[PATCH v3] Fix PTRACE_GETREGSET failure for compat inferiors on arm64

[Kees Cook <keescook@chromium.org>]

When running a 32-bit ARM inferior with a 32-bit ARM GDB on a 64-bit
AArch64 host, only VFP registers (NT_ARM_VFP) are available. The FPA
registers (NT_PRFPREG) are not available so GDB must not request them, as
this will fail with -EINVAL.  This is most noticeably exposed when running
"generate-core-file":

(gdb) generate-core-file myprog.core
Unable to fetch the floating point registers.: Invalid argument.

ptrace(PTRACE_GETREGSET, 27642, NT_FPREGSET, 0xffcc67f0) = -1 EINVAL (Invalid argument)

gdb/ChangeLog:

2016-12-19  Kees Cook  <keescook@google.com>

    * gdb/arm-linux-nat.c: Skip soft-float registers when using hard-float.
---
v3:
- argh, actually drop needless other change.
v2:
- check have_fpa_registers instead, dropped needless other change: qiyaoltc
---
 gdb/arm-linux-nat.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/gdb/arm-linux-nat.c b/gdb/arm-linux-nat.c
index d11bdc6..4fa5204 100644
--- a/gdb/arm-linux-nat.c
+++ b/gdb/arm-linux-nat.c
@@ -384,13 +384,14 @@ arm_linux_fetch_inferior_registers (struct target_ops *ops,
   if (-1 == regno)
     {
       fetch_regs (regcache);
-      fetch_fpregs (regcache);
       if (tdep->have_wmmx_registers)
 	fetch_wmmx_regs (regcache);
       if (tdep->vfp_register_count > 0)
 	fetch_vfp_regs (regcache);
+      if (tdep->have_fpa_registers)
+	fetch_fpregs (regcache);
     }
-  else 
+  else
     {
       if (regno < ARM_F0_REGNUM || regno == ARM_PS_REGNUM)
 	fetch_regs (regcache);
@@ -420,11 +421,12 @@ arm_linux_store_inferior_registers (struct target_ops *ops,
   if (-1 == regno)
     {
       store_regs (regcache);
-      store_fpregs (regcache);
       if (tdep->have_wmmx_registers)
 	store_wmmx_regs (regcache);
       if (tdep->vfp_register_count > 0)
 	store_vfp_regs (regcache);
+      if (tdep->have_fpa_registers)
+	store_fpregs (regcache);
     }
   else
     {
-- 
2.7.4


-- 
Kees Cook
Nexus Security