[powerpc] Intermittent crashes ( link_path_walk) with linux-next
Michael Ellerman
mpe at ellerman.id.au
Thu Mar 26 22:40:06 AEDT 2020
Sachin Sant <sachinp at linux.vnet.ibm.com> writes:
> I am running into intermittent crashes with linux-next on POWER 9 PowerVM LPAR
> First it was against next-20200324 while running LTP tests. With next-20200325
> I ran into similar crash (a different stack trace but same failure point — link_path_walk)
> while running sosreport command.
>
> BUG: Kernel NULL pointer dereference on read at 0x00000000
> Faulting instruction address: 0xc00000000043f278
> Oops: Kernel access of bad area, sig: 11 [#1]
> LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
> Dumping ftrace buffer:
> (ftrace buffer empty)
> Modules linked in: loop iscsi_target_mod target_core_mod macsec tcp_diag udp_diag inet_diag unix_diag af_packet_diag netlink_diag binfmt_misc overlay dm_mod nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 libcrc32c ip6_tables nft_compat ip_set rfkill nf_tables nfnetlink sunrpc sg pseries_rng uio_pdrv_genirq uio sch_fq_codel ip_tables ext4 mbcache jbd2 sr_mod sd_mod cdrom t10_pi ibmvscsi scsi_transport_srp ibmveth
> CPU: 26 PID: 7771 Comm: avocado Not tainted 5.6.0-rc7-next-20200324-autotest #1
> NIP: c00000000043f278 LR: c00000000043f330 CTR: 00000000000001fb
> REGS: c00000082802f830 TRAP: 0300 Not tainted (5.6.0-rc7-next-20200324-autotest)
> MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 28248442 XER: 20040000
> CFAR: c00000000000dec4 DAR: 0000000000000000 DSISR: 40000000 IRQMASK: 0
> GPR00: c00000000043f330 c00000082802fac0 c00000000155e900 0000000000000000
> GPR04: 0000000000000002 0000000000000000 0000000000000002 c0000008b3400000
> GPR08: 0000000000031419 0000000000000000 0000000000000000 ffffffffffff0000
> GPR12: 0000000000008000 c00000001ec48600 00007fffa08a53f8 0000000000000001
> GPR16: 00007fff9faf9a63 00000100073bec00 00007fff9f2493b0 0000000000000000
> GPR20: 00007fffa1143bf8 00007fffa1103b18 c00000087f547cb3 2f2f2f2f2f2f2f2f
> GPR24: 0000000000000003 0000000000000000 c00000082802fbc8 fffffffffffff000
> GPR28: 0000000000200000 ffffffffffffffff 61c8864680b583eb 0000000000000000
> NIP [c00000000043f278] link_path_walk.part.49+0x228/0x400
> LR [c00000000043f330] link_path_walk.part.49+0x2e0/0x400
> Call Trace:
> [c00000082802fac0] [c00000000043f330] link_path_walk.part.49+0x2e0/0x400 (unreliable)
> [c00000082802fb50] [c00000000043f5a4] path_lookupat.isra.51+0x64/0x1f0
> [c00000082802fba0] [c000000000441c00] filename_lookup.part.69+0xa0/0x1b0
> [c00000082802fce0] [c00000000042ff38] vfs_statx+0xa8/0x190
> [c00000082802fd60] [c0000000004302a0] __do_sys_newstat+0x40/0x90
> [c00000082802fe20] [c00000000000b278] system_call+0x5c/0x68
> Instruction dump:
> 3bffffff e93a0058 38800000 7f43d378 7fff07b4 1d5f0030 7d295214 eac90020
> 4bfffb21 2fa30000 409e00c8 e93a0008 <81290000> 55290256 7f89e000 419efecc
> ---[ end trace 34abf29ebd56e423 ]—
>
> Relevant snippet from obj dump:
>
> 6dc4: 20 00 c9 ea ld r22,32(r9)
> link = walk_component(nd, 0);
> 6db4: 78 d3 43 7f mr r3,r26
> name = nd->stack[--depth].name;
> 6db8: b4 07 ff 7f extsw r31,r31
> 6dbc: 30 00 5f 1d mulli r10,r31,48
> 6dc0: 14 52 29 7d add r9,r9,r10
> 6dc4: 20 00 c9 ea ld r22,32(r9)
> link = walk_component(nd, 0);
> 6dc8: 01 00 00 48 bl 6dc8 <link_path_walk.part.49+0x218>
> if (unlikely(link)) {
> 6dcc: 00 00 a3 2f cmpdi cr7,r3,0
> 6dd0: c8 00 9e 40 bne cr7,6e98 <link_path_walk.part.49+0x2e8>
> return dentry->d_flags & DCACHE_ENTRY_TYPE;
> 6dd4: 08 00 3a e9 ld r9,8(r26)
> 6dd8: 00 00 29 81 lwz r9,0(r9) <<=== crashes here ??
