On Wed, May 15, 2019 at 10:11:53PM +0200, Ard Biesheuvel wrote: > On Wed, 15 May 2019 at 12:24, Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> wrote: > > > > On Tue, May 14, 2019 at 11:42 PM Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote: > > > > > I'm not sure if early console is available at the time kaslr_early_init() > > > is called, but if yes, running with memblock=debug may shed some light. > > > > > > > I didn't trace the real reason causing this. But in this case, maybe > > > > don't call memblock_reserve() in kaslr? > > > > > > My concern that this uncovered a real bug which might hit us later. > > > > > Hi Mike, > > Thanks for the hint. I tried on my device but seems that earlycon > > happens after the warning call trace, so can't more information. > > > > Since on my device kaslr will be runned, I tried call > > memblock_reserve() in kaslr and not in > > setup_machine_fdt()#fixmap_remap_fdt, but got following warning > > > > I realize this is not documented sufficiently in the commit log, but > the reason I introduced the separate __fixmap_remap_fdt() [which does > not call memblock_reserve()] was that the KASLR init code should set > as little global state as possible, given that it is called with the > kernel mapped at the wrong virtual address. > > The KASLR boot sequence is something like > - map kernel at default [unrandomized] address > - apply relocations and clear BSS > - run KASLR init to map and parse the FDT [*] > - if KASLR is enabled, unmap the kernel and remap it at the randomized address > - apply relocations and clear BSS > - proceed with start_kernel() > > The issue you are seeing is caused by the fact that the memblock > bookkeeping gets into an inconsistent state due to the 2nd clearing of > BSS. Ah, now the warning makes perfect sense :) Thanks! > [*] The reason we need to map the FDT this early is to obtain the > random seed, and to check whether 'nokaslr' was passed on the kernel > command line. The reason arm64 deviates from other architectures in > this regard is that we don't have a decompressor, and so there is no > other execution context available where we can run C code to parse the > FDT etc before we enter the kernel proper. > > > > > > [ 0.000000] memblock_remove: > > [0x0001000000000000-0x0000fffffffffffe] arm64_memblock_init+0x28/0x224 > > [ 0.000000] memblock_remove: > > [0x0000004040000000-0x000000403ffffffe] arm64_memblock_init+0x64/0x224 > > [ 0.000000] memblock_reserve: > > [0x0000000040080000-0x00000000413c3fff] > > arm64_memblock_init+0x188/0x224 > > [ 0.000000] WARNING: CPU: 0 PID: 0 at > > /mnt/host/source/src/third_party/kernel/v4.19/mm/memblock.c:583 > > memblock_add_range+0x1bc/0x1c8 > > [ 0.000000] Modules linked in: > > [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.38 #222 > > [ 0.000000] Hardware name: MediaTek kukui rev2 board (DT) > > [ 0.000000] pstate: 60000085 (nZCv daIf -PAN -UAO) > > [ 0.000000] pc : memblock_add_range+0x1bc/0x1c8 > > [ 0.000000] lr : memblock_add_range+0x30/0x1c8 > > [ 0.000000] sp : ffffffab68603ea0 > > [ 0.000000] x29: ffffffab68603ef0 x28: 0000000040954324 > > [ 0.000000] x27: 0000000040080000 x26: 0000000000080000 > > [ 0.000000] x25: 0000000080127e4b x24: ffffffab68716000 > > [ 0.000000] x23: ffffffab680b5000 x22: 0000000001344000 > > [ 0.000000] x21: 0000000040080000 x20: 0000000000000000 > > [ 0.000000] x19: ffffffab6864bf00 x18: 00000000fffffc94 > > [ 0.000000] x17: 000000000000003c x16: ffffffab67d49064 > > [ 0.000000] x15: 0000000000000006 x14: 626d656d5f34366d > > [ 0.000000] x13: 7261205d66666633 x12: 0000000000000000 > > [ 0.000000] x11: 0000000000000000 x10: ffffffffffffffff > > [ 0.000000] x9 : 0000000000011547 x8 : ffffffab68765690 > > [ 0.000000] x7 : 696e695f6b636f6c x6 : ffffffab6875dd41 > > [ 0.000000] x5 : 0000000000000000 x4 : 0000000000000000 > > [ 0.000000] x3 : ffffffab678a24a0 x2 : 0000000001344000 > > [ 0.000000] x1 : 0000000040080000 x0 : ffffffab6864bf00 > > [ 0.000000] Call trace: > > [ 0.000000] memblock_add_range+0x1bc/0x1c8 > > [ 0.000000] memblock_reserve+0x60/0xac > > [ 0.000000] arm64_memblock_init+0x188/0x224 > > [ 0.000000] setup_arch+0x138/0x19c > > [ 0.000000] start_kernel+0x68/0x380 > > [ 0.000000] random: get_random_bytes called from > > print_oops_end_marker+0x3c/0x58 with crng_init=0 > > [ 0.000000] ---[ end trace ea99802b425f7adf ]--- > > [ 0.000000] memblock_reserve: > > [0x000000005f800000-0x000000005f811536] > > early_init_dt_reserve_memory_arch+0x38/0x48 > > [ 0.000000] memblock_reserve: > > [0x00000000ffe00000-0x00000000ffffffff] > > early_init_dt_reserve_memory_arch+0x38/0x48 > > > > So I guess we just can't call memblock_reserve() in kaslr? > -- Sincerely yours, Mike.
