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: Tiejun Chen <tiejun.chen@windriver.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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@ -25,6 +25,7 @@
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#include <asm/processor.h>
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#include <asm/machdep.h>
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#include <asm/debug.h>
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#include <linux/slab.h>
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/*
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* This table contains the mapping between PowerPC hardware trap types, and
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@ -153,6 +154,8 @@ static int kgdb_handle_breakpoint(struct pt_regs *regs)
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static int kgdb_singlestep(struct pt_regs *regs)
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{
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struct thread_info *thread_info, *exception_thread_info;
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struct thread_info *backup_current_thread_info = \
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(struct thread_info *)kmalloc(sizeof(struct thread_info), GFP_KERNEL);
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if (user_mode(regs))
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return 0;
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@ -170,13 +173,17 @@ static int kgdb_singlestep(struct pt_regs *regs)
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thread_info = (struct thread_info *)(regs->gpr[1] & ~(THREAD_SIZE-1));
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exception_thread_info = current_thread_info();
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if (thread_info != exception_thread_info)
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if (thread_info != exception_thread_info) {
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/* Save the original current_thread_info. */
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memcpy(backup_current_thread_info, exception_thread_info, sizeof *thread_info);
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memcpy(exception_thread_info, thread_info, sizeof *thread_info);
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}
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kgdb_handle_exception(0, SIGTRAP, 0, regs);
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if (thread_info != exception_thread_info)
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memcpy(thread_info, exception_thread_info, sizeof *thread_info);
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/* Restore current_thread_info lastly. */
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memcpy(exception_thread_info, backup_current_thread_info, sizeof *thread_info);
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return 1;
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}
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