Re: [Crash-utility] [PATCH] Fix memory driver module build with kernel 5.8+

-----Original Message----- > Kernel commit fe557319aa06c23cffc9346000f119547e0f289a renamed > probe_kernel_{read,write} to copy_{from,to}_kernel_nofault. > > Additionally, commit 0493cb086353e786be56010780a0b7025b5db34c > unexported probe_kernel_write(), so writing kernel memory is > no longer possible from a module. > > I have renamed the functions in source, but I'm also adding wrappers to > allow building the module with older kernel versions. > > Without this patch, build with kernel 5.8 and later fails: > > kbuild/default/crash.c: In function 'crash_write': > kbuild/default/crash.c:189:12: error: implicit declaration of function 'probe_kernel_write'; did you mean > 'kernel_write'? [-Werror=implicit-function-declaration] > 189 | if (probe_kernel_write(vaddr, buffer, count)) { > | ^~~~~~~~~~~~~~~~~~ > | kernel_write > kbuild/default/crash.c: In function 'crash_read': > kbuild/default/crash.c:225:13: error: implicit declaration of function 'probe_kernel_read'; did you mean > 'kernel_read'? [-Werror=implicit-function-declaration] > 225 | if (probe_kernel_read(buffer, vaddr, count)) { > | ^~~~~~~~~~~~~~~~~ > | kernel_read > > Signed-off-by: Petr Tesarik <ptesarik(a)suse.com&gt; Thank you for catching this, the patch looks good to me. Acked-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; additionally, I think we should update the version number of this module. I'll add this change when applying, is it ok? Lianbo, Bhupesh.

-#define CRASH_VERSION "1.4" +#define CRASH_VERSION "1.5" Anyway, please wait for another ack. Thanks, Kazu > > --- > memory_driver/crash.c | 27 +++++++++++++++++++++++++-- > 1 file changed, 25 insertions(+), 2 deletions(-) > > --- a/memory_driver/crash.c > +++ b/memory_driver/crash.c > @@ -25,6 +25,7 @@ > *****************************************************************************/ > > #include <linux/module.h> > +#include <linux/version.h> > #include <linux/types.h> > #include <linux/miscdevice.h> > #include <linux/init.h> > @@ -37,6 +38,22 @@ > > extern int page_is_ram(unsigned long); > > +#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 8, 0) > + > +#define CAN_WRITE_KERNEL 1 > + > +static inline long copy_from_kernel_nofault(void *dst, const void *src, size_t size) > +{ > + return probe_kernel_read(dst, src, size); > +} > + > +static inline long copy_to_kernel_nofault(void *dst, const void *src, size_t size) > +{ > + return probe_kernel_write(dst, src, size); > +} > + > +#endif > + > #ifdef CONFIG_S390 > /* > * For swapped prefix pages get bounce buffer using xlate_dev_mem_ptr() > @@ -160,6 +177,8 @@ crash_llseek(struct file * file, loff_t > } > } > > +#ifdef CAN_WRITE_KERNEL > + > static ssize_t > crash_write(struct file *file, const char *buf, size_t count, loff_t *poff) > { > @@ -186,7 +205,7 @@ crash_write(struct file *file, const cha > return -EFAULT; > } > > - if (probe_kernel_write(vaddr, buffer, count)) { > + if (copy_to_kernel_nofault(vaddr, buffer, count)) { > unmap_virtual(page); > return -EFAULT; > } > @@ -197,6 +216,8 @@ crash_write(struct file *file, const cha > return written; > } > > +#endif > + > /* > * Determine the page address for an address offset value, > * get a virtual address for it, and copy it out. > @@ -222,7 +243,7 @@ crash_read(struct file *file, char *buf, > * Use bounce buffer to bypass the CONFIG_HARDENED_USERCOPY > * kernel text restriction. > */ > - if (probe_kernel_read(buffer, vaddr, count)) { > + if (copy_from_kernel_nofault(buffer, vaddr, count)) { > unmap_virtual(page); > return -EFAULT; > } > @@ -294,7 +315,9 @@ static struct file_operations crash_fops > .owner = THIS_MODULE, > .llseek = crash_llseek, > .read = crash_read, > +#ifdef CAN_WRITE_KERNEL > .write = crash_write, > +#endif > .unlocked_ioctl = crash_ioctl, > .open = crash_open, > .release = crash_release,