On Fri, Feb 12, 2021 at 02:21:04PM -0800, Andrii Nakryiko wrote: > On Fri, Feb 12, 2021 at 2:05 PM Jiri Olsa <jolsa@xxxxxxxxxx> wrote: > > > > Currently when processing DWARF function, we check its entrypoint > > against ftrace addresses, assuming that the ftrace address matches > > with function's entrypoint. > > > > This is not the case on some architectures as reported by Nathan > > when building kernel on arm [1]. > > > > Fixing the check to take into account the whole function not > > just the entrypoint. > > > > Most of the is_ftrace_func code was contributed by Andrii. > > > > [1] https://lore.kernel.org/bpf/20210209034416.GA1669105@ubuntu-m3-large-x86/ > > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> > > --- > > LGTM. But see another suggestion below. In either case: > > Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx> > > > btf_encoder.c | 55 +++++++++++++++++++++++++++++++++++++++++---------- > > 1 file changed, 45 insertions(+), 10 deletions(-) > > > > diff --git a/btf_encoder.c b/btf_encoder.c > > index b124ec20a689..03242f04c55d 100644 > > --- a/btf_encoder.c > > +++ b/btf_encoder.c > > @@ -36,6 +36,7 @@ struct funcs_layout { > > struct elf_function { > > const char *name; > > unsigned long addr; > > + unsigned long size; > > unsigned long sh_addr; > > bool generated; > > }; > > @@ -98,6 +99,7 @@ static int collect_function(struct btf_elf *btfe, GElf_Sym *sym, > > > > functions[functions_cnt].name = name; > > functions[functions_cnt].addr = elf_sym__value(sym); > > + functions[functions_cnt].size = elf_sym__size(sym); > > functions[functions_cnt].sh_addr = sh.sh_addr; > > functions[functions_cnt].generated = false; > > functions_cnt++; > > @@ -236,6 +238,48 @@ get_kmod_addrs(struct btf_elf *btfe, __u64 **paddrs, __u64 *pcount) > > return 0; > > } > > > > +static int is_ftrace_func(struct elf_function *func, __u64 *addrs, > > + __u64 count, bool kmod) > > +{ > > + /* > > + * For vmlinux image both addrs[x] and functions[x]::addr > > + * values are final address and are comparable. > > + * > > + * For kernel module addrs[x] is final address, but > > + * functions[x]::addr is relative address within section > > + * and needs to be relocated by adding sh_addr. > > + */ > > + __u64 start = kmod ? func->addr + func->sh_addr : func->addr; > > + __u64 addr, end = func->addr + func->size; > > + > > + /* > > + * The invariant here is addr[r] that is the smallest address > > + * that is >= than function start addr. Except the corner case > > + * where there is no such r, but for that we have a final check > > + * in the return. > > + */ > > + size_t l = 0, r = count - 1, m; > > + > > + /* make sure we don't use invalid r */ > > + if (count == 0) > > + return false; > > + > > + while (l < r) { > > + m = l + (r - l) / 2; > > + addr = addrs[m]; > > + > > + if (addr >= start) { > > + /* we satisfy invariant, so tighten r */ > > + r = m; > > + } else { > > + /* m is not good enough as l, maybe m + 1 will be */ > > + l = m + 1; > > + } > > + } > > + > > + return start <= addrs[r] && addrs[r] < end; > > +} > > + > > static int setup_functions(struct btf_elf *btfe, struct funcs_layout *fl) > > { > > __u64 *addrs, count, i; > > @@ -275,18 +319,9 @@ static int setup_functions(struct btf_elf *btfe, struct funcs_layout *fl) > > */ > > for (i = 0; i < functions_cnt; i++) { > > struct elf_function *func = &functions[i]; > > - /* > > - * For vmlinux image both addrs[x] and functions[x]::addr > > - * values are final address and are comparable. > > - * > > - * For kernel module addrs[x] is final address, but > > - * functions[x]::addr is relative address within section > > - * and needs to be relocated by adding sh_addr. > > - */ > > - __u64 addr = kmod ? func->addr + func->sh_addr : func->addr; > > if we just... > > if (kmod) > func->addr += func->sh_addr; > > ... here, that would make is_ftrace_func() free of kmod knowledge. If > there are other places that rely on kmod vs non-kmod address of a > function, that would be simplified as well, right? yes, this is the only place for now, I'll make the change thanks, jirka > > > > > /* Make sure function is within ftrace addresses. */ > > - if (bsearch(&addr, addrs, count, sizeof(addrs[0]), addrs_cmp)) { > > + if (is_ftrace_func(func, addrs, count, kmod)) { > > /* > > * We iterate over sorted array, so we can easily skip > > * not valid item and move following valid field into > > -- > > 2.29.2 > > >
