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Message-ID: <d72f6169-4779-0901-ae1d-743a93a196c4@csgroup.eu>
Date: Sat, 11 Dec 2021 07:37:21 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Andrew Morton <akpm@...ux-foundation.org>,
Tiezhu Yang <yangtiezhu@...ngson.cn>
CC: "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
Baoquan He <bhe@...hat.com>,
"linux-sh@...r.kernel.org" <linux-sh@...r.kernel.org>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
"x86@...nel.org" <x86@...nel.org>,
"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
"linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Vivek Goyal <vgoyal@...hat.com>,
"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
Dave Young <dyoung@...hat.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] kdump: vmcore: move copy_to() from vmcore.c to
uaccess.h
Le 10/12/2021 à 17:59, Andrew Morton a écrit :
> On Fri, 10 Dec 2021 21:36:00 +0800 Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>
>> In arch/*/kernel/crash_dump*.c, there exist similar code about
>> copy_oldmem_page(), move copy_to() from vmcore.c to uaccess.h,
>> and then we can use copy_to() to simplify the related code.
>>
>> ...
>>
>> --- a/fs/proc/vmcore.c
>> +++ b/fs/proc/vmcore.c
>> @@ -238,20 +238,6 @@ copy_oldmem_page_encrypted(unsigned long pfn, char *buf, size_t csize,
>> return copy_oldmem_page(pfn, buf, csize, offset, userbuf);
>> }
>>
>> -/*
>> - * Copy to either kernel or user space
>> - */
>> -static int copy_to(void *target, void *src, size_t size, int userbuf)
>> -{
>> - if (userbuf) {
>> - if (copy_to_user((char __user *) target, src, size))
>> - return -EFAULT;
>> - } else {
>> - memcpy(target, src, size);
>> - }
>> - return 0;
>> -}
>> -
>> #ifdef CONFIG_PROC_VMCORE_DEVICE_DUMP
>> static int vmcoredd_copy_dumps(void *dst, u64 start, size_t size, int userbuf)
>> {
>> diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
>> index ac03940..4a6c3e4 100644
>> --- a/include/linux/uaccess.h
>> +++ b/include/linux/uaccess.h
>> @@ -201,6 +201,20 @@ copy_to_user(void __user *to, const void *from, unsigned long n)
>> return n;
>> }
>>
>> +/*
>> + * Copy to either kernel or user space
>> + */
>> +static inline int copy_to(void *target, void *src, size_t size, int userbuf)
>> +{
>> + if (userbuf) {
>> + if (copy_to_user((char __user *) target, src, size))
>> + return -EFAULT;
>> + } else {
>> + memcpy(target, src, size);
>> + }
>> + return 0;
>> +}
>> +
>
> Ordinarily I'd say "this is too large to be inlined". But the function
> has only a single callsite per architecture so inlining it won't cause
> bloat at present.
>
> But hopefully copy_to() will get additional callers in the future, in
> which case it shouldn't be inlined. So I'm thinking it would be best
> to start out with this as a regular non-inlined function, in
> lib/usercopy.c.
>
> Also, copy_to() is a very poor name for a globally-visible helper
> function. Better would be copy_to_user_or_kernel(), although that's
> perhaps a bit long.
>
> And the `userbuf' arg should have type bool, yes?
>
I think keeping it inlined is better.
