Re: [PATCH v2 2/2] linux-user/m68k: Handle EXCP_ADDRESS in cpu_loop

[Laurent Vivier]

Le 09/03/2023 à 21:16, Richard Henderson a écrit :
This exception can be raised by illegal instructions.
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
  linux-user/m68k/cpu_loop.c     |  5 ++++-
  tests/tcg/m68k/excp-address.c  | 32 ++++++++++++++++++++++++++++++++
  tests/tcg/m68k/Makefile.target |  1 +
  3 files changed, 37 insertions(+), 1 deletion(-)
  create mode 100644 tests/tcg/m68k/excp-address.c

diff --git a/linux-user/m68k/cpu_loop.c b/linux-user/m68k/cpu_loop.c
index caead1cb74..84b5d290c0 100644
--- a/linux-user/m68k/cpu_loop.c
+++ b/linux-user/m68k/cpu_loop.c
@@ -35,7 +35,10 @@ void cpu_loop(CPUM68KState *env)
          cpu_exec_end(cs);
          process_queued_cpu_work(cs);
  
-        switch(trapnr) {
+        switch (trapnr) {
+        case EXCP_ADDRESS:
+            force_sig_fault(TARGET_SIGBUS, TARGET_BUS_ADRALN, env->pc);
+            break;
          case EXCP_ILLEGAL:
          case EXCP_LINEA:
          case EXCP_LINEF:
diff --git a/tests/tcg/m68k/excp-address.c b/tests/tcg/m68k/excp-address.c
new file mode 100644
index 0000000000..1dbdddef58
--- /dev/null
+++ b/tests/tcg/m68k/excp-address.c
@@ -0,0 +1,32 @@
+/*
+ * Test m68k address exception
+ */
+
+#define _GNU_SOURCE 1
+#include <signal.h>
+#include <stdlib.h>
+
+static void sig_handler(int sig, siginfo_t *si, void *puc)
+{
+    exit(0);
+}
+
+int main(int argc, char **argv)
+{
+    struct sigaction act = {
+        .sa_sigaction = sig_handler,
+        .sa_flags = SA_SIGINFO
+    };
+
+    sigaction(SIGBUS, &act, NULL);
+
+    /*
+     * addl %d0,#0 -- with immediate as destination is illegal.
+     * Buggy qemu interpreted the insn as 5 words: 2 for immediate source
+     * and another 2 for immediate destination.  Provide all that padding
+     * so that abort gets called.
+     */
+    asm volatile(".word 0xd1bc,0,0,0,0");
+
+    abort();
+}
diff --git a/tests/tcg/m68k/Makefile.target b/tests/tcg/m68k/Makefile.target
index 1163c7ef03..d3b0bc48a3 100644
--- a/tests/tcg/m68k/Makefile.target
+++ b/tests/tcg/m68k/Makefile.target
@@ -4,6 +4,7 @@
  #
  
  VPATH += $(SRC_PATH)/tests/tcg/m68k
+TESTS += excp-address
  TESTS += trap
  
  # On m68k Linux supports 4k and 8k pages (but 8k is currently broken)

Reviewed-by: Laurent Vivier <laur...@vivier.eu>

I've tested tests/tcg/m68k/excp-address.c on a real hardware (Q800), and the result differs from the 
one from QEMU:

On Q800 (etch m68k, kernel 5.14.0):

$ ./excp-address
Illegal instruction
$ strace ./excp-address
...
rt_sigaction(SIGBUS, {0x80000478, [], SA_SIGINFO}, NULL, 8) = 0
--- SIGILL (Illegal instruction) @ 0 (0) ---
+++ killed by SIGILL +++

With QEMU, we have:

# QEMU_STRACE= ./excp-address
...
677354 rt_sigaction(SIGBUS,0x40800454,NULL) = 0
--- SIGBUS {si_signo=SIGBUS, si_code=1, si_addr=0x800004ce} ---
677354 exit_group(0)

Thanks,
Laurent