Yeah.
And r9 is NULL.
It came from r26 + 8, r26 is c00000082802fbc8 which looks OK.
r26 is nd, the nameidata:
struct nameidata {
struct path path;
struct path {
struct vfsmount *mnt;
struct dentry *dentry;
} __randomize_layout;
r26 + 8 should be the dentry in the struct path.
So we have an nd.path with a NULL dentry.
> 6ddc: 56 02 29 55 rlwinm r9,r9,0,9,11
> if (unlikely(!d_can_lookup(nd->path.dentry))) {
> 6de0: 00 e0 89 7f cmpw cr7,r9,r28
>
> The code in question (link_path_walk() in fs/namei.c ) was recently changed by
> following commit:
>
> commit 881386f7e46a:
> link_path_walk(): sample parent's i_uid and i_mode for the last component
That and about 10 other commits.
Unless Al can give us a clue we'll need to bisect.
cheers
> Crash while running sosreport command:
>
> [ 1917.926113] BUG: Kernel NULL pointer dereference on read at 0x00000000
> [ 1917.926126] Faulting instruction address: 0xc00000000043f638
> [ 1917.926131] Oops: Kernel access of bad area, sig: 11 [#1]
> [ 1917.926136] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
> [ 1917.926147] Dumping ftrace buffer:
> [ 1917.926157] (ftrace buffer empty)
> [ 1917.926161] Modules linked in: iscsi_target_mod target_core_mod macsec tcp_diag udp_diag inet_diag unix_diag af_packet_diag netlink_diag binfmt_misc overlay dm_mod nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 libcrc32c ip6_tables nft_compat ip_set rfkill nf_tables nfnetlink sunrpc sg pseries_rng uio_pdrv_genirq uio sch_fq_codel ip_tables ext4 mbcache jbd2 sr_mod cdrom sd_mod t10_pi ibmvscsi scsi_transport_srp ibmveth
> [ 1917.926198] CPU: 12 PID: 20734 Comm: busctl Not tainted 5.6.0-rc7-next-20200325-autotest #1
> [ 1917.926203] NIP: c00000000043f638 LR: c00000000043f6f0 CTR: 0000000000000000
> [ 1917.926209] REGS: c00000082bc1f720 TRAP: 0300 Not tainted (5.6.0-rc7-next-20200325-autotest)
> [ 1917.926215] MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 28022422 XER: 20040000
> [ 1917.926222] CFAR: c00000000000dec4 DAR: 0000000000000000 DSISR: 40000000 IRQMASK: 0
> [ 1917.926222] GPR00: c00000000043f6f0 c00000082bc1f9b0 c00000000155e800 0000000000000000
> [ 1917.926222] GPR04: 0000000000000002 0000000000000000 0000000000000002 c0000008b3400000
> [ 1917.926222] GPR08: 000000000000febb 0000000000000000 0000000000000000 ffffffffffff0000
> [ 1917.926222] GPR12: 0000000000002000 c00000001ec5d600 0000000135ed11e0 c0000008879046d0
> [ 1917.926222] GPR16: 7fffffffffffffff fffffffffffffe00 fffffffffffffffc fffffffffffffff5
