > + return _kexec_kernel_verify_sig(image, buf, buf_len); > > } > > #endif > > >
On Tue, 27 Feb 2018 11:03:07 +0900 AKASHI Takahiro <takahiro.akashi@linaro.org> wrote: > On Mon, Feb 26, 2018 at 12:17:18PM +0100, Philipp Rudo wrote: > > Hi AKASHI > > > > On Thu, 22 Feb 2018 20:17:22 +0900 > > AKASHI Takahiro <takahiro.akashi@linaro.org> wrote: > > > > [...] > > > > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > > > index 990adae52151..a6d14a768b3e 100644 > > > --- a/kernel/kexec_file.c > > > +++ b/kernel/kexec_file.c > > > @@ -26,34 +26,83 @@ > > > #include <linux/vmalloc.h> > > > #include "kexec_internal.h" > > > > > > +const __weak struct kexec_file_ops * const kexec_file_loaders[] = {NULL}; > > > + > > > > Having a weak definition of kexec_file_loaders causes trouble on s390 with > > gcc 4.8 (newer versions seem to work fine). For me it looks like that in this > > version gcc doesn't recognize __weak but use the default value for > > optimization. This leads to _kexec_kernel_image_probe to always return ENOEXEC > > because the for-loop gets optimized out. > > I gave it a try to compile with gcc 4.9 (not 4.8) for arm64 > and didn't see any errors or warnings, but I talked to our compiler guys, and it looks like its a bug in gcc which was introduced with gcc 4.8 and removed again with gcc 4.9. So I was just extremely lucky hitting the sweat spot... > > The problem can easily be worked around by declaring kexec_file_loaders in > > include/linux/kexec.h and defining it in arch code. In particular doing this > > > > diff --git a/include/linux/kexec.h b/include/linux/kexec.h > > index 37e9dce518aa..fc0788540d90 100644 > > --- a/include/linux/kexec.h > > +++ b/include/linux/kexec.h > > @@ -139,6 +139,8 @@ struct kexec_file_ops { > > #endif > > }; > > > > +extern const struct kexec_file_ops * const kexec_file_loaders[]; > > + > > /** > > * struct kexec_buf - parameters for finding a place for a buffer in memory > > * @image: kexec image in which memory to search. > > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > > index 17ba407d0e79..4e3d1e4bc7f6 100644 > > --- a/kernel/kexec_file.c > > +++ b/kernel/kexec_file.c > > @@ -31,8 +31,6 @@ > > #include <linux/vmalloc.h> > > #include "kexec_internal.h" > > > > -const __weak struct kexec_file_ops * const kexec_file_loaders[] = {NULL}; > > - > > #ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY > > static int kexec_calculate_store_digests(struct kimage *image); > > #else > > Your change is just fine with me, too. > I will incorporate it in my next version. Thanks a lot Philipp > Thanks, > -Takahiro AKASHI > > > A nice side effect of this solution is, that a developer who forgets to define > > kexec_file_loaders gets a linker error. So he directly knows what's missing > > instead of first having to find out where/why an error gets returned. > > > > Otherwise the series is fine for me. > > > > Thanks > > Philipp > > > > > #ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY > > > static int kexec_calculate_store_digests(struct kimage *image); > > > #else > > > static int kexec_calculate_store_digests(struct kimage *image) { return 0; }; > > > #endif > > > > > > +int _kexec_kernel_image_probe(struct kimage *image, void *buf, > > > + unsigned long buf_len) > > > +{ > > > + const struct kexec_file_ops * const *fops; > > > + int ret = -ENOEXEC; > > > + > > > + for (fops = &kexec_file_loaders[0]; *fops && (*fops)->probe; ++fops) { > > > + ret = (*fops)->probe(buf, buf_len); > > > + if (!ret) { > > > + image->fops = *fops; > > > + return ret; > > > + } > > > + } > > > + > > > + return ret; > > > +} > > > + > > > /* Architectures can provide this probe function */ > > > int __weak arch_kexec_kernel_image_probe(struct kimage *image, void *buf, > > > unsigned long buf_len) > > > { > > > - return -ENOEXEC; > > > + return _kexec_kernel_image_probe(image, buf, buf_len); > > > +} > > > + > > > +void *_kexec_kernel_image_load(struct kimage *image) > > > +{ > > > + if (!image->fops || !image->fops->load) > > > + return ERR_PTR(-ENOEXEC); > > > + > > > + return image->fops->load(image, image->kernel_buf, > > > + image->kernel_buf_len, image->initrd_buf, > > > + image->initrd_buf_len, image->cmdline_buf, > > > + image->cmdline_buf_len); > > > } > > > > > > void * __weak arch_kexec_kernel_image_load(struct kimage *image) > > > { > > > - return ERR_PTR(-ENOEXEC); > > > + return _kexec_kernel_image_load(image); > > > +} > > > + > > > +int _kimage_file_post_load_cleanup(struct kimage *image) > > > +{ > > > + if (!image->fops || !image->fops->cleanup) > > > + return 0; > > > + > > > + return image->fops->cleanup(image->image_loader_data); > > > } > > > > > > int __weak arch_kimage_file_post_load_cleanup(struct kimage *image) > > > { > > > - return -EINVAL; > > > + return _kimage_file_post_load_cleanup(image); > > > } > > > > > > #ifdef CONFIG_KEXEC_VERIFY_SIG > > > +int _kexec_kernel_verify_sig(struct kimage *image, void *buf, > > > + unsigned long buf_len) > > > +{ > > > + if (!image->fops || !image->fops->verify_sig) { > > > + pr_debug("kernel loader does not support signature verification.\n"); > > > + return -EKEYREJECTED; > > > + } > > > + > > > + return image->fops->verify_sig(buf, buf_len); > > > +} > > > + > > > int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf, > > > unsigned long buf_len) > > > { > > > - return -EKEYREJECTED; > > > + return _kexec_kernel_verify_sig(image, buf, buf_len); > > > } > > > #endif > > > > > >
diff --git a/include/linux/kexec.h b/include/linux/kexec.h index 37e9dce518aa..fc0788540d90 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -139,6 +139,8 @@ struct kexec_file_ops { #endif }; +extern const struct kexec_file_ops * const kexec_file_loaders[]; + /** * struct kexec_buf - parameters for finding a place for a buffer in memory * @image: kexec image in which memory to search. diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index 17ba407d0e79..4e3d1e4bc7f6 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -31,8 +31,6 @@ #include <linux/vmalloc.h> #include "kexec_internal.h" -const __weak struct kexec_file_ops * const kexec_file_loaders[] = {NULL}; - #ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY static int kexec_calculate_store_digests(struct kimage *image); #else