[Qemu-devel] [PATCH v3 08/30] linux-user/sh4: Notice gUSA regions during signal delivery

[Richard Henderson]

We translate gUSA regions atomically in a parallel context.
But in a serial context a gUSA region may be interrupted.
In that case, restart the region as the kernel would.

Reviewed-by: Aurelien Jarno <address@hidden>
Signed-off-by: Richard Henderson <address@hidden>
---
 linux-user/signal.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/linux-user/signal.c b/linux-user/signal.c
index ddfd75c..27867a4 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -3471,6 +3471,30 @@ static abi_ulong get_sigframe(struct target_sigaction 
*ka,
     return (sp - frame_size) & -8ul;
 }
 
+/* Notice when we're in the middle of a gUSA region and reset.
+   Note that this will only occur for !parallel_cpus, as we will
+   translate such sequences differently in a parallel context.  */
+static void unwind_gusa(CPUSH4State *regs)
+{
+    /* If the stack pointer is sufficiently negative, and we haven't
+       completed the sequence, then reset to the entry to the region.  */
+    /* ??? The SH4 kernel checks for and address above 0xC0000000.
+       However, the page mappings in qemu linux-user aren't as restricted
+       and we wind up with the normal stack mapped above 0xF0000000.
+       That said, there is no reason why the kernel should be allowing
+       a gUSA region that spans 1GB.  Use a tighter check here, for what
+       can actually be enabled by the immediate move.  */
+    if (regs->gregs[15] >= -128u && regs->pc < regs->gregs[0]) {
+        /* Reset the PC to before the gUSA region, as computed from
+           R0 = region end, SP = -(region size), plus one more for the
+           insn that actually initializes SP to the region size.  */
+        regs->pc = regs->gregs[0] + regs->gregs[15] - 2;
+
+        /* Reset the SP to the saved version in R1.  */
+        regs->gregs[15] = regs->gregs[1];
+    }
+}
+
 static void setup_sigcontext(struct target_sigcontext *sc,
                              CPUSH4State *regs, unsigned long mask)
 {
@@ -3534,6 +3558,8 @@ static void setup_frame(int sig, struct target_sigaction 
*ka,
     abi_ulong frame_addr;
     int i;
 
+    unwind_gusa(regs);
+
     frame_addr = get_sigframe(ka, regs->gregs[15], sizeof(*frame));
     trace_user_setup_frame(regs, frame_addr);
     if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
@@ -3584,6 +3610,8 @@ static void setup_rt_frame(int sig, struct 
target_sigaction *ka,
     abi_ulong frame_addr;
     int i;
 
+    unwind_gusa(regs);
+
     frame_addr = get_sigframe(ka, regs->gregs[15], sizeof(*frame));
     trace_user_setup_rt_frame(regs, frame_addr);
     if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
-- 
2.9.4