parisc: Unbreak handling exceptions from kernel modules

Handling exceptions from modules never worked on parisc.
It was just masked by the fact that exceptions from modules
don't happen during normal use.

When a module triggers an exception in get_user() we need to load the
main kernel dp value before accessing the exception_data structure, and
afterwards restore the original dp value of the module on exit.

Noticed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org

4 files changed, 9 insertions, 0 deletions

diff --git a/arch/parisc/include/asm/uaccess.h b/arch/parisc/include/asm/uaccess.h
index d4dd6e58682c..6f893d29f1b2 100644
--- a/arch/parisc/include/asm/uaccess.h
+++ b/arch/parisc/include/asm/uaccess.h
@@ -77,6 +77,7 @@ struct exception_table_entry {
  */
 struct exception_data {
         unsigned long fault_ip;
+        unsigned long fault_gp;
         unsigned long fault_space;
         unsigned long fault_addr;
 };
diff --git a/arch/parisc/kernel/asm-offsets.c b/arch/parisc/kernel/asm-offsets.c
index d2f62570a7b1..78d30d2ea2d8 100644
--- a/arch/parisc/kernel/asm-offsets.c
+++ b/arch/parisc/kernel/asm-offsets.c
@@ -299,6 +299,7 @@ int main(void)
 #endif
         BLANK();
         DEFINE(EXCDATA_IP, offsetof(struct exception_data, fault_ip));
+        DEFINE(EXCDATA_GP, offsetof(struct exception_data, fault_gp));
         DEFINE(EXCDATA_SPACE, offsetof(struct exception_data, fault_space));
         DEFINE(EXCDATA_ADDR, offsetof(struct exception_data, fault_addr));
         BLANK();
diff --git a/arch/parisc/lib/fixup.S b/arch/parisc/lib/fixup.S
index 536ef66bb94b..1052b747e011 100644
--- a/arch/parisc/lib/fixup.S
+++ b/arch/parisc/lib/fixup.S
@@ -26,6 +26,7 @@
 
 #ifdef CONFIG_SMP
         .macro  get_fault_ip t1 t2
+        loadgp
         addil LT%__per_cpu_offset,%r27
         LDREG RT%__per_cpu_offset(%r1),\t1
         /* t2 = smp_processor_id() */
@@ -40,14 +41,19 @@
         LDREG RT%exception_data(%r1),\t1
         /* t1 = this_cpu_ptr(&exception_data) */
         add,l \t1,\t2,\t1
+        /* %r27 = t1->fault_gp - restore gp */
+        LDREG EXCDATA_GP(\t1), %r27
         /* t1 = t1->fault_ip */
         LDREG EXCDATA_IP(\t1), \t1
         .endm
 #else
         .macro  get_fault_ip t1 t2
+        loadgp
         /* t1 = this_cpu_ptr(&exception_data) */
         addil LT%exception_data,%r27
         LDREG RT%exception_data(%r1),\t2
+        /* %r27 = t2->fault_gp - restore gp */
+        LDREG EXCDATA_GP(\t2), %r27
         /* t1 = t2->fault_ip */
         LDREG EXCDATA_IP(\t2), \t1
         .endm
diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
index 26fac9c671c9..16dbe81c97c9 100644
--- a/arch/parisc/mm/fault.c
+++ b/arch/parisc/mm/fault.c
@@ -145,6 +145,7 @@ int fixup_exception(struct pt_regs *regs)
                 struct exception_data *d;
                 d = this_cpu_ptr(&exception_data);
                 d->fault_ip = regs->iaoq[0];
+                d->fault_gp = regs->gr[27];
                 d->fault_space = regs->isr;
                 d->fault_addr = regs->ior;