parisc: Unbreak handling exceptions from kernel modules

commit 2ef4dfd9d9f288943e249b78365a69e3ea3ec072 upstream.

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>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/parisc/include/asm/uaccess.h b/arch/parisc/include/asm/uaccess.h
index ff4cf9d..337353d 100644 (file)
--- a/arch/parisc/include/asm/uaccess.h
+++ b/arch/parisc/include/asm/uaccess.h
@@ -79,6 +79,7 @@ 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 dcd5510..a0dc1e5 100644 (file)
--- a/arch/parisc/kernel/asm-offsets.c
+++ b/arch/parisc/kernel/asm-offsets.c
@@ -292,6 +292,7 @@ int main(void)
        DEFINE(ASM_PT_INITIAL, PT_INITIAL);
        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 f8c45cc..138dd1e 100644 (file)
--- 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 = &__get_cpu_var(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 = &__get_cpu_var(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 a9b765a..6471abb 100644 (file)
--- a/arch/parisc/mm/fault.c
+++ b/arch/parisc/mm/fault.c
@@ -147,6 +147,7 @@ int fixup_exception(struct pt_regs *regs)
                struct exception_data *d;
                d = &__get_cpu_var(exception_data);
                d->fault_ip = regs->iaoq[0];
+               d->fault_gp = regs->gr[27];
                d->fault_space = regs->isr;
                d->fault_addr = regs->ior;