[PULL 1/3] linux-user/sparc: Fix errors in target_ucontext structures

[Laurent Vivier <laurent@vivier.eu>]

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

The various structs that make up the SPARC target_ucontext had some
errors:
 * target structures must not include fields which are host pointers,
   which might be the wrong size.  These should be abi_ulong instead
 * because we don't have the 'long double' part of the mcfpu_fregs
   union in our version of the target_mc_fpu struct, we need to
   manually force it to be 16-aligned

In particular, the lack of 16-alignment caused sparc64_get_context()
and sparc64_set_context() to read and write all the registers at the
wrong offset, which triggered a guest glibc stack check in
siglongjmp:
  *** longjmp causes uninitialized stack frame ***: terminated
when trying to run bash.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20201105212314.9628-2-peter.maydell@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 linux-user/sparc/signal.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/linux-user/sparc/signal.c b/linux-user/sparc/signal.c
index d796f50f665b..57ea1593bfc9 100644
--- a/linux-user/sparc/signal.c
+++ b/linux-user/sparc/signal.c
@@ -349,10 +349,15 @@ typedef abi_ulong target_mc_greg_t;
 typedef target_mc_greg_t target_mc_gregset_t[SPARC_MC_NGREG];
 
 struct target_mc_fq {
-    abi_ulong *mcfq_addr;
+    abi_ulong mcfq_addr;
     uint32_t mcfq_insn;
 };
 
+/*
+ * Note the manual 16-alignment; the kernel gets this because it
+ * includes a "long double qregs[16]" in the mcpu_fregs union,
+ * which we can't do.
+ */
 struct target_mc_fpu {
     union {
         uint32_t sregs[32];
@@ -362,11 +367,11 @@ struct target_mc_fpu {
     abi_ulong mcfpu_fsr;
     abi_ulong mcfpu_fprs;
     abi_ulong mcfpu_gsr;
-    struct target_mc_fq *mcfpu_fq;
+    abi_ulong mcfpu_fq;
     unsigned char mcfpu_qcnt;
     unsigned char mcfpu_qentsz;
     unsigned char mcfpu_enab;
-};
+} __attribute__((aligned(16)));
 typedef struct target_mc_fpu target_mc_fpu_t;
 
 typedef struct {
@@ -377,7 +382,7 @@ typedef struct {
 } target_mcontext_t;
 
 struct target_ucontext {
-    struct target_ucontext *tuc_link;
+    abi_ulong tuc_link;
     abi_ulong tuc_flags;
     target_sigset_t tuc_sigmask;
     target_mcontext_t tuc_mcontext;
-- 
2.28.0