> [ 1917.926222] GPR20: c00000089fa27200 0000000000000000 c00000008609bf33 2f2f2f2f2f2f2f2f
> [ 1917.926222] GPR24: 0000000000000003 0000000000000000 c00000082bc1fab8 fffffffffffff000
> [ 1917.926222] GPR28: 0000000000200000 ffffffffffffffff 61c8864680b583eb 0000000000000001
> [ 1917.926270] NIP [c00000000043f638] link_path_walk.part.49+0x228/0x400
> [ 1917.926275] LR [c00000000043f6f0] link_path_walk.part.49+0x2e0/0x400
> [ 1917.926280] Call Trace:
> [ 1917.926284] [c00000082bc1f9b0] [c00000000043f6f0] link_path_walk.part.49+0x2e0/0x400 (unreliable)
> [ 1917.926291] [c00000082bc1fa40] [c00000000043f964] path_lookupat.isra.51+0x64/0x1f0
> [ 1917.926296] [c00000082bc1fa90] [c000000000441fc0] filename_lookup.part.69+0xa0/0x1b0
> [ 1917.926303] [c00000082bc1fbd0] [c000000000ae0784] unix_find_other+0x64/0x3f0
> [ 1917.926309] [c00000082bc1fc60] [c000000000ae1b78] unix_stream_connect+0x148/0x930
> [ 1917.926316] [c00000082bc1fd30] [c000000000933010] __sys_connect+0x140/0x170
> [ 1917.926322] [c00000082bc1fe00] [c000000000933068] sys_connect+0x28/0x40
> [ 1917.926328] [c00000082bc1fe20] [c00000000000b278] system_call+0x5c/0x68
> [ 1917.926332] Instruction dump:
> [ 1917.926336] 3bffffff e93a0058 38800000 7f43d378 7fff07b4 1d5f0030 7d295214 eac90020
> [ 1917.926343] 4bfffb21 2fa30000 409e00c8 e93a0008 <81290000> 55290256 7f89e000 419efecc
> [ 1917.926351] ---[ end trace 1b673f0e7295c08b ]---
>
> Objdump o/p
> ===========
>
>
> fs/namei.o: file format elf64-powerpcle
>
>
> Disassembly of section .text:
>
> 0000000000000000 <full_name_hash>:
> * In particular, we must end by hashing a final word containing 0..7
> * payload bytes, to match the way that hash_name() iterates until it
> * finds the delimiter after the name.
> */
> unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
> {
> 0: a6 02 08 7c mflr r0
> 4: 01 00 00 48 bl 4 <full_name_hash+0x4>
> unsigned long a, x = 0, y = (unsigned long)salt;
>
> for (;;) {
> if (!len)
> .........
> .........
>
> 0000000000006bb0 <link_path_walk.part.49>:
> static int link_path_walk(const char *name, struct nameidata *nd)
> 6bb0: 00 00 4c 3c addis r2,r12,0
> 6bb4: 00 00 42 38 addi r2,r2,0
> 6bb8: a6 02 08 7c mflr r0
> 6bbc: 01 00 00 48 bl 6bbc <link_path_walk.part.49+0xc>
> 6bc0: b0 ff c1 fa std r22,-80(r1)
> 6bc4: d0 ff 41 fb std r26,-48(r1)
> 6bc8: c0 ff 01 fb std r24,-64(r1)
> 6bcc: 78 1b 76 7c mr r22,r3
> 6bd0: 71 ff 21 f8 stdu r1,-144(r1)
> 6bd4: 78 23 9a 7c mr r26,r4
> 6bd8: 18 00 41 f8 std r2,24(r1)
> 6bdc: 78 11 2d e9 ld r9,4472(r13)
