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SubjectRe: [PATCH v3] m68k: Fix memblock-related crashes
On Fri, Dec 07, 2018 at 05:50:11PM +0100, Geert Uytterhoeven wrote:
> When running the kernel in Fast RAM on Atari:
>
> Ignoring memory chunk at 0x0:0xe00000 before the first chunk
> ...
> Unable to handle kernel NULL pointer dereference at virtual address (ptrval)
> Oops: 00000000
> Modules linked in:
> PC: [<0069dbac>] free_all_bootmem+0x12c/0x186
> SR: 2714 SP: (ptrval) a2: 005e3314
> d0: 00000000 d1: 0000000a d2: 00000e00 d3: 00000000
> d4: 005e1fc0 d5: 0000001a a0: 01000000 a1: 00000000
> Process swapper (pid: 0, task=(ptrval))
> Frame format=7 eff addr=00000736 ssw=0505 faddr=00000736
> wb 1 stat/addr/data: 0000 00000000 00000000
> wb 2 stat/addr/data: 0000 00000000 00000000
> wb 3 stat/addr/data: 0000 00000736 00000000
> push data: 00000000 00000000 00000000 00000000
> Stack from 005e1f84:
> 00000000 0000000a 027d3260 006b5006 00000000 00000000 00000000 00000000
> 0004f062 0003a220 0069e272 005e1ff8 0000054c 00000000 00e00000 00000000
> 00000001 00693cd8 027d3260 0004f062 0003a220 00691be6 00000000 00000000
> 00000000 00000000 00000000 00000000 006b5006 00000000 00690872
> Call Trace: [<0004f062>] printk+0x0/0x18
> [<0003a220>] parse_args+0x0/0x2d4
> [<0069e272>] memblock_virt_alloc_try_nid+0x0/0xa4
> [<00693cd8>] mem_init+0xa/0x5c
> [<0004f062>] printk+0x0/0x18
> [<0003a220>] parse_args+0x0/0x2d4
> [<00691be6>] start_kernel+0x1ca/0x462
> [<00690872>] _sinittext+0x872/0x11f8
> Code: 7a1a eaae 2270 6db0 0061 ef14 2f01 2f03 <96a9> 0736 2203 e589 d681 e78b d6a9 0732 2f03 2f40 0034 4eb9 0069 b8d0 260e 4fef
> Disabling lock debugging due to kernel taint
> Kernel panic - not syncing: Attempted to kill the idle task!
>
> As the kernel must run in the memory chunk with the lowest address,
> ST-RAM is ignored, and removed from the m68k_memory[] array.
> However, it is not removed from memblock, causing a crash later.
>
> More investigation shows that there are 3 places where memory chunks are
> ignored, all after the calls to memblock_add() in m68k_parse_bootinfo(),
> and thus causing crashes:
> 1. On classic m68k CPUs with a MMU, paging_init() ignores all memory
> chunks below the first chunk, cfr. above,
> 2. On Amigas equipped with a Zorro III bus, config_amiga() ignores all
> Zorro II memory,
> 3. If CONFIG_SINGLE_MEMORY_CHUNK=y, m68k_parse_bootinfo() ignores all
> but the first memory chunk.
>
> Fix this by moving the calls to memblock_add() from
> m68k_parse_bootinfo() to paging_init(), after all ignored memory chunks
> have been removed from m68k_memory[].
>
> Reported-by: Andreas Schwab <schwab@linux-m68k.org>
> Fixes: 1008a11590b966b4 ("m68k: switch to MEMBLOCK + NO_BOOTMEM")
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> ---
> As all 3 cases involve ignoring memory chunks, thus not requiring real
> memory present in the ignored chunks, I managed to test all 3 cases on
> my Amiga 4000 by using a memfile describing nonexistent memory in the
> Zorro II or 32-bit address space, below system RAM.
>
> Sun-3 must be broken before this fix, as it fills in m68k_memory[0] in
> config_sun3(), i.e. after m68k_parse_bootinfo().
> Sun-3 is not fixed by this fix, as it uses its own paging_init(), not
> the one in motorola.c.
> Fixing Sun-3 requires adding memblock_add()/memblock_reserve() calls to
> the Sun-3 memory management code.

I think that adding memblock_add() to config_sun3 would be sufficient,
something like the diff below. This will make memblock aware of the
available physical memory and it seems there no allocations in sun3 before
paging_init().

diff --git a/arch/m68k/sun3/config.c b/arch/m68k/sun3/config.c
index 542c440..9a5b9dd 100644
--- a/arch/m68k/sun3/config.c
+++ b/arch/m68k/sun3/config.c
@@ -150,6 +150,7 @@ void __init config_sun3(void)

m68k_num_memory=1;
m68k_memory[0].size=*(romvec->pv_sun3mem);
+ memblock_add(memory_start, memory_end - memory_start);

sun3_bootmem_alloc(memory_start, memory_end);
}
> v3:
> - Move memblock_add() after memory block removal instead of sprinkling
> memblock_remove() all over the place,
> - Remove Suggested-by, Tested-by.
>
> v2:
> - Add missing #include <linux/memblock.h>.
> ---
> arch/m68k/kernel/setup_mm.c | 2 --
> arch/m68k/mm/motorola.c | 2 ++
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/m68k/kernel/setup_mm.c b/arch/m68k/kernel/setup_mm.c
> index a1a3eaeaf58c960d..ad0195cbe04255ea 100644
> --- a/arch/m68k/kernel/setup_mm.c
> +++ b/arch/m68k/kernel/setup_mm.c
> @@ -164,8 +164,6 @@ static void __init m68k_parse_bootinfo(const struct bi_record *record)
> be32_to_cpu(m->addr);
> m68k_memory[m68k_num_memory].size =
> be32_to_cpu(m->size);
> - memblock_add(m68k_memory[m68k_num_memory].addr,
> - m68k_memory[m68k_num_memory].size);
> m68k_num_memory++;
> } else
> pr_warn("%s: too many memory chunks\n",
> diff --git a/arch/m68k/mm/motorola.c b/arch/m68k/mm/motorola.c
> index 7497cf30bf1cd41b..3f3d0bf360910c0d 100644
> --- a/arch/m68k/mm/motorola.c
> +++ b/arch/m68k/mm/motorola.c
> @@ -228,6 +228,7 @@ void __init paging_init(void)
>
> min_addr = m68k_memory[0].addr;
> max_addr = min_addr + m68k_memory[0].size;
> + memblock_add(m68k_memory[0].addr, m68k_memory[0].size);
> for (i = 1; i < m68k_num_memory;) {
> if (m68k_memory[i].addr < min_addr) {
> printk("Ignoring memory chunk at 0x%lx:0x%lx before the first chunk\n",
> @@ -238,6 +239,7 @@ void __init paging_init(void)
> (m68k_num_memory - i) * sizeof(struct m68k_mem_info));
> continue;
> }
> + memblock_add(m68k_memory[i].addr, m68k_memory[i].size);
> addr = m68k_memory[i].addr + m68k_memory[i].size;
> if (addr > max_addr)
> max_addr = addr;
> --
> 2.17.1
>

--
Sincerely yours,
Mike.

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