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Thu, 10 Apr 2025 00:05:34 -0700 (PDT) From: Cyril Bur To: palmer@dabbelt.com, aou@eecs.berkeley.edu, paul.walmsley@sifive.com, charlie@rivosinc.com, jrtc27@jrtc27.com, ben.dooks@codethink.co.uk, alex@ghiti.fr Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, jszhang@kernel.org Subject: [PATCH v6 5/5] riscv: uaccess: use 'asm_goto_output' for get_user() Date: Thu, 10 Apr 2025 07:05:26 +0000 Message-Id: <20250410070526.3160847-6-cyrilbur@tenstorrent.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250410070526.3160847-1-cyrilbur@tenstorrent.com> References: <20250410070526.3160847-1-cyrilbur@tenstorrent.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Jisheng Zhang With 'asm goto' we don't need to test the error etc, the exception just jumps to the error handling directly. Unlike put_user(), get_user() must work around GCC bugs [1] when using output clobbers in an asm goto statement. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113921 # 1 Signed-off-by: Jisheng Zhang [Cyril Bur: Rewritten commit message] Signed-off-by: Cyril Bur Reviewed-by: Alexandre Ghiti --- arch/riscv/include/asm/uaccess.h | 95 +++++++++++++++++++++++--------- 1 file changed, 68 insertions(+), 27 deletions(-) diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uacc= ess.h index 719c9179a751..87d01168f80a 100644 --- a/arch/riscv/include/asm/uaccess.h +++ b/arch/riscv/include/asm/uaccess.h @@ -96,27 +96,58 @@ static inline unsigned long __untagged_addr_remote(stru= ct mm_struct *mm, unsigne * call. */ =20 -#define __get_user_asm(insn, x, ptr, err) \ +#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT +#define __get_user_asm(insn, x, ptr, label) \ + asm_goto_output( \ + "1:\n" \ + " " insn " %0, %1\n" \ + _ASM_EXTABLE_UACCESS_ERR(1b, %l2, %0) \ + : "=3D&r" (x) \ + : "m" (*(ptr)) : : label) +#else /* !CONFIG_CC_HAS_ASM_GOTO_OUTPUT */ +#define __get_user_asm(insn, x, ptr, label) \ do { \ - __typeof__(x) __x; \ + long __gua_err =3D 0; \ __asm__ __volatile__ ( \ "1:\n" \ " " insn " %1, %2\n" \ "2:\n" \ _ASM_EXTABLE_UACCESS_ERR_ZERO(1b, 2b, %0, %1) \ - : "+r" (err), "=3D&r" (__x) \ + : "+r" (__gua_err), "=3D&r" (x) \ : "m" (*(ptr))); \ - (x) =3D __x; \ + if (__gua_err) \ + goto label; \ } while (0) +#endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */ =20 #ifdef CONFIG_64BIT -#define __get_user_8(x, ptr, err) \ - __get_user_asm("ld", x, ptr, err) +#define __get_user_8(x, ptr, label) \ + __get_user_asm("ld", x, ptr, label) #else /* !CONFIG_64BIT */ -#define __get_user_8(x, ptr, err) \ + +#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT +#define __get_user_8(x, ptr, label) \ + u32 __user *__ptr =3D (u32 __user *)(ptr); \ + u32 __lo, __hi; \ + asm_goto_output( \ + "1:\n" \ + " lw %0, %2\n" \ + "2:\n" \ + " lw %1, %3\n" \ + _ASM_EXTABLE_UACCESS_ERR(1b, %l4, %0) \ + _ASM_EXTABLE_UACCESS_ERR(2b, %l4, %0) \ + : "=3D&r" (__lo), "=3Dr" (__hi) \ + : "m" (__ptr[__LSW]), "m" (__ptr[__MSW]) \ + : : label); \ + (x) =3D (__typeof__(x))((__typeof__((x) - (x)))( \ + (((u64)__hi << 32) | __lo))); \ + +#else /* !CONFIG_CC_HAS_ASM_GOTO_OUTPUT */ +#define __get_user_8(x, ptr, label) \ do { \ u32 __user *__ptr =3D (u32 __user *)(ptr); \ u32 __lo, __hi; \ + long __gu8_err =3D 0; \ __asm__ __volatile__ ( \ "1:\n" \ " lw %1, %3\n" \ @@ -125,35 +156,51 @@ do { \ "3:\n" \ _ASM_EXTABLE_UACCESS_ERR_ZERO(1b, 3b, %0, %1) \ _ASM_EXTABLE_UACCESS_ERR_ZERO(2b, 3b, %0, %1) \ - : "+r" (err), "=3D&r" (__lo), "=3Dr" (__hi) \ + : "+r" (__gu8_err), "=3D&r" (__lo), "=3Dr" (__hi) \ : "m" (__ptr[__LSW]), "m" (__ptr[__MSW])); \ - if (err) \ + if (__gu8_err) { \ __hi =3D 0; \ - (x) =3D (__typeof__(x))((__typeof__((x)-(x)))( \ + goto label; \ + } \ + (x) =3D (__typeof__(x))((__typeof__((x) - (x)))( \ (((u64)__hi << 32) | __lo))); \ } while (0) +#endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */ + #endif /* CONFIG_64BIT */ =20 -#define __get_user_nocheck(x, __gu_ptr, __gu_err) \ +#define __get_user_nocheck(x, __gu_ptr, label) \ do { \ switch (sizeof(*__gu_ptr)) { \ case 1: \ - __get_user_asm("lb", (x), __gu_ptr, __gu_err); \ + __get_user_asm("lb", (x), __gu_ptr, label); \ break; \ case 2: \ - __get_user_asm("lh", (x), __gu_ptr, __gu_err); \ + __get_user_asm("lh", (x), __gu_ptr, label); \ break; \ case 4: \ - __get_user_asm("lw", (x), __gu_ptr, __gu_err); \ + __get_user_asm("lw", (x), __gu_ptr, label); \ break; \ case 8: \ - __get_user_8((x), __gu_ptr, __gu_err); \ + __get_user_8((x), __gu_ptr, label); \ break; \ default: \ BUILD_BUG(); \ } \ } while (0) =20 +#define __get_user_error(x, ptr, err) \ +do { \ + __label__ __gu_failed; \ + \ + __get_user_nocheck(x, ptr, __gu_failed); \ + err =3D 0; \ + break; \ +__gu_failed: \ + x =3D 0; \ + err =3D -EFAULT; \ +} while (0) + /** * __get_user: - Get a simple variable from user space, with less checking. * @x: Variable to store result. @@ -178,13 +225,16 @@ do { \ ({ \ const __typeof__(*(ptr)) __user *__gu_ptr =3D untagged_addr(ptr); \ long __gu_err =3D 0; \ + __typeof__(x) __gu_val; \ \ __chk_user_ptr(__gu_ptr); \ \ __enable_user_access(); \ - __get_user_nocheck(x, __gu_ptr, __gu_err); \ + __get_user_error(__gu_val, __gu_ptr, __gu_err); \ __disable_user_access(); \ \ + (x) =3D __gu_val; \ + \ __gu_err; \ }) =20 @@ -369,13 +419,7 @@ unsigned long __must_check clear_user(void __user *to,= unsigned long n) } =20 #define __get_kernel_nofault(dst, src, type, err_label) \ -do { \ - long __kr_err =3D 0; \ - \ - __get_user_nocheck(*((type *)(dst)), (type *)(src), __kr_err); \ - if (unlikely(__kr_err)) \ - goto err_label; \ -} while (0) + __get_user_nocheck(*((type *)(dst)), (type *)(src), err_label) =20 #define __put_kernel_nofault(dst, src, type, err_label) \ __put_user_nocheck(*((type *)(src)), (type *)(dst), err_label) @@ -401,12 +445,9 @@ static inline void user_access_restore(unsigned long e= nabled) { } __put_user_nocheck(x, (ptr), label) =20 #define unsafe_get_user(x, ptr, label) do { \ - long __err =3D 0; \ __inttype(*(ptr)) __gu_val; \ - __get_user_nocheck(__gu_val, (ptr), __err); \ + __get_user_nocheck(__gu_val, (ptr), label); \ (x) =3D (__force __typeof__(*(ptr)))__gu_val; \ - if (__err) \ - goto label; \ } while (0) =20 #define unsafe_copy_loop(dst, src, len, type, op, label) \ --=20 2.34.1