[PULL 5/7] linux-user: Provide new force_sig_fault() function

[Laurent Vivier <laurent@vivier.eu>]

From: Peter Maydell <peter.maydell@linaro.org>

In many places in the linux-user code we need to queue a signal for
the guest using the QEMU_SI_FAULT si_type.  This requires that the
caller sets up and passes us a target_siginfo, including setting the
appropriate part of the _sifields union for the si_type. In a number
of places the code forgets to set the _sifields union field.

Provide a new force_sig_fault() function, which does the same thing
as the Linux kernel function of that name -- it takes the signal
number, the si_code value and the address to use in
_sifields._sigfault, and assembles the target_siginfo itself.  This
makes the callsites simpler and means it's harder to forget to pass
in an address value.

We follow force_sig() and the kernel's force_sig_fault() in not
requiring the caller to pass in the CPU pointer but always acting
on the CPU of the current thread.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210813131809.28655-6-peter.maydell@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 linux-user/signal-common.h |  1 +
 linux-user/signal.c        | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/linux-user/signal-common.h b/linux-user/signal-common.h
index 58ea23f6ea94..79511becb4e7 100644
--- a/linux-user/signal-common.h
+++ b/linux-user/signal-common.h
@@ -40,6 +40,7 @@ void tswap_siginfo(target_siginfo_t *tinfo,
 void set_sigmask(const sigset_t *set);
 void force_sig(int sig);
 void force_sigsegv(int oldsig);
+void force_sig_fault(int sig, int code, abi_ulong addr);
 #if defined(TARGET_ARCH_HAS_SETUP_FRAME)
 void setup_frame(int sig, struct target_sigaction *ka,
                  target_sigset_t *set, CPUArchState *env);
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 910b9dc6f7d1..203821645509 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -651,6 +651,23 @@ void force_sig(int sig)
     queue_signal(env, info.si_signo, QEMU_SI_KILL, &info);
 }
 
+/*
+ * Force a synchronously taken QEMU_SI_FAULT signal. For QEMU the
+ * 'force' part is handled in process_pending_signals().
+ */
+void force_sig_fault(int sig, int code, abi_ulong addr)
+{
+    CPUState *cpu = thread_cpu;
+    CPUArchState *env = cpu->env_ptr;
+    target_siginfo_t info = {};
+
+    info.si_signo = sig;
+    info.si_errno = 0;
+    info.si_code = code;
+    info._sifields._sigfault._addr = addr;
+    queue_signal(env, sig, QEMU_SI_FAULT, &info);
+}
+
 /* Force a SIGSEGV if we couldn't write to memory trying to set
  * up the signal frame. oldsig is the signal we were trying to handle
  * at the point of failure.
-- 
2.31.1