Em Sat, Feb 13, 2021 at 08:11:40PM +0100, Sedat Dilek escreveu:
> On Sat, Feb 13, 2021 at 5:46 PM Jiri Olsa <jo...@kernel.org> 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/
> > Acked-by: Andrii Nakryiko <and...@kernel.org>
> > Signed-off-by: Jiri Olsa <jo...@kernel.org>
>
> Tested this v2 together with "btf_encoder: sanitize non-regular int
> base type" v2 on top of pahole v1.20
>
> Tested-by: Sedat Dilek <sedat.di...@gmail.com> # Linux v5.11-rc7+ and
> LLVM/Clang v12.0.0-rc1 on x86 (64bit)
Thanks, added to the cset,
- Arnaldo
> - Sedat -
>
> > ---
> > v2 changes:
> > - update functions addr directly [Andrii]
> >
> > btf_encoder.c | 40 ++++++++++++++++++++++++++++++++++++++--
> > 1 file changed, 38 insertions(+), 2 deletions(-)
> >
> > diff --git a/btf_encoder.c b/btf_encoder.c
> > index b124ec20a689..80e896961d4e 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 +238,39 @@ 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)
> > +{
> > + __u64 start = 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;
> > @@ -283,10 +318,11 @@ static int setup_functions(struct btf_elf *btfe,
> > struct funcs_layout *fl)
> > * 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 (kmod)
> > + func->addr += func->sh_addr;
> >
> > /* Make sure function is within ftrace addresses. */
> > - if (bsearch(&addr, addrs, count, sizeof(addrs[0]),
> > addrs_cmp)) {
> > + if (is_ftrace_func(func, addrs, count)) {
> > /*
> > * We iterate over sorted array, so we can easily
> > skip
> > * not valid item and move following valid field
> > into
> > --
> > 2.29.2
> >
--
- Arnaldo
