parisc: Unbreak handling exceptions from kernel modules

PATCH New Helge Deller 1 participant 1 message Apr 8, 2016 PA-RISC architecture

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Helge Deller

author maintainer

2016-04-08 19:30 UTC #0 lore raw

PATCH 1/1 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 <[email protected]>

Signed-off-by Helge Deller <[email protected]>

Cc [email protected]

arch/parisc/include/asm/uaccess.h +1 -0

index d4dd6e5..6f893d2 100644
@@ -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;
 };

arch/parisc/kernel/asm-offsets.c +1 -0

index d2f6257..78d30d2 100644
@@ -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();

arch/parisc/lib/fixup.S +6 -0

index 536ef66..1052b74 100644
@@ -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

arch/parisc/mm/fault.c +1 -0

index 26fac9c..16dbe81 100644
@@ -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;