> 6be0: 38 00 21 f9 std r9,56(r1)
> 6be4: 00 00 20 39 li r9,0
> while (*name=='/')
> 6be8: 00 00 23 89 lbz r9,0(r3)
> 6bec: 2f 00 89 2b cmplwi cr7,r9,47
> 6bf0: 1c 00 9e 40 bne cr7,6c0c <link_path_walk.part.49+0x5c>
> 6bf4: 00 00 00 60 nop
> 6bf8: 00 00 00 60 nop
> 6bfc: 00 00 00 60 nop
> 6c00: 01 00 36 8d lbzu r9,1(r22)
> 6c04: 2f 00 89 2b cmplwi cr7,r9,47
> 6c08: f8 ff 9e 41 beq cr7,6c00 <link_path_walk.part.49+0x50>
> if (!*name)
> 6c0c: 00 00 a9 2f cmpdi cr7,r9,0
> return 0;
> 6c10: 00 00 00 3b li r24,0
> if (!*name)
> 6c14: 3c 00 9e 40 bne cr7,6c50 <link_path_walk.part.49+0xa0>
> }
> 6c18: 38 00 21 e9 ld r9,56(r1)
> 6c1c: 78 11 4d e9 ld r10,4472(r13)
> 6c20: 79 52 29 7d xor. r9,r9,r10
> 6c24: 00 00 40 39 li r10,0
> 6c28: 78 c3 03 7f mr r3,r24
> 6c2c: 54 03 82 40 bne 6f80 <link_path_walk.part.49+0x3d0>
> 6c30: 90 00 21 38 addi r1,r1,144
> 6c34: b0 ff c1 ea ld r22,-80(r1)
> 6c38: c0 ff 01 eb ld r24,-64(r1)
> 6c3c: d0 ff 41 eb ld r26,-48(r1)
> 6c40: 20 00 80 4e blr
> 6c44: 00 00 00 60 nop
> 6c48: 00 00 00 60 nop
> 6c4c: 00 00 00 60 nop
> 6c50: 48 00 e1 fa std r23,72(r1)
> 6c54: 80 00 c1 fb std r30,128(r1)
> b = a ^ REPEAT_BYTE('/');
> 6c58: 2f 2f e0 3e lis r23,12079
> 6c5c: 2f 2f f7 62 ori r23,r23,12079
> 6c60: a6 02 08 7c mflr r0
> y ^= x * GOLDEN_RATIO_64;
> 6c64: c8 61 c0 3f lis r30,25032
> 6c68: 46 86 de 63 ori r30,r30,34374
> 6c6c: 58 00 21 fb std r25,88(r1)
> 6c70: 68 00 61 fb std r27,104(r1)
> unsigned long a = 0, b, x = 0, y = (unsigned long)salt;
> 6c74: 00 00 20 3b li r25,0
> 6c78: 70 00 81 fb std r28,112(r1)
> 6c7c: 78 00 a1 fb std r29,120(r1)
> 6c80: 88 00 e1 fb std r31,136(r1)
> x ^= a & zero_bytemask(mask);
> 6c84: ff ff a0 3b li r29,-1
> int depth = 0; // depth <= nd->depth
> 6c88: 00 00 e0 3b li r31,0
> if (unlikely(!d_can_lookup(nd->path.dentry))) {
> 6c8c: 20 00 80 3f lis r28,32
> if (IS_ERR(link))
> 6c90: 00 f0 60 3b li r27,-4096
> b = a ^ REPEAT_BYTE('/');
> 6c94: c6 07 f7 7a rldicr r23,r23,32,31
> y ^= x * GOLDEN_RATIO_64;
> 6c98: c6 07 de 7b rldicr r30,r30,32,31
> b = a ^ REPEAT_BYTE('/');
> 6c9c: 2f 2f f7 66 oris r23,r23,12079
> 6ca0: a0 00 01 f8 std r0,160(r1)
> y ^= x * GOLDEN_RATIO_64;
> 6ca4: b5 80 de 67 oris r30,r30,32949
> b = a ^ REPEAT_BYTE('/');
> 6ca8: 2f 2f f7 62 ori r23,r23,12079
> y ^= x * GOLDEN_RATIO_64;
> 6cac: eb 83 de 63 ori r30,r30,33771
> if (nd->flags & LOOKUP_RCU) {
> 6cb0: 38 00 3a 81 lwz r9,56(r26)
> 6cb4: 30 00 7a e8 ld r3,48(r26)
> 6cb8: 40 00 29 71 andi. r9,r9,64
> 6cbc: 08 02 82 41 beq 6ec4 <link_path_walk.part.49+0x314>
