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Peter Anvin" To: "H. Peter Anvin" , "Jason A. Donenfeld" , "Peter Zijlstra (Intel)" , "Theodore Ts'o" , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Xin Li , Andrew Cooper , Andy Lutomirski , Ard Biesheuvel , Borislav Petkov , Brian Gerst , Dave Hansen , Ingo Molnar , James Morse , Jarkko Sakkinen , Josh Poimboeuf , Kees Cook , Nam Cao , Oleg Nesterov , Perry Yuan , Thomas Gleixner , Thomas Huth , Uros Bizjak , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-sgx@vger.kernel.org, x86@kernel.org Subject: [PATCH v2 9/9] x86/entry/vdso32: when using int $0x80, use it directly Date: Tue, 11 Nov 2025 20:37:27 -0800 Message-ID: <20251112043730.992152-10-hpa@zytor.com> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251112043730.992152-1-hpa@zytor.com> References: <20251112043730.992152-1-hpa@zytor.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 8E5BCA0003 X-Stat-Signature: uhk4xt9d4y4z391ue4bnxwysfq5t733e X-Rspam-User: X-HE-Tag: 1762922306-122290 X-HE-Meta: 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 vgGZ05mC j5xqSykEndlTlYk4EEwIX6uvi3LxtdiY/dWFNzvTqyBVj7gOayJI6xl42Zr9DlwpAcebUpWrtbI92pvgyxkmzkWuzeX5BjaEFRuyOTIqxy+KfFsu+2byu36PcrLso+nDcsLb2R6fLn3lGaBAtJNyAr+D5kQGJ3Svu9IEZgkxhvXTBWvOHvRHOnZfhLs7s2j8ihyYYFLAdd8lBwEPF0DmHMjdyoyuCk64ZuQV/BtTr28xFsK9nLE+QS7V1tu0SWP3HCziitTkVRCPCLp2DBbWxtHWi8+grh3EDf6eO2axEDUtW/R6qvGGV5Lau/uQwV/lYESdsszr9z7kHp2I= 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: When neither sysenter32 nor syscall32 is available (on either FRED-capable 64-bit hardware or old 32-bit hardware), there is no reason to do a bunch of stack shuffling in __kernel_vsyscall. Unfortunately, just overwriting the initial "push" instructions will mess up the CFI annotations, so suffer the 3-byte NOP if not applicable. Similarly, inline the int $0x80 when doing inline system calls in the vdso instead of calling __kernel_vsyscall. Signed-off-by: H. Peter Anvin (Intel) --- arch/x86/entry/vdso/vdso32/system_call.S | 18 ++++++++++++++---- arch/x86/include/asm/vdso/sys_call.h | 4 +++- 2 files changed, 17 insertions(+), 5 deletions(-) diff --git a/arch/x86/entry/vdso/vdso32/system_call.S b/arch/x86/entry/vdso/vdso32/system_call.S index 7b1c0f16e511..9157cf9c5749 100644 --- a/arch/x86/entry/vdso/vdso32/system_call.S +++ b/arch/x86/entry/vdso/vdso32/system_call.S @@ -14,6 +14,18 @@ ALIGN __kernel_vsyscall: CFI_STARTPROC + + /* + * If using int $0x80, there is no reason to muck about with the + * stack here. Unfortunately just overwriting the push instructions + * would mess up the CFI annotations, but it is only a 3-byte + * NOP in that case. This could be avoided by patching the + * vdso symbol table (not the code) and entry point, but that + * would a fair bit of tooling work or by simply compiling + * two different vDSO images, but that doesn't seem worth it. + */ + ALTERNATIVE "int $0x80; ret", "", X86_FEATURE_SYSFAST32 + /* * Reshuffle regs so that all of any of the entry instructions * will preserve enough state. @@ -52,11 +64,9 @@ __kernel_vsyscall: #define SYSENTER_SEQUENCE "movl %esp, %ebp; sysenter" #define SYSCALL_SEQUENCE "movl %ecx, %ebp; syscall" - /* If SYSENTER (Intel) or SYSCALL32 (AMD) is available, use it. */ - ALTERNATIVE_2 "", SYSENTER_SEQUENCE, X86_FEATURE_SYSFAST32, \ - SYSCALL_SEQUENCE, X86_FEATURE_SYSCALL32 + ALTERNATIVE SYSENTER_SEQUENCE, SYSCALL_SEQUENCE, X86_FEATURE_SYSCALL32 - /* Enter using int $0x80 */ + /* Re-enter using int $0x80 */ int $0x80 SYM_INNER_LABEL(int80_landing_pad, SYM_L_GLOBAL) diff --git a/arch/x86/include/asm/vdso/sys_call.h b/arch/x86/include/asm/vdso/sys_call.h index 6b1fbcdcbd5c..603ad8a83c66 100644 --- a/arch/x86/include/asm/vdso/sys_call.h +++ b/arch/x86/include/asm/vdso/sys_call.h @@ -27,7 +27,9 @@ #define __sys_reg5 "r8" #define __sys_reg6 "r9" #else -#define __sys_instr "call __kernel_vsyscall" +#define __sys_instr ALTERNATIVE("ds;ds;ds;int $0x80", \ + "call __kernel_vsyscall", \ + X86_FEATURE_SYSFAST32) #define __sys_clobber "memory" #define __sys_nr(x,y) __NR_ ## x ## y #define __sys_reg1 "ebx" -- 2.51.1