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uprobes: Kill set_orig_insn()->is_swbp_at_addr()
Unlike set_swbp(), set_orig_insn()->is_swbp_at_addr() makes sense, although it can't prevent all confusions. But the usage of is_swbp_at_addr() is equally confusing, and it adds the extra get_user_pages() we can avoid. This patch removes set_orig_insn()->is_swbp_at_addr() but changes write_opcode() to do the necessary checks before replace_page(). Perhaps it also makes sense to ensure PAGE_MAPPING_ANON in unregister case. find_active_uprobe() becomes the only user of is_swbp_at_addr(), we can change its semantics. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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@ -190,6 +190,25 @@ static void copy_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t
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kunmap_atomic(kaddr);
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}
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static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode)
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{
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uprobe_opcode_t old_opcode;
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bool is_swbp;
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copy_opcode(page, vaddr, &old_opcode);
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is_swbp = is_swbp_insn(&old_opcode);
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if (is_swbp_insn(new_opcode)) {
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if (is_swbp) /* register: already installed? */
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return 0;
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} else {
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if (!is_swbp) /* unregister: was it changed by us? */
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return -EINVAL;
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}
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return 1;
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}
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/*
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* NOTE:
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* Expect the breakpoint instruction to be the smallest size instruction for
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@ -226,6 +245,10 @@ retry:
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if (ret <= 0)
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return ret;
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ret = verify_opcode(old_page, vaddr, &opcode);
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if (ret <= 0)
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goto put_old;
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ret = -ENOMEM;
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new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
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if (!new_page)
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@ -311,15 +334,6 @@ int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned
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int __weak
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set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
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{
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int result;
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result = is_swbp_at_addr(mm, vaddr);
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if (!result)
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return -EINVAL;
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if (result != 1)
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return result;
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return write_opcode(mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
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}
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