uprobes: Move BUG_ON(UPROBE_SWBP_INSN_SIZE) from write_opcode() to install_breakpoint()
write_opcode() ensures that UPROBE_SWBP_INSN doesn't cross the page boundary. This looks a bit confusing, the check does not depend on vaddr and it is enough to do it only once right after install_breakpoint()->arch_uprobe_analyze_insn(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Anton Arapov <anton@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20120615154350.GA9611@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -210,7 +210,6 @@ static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
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void *vaddr_old, *vaddr_new;
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struct vm_area_struct *vma;
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struct uprobe *uprobe;
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unsigned long pgoff;
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int ret;
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retry:
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/* Read the page with vaddr into memory */
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@ -251,11 +250,7 @@ retry:
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vaddr_new = kmap_atomic(new_page);
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memcpy(vaddr_new, vaddr_old, PAGE_SIZE);
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/* poke the new insn in, ASSUMES we don't cross page boundary */
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pgoff = (vaddr & ~PAGE_MASK);
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BUG_ON(pgoff + UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
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memcpy(vaddr_new + pgoff, &opcode, UPROBE_SWBP_INSN_SIZE);
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memcpy(vaddr_new + (vaddr & ~PAGE_MASK), &opcode, UPROBE_SWBP_INSN_SIZE);
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kunmap_atomic(vaddr_new);
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kunmap_atomic(vaddr_old);
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@ -699,6 +694,10 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
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if (ret)
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return ret;
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/* write_opcode() assumes we don't cross page boundary */
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BUG_ON((uprobe->offset & ~PAGE_MASK) +
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UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
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uprobe->flags |= UPROBE_COPY_INSN;
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}
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