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x86/entry: Convert INT 0x80 emulation to IDTENTRY
There is no real reason to have a separate ASM entry point implementation for the legacy INT 0x80 syscall emulation on 64-bit. IDTENTRY provides all the functionality needed with the only difference that it does not: - save the syscall number (AX) into pt_regs::orig_ax - set pt_regs::ax to -ENOSYS Both can be done safely in the C code of an IDTENTRY before invoking any of the syscall related functions which depend on this convention. Aside of ASM code reduction this prepares for detecting and handling a local APIC injected vector 0x80. [ kirill.shutemov: More verbose comments ] Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de> Cc: <stable@vger.kernel.org> # v6.0+
This commit is contained in:
Thomas Gleixner
Dave Hansen
parent
b82a8dbd3d
commit
be5341eb0d
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@ -167,7 +167,62 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs, int nr)
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}
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}
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/* Handles int $0x80 */
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#ifdef CONFIG_IA32_EMULATION
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/**
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* int80_emulation - 32-bit legacy syscall entry
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*
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* This entry point can be used by 32-bit and 64-bit programs to perform
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* 32-bit system calls. Instances of INT $0x80 can be found inline in
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* various programs and libraries. It is also used by the vDSO's
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* __kernel_vsyscall fallback for hardware that doesn't support a faster
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* entry method. Restarted 32-bit system calls also fall back to INT
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* $0x80 regardless of what instruction was originally used to do the
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* system call.
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*
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* This is considered a slow path. It is not used by most libc
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* implementations on modern hardware except during process startup.
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*
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* The arguments for the INT $0x80 based syscall are on stack in the
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* pt_regs structure:
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* eax: system call number
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* ebx, ecx, edx, esi, edi, ebp: arg1 - arg 6
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*/
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DEFINE_IDTENTRY_RAW(int80_emulation)
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{
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int nr;
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/* Establish kernel context. */
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enter_from_user_mode(regs);
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instrumentation_begin();
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add_random_kstack_offset();
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/*
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* The low level idtentry code pushed -1 into regs::orig_ax
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* and regs::ax contains the syscall number.
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*
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* User tracing code (ptrace or signal handlers) might assume
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* that the regs::orig_ax contains a 32-bit number on invoking
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* a 32-bit syscall.
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*
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* Establish the syscall convention by saving the 32bit truncated
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* syscall number in regs::orig_ax and by invalidating regs::ax.
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*/
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regs->orig_ax = regs->ax & GENMASK(31, 0);
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regs->ax = -ENOSYS;
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nr = syscall_32_enter(regs);
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local_irq_enable();
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nr = syscall_enter_from_user_mode_work(regs, nr);
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do_syscall_32_irqs_on(regs, nr);
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instrumentation_end();
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syscall_exit_to_user_mode(regs);
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}
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#else /* CONFIG_IA32_EMULATION */
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/* Handles int $0x80 on a 32bit kernel */
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__visible noinstr void do_int80_syscall_32(struct pt_regs *regs)
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{
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int nr = syscall_32_enter(regs);
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@ -186,6 +241,7 @@ __visible noinstr void do_int80_syscall_32(struct pt_regs *regs)
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instrumentation_end();
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syscall_exit_to_user_mode(regs);
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}
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#endif /* !CONFIG_IA32_EMULATION */
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static noinstr bool __do_fast_syscall_32(struct pt_regs *regs)
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{
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@ -275,80 +275,3 @@ SYM_INNER_LABEL(entry_SYSRETL_compat_end, SYM_L_GLOBAL)
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ANNOTATE_NOENDBR
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int3
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SYM_CODE_END(entry_SYSCALL_compat)
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/*
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* 32-bit legacy system call entry.
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*
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* 32-bit x86 Linux system calls traditionally used the INT $0x80
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* instruction. INT $0x80 lands here.
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*
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* This entry point can be used by 32-bit and 64-bit programs to perform
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* 32-bit system calls. Instances of INT $0x80 can be found inline in
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* various programs and libraries. It is also used by the vDSO's
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* __kernel_vsyscall fallback for hardware that doesn't support a faster
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* entry method. Restarted 32-bit system calls also fall back to INT
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* $0x80 regardless of what instruction was originally used to do the
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* system call.
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*
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* This is considered a slow path. It is not used by most libc
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* implementations on modern hardware except during process startup.
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*
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* Arguments:
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* eax system call number
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* ebx arg1
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* ecx arg2
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* edx arg3
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* esi arg4
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* edi arg5
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* ebp arg6
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*/
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SYM_CODE_START(entry_INT80_compat)
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UNWIND_HINT_ENTRY
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ENDBR
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/*
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* Interrupts are off on entry.
