Add hello assignment in skels #11
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| #include <linux/kernel.h> | |||
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Please run ./scripts/checkpatch.pl -f --strict hello.c to verify for coding style problems
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| static int hello_init(void) | ||
| { | ||
| printk(KERN_DEBUG "Hello, World!\n"); |
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I want to avoid using printk where possible, it is now recommended to use pr_debug, pr_info, etc. I think we can replace this with pr_info.
Also, I think we should add a TODO comment here so that this line is removed when the skel is generated.
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| EXTRA_CFLAGS = -Wall -g -m32 | |||
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Do we need the extra sol directory?
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it should be called hello-world.
I assumed this as the source directory, it can have any name. checker directory is supposed to exist in order to be recursively copied to vm disdk
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| KDIR=/usr/src/linux-so2 | |||
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The Makefile is not needed anymore, the top level makefile should take care of building
| MODULE_DESCRIPTION("Hello World"); | ||
| MODULE_AUTHOR("Psoru Lesfo Rever"); | ||
| MODULE_LICENSE("GPL"); | ||
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Since we are here I think we should also find a better name for module author. I don't have good names now, but I think kernel people recommend to use real names here.
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Agree. It should still be a generic name. I recommend we use "Linux Kernel Labs [email protected]", or we can create a new e-mail address.
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We should use the same author for all modules. I suggest changing this for all modules in a future commit.
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@tavip, can we merge this PR? |
There are three places where we access uninitialized memmaps, namely: - /proc/kpagecount - /proc/kpageflags - /proc/kpagecgroup We have initialized memmaps either when the section is online or when the page was initialized to the ZONE_DEVICE. Uninitialized memmaps contain garbage and in the worst case trigger kernel BUGs, especially with CONFIG_PAGE_POISONING. For example, not onlining a DIMM during boot and calling /proc/kpagecount with CONFIG_PAGE_POISONING: :/# cat /proc/kpagecount > tmp.test BUG: unable to handle page fault for address: fffffffffffffffe #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 114616067 P4D 114616067 PUD 114618067 PMD 0 Oops: 0000 [#1] SMP NOPTI CPU: 0 PID: 469 Comm: cat Not tainted 5.4.0-rc1-next-20191004+ linux-kernel-labs#11 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.4 RIP: 0010:kpagecount_read+0xce/0x1e0 Code: e8 09 83 e0 3f 48 0f a3 02 73 2d 4c 89 e7 48 c1 e7 06 48 03 3d ab 51 01 01 74 1d 48 8b 57 08 480 RSP: 0018:ffffa14e409b7e78 EFLAGS: 00010202 RAX: fffffffffffffffe RBX: 0000000000020000 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 00007f76b5595000 RDI: fffff35645000000 RBP: 00007f76b5595000 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000140000 R13: 0000000000020000 R14: 00007f76b5595000 R15: ffffa14e409b7f08 FS: 00007f76b577d580(0000) GS:ffff8f41bd400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: fffffffffffffffe CR3: 0000000078960000 CR4: 00000000000006f0 Call Trace: proc_reg_read+0x3c/0x60 vfs_read+0xc5/0x180 ksys_read+0x68/0xe0 do_syscall_64+0x5c/0xa0 entry_SYSCALL_64_after_hwframe+0x49/0xbe For now, let's drop support for ZONE_DEVICE from the three pseudo files in order to fix this. To distinguish offline memory (with garbage memmap) from ZONE_DEVICE memory with properly initialized memmaps, we would have to check get_dev_pagemap() and pfn_zone_device_reserved() right now. The usage of both (especially, special casing devmem) is frowned upon and needs to be reworked. The fundamental issue we have is: if (pfn_to_online_page(pfn)) { /* memmap initialized */ } else if (pfn_valid(pfn)) { /* * ??? * a) offline memory. memmap garbage. * b) devmem: memmap initialized to ZONE_DEVICE. * c) devmem: reserved for driver. memmap garbage. * (d) devmem: memmap currently initializing - garbage) */ } We'll leave the pfn_zone_device_reserved() check in stable_page_flags() in place as that function is also used from memory failure. We now no longer dump information about pages that are not in use anymore - offline. Link: http://lkml.kernel.org/r/[email protected] Fixes: f1dd2cd ("mm, memory_hotplug: do not associate hotadded memory to zones until online") [visible after d0dc12e] Signed-off-by: David Hildenbrand <[email protected]> Reported-by: Qian Cai <[email protected]> Acked-by: Michal Hocko <[email protected]> Cc: Dan Williams <[email protected]> Cc: Alexey Dobriyan <[email protected]> Cc: Stephen Rothwell <[email protected]> Cc: Toshiki Fukasawa <[email protected]> Cc: Pankaj gupta <[email protected]> Cc: Mike Rapoport <[email protected]> Cc: Anthony Yznaga <[email protected]> Cc: "Aneesh Kumar K.V" <[email protected]> Cc: <[email protected]> [4.13+] Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
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