> int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
> 6cc0: 81 00 80 38 li r4,129
> 6cc4: 01 00 00 48 bl 6cc4 <link_path_walk.part.49+0x114>
> if (err != -ECHILD)
> 6cc8: f6 ff 83 2f cmpwi cr7,r3,-10
> int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
> 6ccc: 78 1b 78 7c mr r24,r3
> if (err != -ECHILD)
> 6cd0: e0 01 9e 41 beq cr7,6eb0 <link_path_walk.part.49+0x300>
> if (err)
> 6cd4: 00 00 b8 2f cmpdi cr7,r24,0
> 6cd8: 30 01 9e 40 bne cr7,6e08 <link_path_walk.part.49+0x258>
> hash_len = hash_name(nd->path.dentry, name);
> 6cdc: 08 00 7a e8 ld r3,8(r26)
> len = 0;
> 6ce0: 00 00 a0 38 li r5,0
> unsigned long a = 0, b, x = 0, y = (unsigned long)salt;
> 6ce4: 00 00 c0 38 li r6,0
> 6ce8: 78 1b 67 7c mr r7,r3
> goto inside;
> 6cec: 24 00 00 48 b 6d10 <link_path_walk.part.49+0x160>
> HASH_MIX(x, y, a);
> 6cf0: 78 4a c9 7c xor r9,r6,r9
> len += sizeof(unsigned long);
> 6cf4: 08 00 a5 38 addi r5,r5,8
> HASH_MIX(x, y, a);
> 6cf8: 78 3a 26 7d xor r6,r9,r7
> 6cfc: 00 60 29 79 rotldi r9,r9,12
> 6d00: 02 68 c7 78 rotldi r7,r6,45
> 6d04: 14 4a c6 7c add r6,r6,r9
> 6d08: 24 1f e9 78 rldicr r9,r7,3,60
> 6d0c: 14 3a e9 7c add r7,r9,r7
> a = load_unaligned_zeropad(name+len);
> 6d10: 14 2a 56 7d add r10,r22,r5
> asm(
> 6d14: 00 00 2a e9 ld r9,0(r10)
> b = a ^ REPEAT_BYTE('/');
> 6d18: 78 ba 2a 7d xor r10,r9,r23
> asm("cmpb %0,%1,%2" : "=r" (ret) : "r" (a), "r" (zero));
> 6d1c: f8 cb 28 7d cmpb r8,r9,r25
> 6d20: f8 cb 4a 7d cmpb r10,r10,r25
> } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
> 6d24: 79 53 0a 7d or. r10,r8,r10
> 6d28: c8 ff 82 41 beq 6cf0 <link_path_walk.part.49+0x140>
> asm("addi %1,%2,-1\n\t"
> 6d2c: ff ff 0a 39 addi r8,r10,-1
> 6d30: 78 50 08 7d andc r8,r8,r10
> 6d34: f4 03 0a 7d popcntd r10,r8
> x ^= a & zero_bytemask(mask);
> 6d38: 36 50 ab 7f sld r11,r29,r10
> return mask >> 3;
> 6d3c: c2 e8 48 79 rldicl r8,r10,61,3
> if (name[0] == '.') switch (hashlen_len(hash_len)) {
> 6d40: 00 00 96 88 lbz r4,0(r22)
> x ^= a & zero_bytemask(mask);
> 6d44: 78 58 2a 7d andc r10,r9,r11
> return hashlen_create(fold_hash(x, y), len + find_zero(mask));
> 6d48: 14 2a 08 7d add r8,r8,r5
> x ^= a & zero_bytemask(mask);
> 6d4c: 78 32 49 7d xor r9,r10,r6
> if (name[0] == '.') switch (hashlen_len(hash_len)) {
> 6d50: 2e 00 84 2f cmpwi cr7,r4,46
> y ^= x * GOLDEN_RATIO_64;
> 6d54: d2 f1 29 7d mulld r9,r9,r30
> 6d58: 78 3a 29 7d xor r9,r9,r7
> y *= GOLDEN_RATIO_64;
> 6d5c: d2 f1 29 7d mulld r9,r9,r30
> return y >> 32;
> 6d60: 22 00 29 79 rldicl r9,r9,32,32
