uaccess: fix type mismatch warnings from access_ok()

On some architectures, access_ok() does not do any argument type
checking, so replacing the definition with a generic one causes
a few warnings for harmless issues that were never caught before.

Fix the ones that I found either through my own test builds or
that were reported by the 0-day bot.

Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

perf: Drop dead and useless guest "support" from arm, csky, nds32 and riscv

Drop "support" for guest callbacks from architectures that don't implement
the guest callbacks. Future patches will convert the callbacks to
static_call; rather than churn a bunch of arch code (that was presumably
copy+pasted from x86), remove it wholesale as it's useless and at best
wasting cycles.

A future patch will also add a Kconfig to force architcture to opt into
the callbacks to make it more difficult for uses "support" to sneak in in
the future.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20211111020738.2512932-6-seanjc@google.com

perf: Protect perf_guest_cbs with RCU

Protect perf_guest_cbs with RCU to fix multiple possible errors. Luckily,
all paths that read perf_guest_cbs already require RCU protection, e.g. to
protect the callback chains, so only the direct perf_guest_cbs touchpoints
need to be modified.

Bug #1 is a simple lack of WRITE_ONCE/READ_ONCE behavior to ensure
perf_guest_cbs isn't reloaded between a !NULL check and a dereference.
Fixed via the READ_ONCE() in rcu_dereference().

Bug #2 is that on weakly-ordered architectures, updates to the callbacks
themselves are not guaranteed to be visible before the pointer is made
visible to readers. Fixed by the smp_store_release() in
rcu_assign_pointer() when the new pointer is non-NULL.

Bug #3 is that, because the callbacks are global, it's possible for
readers to run in parallel with an unregisters, and thus a module
implementing the callbacks can be unloaded while readers are in flight,
resulting in a use-after-free. Fixed by a synchronize_rcu() call when
unregistering callbacks.

Bug #1 escaped notice because it's extremely unlikely a compiler will
reload perf_guest_cbs in this sequence. perf_guest_cbs does get reloaded
for future derefs, e.g. for ->is_user_mode(), but the ->is_in_guest()
guard all but guarantees the consumer will win the race, e.g. to nullify
perf_guest_cbs, KVM has to completely exit the guest and teardown down
all VMs before KVM start its module unload / unregister sequence. This
also makes it all but impossible to encounter bug #3.

Bug #2 has not been a problem because all architectures that register
callbacks are strongly ordered and/or have a static set of callbacks.

But with help, unloading kvm_intel can trigger bug #1 e.g. wrapping
perf_guest_cbs with READ_ONCE in perf_misc_flags() while spamming
kvm_intel module load/unload leads to:

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP
CPU: 6 PID: 1825 Comm: stress Not tainted 5.14.0-rc2+ #459
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:perf_misc_flags+0x1c/0x70
Call Trace:
perf_prepare_sample+0x53/0x6b0
perf_event_output_forward+0x67/0x160
__perf_event_overflow+0x52/0xf0
handle_pmi_common+0x207/0x300
intel_pmu_handle_irq+0xcf/0x410
perf_event_nmi_handler+0x28/0x50
nmi_handle+0xc7/0x260
default_do_nmi+0x6b/0x170
exc_nmi+0x103/0x130
asm_exc_nmi+0x76/0xbf

Fixes: 39447b386c84 ("perf: Enhance perf to allow for guest statistic collection from host")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211111020738.2512932-2-seanjc@google.com

