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b=GP5rlVgpsY3gf41iBrWBR4PLFsSSpt1cwhq0UZGWW6D9fMZSfNHAbDFsae+n9TPnm RXbcB/gLI0Cpe6u4lWuu/0/6JGamdELFyme9j9YYAZoEbEm8aCrqWZL/aVIPGR3cvN +VyPRYH08FzJokPuJd0sb5gJKt8UuIIuT14MPVQ6fPHtC2fFwn4NJrA0I4nBrvsYnf P/zJZubL/Wme1lBZ6W98okrOSqrjHFSeJFsFTfiR4zr5LWfIYIOwG3nAApXO0xCPbK NS3BNUGa19SLVjR+PbDK5XdshLte8R/6CovgVosy+zmgzlhNbuHt/fxGYKn/+Fd7UE JlFnT5B+CgRUA== Received: by mail-lj1-f170.google.com with SMTP id 38308e7fff4ca-2cca5d81826so13034891fa.2 for ; Fri, 22 Dec 2023 01:35:33 -0800 (PST) X-Gm-Message-State: AOJu0YyewwYGTVJKLuyv8/MUevsrRmmlkEXSySjoE3cSOm7dO98BtduK H25IenGbZLw3qQOhVmptBxetmvxVRqE5dcYGB7s= X-Google-Smtp-Source: AGHT+IFBolUEPY720dl+czfO4qrssPxC1JJ7OwVqlpuBUwcp3tL3lhllAYTVKtUab1jFGi/GhzBcG2KsIGCJdxQjS+s= X-Received: by 2002:a19:384e:0:b0:50e:384c:6982 with SMTP id d14-20020a19384e000000b0050e384c6982mr452303lfj.42.1703237732207; Fri, 22 Dec 2023 01:35:32 -0800 (PST) MIME-Version: 1.0 References: <20231222074605.452452-1-leobras@redhat.com> <20231222074605.452452-3-leobras@redhat.com> In-Reply-To: <20231222074605.452452-3-leobras@redhat.com> From: Guo Ren Date: Fri, 22 Dec 2023 17:35:20 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH 2/4] riscv: add compile-time test into is_compat_task() To: Leonardo Bras Cc: Paul Walmsley , Palmer Dabbelt , Albert Ou , Eric Biederman , Kees Cook , Oleg Nesterov , Conor Dooley , Andy Chiu , Greg Ungerer , Vincent Chen , Xiao Wang , Charlie Jenkins , Andrew Morton , Alexandre Ghiti , Kemeng Shi , David Hildenbrand , "Matthew Wilcox (Oracle)" , Qinglin Pan , Greentime Hu , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , =?UTF-8?B?Q2zDqW1lbnQgTMOpZ2Vy?= , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: C0C6710000D X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: noer6ta8n5wxaw9b835ibs8k851ptnmx X-HE-Tag: 1703237742-731085 X-HE-Meta: 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 6w/Cr2zT +rZ5eui14ya4UhyP6b9Uhq3IBfHhI4/FwpDMwn5+WNSpQC44oxgHXn4wR87r/C8hthIc8Q9epmnFUvtV2rJ5f1B0ZUUoPSYT6NHjLENC3ymnTNnA3SyW2BzHtchSFGSar6ug8drHCi6pemjXb+TC5KAsRwvlrSUzJ+XY4eJzIqckFuuzg2uisHGVCUi/VS7jMe13xWLlbq6toFgkkvcbu1WTcFJzwQlksZH/kMrvO3MQZB3Fz4Ca8310A+bvgkOp4PIq/cG2mHq66zFu2GVDfgNTBRUHvESVJRyhU2FKsZK59or5Euxe04Jri+UB/FRjkjjVpFCyL3tIBoS1s+2qZETq94A== 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: List-Subscribe: List-Unsubscribe: On Fri, Dec 22, 2023 at 5:02=E2=80=AFPM Leonardo Bras = wrote: > > Currently several places will test for CONFIG_COMPAT before testing > is_compat_task(), probably in order to avoid a run-time test into the tas= k > structure. > > Since is_compat_task() is an inlined function, it would be helpful to add= a > compile-time test of CONFIG_COMPAT, making sure it always returns zero wh= en > the option is not enabled during the kernel build. > > With this, the compiler is able to understand in build-time that > is_compat_task() will always return 0, and optimize-out some of the extra > code introduced by the option. > > This will also allow removing a lot #ifdefs that were introduced, and mak= e > the