Messages in this thread | | | Date | Fri, 19 Jul 2019 13:31:25 -0500 | From | Josh Poimboeuf <> | Subject | Re: warning: objtool: fn1 uses BP as a scratch register |
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On Fri, Jul 19, 2019 at 11:23:16AM -0700, Nick Desaulniers wrote: > On Fri, Jul 19, 2019 at 11:10 AM Arnd Bergmann <arnd@arndb.de> wrote: > > > > A lot of objtool fixes showed up in linux-next, so I looked at some > > remaining ones. > > This one comes a lot up in some configurations > > > > https://godbolt.org/z/ZZLVD- > > > > struct ov7670_win_size { > > int width; > > int height; > > }; > > struct ov7670_devtype { > > struct ov7670_win_size *win_sizes; > > unsigned n_win_sizes; > > }; > > struct ov7670_info { > > int min_width; > > int min_height; > > struct ov7670_devtype devtype; > > } a; > > int b; > > int fn1() { > > struct ov7670_info c = a; > > int i = 0; > > for (; i < c.devtype.n_win_sizes; i++) { > > struct ov7670_win_size d = c.devtype.win_sizes[i]; > > if (c.min_width && d.width < d.height < c.min_height) > > if (b) > > return 0; > > } > > return 2; > > } > > > > $ clang-8 -O2 -fno-omit-frame-pointer -fno-strict-overflow -c ov7670.i > > $ objtool check --no-unreachable --uaccess ov7670.o > > ov7670.o: warning: objtool: fn1 uses BP as a scratch register > > Thanks for the report and reduced test case. From the godbolt link, I > don't see %rbp, %ebp, %bp, or %bpl being referenced (other that %rbp > in the typical epilogue). Am I missing something? Is objtool maybe > not reporting the precise function at fault?
I haven't looked, but it could very well be an objtool bug (surprise).
-- Josh
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