On Fri, Apr 09, 2021 at 02:14:58AM -0400, Alexandre Ghiti wrote: > This is a preparatory patch for relocatable kernel and sv48 support. > > The kernel used to be linked at PAGE_OFFSET address therefore we could use > the linear mapping for the kernel mapping. But the relocated kernel base > address will be different from PAGE_OFFSET and since in the linear mapping, > two different virtual addresses cannot point to the same physical address, > the kernel mapping needs to lie outside the linear mapping so that we don't > have to copy it at the same physical offset. > > The kernel mapping is moved to the last 2GB of the address space, BPF > is now always after the kernel and modules use the 2GB memory range right > before the kernel, so BPF and modules regions do not overlap. KASLR > implementation will simply have to move the kernel in the last 2GB range > and just take care of leaving enough space for BPF. > > In addition, by moving the kernel to the end of the address space, both > sv39 and sv48 kernels will be exactly the same without needing to be > relocated at runtime. > > Suggested-by: Arnd Bergmann <arnd@xxxxxxxx> > Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx> In next-20210416, when booting a riscv32 image in qemu, this patch results in: [ 0.000000] Linux version 5.12.0-rc7-next-20210416 (groeck@desktop) (riscv32-linux-gcc (GCC) 10.3.0, GNU ld (GNU Binutils) 2.36.1) #1 SMP Fri Apr 16 10:38:09 PDT 2021 [ 0.000000] OF: fdt: Ignoring memory block 0x80000000 - 0xa0000000 [ 0.000000] Machine model: riscv-virtio,qemu [ 0.000000] earlycon: uart8250 at MMIO 0x10000000 (options '115200') [ 0.000000] printk: bootconsole [uart8250] enabled [ 0.000000] efi: UEFI not found. [ 0.000000] Kernel panic - not syncing: init_resources: Failed to allocate 160 bytes [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.12.0-rc7-next-20210416 #1 [ 0.000000] Hardware name: riscv-virtio,qemu (DT) [ 0.000000] Call Trace: [ 0.000000] [<80005292>] walk_stackframe+0x0/0xce [ 0.000000] [<809f4db8>] dump_backtrace+0x38/0x46 [ 0.000000] [<809f4dd4>] show_stack+0xe/0x16 [ 0.000000] [<809ff1d0>] dump_stack+0x92/0xc6 [ 0.000000] [<809f4fee>] panic+0x10a/0x2d8 [ 0.000000] [<80c02b24>] setup_arch+0x2a0/0x4ea [ 0.000000] [<80c006b0>] start_kernel+0x90/0x628 [ 0.000000] ---[ end Kernel panic - not syncing: init_resources: Failed to allocate 160 bytes ]--- Reverting it fixes the problem. I understand that the version in -next is different to this version of the patch, but I also tried v4 and it still crashes with the same error message. Guenter
