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[176.36.0.241]) by smtp.gmail.com with ESMTPSA id mg11-20020a170903348b00b001dccaafe249sm1677176plb.220.2024.02.28.13.33.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Feb 2024 13:33:32 -0800 (PST) Message-ID: <773a54ed9f0cfb91c1b7c1978070bb86e42ac568.camel@gmail.com> Subject: Re: [PATCH dwarves v4 2/2] pahole: Inject kfunc decl tags into BTF From: Eduard Zingerman To: Daniel Xu Cc: acme@kernel.org, jolsa@kernel.org, quentin@isovalent.com, alan.maguire@oracle.com, andrii.nakryiko@gmail.com, ast@kernel.org, daniel@iogearbox.net, bpf@vger.kernel.org Date: Wed, 28 Feb 2024 23:33:28 +0200 In-Reply-To: <7bpvkfzqfawuzltt7jicekwlbxokdbprom6io3fxef3rbng4ud@hwohkmt662ar> References: <28e81ccf28d6dd33f6db50af6526dc1770502b8d.1707071969.git.dxu@dxuuu.xyz> <1853738ac796d75c53970e21b6d61bf5140a6cc1.camel@gmail.com> <7bpvkfzqfawuzltt7jicekwlbxokdbprom6io3fxef3rbng4ud@hwohkmt662ar> Autocrypt: addr=eddyz87@gmail.com; prefer-encrypt=mutual; keydata=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 nYzhLWGcczc6J71q1Dje0l5vIPaSFOgwmWD4DA+WvuxM/shH4rtWeodbv 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 t1iq+gsfnXbPz5AnS598ScZI1oP7OrPSFJkt/z4acEbOQDQs8aUqrd46PV jsdqGvKnXZxzylux29UTNby4jTlz9pNJM+wPrDRmGfchLDUmf6CffaUYCbu4FiId+9+dcTCDvxbABRy1C3OJ8QY7cxfJ+pEZW18fRJ0XCl/fiV/ecAOfB3HsqgTzAn555h0rkFgay0hAvMU/mAW/CFNSIxV397zm749ZNLA0L2dMy1AKuOqH+/B+/ImBfJMDjmdyJQ8WU/OFRuGLdqOd2oZrA1iuPIa+yUYyZkaZfz/emQwpIL1+Q4p1R/OplA4yc301AqruXXUcVDbEB+joHW3hy5FwK5t5OwTKatrSJBkydSF9zdXy98fYzGniRyRA65P0Ix/8J3BYB4edY2/w0Ip/mdYsYQljBY0A== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2024-02-28 at 09:07 -0700, Daniel Xu wrote: > Hi Eduard, > > Apologies for long delay - life has been busy. Hi Daniel, No problem, thank you for reaching back. [...] > > > +static char *get_func_name(const char *sym) > > > +{ > > > + char *func, *end; > > > + > > > + if (strncmp(sym, BTF_ID_FUNC_PFX, sizeof(BTF_ID_FUNC_PFX) - 1)) > > > + return NULL; > > > + > > > + /* Strip prefix */ > > > + func =3D strdup(sym + sizeof(BTF_ID_FUNC_PFX) - 1); > > > + > > > + /* Strip suffix */ > > > + end =3D strrchr(func, '_'); > > > + if (!end || *(end - 1) !=3D '_') { > >=20 > > Nit: this would do out of bounds access on malformed input > > "__BTF_ID__func___" >=20 > I think this is actually ok. Reason is we have the strncmp() above > so we know the prefix is there. Then the strdup() in the malformed cased > returns empty string. And strrchr() will then return NULL, so we don't > enter the branch. >=20 > I tested it with: https://pastes.dxuuu.xyz/c3j4kk >=20 > $ gcc test.c > dxu@kashmir~/scratch $ ./a.out > name=3D(null) >=20 The test is for "__BTF_ID__func__", but nitpick is for "__BTF_ID__func___" (three underscores in the end). E.g. here is a repro: --- 8< --------------------------------------------------------------- $ cat test.c #include #include #include #define BTF_ID_FUNC_PFX "__BTF_ID__func__" static char *get_func_name(const char *sym) { char *func, *end; if (strncmp(sym, BTF_ID_FUNC_PFX, sizeof(BTF_ID_FUNC_PFX) - 1)) return NULL; /* Strip prefix */ func =3D strdup(sym + sizeof(BTF_ID_FUNC_PFX) - 1); /* Strip suffix */ end =3D strrchr(func, '_'); if (!end || *(end - 1) !=3D '_') { free(func); return NULL; } *(end - 1) =3D '\0'; return func; } int main(int argc, char *argv[]) { if (argc < 2) return -1; printf("name=3D'%s;\n", get_func_name(argv[1])); return 0; } $ gcc -g test.c $ valgrind ./a.out __BTF_ID__func___ =3D=3D16856=3D=3D Memcheck, a memory error detector =3D=3D16856=3D=3D Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward = et al. =3D=3D16856=3D=3D Using Valgrind-3.22.0 and LibVEX; rerun with -h for copyr= ight info =3D=3D16856=3D=3D Command: ./a.out __BTF_ID__func___ =3D=3D16856=3D=3D=20 =3D=3D16856=3D=3D Invalid read of size 1 =3D=3D16856=3D=3D at 0x4011EB: get_func_name (test.c:19) =3D=3D16856=3D=3D by 0x401244: main (test.c:32) =3D=3D16856=3D=3D Address 0x4a7e03f is 1 bytes before a block of size 2 al= loc'd =3D=3D16856=3D=3D at 0x4845784: malloc (in /usr/libexec/valgrind/vgprelo= ad_memcheck-amd64-linux.so) =3D=3D16856=3D=3D by 0x492176D: strdup (in /usr/lib64/libc.so.6) =3D=3D16856=3D=3D by 0x4011C2: get_func_name (test.c:15) =3D=3D16856=3D=3D by 0x401244: main (test.c:32) =3D=3D16856=3D=3D=20 name=3D'(null); =3D=3D16856=3D=3D=20 =3D=3D16856=3D=3D HEAP SUMMARY: =3D=3D16856=3D=3D in use at exit: 0 bytes in 0 blocks =3D=3D16856=3D=3D total heap usage: 2 allocs, 2 frees, 1,026 bytes alloca= ted =3D=3D16856=3D=3D=20 =3D=3D16856=3D=3D All heap blocks were freed -- no leaks are possible =3D=3D16856=3D=3D=20 =3D=3D16856=3D=3D For lists of detected and suppressed errors, rerun with: = -s =3D=3D16856=3D=3D ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 fr= om 0) --------------------------------------------------------------- >8 --- Thanks, Eduard