bnxt_en: Fix potential crash when dumping FW log coredump

bnxt_en: Fix potential crash when dumping FW log coredump

If the FW log context memory is retained after FW reset, the existing
code is not handling the condition correctly and zeroes out the data
structures.  This potentially will cause a division by zero crash
when the user runs ethtool -w.  The last_type is also not set
correctly when the context memory is retained.  This will cause errors
because the last_type signals to the FW that all context memory types
have been configured.

Oops: divide error: 0000 1 PREEMPT SMP NOPTI
CPU: 53 UID: 0 PID: 7019 Comm: ethtool Kdump: loaded Tainted: G           OE      6.12.0-rc7+ #1
Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
Hardware name: Supermicro SYS-621C-TN12R/X13DDW-A, BIOS 1.4 08/10/2023
RIP: 0010:__bnxt_copy_ctx_mem.constprop.0.isra.0+0x86/0x160 [bnxt_en]
Code: 0a 31 d2 4c 89 6c 24 10 45 8b a5 fc df ff ff 4c 8b 74 24 20 31 db 66 89 44 24 06 48 63 c5 c1 e5 09 4c 0f af e0 48 8b 44 24 30 <49> f7 f4 4c 89 64 24 08 48 63 c5 4d 89 ec 31 ed 48 89 44 24 18 49
RSP: 0018:ff480591603d78b8 EFLAGS: 00010206
RAX: 0000000000100000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ff23959e46740000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000100000 R09: ff23959e46740000
R10: ff480591603d7a18 R11: 0000000000000010 R12: 0000000000000000
R13: ff23959e46742008 R14: 0000000000000000 R15: 0000000000000000
FS:  00007f04227c1740(0000) GS:ff2395adbf680000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f04225b33a5 CR3: 000000108b9a4001 CR4: 0000000000773ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
 <TASK>
 ? die+0x33/0x90
 ? do_trap+0xd9/0x100
 ? __bnxt_copy_ctx_mem.constprop.0.isra.0+0x86/0x160 [bnxt_en]
 ? do_error_trap+0x65/0x80
 ? __bnxt_copy_ctx_mem.constprop.0.isra.0+0x86/0x160 [bnxt_en]
 ? exc_divide_error+0x36/0x50
 ? __bnxt_copy_ctx_mem.constprop.0.isra.0+0x86/0x160 [bnxt_en]
 ? asm_exc_divide_error+0x16/0x20
 ? __bnxt_copy_ctx_mem.constprop.0.isra.0+0x86/0x160 [bnxt_en]
 ? __bnxt_copy_ctx_mem.constprop.0.isra.0+0xda/0x160 [bnxt_en]
 bnxt_get_ctx_coredump.constprop.0+0x1ed/0x390 [bnxt_en]
 ? __memcg_slab_post_alloc_hook+0x21c/0x3c0
 ? __bnxt_get_coredump+0x473/0x4b0 [bnxt_en]
 __bnxt_get_coredump+0x473/0x4b0 [bnxt_en]
 ? security_file_alloc+0x74/0xe0
 ? cred_has_capability.isra.0+0x78/0x120
 bnxt_get_coredump_length+0x4b/0xf0 [bnxt_en]
 bnxt_get_dump_flag+0x40/0x60 [bnxt_en]
 __dev_ethtool+0x17e4/0x1fc0
 ? syscall_exit_to_user_mode+0xc/0x1d0
 ? do_syscall_64+0x85/0x150
 ? unmap_page_range+0x299/0x4b0
 ? vma_interval_tree_remove+0x215/0x2c0
 ? __kmalloc_cache_noprof+0x10a/0x300
 dev_ethtool+0xa8/0x170
 dev_ioctl+0x1b5/0x580
 ? sk_ioctl+0x4a/0x110
 sock_do_ioctl+0xab/0xf0
 sock_ioctl+0x1ca/0x2e0
 __x64_sys_ioctl+0x87/0xc0
 do_syscall_64+0x79/0x150

Fixes: 24d694aec139 ("bnxt_en: Allocate backing store memory for FW trace logs")
Signed-off-by: Hongguang Gao <hongguang.gao@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20241204215918.1692597-3-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>