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(51-148-40-55.dsl.zen.co.uk. [51.148.40.55]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42bb6deb239sm145970065e9.5.2024.09.02.09.19.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Sep 2024 09:19:21 -0700 (PDT) From: Adhemerval Zanella To: "Jason A . Donenfeld" , Theodore Ts'o , linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, Catalin Marinas , Will Deacon , Thomas Gleixner , Eric Biggers , Christophe Leroy Cc: Mark Rutland Subject: [PATCH v4 1/2] arm64: alternative: make alternative_has_cap_likely() VDSO compatible Date: Mon, 2 Sep 2024 16:15:46 +0000 Message-ID: <20240902161912.2751-2-adhemerval.zanella@linaro.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240902161912.2751-1-adhemerval.zanella@linaro.org> References: <20240902161912.2751-1-adhemerval.zanella@linaro.org> Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Mark Rutland Currently alternative_has_cap_unlikely() can be used in VDSO code, but alternative_has_cap_likely() cannot as it references alt_cb_patch_nops, which is not available when linking the VDSO. This is unfortunate as it would be useful to have alternative_has_cap_likely() available in VDSO code. The use of alt_cb_patch_nops was added in commit: d926079f17bf8aa4 ("arm64: alternatives: add shared NOP callback") ... as removing duplicate NOPs within the kernel Image saved areasonable amount of space. Given the VDSO code will have nowhere near as many alternative branches as the main kernel image, this isn't much of a concern, and a few extra nops isn't a massive problem. Change alternative_has_cap_likely() to only use alt_cb_patch_nops for the main kernel image, and allow duplicate NOPs in VDSO code. Signed-off-by: Mark Rutland Signed-off-by: Adhemerval Zanella --- arch/arm64/include/asm/alternative-macros.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm64/include/asm/alternative-macros.h b/arch/arm64/include/asm/alternative-macros.h index d328f549b1a6..c8c77f9e36d6 100644 --- a/arch/arm64/include/asm/alternative-macros.h +++ b/arch/arm64/include/asm/alternative-macros.h @@ -230,7 +230,11 @@ alternative_has_cap_likely(const unsigned long cpucap) return false; asm goto( +#ifdef BUILD_VDSO + ALTERNATIVE("b %l[l_no]", "nop", %[cpucap]) +#else ALTERNATIVE_CB("b %l[l_no]", %[cpucap], alt_cb_patch_nops) +#endif : : [cpucap] "i" (cpucap) :