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Date: Sat, 6 Mar 2021 19:13:17 -0800 From: Andrii Nakryiko <andrii.nakryiko@...il.com> To: Jiri Olsa <jolsa@...nel.org> Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andriin@...com>, Michael Ellerman <mpe@...erman.id.au>, "Naveen N . Rao" <naveen.n.rao@...ux.vnet.ibm.com>, Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...omium.org>, Toke Høiland-Jørgensen <toke@...hat.com>, Yauheni Kaliuta <ykaliuta@...hat.com> Subject: Re: [PATCHv2 bpf-next] selftests/bpf: Fix test_attach_probe for powerpc uprobes On Fri, Mar 5, 2021 at 5:42 AM Jiri Olsa <jolsa@...nel.org> wrote: > > When testing uprobes we the test gets GEP (Global Entry Point) > address from kallsyms, but then the function is called locally > so the uprobe is not triggered. > > Fixing this by adjusting the address to LEP (Local Entry Point) > for powerpc arch plus instruction check stolen from ppc_function_entry > function pointed out and explained by Michael and Naveen. > > Cc: Michael Ellerman <mpe@...erman.id.au> > Cc: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com> > Signed-off-by: Jiri Olsa <jolsa@...nel.org> > --- > .../selftests/bpf/prog_tests/attach_probe.c | 40 ++++++++++++++++++- > 1 file changed, 39 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c > index a0ee87c8e1ea..9dc4e3dfbcf3 100644 > --- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c > +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c > @@ -2,6 +2,44 @@ > #include <test_progs.h> > #include "test_attach_probe.skel.h" > > +#if defined(__powerpc64__) && defined(_CALL_ELF) && _CALL_ELF == 2 > + > +#define OP_RT_RA_MASK 0xffff0000UL > +#define LIS_R2 0x3c400000UL > +#define ADDIS_R2_R12 0x3c4c0000UL > +#define ADDI_R2_R2 0x38420000UL > + > +static ssize_t get_offset(ssize_t addr, ssize_t base) > +{ > + u32 *insn = (u32 *) addr; > + > + /* > + * A PPC64 ABIv2 function may have a local and a global entry > + * point. We need to use the local entry point when patching > + * functions, so identify and step over the global entry point > + * sequence. > + * > + * The global entry point sequence is always of the form: > + * > + * addis r2,r12,XXXX > + * addi r2,r2,XXXX > + * > + * A linker optimisation may convert the addis to lis: > + * > + * lis r2,XXXX > + * addi r2,r2,XXXX > + */ > + if ((((*insn & OP_RT_RA_MASK) == ADDIS_R2_R12) || > + ((*insn & OP_RT_RA_MASK) == LIS_R2)) && > + ((*(insn + 1) & OP_RT_RA_MASK) == ADDI_R2_R2)) > + return (ssize_t)(insn + 2) - base; > + else > + return addr - base; > +} > +#else > +#define get_offset(addr, base) (addr - base) I turned this into a static function, not sure why you preferred #define here. Applied to bpf-next. > +#endif > + > ssize_t get_base_addr() { > size_t start, offset; > char buf[256]; > @@ -36,7 +74,7 @@ void test_attach_probe(void) > if (CHECK(base_addr < 0, "get_base_addr", > "failed to find base addr: %zd", base_addr)) > return; > - uprobe_offset = (size_t)&get_base_addr - base_addr; > + uprobe_offset = get_offset((size_t)&get_base_addr, base_addr); > > skel = test_attach_probe__open_and_load(); > if (CHECK(!skel, "skel_open", "failed to open skeleton\n")) > -- > 2.27.0 >
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