> return hashlen_create(fold_hash(x, y), len + find_zero(mask));
> 6d64: 0e 00 09 79 rldimi r9,r8,32,0
> if (name[0] == '.') switch (hashlen_len(hash_len)) {
> 6d68: c8 00 9e 41 beq cr7,6e30 <link_path_walk.part.49+0x280>
> 6d6c: 38 00 5a 81 lwz r10,56(r26)
> nd->flags &= ~LOOKUP_JUMPED;
> 6d70: 24 05 4a 55 rlwinm r10,r10,0,20,18
> 6d74: 38 00 5a 91 stw r10,56(r26)
> if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
> 6d78: 00 00 43 81 lwz r10,0(r3)
> 6d7c: 01 00 4a 71 andi. r10,r10,1
> 6d80: 70 01 82 40 bne 6ef0 <link_path_walk.part.49+0x340>
> 6d84: 22 00 28 79 rldicl r8,r9,32,32
> nd->last.hash_len = hash_len;
> 6d88: 10 00 3a f9 std r9,16(r26)
> nd->last.name = name;
> 6d8c: 18 00 da fa std r22,24(r26)
> nd->last_type = type;
> 6d90: 48 00 1a 93 stw r24,72(r26)
> if (!*name)
> 6d94: ee 40 36 7d lbzux r9,r22,r8
> 6d98: 00 00 89 2f cmpwi cr7,r9,0
> 6d9c: d4 00 9e 40 bne cr7,6e70 <link_path_walk.part.49+0x2c0>
> if (!depth) {
> 6da0: 00 00 bf 2f cmpdi cr7,r31,0
> 6da4: ac 01 9e 41 beq cr7,6f50 <link_path_walk.part.49+0x3a0>
> name = nd->stack[--depth].name;
> 6da8: ff ff ff 3b addi r31,r31,-1
> 6dac: 58 00 3a e9 ld r9,88(r26)
> link = walk_component(nd, 0);
> 6db0: 00 00 80 38 li r4,0
> 6db4: 78 d3 43 7f mr r3,r26
> name = nd->stack[--depth].name;
> 6db8: b4 07 ff 7f extsw r31,r31
> 6dbc: 30 00 5f 1d mulli r10,r31,48
> 6dc0: 14 52 29 7d add r9,r9,r10
> 6dc4: 20 00 c9 ea ld r22,32(r9)
> link = walk_component(nd, 0);
> 6dc8: 01 00 00 48 bl 6dc8 <link_path_walk.part.49+0x218>
> if (unlikely(link)) {
> 6dcc: 00 00 a3 2f cmpdi cr7,r3,0
> 6dd0: c8 00 9e 40 bne cr7,6e98 <link_path_walk.part.49+0x2e8>
> return dentry->d_flags & DCACHE_ENTRY_TYPE;
> 6dd4: 08 00 3a e9 ld r9,8(r26)
> 6dd8: 00 00 29 81 lwz r9,0(r9)
> 6ddc: 56 02 29 55 rlwinm r9,r9,0,9,11
> if (unlikely(!d_can_lookup(nd->path.dentry))) {
> 6de0: 00 e0 89 7f cmpw cr7,r9,r28
> 6de4: cc fe 9e 41 beq cr7,6cb0 <link_path_walk.part.49+0x100>
> if (nd->flags & LOOKUP_RCU) {
> 6de8: 38 00 3a 81 lwz r9,56(r26)
> 6dec: 40 00 29 71 andi. r9,r9,64
> 6df0: 38 01 82 41 beq 6f28 <link_path_walk.part.49+0x378>
> if (unlazy_walk(nd))
> 6df4: 78 d3 43 7f mr r3,r26
> 6df8: 01 00 00 48 bl 6df8 <link_path_walk.part.49+0x248>
> 6dfc: 00 00 a3 2f cmpdi cr7,r3,0
> 6e00: 28 01 9e 41 beq cr7,6f28 <link_path_walk.part.49+0x378>
> return -ECHILD;
> 6e04: f6 ff 00 3b li r24,-10
> 6e08: a0 00 01 e8 ld r0,160(r1)
> 6e0c: 48 00 e1 ea ld r23,72(r1)
> 6e10: 58 00 21 eb ld r25,88(r1)
> 6e14: 68 00 61 eb ld r27,104(r1)
> 6e18: 70 00 81 eb ld r28,112(r1)
