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[5.147.80.91]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-458705bcb61sm41269355e9.20.2025.07.24.23.13.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 24 Jul 2025 23:13:31 -0700 (PDT) Message-ID: <2ba0c09d-2783-4dce-a889-06e16abbde61@canonical.com> Date: Fri, 25 Jul 2025 08:13:29 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/11] riscv: add landing pad for asm routines. To: Deepak Gupta Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, rick.p.edgecombe@intel.com, broonie@kernel.org, cleger@rivosinc.com, samitolvanen@google.com, apatel@ventanamicro.com, ajones@ventanamicro.com, conor.dooley@microchip.com, charlie@rivosinc.com, samuel.holland@sifive.com, bjorn@rivosinc.com, fweimer@redhat.com, jeffreyalaw@gmail.com, andrew@sifive.com, ved@rivosinc.com, Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Masahiro Yamada , Nathan Chancellor , Nicolas Schier , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Nick Desaulniers , Bill Wendling , Monk Chiang , Kito Cheng , Justin Stitt References: <20250724-riscv_kcfi-v1-0-04b8fa44c98c@rivosinc.com> <20250724-riscv_kcfi-v1-1-04b8fa44c98c@rivosinc.com> Content-Language: en-US From: Heinrich Schuchardt In-Reply-To: <20250724-riscv_kcfi-v1-1-04b8fa44c98c@rivosinc.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 25.07.25 01:36, Deepak Gupta wrote: > SYM_* macros are used to define assembly routines. In this patch series, > re-define those macros in risc-v arch specific include file to include > a landing pad instruction at the beginning. This is done only when the > compiler flag for landing pad is enabled (i.e. __riscv_zicfilp). > > TODO: Update `lpad 0` with `lpad %lpad_hash(name)` after toolchain > support. > > Signed-off-by: Deepak Gupta > --- > arch/riscv/include/asm/linkage.h | 42 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 42 insertions(+) > > diff --git a/arch/riscv/include/asm/linkage.h b/arch/riscv/include/asm/linkage.h > index 9e88ba23cd2b..162774b81158 100644 > --- a/arch/riscv/include/asm/linkage.h > +++ b/arch/riscv/include/asm/linkage.h > @@ -6,7 +6,49 @@ > #ifndef _ASM_RISCV_LINKAGE_H > #define _ASM_RISCV_LINKAGE_H > > +#ifdef __ASSEMBLY__ > +#include > +#endif > + > #define __ALIGN .balign 4 > #define __ALIGN_STR ".balign 4" > > +#ifdef __riscv_zicfilp > +/* > + * A landing pad instruction is needed at start of asm routines > + * re-define macros for asm routines to have a landing pad at > + * the beginning of function. Currently use label value of 0x1. Your code below uses label value 0 which disables tag checking. As long as we don't have tool support for calculating function hashes that is an appropriate approach. %s/Currently use label value of 0x1./Label value 0x0 disables tag checking./ Best regards Heinrich > + * Eventually, label should be calculated as a hash over function > + * signature. > + */ > +#define SYM_FUNC_START(name) \ > + SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN) \ > + lpad 0; > + > +#define SYM_FUNC_START_NOALIGN(name) \ > + SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE) \ > + lpad 0; > + > +#define SYM_FUNC_START_LOCAL(name) \ > + SYM_START(name, SYM_L_LOCAL, SYM_A_ALIGN) \ > + lpad 0; > + > +#define SYM_FUNC_START_LOCAL_NOALIGN(name) \ > + SYM_START(name, SYM_L_LOCAL, SYM_A_NONE) \ > + lpad 0; > + > +#define SYM_FUNC_START_WEAK(name) \ > + SYM_START(name, SYM_L_WEAK, SYM_A_ALIGN) \ > + lpad 0; > + > +#define SYM_FUNC_START_WEAK_NOALIGN(name) \ > + SYM_START(name, SYM_L_WEAK, SYM_A_NONE) \ > + lpad 0; > + > +#define SYM_TYPED_FUNC_START(name) \ > + SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_A_ALIGN) \ > + lpad 0; > + > +#endif > + > #endif /* _ASM_RISCV_LINKAGE_H */ >