copy_oldmem_page() is bigger with v2 (outlined) than with v1 (inlined),
see both below:
v1:
00000000 <copy_oldmem_page>:
0: 94 21 ff e0 stwu r1,-32(r1)
4: 93 e1 00 1c stw r31,28(r1)
8: 7c bf 2b 79 mr. r31,r5
c: 40 82 00 14 bne 20 <copy_oldmem_page+0x20>
10: 83 e1 00 1c lwz r31,28(r1)
14: 38 60 00 00 li r3,0
18: 38 21 00 20 addi r1,r1,32
1c: 4e 80 00 20 blr
20: 28 1f 10 00 cmplwi r31,4096
24: 93 61 00 0c stw r27,12(r1)
28: 7c 08 02 a6 mflr r0
2c: 93 81 00 10 stw r28,16(r1)
30: 93 a1 00 14 stw r29,20(r1)
34: 7c 9b 23 78 mr r27,r4
38: 90 01 00 24 stw r0,36(r1)
3c: 7c dd 33 78 mr r29,r6
40: 93 c1 00 18 stw r30,24(r1)
44: 7c fc 3b 78 mr r28,r7
48: 40 81 00 08 ble 50 <copy_oldmem_page+0x50>
4c: 3b e0 10 00 li r31,4096
50: 54 7e 60 26 rlwinm r30,r3,12,0,19
54: 7f c3 f3 78 mr r3,r30
58: 7f e4 fb 78 mr r4,r31
5c: 48 00 00 01 bl 5c <copy_oldmem_page+0x5c>
5c: R_PPC_REL24 memblock_is_region_memory
60: 2c 03 00 00 cmpwi r3,0
64: 41 82 00 30 beq 94 <copy_oldmem_page+0x94>
68: 2c 1c 00 00 cmpwi r28,0
6c: 3f de c0 00 addis r30,r30,-16384
70: 7f 63 db 78 mr r3,r27
74: 7f e5 fb 78 mr r5,r31
78: 7c 9e ea 14 add r4,r30,r29
7c: 41 82 00 7c beq f8 <copy_oldmem_page+0xf8>
80: 48 00 00 01 bl 80 <copy_oldmem_page+0x80>
80: R_PPC_REL24 _copy_to_user
84: 2c 03 00 00 cmpwi r3,0
88: 41 a2 00 48 beq d0 <copy_oldmem_page+0xd0>
8c: 3b e0 ff f2 li r31,-14
90: 48 00 00 40 b d0 <copy_oldmem_page+0xd0>
94: 7f c3 f3 78 mr r3,r30
98: 38 a0 05 91 li r5,1425
9c: 38 80 10 00 li r4,4096
a0: 48 00 00 01 bl a0 <copy_oldmem_page+0xa0>
a0: R_PPC_REL24 ioremap_prot
a4: 2c 1c 00 00 cmpwi r28,0
a8: 7c 7e 1b 78 mr r30,r3
ac: 7c 83 ea 14 add r4,r3,r29
b0: 7f e5 fb 78 mr r5,r31
b4: 7f 63 db 78 mr r3,r27
b8: 41 82 00 48 beq 100 <copy_oldmem_page+0x100>
bc: 48 00 00 01 bl bc <copy_oldmem_page+0xbc>
bc: R_PPC_REL24 _copy_to_user
c0: 2c 03 00 00 cmpwi r3,0
c4: 40 82 00 44 bne 108 <copy_oldmem_page+0x108>
c8: 7f c3 f3 78 mr r3,r30
cc: 48 00 00 01 bl cc <copy_oldmem_page+0xcc>
cc: R_PPC_REL24 iounmap
d0: 80 01 00 24 lwz r0,36(r1)
d4: 7f e3 fb 78 mr r3,r31
d8: 83 61 00 0c lwz r27,12(r1)
dc: 83 81 00 10 lwz r28,16(r1)
e0: 7c 08 03 a6 mtlr r0
e4: 83 a1 00 14 lwz r29,20(r1)
e8: 83 c1 00 18 lwz r30,24(r1)
ec: 83 e1 00 1c lwz r31,28(r1)
f0: 38 21 00 20 addi r1,r1,32
f4: 4e 80 00 20 blr
f8: 48 00 00 01 bl f8 <copy_oldmem_page+0xf8>
f8: R_PPC_REL24 memcpy
fc: 4b ff ff d4 b d0 <copy_oldmem_page+0xd0>
100: 48 00 00 01 bl 100 <copy_oldmem_page+0x100>
100: R_PPC_REL24 memcpy
104: 4b ff ff c4 b c8 <copy_oldmem_page+0xc8>
108: 3b e0 ff f2 li r31,-14
