Messages in this thread Patch in this message | | | Date | Mon, 24 Sep 2012 18:02:50 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/4] uprobes: Kill set_swbp()->is_swbp_at_addr() |
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On 09/24, Ananth N Mavinakayanahalli wrote: > > On Sun, Sep 23, 2012 at 10:19:45PM +0200, Oleg Nesterov wrote: > > > It doesn't matter if this "int3" was in fact > > installed by gdb or application itself, we are going to "steal" this > > breakpoint anyway and execute the original insn from vm_file even if > > it no longer matches the memory. > > Wouldn't this text make more sense: > > It doesn't matter if this 'breakpoint' was in fact... > > 'int3' is still an x86 artifact.
Agreed, will update the changelog.
> On powerpc, we don't even get to install_breakpoint() ->set_swbp() > ->is_swbp_at_addr() because arch_uprobe_analyze_insn() would've already > caused install_breakpoint() to return -ENOTSUPP. > > > OTOH, handle_swbp()->find_active_uprobe() uses is_swbp_at_addr() to > > figure out whether we need to send SIGTRAP or not if we can not find > > uprobe, so in this case it should return true for all trap variants, > > not only for UPROBE_SWBP_INSN. > > So, we will need a powerpc specific is_swbp_insn()... ok.
I think yes.
But again, we need 2 helpers. One for is_swbp_at_addr(), and another for verify_opcode() which only checks UPROBE_SWBP_INSN. IOW, something like the patch below (on top of this series).
Do you agree?
Oleg.
--- x/kernel/events/uprobes.c +++ x/kernel/events/uprobes.c @@ -178,6 +178,11 @@ static int __replace_page(struct vm_area * Default implementation of is_swbp_insn * Returns true if @insn is a breakpoint instruction. */ +static bool is_uprobe_opcode(uprobe_opcode_t *insn) +{ + return *insn == UPROBE_SWBP_INSN; +} + bool __weak is_swbp_insn(uprobe_opcode_t *insn) { return *insn == UPROBE_SWBP_INSN; @@ -196,9 +201,9 @@ static int verify_opcode(struct page *pa bool is_swbp; copy_opcode(page, vaddr, &old_opcode); - is_swbp = is_swbp_insn(&old_opcode); + is_swbp = is_uprobe_opcode(&old_opcode); - if (is_swbp_insn(new_opcode)) { + if (is_uprobe_opcode(new_opcode)) { if (is_swbp) /* register: already installed? */ return 0; } else { @@ -585,7 +590,7 @@ install_breakpoint(struct uprobe *uprobe if (ret) return ret; - if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn)) + if (is_uprobe_opcode((uprobe_opcode_t *)uprobe->arch.insn)) return -ENOTSUPP; ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
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