[PATCH v2 03/30] linux-user/arm: Use force_sig() to deliver fpa11 emulation SIGFPE

From: Richard Henderson <richard.henderson@linaro.org>
To: qemu-devel@nongnu.org
Cc: peter.maydell@linaro.org, laurent@vivier.eu
Subject: [PATCH v2 03/30] linux-user/arm: Use force_sig() to deliver fpa11 emulation SIGFPE
Date: Sat, 21 Aug 2021 20:55:10 -0700	[thread overview]
Message-ID: <20210822035537.283193-4-richard.henderson@linaro.org> (raw)
In-Reply-To: <20210822035537.283193-1-richard.henderson@linaro.org>

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

In the Arm target code, when the fpa11 emulation code tells us we
need to send the guest a SIGFPE, we do this with queue_signal(), but
we are using the wrong si_type, and we aren't setting the _sifields
union members corresponding to either the si_type we are using or the
si_type we should be using.

As the existing comment notes, the kernel code for this calls the old
send_sig() function to deliver the signal.  This eventually results
in the kernel's signal handling code fabricating a siginfo_t with a
SI_KERNEL code and a zero pid and uid.  For QEMU this means we need
to use QEMU_SI_KILL.  We already have a function for that:
force_sig() sets up the whole target_siginfo_t the way we need it.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20210813131809.28655-4-peter.maydell@linaro.org>
[rth: Include signal-common.h]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/arm/cpu_loop.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/linux-user/arm/cpu_loop.c b/linux-user/arm/cpu_loop.c
index 007752f5b7..b8ece169f9 100644
--- a/linux-user/arm/cpu_loop.c
+++ b/linux-user/arm/cpu_loop.c
@@ -22,6 +22,7 @@
 #include "qemu.h"
 #include "elf.h"
 #include "cpu_loop-common.h"
+#include "signal-common.h"
 #include "semihosting/common-semi.h"
 
 #define get_user_code_u32(x, gaddr, env)                \
@@ -266,16 +267,13 @@ static bool emulate_arm_fpa11(CPUARMState *env, uint32_t opcode)
     ts->fpa.fpsr |= raise & ~enabled;
 
     if (raise & enabled) {
-        target_siginfo_t info = { };
-
         /*
          * The kernel's nwfpe emulator does not pass a real si_code.
-         * It merely uses send_sig(SIGFPE, current, 1).
+         * It merely uses send_sig(SIGFPE, current, 1), which results in
+         * __send_signal() filling out SI_KERNEL with pid and uid 0 (under
+         * the "SEND_SIG_PRIV" case). That's what our force_sig() does.
          */
-        info.si_signo = TARGET_SIGFPE;
-        info.si_code = TARGET_SI_KERNEL;
-
-        queue_signal(env, info.si_signo, QEMU_SI_FAULT, &info);
+        force_sig(TARGET_SIGFPE);
     } else {
         env->regs[15] += 4;
     }
-- 
2.25.1


