[PATCH] Threaded core dumps for PPC32

At the moment, ppc32 kernels will oops if a threaded program tries to
dump core.  We call dump_fpu with a NULL regs pointer, which it tries
to dereference.

This fixes the issue by implementing the hooks used in doing threaded
core dumps properly.

arch/ppc/kernel/process.c

@@ -45,7 +45,6 @@
 #include <asm/prom.h>
 #include <asm/hardirq.h>
 
-int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpregs);
 extern unsigned long _get_SP(void);
 
 struct task_struct *last_task_used_math = NULL;
@@ -189,11 +188,11 @@ enable_kernel_fp(void)
 }
 
 int
-dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpregs)
+dump_task_fpu(struct task_struct *tsk, elf_fpregset_t *fpregs)
 {
-	if (regs->msr & MSR_FP)
-		giveup_fpu(current);
-	memcpy(fpregs, &current->thread.fpr[0], sizeof(*fpregs));
+	if (tsk->thread.regs && tsk->thread.regs->msr & MSR_FP)
+		giveup_fpu(tsk);
+	memcpy(fpregs, &tsk->thread.fpr[0], sizeof(*fpregs));
 	return 1;
 }
 

include/asm-ppc/elf.h

@@ -90,11 +90,17 @@ typedef elf_vrreg_t elf_vrregset_t[ELF_NVRREG];
 #define USE_ELF_CORE_DUMP
 #define ELF_EXEC_PAGESIZE	4096
 
-#define ELF_CORE_COPY_REGS(gregs, regs) \
-	memcpy(gregs, regs, \
-	       sizeof(struct pt_regs) < sizeof(elf_gregset_t)? \
-	       sizeof(struct pt_regs): sizeof(elf_gregset_t));
+#define ELF_CORE_COPY_REGS(gregs, regs)				\
+	memcpy((gregs), (regs), sizeof(struct pt_regs));	\
+	memset((char *)(gregs) + sizeof(struct pt_regs), 0,	\
+	       sizeof(elf_gregset_t) - sizeof(struct pt_regs));
 
+#define ELF_CORE_COPY_TASK_REGS(t, elfregs)			\
+	((t)->thread.regs?					\
+	 ({ ELF_CORE_COPY_REGS((elfregs), (t)->thread.regs); 1; }): 0)
+
+extern int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpu);
+#define ELF_CORE_COPY_FPREGS(t, fpu)	dump_task_fpu((t), (fpu))
 
 /* This yields a mask that user programs can use to figure out what
    instruction set this cpu supports.  This could be done in userspace,