On Sat, Feb 13, 2021 at 5:46 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/ > Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx> > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> 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.dilek@xxxxxxxxx> # Linux v5.11-rc7+ and LLVM/Clang v12.0.0-rc1 on x86 (64bit) - 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 >
