[Qemu-devel] Fwd: [PATCH v2.5] fixup! linux-user/sh4: Notice gUSA regions during signal delivery

[Richard Henderson]

Bah.  Should have gone to the list as well.

r~
---------- Forwarded message ----------
From: Richard Henderson <address@hidden>
Date: Fri, Jul 7, 2017 at 6:38 AM
Subject: [PATCH v2.5] fixup! linux-user/sh4: Notice gUSA regions during
signal delivery
To: address@hidden
Cc: address@hidden


This fixes the signal delivery problem reported.  I'll fold this into
the patch properly for v3, but this will allow reasonable testing to
proceed in the meantime.

r~
---
 linux-user/signal.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/linux-user/signal.c b/linux-user/signal.c
index 8c0b851..d68bd26 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -3476,13 +3476,18 @@ static abi_ulong get_sigframe(struct
target_sigaction *ka,
    translate such sequences differently in a parallel context.  */
 static void unwind_gusa(CPUSH4State *regs)
 {
-    /* If the stack pointer is sufficiently negative ... */
-    if ((regs->gregs[15] & 0xc0000000u) == 0xc0000000u
-        /* ... and we haven't completed the sequence ... */
-        && regs->pc < regs->gregs[0]) {
+    /* 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 insn
-           that actually sets SP to the region size.  */
+           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.  */
--
2.9.4