code more clean. > > Signed-off-by: Leonardo Bras > --- > arch/riscv/include/asm/compat.h | 3 +++ > arch/riscv/include/asm/elf.h | 4 ---- > arch/riscv/include/asm/pgtable.h | 6 ------ > arch/riscv/include/asm/processor.h | 4 ++-- > 4 files changed, 5 insertions(+), 12 deletions(-) > > diff --git a/arch/riscv/include/asm/compat.h b/arch/riscv/include/asm/com= pat.h > index 2ac955b51148f..91517b51b8e27 100644 > --- a/arch/riscv/include/asm/compat.h > +++ b/arch/riscv/include/asm/compat.h > @@ -14,6 +14,9 @@ > > static inline int is_compat_task(void) > { > + if (!IS_ENABLED(CONFIG_COMPAT)) > + return 0; > + > return test_thread_flag(TIF_32BIT); > } > > diff --git a/arch/riscv/include/asm/elf.h b/arch/riscv/include/asm/elf.h > index 59a08367fddd7..2e88257cafaea 100644 > --- a/arch/riscv/include/asm/elf.h > +++ b/arch/riscv/include/asm/elf.h > @@ -53,13 +53,9 @@ extern bool compat_elf_check_arch(Elf32_Ehdr *hdr); > #define ELF_ET_DYN_BASE ((DEFAULT_MAP_WINDOW / 3) * 2) > > #ifdef CONFIG_64BIT > -#ifdef CONFIG_COMPAT > #define STACK_RND_MASK (is_compat_task() ? \ > 0x7ff >> (PAGE_SHIFT - 12) : \ > 0x3ffff >> (PAGE_SHIFT - 12)) > -#else > -#define STACK_RND_MASK (0x3ffff >> (PAGE_SHIFT - 12)) > -#endif > #endif > > /* > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pg= table.h > index 1d472b31e0cfe..ea5b269be223a 100644 > --- a/arch/riscv/include/asm/pgtable.h > +++ b/arch/riscv/include/asm/pgtable.h > @@ -127,16 +127,10 @@ > #define VA_USER_SV48 (UL(1) << (VA_BITS_SV48 - 1)) > #define VA_USER_SV57 (UL(1) << (VA_BITS_SV57 - 1)) > > -#ifdef CONFIG_COMPAT > #define MMAP_VA_BITS_64 ((VA_BITS >=3D VA_BITS_SV48) ? VA_BITS_SV48 : VA= _BITS) > #define MMAP_MIN_VA_BITS_64 (VA_BITS_SV39) > #define MMAP_VA_BITS (is_compat_task() ? VA_BITS_SV32 : MMAP_VA_BITS_64) > #define MMAP_MIN_VA_BITS (is_compat_task() ? VA_BITS_SV32 : MMAP_MIN_VA_= BITS_64) > -#else > -#define MMAP_VA_BITS ((VA_BITS >=3D VA_BITS_SV48) ? VA_BITS_SV48 : VA_BI= TS) > -#define MMAP_MIN_VA_BITS (VA_BITS_SV39) > -#endif /* CONFIG_COMPAT */ > - > #else > #include > #endif /* CONFIG_64BIT */ > diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/= processor.h > index f19f861cda549..ed32e53e55999 100644 > --- a/arch/riscv/include/asm/processor.h > +++ b/arch/riscv/include/asm/processor.h > @@ -22,7 +22,7 @@ > ({ \ > unsigned long mmap_end; \ > typeof(addr) _addr =3D (addr); \ > - if ((_addr) =3D=3D 0 || (IS_ENABLED(CONFIG_COMPAT) && is_compat_t= ask())) \ > + if ((_addr) =3D=3D 0 || is_compat_task()) \ > mmap_end =3D STACK_TOP_MAX; \ > else if ((_addr) >=3D VA_USER_SV57) \ > mmap_end =3D STACK_TOP_MAX; \ > @@ -39,7 +39,7 @@ > typeof(addr) _addr =3D (addr); \ > typeof(base) _base =3D (base); \ > unsigned long rnd_gap =3D DEFAULT_MAP_WINDOW - (_base); \ > - if ((_addr) =3D=3D 0 || (IS_ENABLED(CONFIG_COMPAT) && is_compat_t= ask())) \ > + if ((_addr) =3D=3D 0 || is_compat_task()) \ > mmap_base =3D (_base); \ > else if (((_addr) >=3D VA_USER_SV57) && (VA_BITS >=3D VA_BITS_SV5= 7)) \ > mmap_base =3D VA_USER_SV57 - rnd_gap; \ > -- > 2.43.0 > Reviewed-by: Guo Ren --=20 Best Regards Guo Ren