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*/
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ASM_CLAC /* Do this early to minimize exposure */
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ALTERNATIVE "swapgs", "", X86_FEATURE_XENPV
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/*
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* User tracing code (ptrace or signal handlers) might assume that
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* the saved RAX contains a 32-bit number when we're invoking a 32-bit
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* syscall. Just in case the high bits are nonzero, zero-extend
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* the syscall number. (This could almost certainly be deleted
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* with no ill effects.)
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*/
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movl %eax, %eax
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/* switch to thread stack expects orig_ax and rdi to be pushed */
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pushq %rax /* pt_regs->orig_ax */
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/* Need to switch before accessing the thread stack. */
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SWITCH_TO_KERNEL_CR3 scratch_reg=%rax
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/* In the Xen PV case we already run on the thread stack. */
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ALTERNATIVE "", "jmp .Lint80_keep_stack", X86_FEATURE_XENPV
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movq %rsp, %rax
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movq PER_CPU_VAR(pcpu_hot + X86_top_of_stack), %rsp
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pushq 5*8(%rax) /* regs->ss */
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pushq 4*8(%rax) /* regs->rsp */
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pushq 3*8(%rax) /* regs->eflags */
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pushq 2*8(%rax) /* regs->cs */
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pushq 1*8(%rax) /* regs->ip */
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pushq 0*8(%rax) /* regs->orig_ax */
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.Lint80_keep_stack:
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PUSH_AND_CLEAR_REGS rax=$-ENOSYS
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UNWIND_HINT_REGS
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cld
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IBRS_ENTER
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UNTRAIN_RET
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movq %rsp, %rdi
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call do_int80_syscall_32
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jmp swapgs_restore_regs_and_return_to_usermode
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SYM_CODE_END(entry_INT80_compat)
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@ -569,6 +569,10 @@ DECLARE_IDTENTRY_RAW(X86_TRAP_UD, exc_invalid_op);
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DECLARE_IDTENTRY_RAW(X86_TRAP_BP, exc_int3);
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DECLARE_IDTENTRY_RAW_ERRORCODE(X86_TRAP_PF, exc_page_fault);
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#if defined(CONFIG_IA32_EMULATION)
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DECLARE_IDTENTRY_RAW(IA32_SYSCALL_VECTOR, int80_emulation);
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#endif
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#ifdef CONFIG_X86_MCE
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#ifdef CONFIG_X86_64
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DECLARE_IDTENTRY_MCE(X86_TRAP_MC, exc_machine_check);
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@ -32,10 +32,6 @@ void entry_SYSCALL_compat(void);
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void entry_SYSCALL_compat_safe_stack(void);
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void entry_SYSRETL_compat_unsafe_stack(void);
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void entry_SYSRETL_compat_end(void);
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void entry_INT80_compat(void);
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#ifdef CONFIG_XEN_PV
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void xen_entry_INT80_compat(void);
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#endif
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#else /* !CONFIG_IA32_EMULATION */
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#define entry_SYSCALL_compat NULL
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#define entry_SYSENTER_compat NULL
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@ -121,7 +121,7 @@ static const __initconst struct idt_data def_idts[] = {
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static const struct idt_data ia32_idt[] __initconst = {
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#if defined(CONFIG_IA32_EMULATION)
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SYSG(IA32_SYSCALL_VECTOR, entry_INT80_compat),
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SYSG(IA32_SYSCALL_VECTOR, asm_int80_emulation),
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#elif defined(CONFIG_X86_32)
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SYSG(IA32_SYSCALL_VECTOR, entry_INT80_32),
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#endif
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@ -704,7 +704,7 @@ static struct trap_array_entry trap_array[] = {
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TRAP_ENTRY(exc_int3, false ),
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TRAP_ENTRY(exc_overflow, false ),
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#ifdef CONFIG_IA32_EMULATION
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{ entry_INT80_compat, xen_entry_INT80_compat, false },
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TRAP_ENTRY(int80_emulation, false ),
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#endif
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TRAP_ENTRY(exc_page_fault, false ),
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TRAP_ENTRY(exc_divide_error, false ),
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@ -156,7 +156,7 @@ xen_pv_trap asm_xenpv_exc_machine_check
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#endif /* CONFIG_X86_MCE */
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xen_pv_trap asm_exc_simd_coprocessor_error
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#ifdef CONFIG_IA32_EMULATION
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xen_pv_trap entry_INT80_compat
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xen_pv_trap asm_int80_emulation
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#endif
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xen_pv_trap asm_exc_xen_unknown_trap
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xen_pv_trap asm_exc_xen_hypervisor_callback
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