csky: Fixup perf callchain unwind

[ 5221.974084] Unable to handle kernel paging request at virtual address 0xfffff000, pc: 0x8002c18e
[ 5221.985929] Oops: 00000000
[ 5221.989488]
[ 5221.989488] CURRENT PROCESS:
[ 5221.989488]
[ 5221.992877] COMM=callchain_test PID=11962
[ 5221.995213] TEXT=00008000-000087e0 DATA=00009f1c-0000a018 BSS=0000a018-0000b000
[ 5221.999037] USER-STACK=7fc18e20 KERNEL-STACK=be204680
[ 5221.999037]
[ 5222.003292] PC: 0x8002c18e (perf_callchain_kernel+0x3e/0xd4)
[ 5222.007957] LR: 0x8002c198 (perf_callchain_kernel+0x48/0xd4)
[ 5222.074873] Call Trace:
[ 5222.074873] [<800a248e>] get_perf_callchain+0x20a/0x29c
[ 5222.074873] [<8009d964>] perf_callchain+0x64/0x80
[ 5222.074873] [<8009dc1c>] perf_prepare_sample+0x29c/0x4b8
[ 5222.074873] [<8009de6e>] perf_event_output_forward+0x36/0x98
[ 5222.074873] [<800497e0>] search_exception_tables+0x20/0x44
[ 5222.074873] [<8002cbb6>] do_page_fault+0x92/0x378
[ 5222.074873] [<80098608>] __perf_event_overflow+0x54/0xdc
[ 5222.074873] [<80098778>] perf_swevent_hrtimer+0xe8/0x164
[ 5222.074873] [<8002ddd0>] update_mmu_cache+0x0/0xd8
[ 5222.074873] [<8002c014>] user_backtrace+0x58/0xc4
[ 5222.074873] [<8002c0b4>] perf_callchain_user+0x34/0xd0
[ 5222.074873] [<800a2442>] get_perf_callchain+0x1be/0x29c
[ 5222.074873] [<8009d964>] perf_callchain+0x64/0x80
[ 5222.074873] [<8009d834>] perf_output_sample+0x78c/0x858
[ 5222.074873] [<8009dc1c>] perf_prepare_sample+0x29c/0x4b8
[ 5222.074873] [<8009de94>] perf_event_output_forward+0x5c/0x98
[ 5222.097846]
[ 5222.097846] [<800a0300>] perf_event_exit_task+0x58/0x43c
[ 5222.097846] [<8006c874>] hrtimer_interrupt+0x104/0x2ec
[ 5222.097846] [<800a0300>] perf_event_exit_task+0x58/0x43c
[ 5222.097846] [<80437bb6>] dw_apb_clockevent_irq+0x2a/0x4c
[ 5222.097846] [<8006c770>] hrtimer_interrupt+0x0/0x2ec
[ 5222.097846] [<8005f2e4>] __handle_irq_event_percpu+0xac/0x19c
[ 5222.097846] [<80437bb6>] dw_apb_clockevent_irq+0x2a/0x4c
[ 5222.097846] [<8005f408>] handle_irq_event_percpu+0x34/0x88
[ 5222.097846] [<8005f480>] handle_irq_event+0x24/0x64
[ 5222.097846] [<8006218c>] handle_level_irq+0x68/0xdc
[ 5222.097846] [<8005ec76>] __handle_domain_irq+0x56/0xa8
[ 5222.097846] [<80450e90>] ck_irq_handler+0xac/0xe4
[ 5222.097846] [<80029012>] csky_do_IRQ+0x12/0x24
[ 5222.097846] [<8002a3a0>] csky_irq+0x70/0x80
[ 5222.097846] [<800ca612>] alloc_set_pte+0xd2/0x238
[ 5222.097846] [<8002ddd0>] update_mmu_cache+0x0/0xd8
[ 5222.097846] [<800a0340>] perf_event_exit_task+0x98/0x43c

The original fp check doesn't base on the real kernal stack region.
Invalid fp address may cause kernel panic.

Signed-off-by: Mao Han <han_mao@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>

csky: Add perf callchain support

This patch add support for perf callchain sampling on csky platform.
As fp is used to unwind the stack, the program being sampled and the
C library need to be compiled with -mbacktrace for user callchains,
kernel callchains require CONFIG_STACKTRACE = y.

Changelog:
- Coding convention with Christoph's advice for riscv's.

Signed-off-by: Mao Han <han_mao@c-sky.com>
Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Cc: Christoph Hellwig <hch@infradead.org>