10c: 4b ff ff bc b c8 <copy_oldmem_page+0xc8>
v2:
00000000 <copy_oldmem_page>:
0: 94 21 ff e0 stwu r1,-32(r1)
4: 93 e1 00 1c stw r31,28(r1)
8: 7c bf 2b 79 mr. r31,r5
c: 93 c1 00 18 stw r30,24(r1)
10: 3b c0 00 00 li r30,0
14: 40 82 00 18 bne 2c <copy_oldmem_page+0x2c>
18: 7f c3 f3 78 mr r3,r30
1c: 83 e1 00 1c lwz r31,28(r1)
20: 83 c1 00 18 lwz r30,24(r1)
24: 38 21 00 20 addi r1,r1,32
28: 4e 80 00 20 blr
2c: 28 1f 10 00 cmplwi r31,4096
30: 93 61 00 0c stw r27,12(r1)
34: 7c 08 02 a6 mflr r0
38: 93 81 00 10 stw r28,16(r1)
3c: 93 a1 00 14 stw r29,20(r1)
40: 7c db 33 78 mr r27,r6
44: 90 01 00 24 stw r0,36(r1)
48: 7c 9d 23 78 mr r29,r4
4c: 7c fc 3b 78 mr r28,r7
50: 40 81 00 08 ble 58 <copy_oldmem_page+0x58>
54: 3b e0 10 00 li r31,4096
58: 54 7e 60 26 rlwinm r30,r3,12,0,19
5c: 7f c3 f3 78 mr r3,r30
60: 7f e4 fb 78 mr r4,r31
64: 48 00 00 01 bl 64 <copy_oldmem_page+0x64>
64: R_PPC_REL24 memblock_is_region_memory
68: 2c 03 00 00 cmpwi r3,0
6c: 41 82 00 54 beq c0 <copy_oldmem_page+0xc0>
70: 3f de c0 00 addis r30,r30,-16384
74: 7c 9e da 14 add r4,r30,r27
78: 7f 86 e3 78 mr r6,r28
7c: 7f a3 eb 78 mr r3,r29
80: 7f e5 fb 78 mr r5,r31
84: 48 00 00 01 bl 84 <copy_oldmem_page+0x84>
84: R_PPC_REL24 copy_to_user_or_kernel
88: 3b c0 ff f2 li r30,-14
8c: 2c 03 00 00 cmpwi r3,0
90: 40 82 00 08 bne 98 <copy_oldmem_page+0x98>
94: 7f fe fb 78 mr r30,r31
98: 80 01 00 24 lwz r0,36(r1)
9c: 83 61 00 0c lwz r27,12(r1)
a0: 83 81 00 10 lwz r28,16(r1)
a4: 7c 08 03 a6 mtlr r0
a8: 83 a1 00 14 lwz r29,20(r1)
ac: 7f c3 f3 78 mr r3,r30
b0: 83 e1 00 1c lwz r31,28(r1)
b4: 83 c1 00 18 lwz r30,24(r1)
b8: 38 21 00 20 addi r1,r1,32
bc: 4e 80 00 20 blr
c0: 7f c3 f3 78 mr r3,r30
c4: 93 41 00 08 stw r26,8(r1)
c8: 38 a0 05 91 li r5,1425
cc: 38 80 10 00 li r4,4096
d0: 48 00 00 01 bl d0 <copy_oldmem_page+0xd0>
d0: R_PPC_REL24 ioremap_prot
d4: 7f 86 e3 78 mr r6,r28
d8: 7c 83 da 14 add r4,r3,r27
dc: 7c 7a 1b 78 mr r26,r3
e0: 7f e5 fb 78 mr r5,r31
e4: 7f a3 eb 78 mr r3,r29
e8: 48 00 00 01 bl e8 <copy_oldmem_page+0xe8>
e8: R_PPC_REL24 copy_to_user_or_kernel
ec: 3b c0 ff f2 li r30,-14
f0: 2c 03 00 00 cmpwi r3,0
f4: 40 82 00 08 bne fc <copy_oldmem_page+0xfc>
f8: 7f fe fb 78 mr r30,r31
fc: 7f 43 d3 78 mr r3,r26
100: 48 00 00 01 bl 100 <copy_oldmem_page+0x100>
100: R_PPC_REL24 iounmap
104: 80 01 00 24 lwz r0,36(r1)
108: 83 41 00 08 lwz r26,8(r1)
10c: 83 61 00 0c lwz r27,12(r1)
110: 7c 08 03 a6 mtlr r0
114: 83 81 00 10 lwz r28,16(r1)
118: 83 a1 00 14 lwz r29,20(r1)
11c: 4b ff ff 90 b ac <copy_oldmem_page+0xac>
Christophe
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