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[89.40.234.69]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45e015ad780sm38311015e9.10.2025.09.12.13.47.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Sep 2025 13:47:55 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Fri, 12 Sep 2025 22:47:52 +0200 To: Stephen Rothwell Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Peter Zijlstra , Daniel Borkmann , Alexei Starovoitov , Andrii Nakryiko , Jiawei Zhao , bpf , Networking , Linux Kernel Mailing List , Linux Next Mailing List Subject: Re: linux-next: manual merge of the tip tree with the bpf-next tree Message-ID: References: <20250912124059.0428127b@canb.auug.org.au> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250912124059.0428127b@canb.auug.org.au> On Fri, Sep 12, 2025 at 12:40:59PM +1000, Stephen Rothwell wrote: > Hi all, > > Today's linux-next merge of the tip tree got a conflict in: > > tools/testing/selftests/bpf/prog_tests/usdt.c > > between commit: > > 69424097ee10 ("selftests/bpf: Enrich subtest_basic_usdt case in selftests to cover SIB handling logic") > > from the bpf-next tree and commit: > > 875e1705ad99 ("selftests/bpf: Add optimized usdt variant for basic usdt test") > > from the tip tree. > > I fixed it up (see below) and can carry the fix as necessary. This > is now fixed as far as linux-next is concerned, but any non trivial > conflicts should be mentioned to your upstream maintainer when your tree > is submitted for merging. You may also want to consider cooperating > with the maintainer of the conflicting tree to minimise any particularly > complex conflicts. hi, fwiw the conflict was mentioned in here: https://lore.kernel.org/bpf/aMAiMrLlfmG9FbQ3@krava/ the fix looks good, thanks jirka > > -- > Cheers, > Stephen Rothwell > > diff --cc tools/testing/selftests/bpf/prog_tests/usdt.c > index 615e9c3e93bf,833eb87483a1..000000000000 > --- a/tools/testing/selftests/bpf/prog_tests/usdt.c > +++ b/tools/testing/selftests/bpf/prog_tests/usdt.c > @@@ -40,73 -40,20 +40,80 @@@ static void __always_inline trigger_fun > } > } > > +#if defined(__x86_64__) || defined(__i386__) > +/* > + * SIB (Scale-Index-Base) addressing format: "size@(base_reg, index_reg, scale)" > + * - 'size' is the size in bytes of the array element, and its sign indicates > + * whether the type is signed (negative) or unsigned (positive). > + * - 'base_reg' is the register holding the base address, normally rdx or edx > + * - 'index_reg' is the register holding the index, normally rax or eax > + * - 'scale' is the scaling factor (typically 1, 2, 4, or 8), which matches the > + * size of the element type. > + * > + * For example, for an array of 'short' (signed 2-byte elements), the SIB spec would be: > + * - size: -2 (negative because 'short' is signed) > + * - scale: 2 (since sizeof(short) == 2) > + * > + * The resulting SIB format: "-2@(%%rdx,%%rax,2)" for x86_64, "-2@(%%edx,%%eax,2)" for i386 > + */ > +static volatile short array[] = {-1, -2, -3, -4}; > + > +#if defined(__x86_64__) > +#define USDT_SIB_ARG_SPEC -2@(%%rdx,%%rax,2) > +#else > +#define USDT_SIB_ARG_SPEC -2@(%%edx,%%eax,2) > +#endif > + > +unsigned short test_usdt_sib_semaphore SEC(".probes"); > + > +static void trigger_sib_spec(void) > +{ > + /* > + * Force SIB addressing with inline assembly. > + * > + * You must compile with -std=gnu99 or -std=c99 to use