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[14.203.144.177]) by smtp.gmail.com with ESMTPSA id c192sm4160615pfb.110.2021.10.15.00.00.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Oct 2021 00:00:15 -0700 (PDT) Date: Fri, 15 Oct 2021 17:00:10 +1000 From: Nicholas Piggin Subject: Re: [PATCH v2 08/13] asm-generic: Refactor dereference_[kernel]_function_descriptor() To: Andrew Morton , Arnd Bergmann , Benjamin Herrenschmidt , Christophe Leroy , Helge Deller , Greg Kroah-Hartman , "James E.J. Bottomley" , Kees Cook , Michael Ellerman , Paul Mackerras Cc: linux-arch@vger.kernel.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <865b5c872814e3291fe7afabcc110f53b3457b56.1634190022.git.christophe.leroy@csgroup.eu> In-Reply-To: <865b5c872814e3291fe7afabcc110f53b3457b56.1634190022.git.christophe.leroy@csgroup.eu> MIME-Version: 1.0 Message-Id: <1634279175.w0z6ck2mpb.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Stat-Signature: s8x5sp8k8krwad7ukf5gnsuy8o4ea4fu Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=dawJA0pl; spf=pass (imf10.hostedemail.com: domain of npiggin@gmail.com designates 209.85.216.47 as permitted sender) smtp.mailfrom=npiggin@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 2E3AB6001993 X-HE-Tag: 1634281215-755808 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm: > dereference_function_descriptor() and > dereference_kernel_function_descriptor() are identical on the > three architectures implementing them. >=20 > Make them common and put them out-of-line in kernel/extable.c > which is one of the users and has similar type of functions. We should be moving more stuff out of extable.c (including all the kernel address tests). lib/kimage.c or kelf.c or something.=20 It could be after your series though. >=20 > Reviewed-by: Kees Cook > Reviewed-by: Arnd Bergmann > Signed-off-by: Christophe Leroy > --- > arch/ia64/include/asm/sections.h | 19 ------------------- > arch/parisc/include/asm/sections.h | 9 --------- > arch/parisc/kernel/process.c | 21 --------------------- > arch/powerpc/include/asm/sections.h | 23 ----------------------- > include/asm-generic/sections.h | 2 ++ > kernel/extable.c | 23 ++++++++++++++++++++++- > 6 files changed, 24 insertions(+), 73 deletions(-) >=20 > diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sec= tions.h > index 1aaed8882294..96c9bb500c34 100644 > --- a/arch/ia64/include/asm/sections.h > +++ b/arch/ia64/include/asm/sections.h > @@ -31,23 +31,4 @@ extern char __start_gate_brl_fsys_bubble_down_patchlis= t[], __end_gate_brl_fsys_b > extern char __start_unwind[], __end_unwind[]; > extern char __start_ivt_text[], __end_ivt_text[]; > =20 > -#undef dereference_function_descriptor > -static inline void *dereference_function_descriptor(void *ptr) > -{ > - struct fdesc *desc =3D ptr; > - void *p; > - > - if (!get_kernel_nofault(p, (void *)&desc->addr)) > - ptr =3D p; > - return ptr; > -} > - > -#undef dereference_kernel_function_descriptor > -static inline void *dereference_kernel_function_descriptor(void *ptr) > -{ > - if (ptr < (void *)__start_opd || ptr >=3D (void *)__end_opd) > - return ptr; > - return dereference_function_descriptor(ptr); > -} > - > #endif /* _ASM_IA64_SECTIONS_H */ > diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm= /sections.h > index 37b34b357cb5..6b1fe22baaf5 100644 > --- a/arch/parisc/include/asm/sections.h > +++ b/arch/parisc/include/asm/sections.h > @@ -13,13 +13,4 @@ typedef Elf64_Fdesc func_desc_t; > =20 > extern char __alt_instructions[], __alt_instructions_end[]; > =20 > -#ifdef CONFIG_64BIT > - > -#undef dereference_function_descriptor > -void *dereference_function_descriptor(void *); > - > -#undef dereference_kernel_function_descriptor > -void *dereference_kernel_function_descriptor(void *); > -#endif > - > #endif > diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c > index 38ec4ae81239..7382576b52a8 100644 > --- a/arch/parisc/kernel/process.c > +++ b/arch/parisc/kernel/process.c > @@ -266,27 +266,6 @@ get_wchan(struct task_struct *p) > return 0; > } > =20 > -#ifdef CONFIG_64BIT > -void *dereference_function_descriptor(void *ptr) > -{ > - Elf64_Fdesc *desc =3D ptr; > - void *p; > - > - if (!get_kernel_nofault(p, (void *)&desc->addr)) > - ptr =3D p; > - return ptr; > -} > - > -void *dereference_kernel_function_descriptor(void *ptr) > -{ > - if (ptr < (void *)__start_opd || > - ptr >=3D (void *)__end_opd) > - return ptr; > - > - return dereference_function_descriptor(ptr); > -} > -#endif > - > static inline unsigned long brk_rnd(void) > { > return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT; > diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/a= sm/sections.h > index 1322d7b2f1a3..fbfe1957edbe 100644 > --- a/arch/powerpc/include/asm/sections.h > +++ b/arch/powerpc/include/asm/sections.h > @@ -72,29 +72,6 @@ static inline int overlaps_kernel_text(unsigned long s= tart, unsigned long end) > (unsigned long)_stext < end; > } > =20 > -#ifdef PPC64_ELF_ABI_v1 > - > -#undef dereference_function_descriptor > -static inline void *dereference_function_descriptor(void *ptr) > -{ > - struct ppc64_opd_entry *desc =3D ptr; > - void *p; > - > - if (!get_kernel_nofault(p, (void *)&desc->addr)) > - ptr =3D p; > - return ptr; > -} > - > -#undef dereference_kernel_function_descriptor > -static inline void *dereference_kernel_function_descriptor(void *ptr) > -{ > - if (ptr < (void *)__start_opd || ptr >=3D (void *)__end_opd) > - return ptr; > - > - return dereference_function_descriptor(ptr); > -} > -#endif /* PPC64_ELF_ABI_v1 */ > - > #endif > =20 > #endif /* __KERNEL__ */ > diff --git a/include/asm-generic/sections.h b/include/asm-generic/section= s.h > index cbec7d5f1678..76163883c6ff 100644 > --- a/include/asm-generic/sections.h > +++ b/include/asm-generic/sections.h > @@ -60,6 +60,8 @@ extern __visible const void __nosave_begin, __nosave_en= d; > =20 > /* Function descriptor handling (if any). Override in asm/sections.h */ > #ifdef HAVE_FUNCTION_DESCRIPTORS > +void *dereference_function_descriptor(void *ptr); > +void *dereference_kernel_function_descriptor(void *ptr); > #else > #define dereference_function_descriptor(p) ((void *)(p)) > #define dereference_kernel_function_descriptor(p) ((void *)(p)) > diff --git a/kernel/extable.c b/kernel/extable.c > index b0ea5eb0c3b4..013ccffade11 100644 > --- a/kernel/extable.c > +++ b/kernel/extable.c > @@ -3,6 +3,7 @@ > Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM. > =20 > */ > +#include > #include > #include > #include > @@ -159,12 +160,32 @@ int kernel_text_address(unsigned long addr) > } > =20 > /* > - * On some architectures (PPC64, IA64) function pointers > + * On some architectures (PPC64, IA64, PARISC) function pointers > * are actually only tokens to some data that then holds the > * real function address. As a result, to find if a function > * pointer is part of the kernel text, we need to do some > * special dereferencing first. > */ > +#ifdef HAVE_FUNCTION_DESCRIPTORS > +void *dereference_function_descriptor(void *ptr) > +{ > + func_desc_t *desc =3D ptr; > + void *p; > + > + if (!get_kernel_nofault(p, (void *)&desc->addr)) > + ptr =3D p; I know you're just copying existing code. This seems a bit risky though.=20 I don't think anything good could come of just treating the descriptor address like a function entry address if we failed to load from it for whatever reason. Existing callers might be benign but the API is not good. It should give a nice fail return or BUG. If we change that then we should also change the name and pass the correct type to it too. Thanks, Nick