From: Magnus Damm <damm@xxxxxxxxxxxxx> Update the copy_oldmem_page() function to ioremap() only when accessing memory that is outside the regular range of system memory that is managed by the kernel. Without this patch a warning is triggered in the ARM-specific ioremap implementation, see WARN_ON(pfn_valid()) in ioremap.c The copy_oldmem_page() function is used by the secondary crash kernel to access memory using the /proc/vmcore code implemented in fs/proc/vmcore.c. To pass information from the first kernel to the secondary crash kernel a kernel command line option is used to point out where the elf core hdr is located. The crash kernel is loaded through kexec-tools which also contains code that reserves memory for the elfcorehdr= option. This memory block is reserved _inside_ the main system memory of the secondary kernel. The /proc/vmcore code in the secondary kernel is however using copy_oldmem_page() to access both this elfcorehdr area and the rest of the memory used by the the first kernel. So the copy_oldmem_page() function is used to access data that may be located in system memory, or it may be outside. Always using ioremap will not work, so this patch makes it conditional based on pfn_valid(). For more details please look at the sh7372-based example here: http://permalink.gmane.org/gmane.linux.ports.sh.devel/11502 Signed-off-by: Magnus Damm <damm at opensource.se> --- arch/arm/kernel/crash_dump.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) --- 0001/arch/arm/kernel/crash_dump.c +++ work/arch/arm/kernel/crash_dump.c 2011-06-18 20:59:49.000000000 +0900 @@ -39,9 +39,13 @@ ssize_t copy_oldmem_page(unsigned long p if (!csize) return 0; - vaddr = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE); - if (!vaddr) - return -ENOMEM; + if (pfn_valid(pfn)) { + vaddr = phys_to_virt(pfn << PAGE_SHIFT); + } else { + vaddr = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE); + if (!vaddr) + return -ENOMEM; + } if (userbuf) { if (copy_to_user(buf, vaddr + offset, csize)) { @@ -52,6 +56,8 @@ ssize_t copy_oldmem_page(unsigned long p memcpy(buf, vaddr + offset, csize); } - iounmap(vaddr); + if (!pfn_valid(pfn)) + iounmap(vaddr); + return csize; }