the > + * STAP_PROBE_ASM macro. > + * > + * The STAP_PROBE_ASM macro generates a quoted string that gets > + * inserted between the surrounding assembly instructions. In this > + * case, USDT_SIB_ARG_SPEC is embedded directly into the instruction > + * stream, creating a probe point between the asm statement boundaries. > + * It works fine with gcc/clang. > + * > + * Register constraints: > + * - "d"(array): Binds the 'array' variable to %rdx or %edx register > + * - "a"(0): Binds the constant 0 to %rax or %eax register > + * These ensure that when USDT_SIB_ARG_SPEC references %%rdx(%edx) and > + * %%rax(%eax), they contain the expected values for SIB addressing. > + * > + * The "memory" clobber prevents the compiler from reordering memory > + * accesses around the probe point, ensuring that the probe behavior > + * is predictable and consistent. > + */ > + asm volatile( > + STAP_PROBE_ASM(test, usdt_sib, USDT_SIB_ARG_SPEC) > + : > + : "d"(array), "a"(0) > + : "memory" > + ); > +} > +#endif > + > - static void subtest_basic_usdt(void) > + static void subtest_basic_usdt(bool optimized) > { > LIBBPF_OPTS(bpf_usdt_opts, opts); > struct test_usdt *skel; > struct test_usdt__bss *bss; > - int err, i; > + int err, i, called; > + const __u64 expected_cookie = 0xcafedeadbeeffeed; > > + #define TRIGGER(x) ({ \ > + trigger_func(x); \ > + if (optimized) \ > + trigger_func(x); \ > + optimized ? 2 : 1; \ > + }) > + > skel = test_usdt__open_and_load(); > if (!ASSERT_OK_PTR(skel, "skel_open")) > return; > @@@ -126,22 -73,13 +133,22 @@@ > if (!ASSERT_OK_PTR(skel->links.usdt0, "usdt0_link")) > goto cleanup; > > +#if defined(__x86_64__) || defined(__i386__) > + opts.usdt_cookie = expected_cookie; > + skel->links.usdt_sib = bpf_program__attach_usdt(skel->progs.usdt_sib, > + 0 /*self*/, "/proc/self/exe", > + "test", "usdt_sib", &opts); > + if (!ASSERT_OK_PTR(skel->links.usdt_sib, "usdt_sib_link")) > + goto cleanup; > +#endif > + > - trigger_func(1); > + called = TRIGGER(1); > > - ASSERT_EQ(bss->usdt0_called, 1, "usdt0_called"); > - ASSERT_EQ(bss->usdt3_called, 1, "usdt3_called"); > - ASSERT_EQ(bss->usdt12_called, 1, "usdt12_called"); > + ASSERT_EQ(bss->usdt0_called, called, "usdt0_called"); > + ASSERT_EQ(bss->usdt3_called, called, "usdt3_called"); > + ASSERT_EQ(bss->usdt12_called, called, "usdt12_called"); > > - ASSERT_EQ(bss->usdt0_cookie, 0xcafedeadbeeffeed, "usdt0_cookie"); > + ASSERT_EQ(bss->usdt0_cookie, expected_cookie, "usdt0_cookie"); > ASSERT_EQ(bss->usdt0_arg_cnt, 0, "usdt0_arg_cnt"); > ASSERT_EQ(bss->usdt0_arg_ret, -ENOENT, "usdt0_arg_ret"); > ASSERT_EQ(bss->usdt0_arg_size, -ENOENT, "usdt0_arg_size"); > @@@ -225,18 -163,9 +232,19 @@@ > ASSERT_EQ(bss->usdt3_args[1], 42, "usdt3_arg2"); > ASSERT_EQ(bss->usdt3_args[2], (uintptr_t)&bla, "usdt3_arg3"); > > +#if defined(__x86_64__) || defined(__i386__) > + trigger_sib_spec(); > + ASSERT_EQ(bss->usdt_sib_called, 1, "usdt_sib_called"); > + ASSERT_EQ(bss->usdt_sib_cookie, expected_cookie, "usdt_sib_cookie"); > + ASSERT_EQ(bss->usdt_sib_arg_cnt, 1, "usdt_sib_arg_cnt"); > + ASSERT_EQ(bss->usdt_sib_arg, nums[0], "usdt_sib_arg"); > + ASSERT_EQ(bss->usdt_sib_arg_ret, 0, "usdt_sib_arg_ret"); > + ASSERT_EQ(bss->usdt_sib_arg_size, sizeof(nums[0]), "usdt_sib_arg_size"); > +#endif > + > cleanup: > test_usdt__destroy(skel); > + #undef TRIGGER > } > > unsigned short test_usdt_100_semaphore SEC(".probes");