> 6e1c: 78 00 a1 eb ld r29,120(r1)
> 6e20: 80 00 c1 eb ld r30,128(r1)
> 6e24: 88 00 e1 eb ld r31,136(r1)
> 6e28: a6 03 08 7c mtlr r0
> 6e2c: ec fd ff 4b b 6c18 <link_path_walk.part.49+0x68>
> if (name[0] == '.') switch (hashlen_len(hash_len)) {
> 6e30: 22 00 28 79 rldicl r8,r9,32,32
> 6e34: 20 00 0a 79 clrldi r10,r8,32
> 6e38: 01 00 8a 2b cmplwi cr7,r10,1
> 6e3c: a4 00 9e 41 beq cr7,6ee0 <link_path_walk.part.49+0x330>
> 6e40: 02 00 8a 2b cmplwi cr7,r10,2
> 6e44: 28 ff 9e 40 bne cr7,6d6c <link_path_walk.part.49+0x1bc>
> if (name[1] == '.') {
> 6e48: 01 00 f6 88 lbz r7,1(r22)
> 6e4c: 38 00 5a 81 lwz r10,56(r26)
> 6e50: 2e 00 87 2f cmpwi cr7,r7,46
> 6e54: 1c ff 9e 40 bne cr7,6d70 <link_path_walk.part.49+0x1c0>
> nd->flags |= LOOKUP_JUMPED;
> 6e58: 00 10 4a 61 ori r10,r10,4096
> type = LAST_DOTDOT;
> 6e5c: 03 00 00 3b li r24,3
> nd->flags |= LOOKUP_JUMPED;
> 6e60: 38 00 5a 91 stw r10,56(r26)
> if (likely(type == LAST_NORM)) {
> 6e64: 24 ff ff 4b b 6d88 <link_path_walk.part.49+0x1d8>
> 6e68: 00 00 00 60 nop
> 6e6c: 00 00 00 60 nop
> } while (unlikely(*name == '/'));
> 6e70: 01 00 36 8d lbzu r9,1(r22)
> 6e74: 2f 00 89 2b cmplwi cr7,r9,47
> 6e78: f8 ff 9e 41 beq cr7,6e70 <link_path_walk.part.49+0x2c0>
> if (unlikely(!*name)) {
> 6e7c: 00 00 a9 2f cmpdi cr7,r9,0
> 6e80: 20 ff 9e 41 beq cr7,6da0 <link_path_walk.part.49+0x1f0>
> link = walk_component(nd, WALK_MORE);
> 6e84: 02 00 80 38 li r4,2
> 6e88: 78 d3 43 7f mr r3,r26
> 6e8c: 01 00 00 48 bl 6e8c <link_path_walk.part.49+0x2dc>
> if (unlikely(link)) {
> 6e90: 00 00 a3 2f cmpdi cr7,r3,0
> 6e94: 40 ff 9e 41 beq cr7,6dd4 <link_path_walk.part.49+0x224>
> if (IS_ERR(link))
> 6e98: 40 d8 a3 7f cmpld cr7,r3,r27
> 6e9c: 94 00 9d 40 ble cr7,6f30 <link_path_walk.part.49+0x380>
> return PTR_ERR(link);
> 6ea0: b4 07 78 7c extsw r24,r3
> 6ea4: 64 ff ff 4b b 6e08 <link_path_walk.part.49+0x258>
> 6ea8: 00 00 00 60 nop
> 6eac: 00 00 00 60 nop
> if (unlazy_walk(nd))
> 6eb0: 78 d3 43 7f mr r3,r26
> 6eb4: 01 00 00 48 bl 6eb4 <link_path_walk.part.49+0x304>
> 6eb8: 00 00 a3 2f cmpdi cr7,r3,0
> 6ebc: 48 ff 9e 40 bne cr7,6e04 <link_path_walk.part.49+0x254>
> 6ec0: 30 00 7a e8 ld r3,48(r26)
> return inode_permission(nd->inode, MAY_EXEC);
> 6ec4: 01 00 80 38 li r4,1
> 6ec8: 01 00 00 48 bl 6ec8 <link_path_walk.part.49+0x318>
> 6ecc: 78 1b 78 7c mr r24,r3
> 6ed0: 04 fe ff 4b b 6cd4 <link_path_walk.part.49+0x124>
> 6ed4: 00 00 00 60 nop
> 6ed8: 00 00 00 60 nop
> 6edc: 00 00 00 60 nop
> type = LAST_DOT;
> 6ee0: 02 00 00 3b li r24,2
> 6ee4: a4 fe ff 4b b 6d88 <link_path_walk.part.49+0x1d8>
