riscv: provide riscv-specific is_trap_insn()

uprobes expects is_trap_insn() to return true for any trap instructions,
not just the one used for installing uprobe. The current default
implementation only returns true for 16-bit c.ebreak if C extension is
enabled. This can confuse uprobes if a 32-bit ebreak generates a trap
exception from userspace: uprobes asks is_trap_insn() who says there is no
trap, so uprobes assume a probe was there before but has been removed, and
return to the trap instruction. This causes an infinite loop of entering
and exiting trap handler.

Instead of using the default implementation, implement this function
speficially for riscv with checks for both ebreak and c.ebreak.

Fixes: 74784081aac8 ("riscv: Add uprobes supported")
Signed-off-by: Nam Cao <namcaov@gmail.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/20230829083614.117748-1-namcaov@gmail.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

riscv: uprobes: Restore thread.bad_cause

thread.bad_cause is saved in arch_uprobe_pre_xol(), it should be restored
in arch_uprobe_{post,abort}_xol() accordingly, otherwise the save operation
is meaningless, this change is similar with x86 and powerpc.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Fixes: 74784081aac8 ("riscv: Add uprobes supported")
Link: https://lore.kernel.org/r/1682214146-3756-1-git-send-email-yangtiezhu@loongson.cn
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

riscv:uprobe fix SR_SPIE set/clear handling

In riscv the process of uprobe going to clear spie before exec
the origin insn,and set spie after that.But When access the page
which origin insn has been placed a page fault may happen and
irq was disabled in arch_uprobe_pre_xol function,It cause a WARN
as follows.
There is no need to clear/set spie in arch_uprobe_pre/post/abort_xol.
We can just remove it.

[ 31.684157] BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1488
[ 31.684677] in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 76, name: work
[ 31.684929] preempt_count: 0, expected: 0
[ 31.685969] CPU: 2 PID: 76 Comm: work Tainted: G
[ 31.686542] Hardware name: riscv-virtio,qemu (DT)
[ 31.686797] Call Trace:
[ 31.687053] [<ffffffff80006442>] dump_backtrace+0x30/0x38
[ 31.687699] [<ffffffff80812118>] show_stack+0x40/0x4c
[ 31.688141] [<ffffffff8081817a>] dump_stack_lvl+0x44/0x5c
[ 31.688396] [<ffffffff808181aa>] dump_stack+0x18/0x20
[ 31.688653] [<ffffffff8003e454>] __might_resched+0x114/0x122
[ 31.688948] [<ffffffff8003e4b2>] __might_sleep+0x50/0x7a
[ 31.689435] [<ffffffff80822676>] down_read+0x30/0x130
[ 31.689728] [<ffffffff8000b650>] do_page_fault+0x166/x446
[ 31.689997] [<ffffffff80003c0c>] ret_from_exception+0x0/0xc

Fixes: 74784081aac8 ("riscv: Add uprobes supported")
Signed-off-by: Yipeng Zou <zouyipeng@huawei.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220721065820.245755-1-zouyipeng@huawei.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

riscv: Add uprobes supported

This patch adds support for uprobes on riscv architecture.

Just like kprobe, it support single-step and simulate instructions.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>