livepatch/ppc64: Make sure caller function in stack

hulk inclusion
category: bugfix
bugzilla: 34578/46793/51924
CVE: NA

-------------------------------------------------------------------------

When we make a livepatch, since we did not save the stack frame
according to the call requirementsthen, we can't see that the
caller function in the stack after the patch is activated.

At this time, if we also patch the caller function, because it's
is not seen in the stack, then this patch can be enabled normally
without being checked by the stack check.

This is very dangerous. If there are other processes running or
sleeping in the context of the first patched callee function, then
after the caller function is patched, we have changed the first few
instructions of the caller to bstub to jump directly, so the context
of the process will be destroyed, after he returns to the caller,
the wrong instruction will be executed.

The following problems can occur in our testcase:
	Unrecoverable FP Unavailable Exception 800 at 80000000000c80d8
	Oops: Unrecoverable FP Unavailable Exception, sig: 6 [#1]
	PREEMPT SMP NR_CPUS=4 QEMU e500
	Modules linked in: level2_delay_patch(O) delay_patch(O) delay(O)
	CPU: 1 PID: 328 Comm: cat Tainted: G           O  K 4.4.222 #334
	task: c0000000f02da100 task.stack: c00000007a52c000
	NIP: 80000000000c80d8 LR: 80000000000c80d8 CTR: c0000000003cef10
	REGS: c00000007a52eea0 TRAP: 0800   Tainted: G O  K  (4.4.222)
	MSR: 0000000080009000 <EE,ME>  CR: 28022882  XER: 00000000
	NIP [80000000000c80d8] .foo_show+0x18/0x48 [delay]
	LR [80000000000c80d8] .foo_show+0x18/0x48 [delay]
	Call Trace:
	[c00000007a52f120] [c00000007e015af8] 0xc00000007e015af8(unreliable)
	[c00000007a52f1a0] [c00000000032d11c].kobj_attr_show+0x2c/0x50
	[c00000007a52f210] [c000000000230b74].sysfs_kf_seq_show+0xf4/0x1d0
	[c00000007a52f2b0] [c00000000022ea2c].kernfs_seq_show+0x3c/0x50
	[c00000007a52f320] [c0000000001c1f88].seq_read+0x118/0x5c0
	[c00000007a52f420] [c00000000022fa04].kernfs_fop_read+0x194/0x240
	[c00000007a52f4c0] [c00000000018e27c].do_loop_readv_writev+0xac/0x100
	[c00000007a52f560] [c00000000018f284].do_readv_writev+0x2a4/0x2f0
	[c00000007a52f6d0] [c0000000001cf3cc].default_file_splice_read+0x22c/0x490
	[c00000007a52fa60] [c0000000001cd704].do_splice_to+0x94/0xe0
	[c00000007a52fb00] [c0000000001cd814].splice_direct_to_actor+0xc4/0x320
	[c00000007a52fbd0] [c0000000001cdb14].do_splice_direct+0xa4/0x120
	[c00000007a52fc90] [c00000000018f9fc].do_sendfile+0x27c/0x440
	[c00000007a52fd80] [c0000000001910f4].compat_SyS_sendfile64+0xe4/0x140
	[c00000007a52fe30] [c00000000000058c]system_call+0x40/0xc8
	Instruction dump:
	ebe1fff8 7c0803a6 4e800020 60000000 60000000 60000000 3d62ffff 396b7bf0
	e98b0018 7d8903a6 4e800420 73747563 <c0000000> f030a948 7fe3fb78 38a00001
	---[ end trace 07a14bdffccc341f ]---

We solve this problem by disguising the stack frame, so that the caller
function will appear in the stack, which can be detected by the stack
check, so that when the patch is enabled, it will be found

Ather this patch, when enable the second livepatch, we will find the
caller on the stack.

	livepatch_64: func .foo_show is in use!
	livepatch_64: PID: 328 Comm: cat
	Call Trace:
	[c00000007a596bd0] [c00000007a596cd0] 0xc00000007a596cd0(unreliable)
	[c00000007a596da0] [c000000000008b20].__switch_to+0x70/0xa0
	[c00000007a596e20] [c000000000557a5c].__schedule+0x2fc/0x830
	[c00000007a596ed0] [c0000000005581b8] .schedule+0x38/0xc0
	[c00000007a596f40] [c00000000055c7e8].schedule_timeout+0x148/0x210
	[c00000007a597030] [80000000000ff054].new_stack_func+0x54/0x90 [delay_patch]
	[c00000007a5970b0] [c0000000f025d67c] 0xc0000000f025d67c
	[c00000007a597120] [80000000000c80d8] .foo_show+0x18/0x48 [delay]
	[c00000007a5971a0] [c00000000032d11c].kobj_attr_show+0x2c/0x50
	[c00000007a597210] [c000000000230b74].sysfs_kf_seq_show+0xf4/0x1d0
	[c00000007a5972b0] [c00000000022ea2c].kernfs_seq_show+0x3c/0x50
	[c00000007a597320] [c0000000001c1f88].seq_read+0x118/0x5c0
	[c00000007a597420] [c00000000022fa04].kernfs_fop_read+0x194/0x240
	[c00000007a5974c0] [c00000000018e27c].do_loop_readv_writev+0xac/0x100
	[c00000007a597560] [c00000000018f284].do_readv_writev+0x2a4/0x2f0
	[c00000007a5976d0] [c0000000001cf3cc].default_file_splice_read+0x22c/0x490
	[c00000007a597a60] [c0000000001cd704].do_splice_to+0x94/0xe0
	[c00000007a597b00] [c0000000001cd814].splice_direct_to_actor+0xc4/0x320
	[c00000007a597bd0] [c0000000001cdb14].do_splice_direct+0xa4/0x120
	[c00000007a597c90] [c00000000018f9fc].do_sendfile+0x27c/0x440
	[c00000007a597d80] [c0000000001910f4].compat_SyS_sendfile64+0xe4/0x140
	[c00000007a597e30] [c00000000000058c]system_call+0x40/0xc8

Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: yangerkun <yangerkun@huawei.com>

Signed-off-by: Dong Kai <dongkai11@huawei.com>

Signed-off-by: Ye Weihua <yeweihua4@huawei.com>
Reviewed-by: Yang Jihong <yangjihong1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>