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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