> 6ee8: 00 00 00 60 nop
> 6eec: 00 00 00 60 nop
> err = parent->d_op->d_hash(parent, &this);
> 6ef0: 60 00 43 e9 ld r10,96(r3)
> struct qstr this = { { .hash_len = hash_len }, .name = name };
> 6ef4: 28 00 21 f9 std r9,40(r1)
> 6ef8: 30 00 c1 fa std r22,48(r1)
> err = parent->d_op->d_hash(parent, &this);
> 6efc: 28 00 81 38 addi r4,r1,40
> 6f00: 10 00 2a e9 ld r9,16(r10)
> 6f04: 78 4b 2c 7d mr r12,r9
> 6f08: a6 03 29 7d mtctr r9
> 6f0c: 21 04 80 4e bctrl
> 6f10: 18 00 41 e8 ld r2,24(r1)
> if (err < 0)
> 6f14: 00 00 83 2f cmpwi cr7,r3,0
> 6f18: 60 00 9c 41 blt cr7,6f78 <link_path_walk.part.49+0x3c8>
> hash_len = this.hash_len;
> 6f1c: 28 00 21 e9 ld r9,40(r1)
> name = this.name;
> 6f20: 30 00 c1 ea ld r22,48(r1)
> 6f24: 60 fe ff 4b b 6d84 <link_path_walk.part.49+0x1d4>
> return -ENOTDIR;
> 6f28: ec ff 00 3b li r24,-20
> 6f2c: dc fe ff 4b b 6e08 <link_path_walk.part.49+0x258>
> nd->stack[depth++].name = name;
> 6f30: 30 00 5f 1d mulli r10,r31,48
> 6f34: 58 00 3a e9 ld r9,88(r26)
> 6f38: 01 00 ff 3b addi r31,r31,1
> 6f3c: b4 07 ff 7f extsw r31,r31
> 6f40: 14 52 29 7d add r9,r9,r10
> 6f44: 20 00 c9 fa std r22,32(r9)
> 6f48: 78 1b 76 7c mr r22,r3
> 6f4c: 64 fd ff 4b b 6cb0 <link_path_walk.part.49+0x100>
> nd->dir_uid = nd->inode->i_uid;
> 6f50: 30 00 5a e9 ld r10,48(r26)
> nd->flags &= ~LOOKUP_PARENT;
> 6f54: 38 00 3a 81 lwz r9,56(r26)
> return 0;
> 6f58: 00 00 00 3b li r24,0
> nd->dir_uid = nd->inode->i_uid;
> 6f5c: 04 00 0a 81 lwz r8,4(r10)
> nd->flags &= ~LOOKUP_PARENT;
> 6f60: 34 07 29 55 rlwinm r9,r9,0,28,26
> nd->dir_uid = nd->inode->i_uid;
> 6f64: d8 00 1a 91 stw r8,216(r26)
> nd->dir_mode = nd->inode->i_mode;
> 6f68: 00 00 4a a1 lhz r10,0(r10)
> nd->flags &= ~LOOKUP_PARENT;
> 6f6c: 38 00 3a 91 stw r9,56(r26)
> nd->dir_mode = nd->inode->i_mode;
> 6f70: dc 00 5a b1 sth r10,220(r26)
> return 0;
> 6f74: 94 fe ff 4b b 6e08 <link_path_walk.part.49+0x258>
> err = parent->d_op->d_hash(parent, &this);
> 6f78: 78 1b 78 7c mr r24,r3
> 6f7c: 8c fe ff 4b b 6e08 <link_path_walk.part.49+0x258>
> 6f80: a6 02 08 7c mflr r0
> 6f84: 48 00 e1 fa std r23,72(r1)
> 6f88: 58 00 21 fb std r25,88(r1)
> 6f8c: 68 00 61 fb std r27,104(r1)
> 6f90: 70 00 81 fb std r28,112(r1)
> 6f94: 78 00 a1 fb std r29,120(r1)
> 6f98: 80 00 c1 fb std r30,128(r1)
> 6f9c: 88 00 e1 fb std r31,136(r1)
> 6fa0: a0 00 01 f8 std r0,160(r1)
> }
> 6fa4: 01 00 00 48 bl 6fa4 <link_path_walk.part.49+0x3f4>
> 6fa8: 00 00 00 60 nop
> 6fac: 00 00 00 60 nop
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