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Commit 5f630401 authored by Tiejun Chen's avatar Tiejun Chen Committed by Benjamin Herrenschmidt
Browse files

powerpc/kgdb: Restore current_thread_info properly 



For powerpc BooKE and e200, singlestep is handled on the critical/dbg
exception stack. This causes current_thread_info() to fail for kgdb
internal, so previously We work around this issue by copying
the thread_info from the kernel stack before calling kgdb_handle_exception,
and copying it back afterwards.

But actually we don't do this properly. We should backup current_thread_info
then restore that when exit.

Signed-off-by: default avatarTiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 949616cf

arch/powerpc/kernel/kgdb.c

+9 −2
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ 
#include <asm/processor.h>

#include <asm/machdep.h>

#include <asm/debug.h>

#include <linux/slab.h>



/*

 * This table contains the mapping between PowerPC hardware trap types, and
@@ -153,6 +154,8 @@ static int kgdb_handle_breakpoint(struct pt_regs *regs) 
static int kgdb_singlestep(struct pt_regs *regs)

{

	struct thread_info *thread_info, *exception_thread_info;

	struct thread_info *backup_current_thread_info = \

		(struct thread_info *)kmalloc(sizeof(struct thread_info), GFP_KERNEL);



	if (user_mode(regs))

		return 0;
@@ -170,13 +173,17 @@ static int kgdb_singlestep(struct pt_regs *regs) 
	thread_info = (struct thread_info *)(regs->gpr[1] & ~(THREAD_SIZE-1));

	exception_thread_info = current_thread_info();



	if (thread_info != exception_thread_info)

	if (thread_info != exception_thread_info) {

		/* Save the original current_thread_info. */

		memcpy(backup_current_thread_info, exception_thread_info, sizeof *thread_info);

		memcpy(exception_thread_info, thread_info, sizeof *thread_info);

	}



	kgdb_handle_exception(0, SIGTRAP, 0, regs);



	if (thread_info != exception_thread_info)

		memcpy(thread_info, exception_thread_info, sizeof *thread_info);

		/* Restore current_thread_info lastly. */

		memcpy(exception_thread_info, backup_current_thread_info, sizeof *thread_info);



	return 1;

}