Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 279 insertions, 0 deletions

diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S
new file mode 100644
index 000000000..d6c08d898
--- /dev/null
+++ b/arch/x86/entry/entry_64_compat.S
@@ -0,0 +1,279 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Compatibility mode system call entry point for x86-64.
+ *
+ * Copyright 2000-2002 Andi Kleen, SuSE Labs.
+ */
+#include <asm/asm-offsets.h>
+#include <asm/current.h>
+#include <asm/errno.h>
+#include <asm/ia32_unistd.h>
+#include <asm/thread_info.h>
+#include <asm/segment.h>
+#include <asm/irqflags.h>
+#include <asm/asm.h>
+#include <asm/smap.h>
+#include <asm/nospec-branch.h>
+#include <linux/linkage.h>
+#include <linux/err.h>
+
+#include "calling.h"
+
+	.section .entry.text, "ax"
+
+/*
+ * 32-bit SYSENTER entry.
+ *
+ * 32-bit system calls through the vDSO's __kernel_vsyscall enter here
+ * on 64-bit kernels running on Intel CPUs.
+ *
+ * The SYSENTER instruction, in principle, should *only* occur in the
+ * vDSO.  In practice, a small number of Android devices were shipped
+ * with a copy of Bionic that inlined a SYSENTER instruction.  This
+ * never happened in any of Google's Bionic versions -- it only happened
+ * in a narrow range of Intel-provided versions.
+ *
+ * SYSENTER loads SS, RSP, CS, and RIP from previously programmed MSRs.
+ * IF and VM in RFLAGS are cleared (IOW: interrupts are off).
+ * SYSENTER does not save anything on the stack,
+ * and does not save old RIP (!!!), RSP, or RFLAGS.
+ *
+ * Arguments:
+ * eax  system call number
+ * ebx  arg1
+ * ecx  arg2
+ * edx  arg3
+ * esi  arg4
+ * edi  arg5
+ * ebp  user stack
+ * 0(%ebp) arg6
+ */
+SYM_CODE_START(entry_SYSENTER_compat)
+	UNWIND_HINT_ENTRY
+	ENDBR
+	/* Interrupts are off on entry. */
+	swapgs
+
+	pushq	%rax
+	SWITCH_TO_KERNEL_CR3 scratch_reg=%rax
+	popq	%rax
+
+	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp
+
+	/* Construct struct pt_regs on stack */
+	pushq	$__USER32_DS		/* pt_regs->ss */
+	pushq	$0			/* pt_regs->sp = 0 (placeholder) */
+
+	/*
+	 * Push flags.  This is nasty.  First, interrupts are currently
+	 * off, but we need pt_regs->flags to have IF set.  Second, if TS
+	 * was set in usermode, it's still set, and we're singlestepping
+	 * through this code.  do_SYSENTER_32() will fix up IF.
+	 */
+	pushfq				/* pt_regs->flags (except IF = 0) */
+	pushq	$__USER32_CS		/* pt_regs->cs */
+	pushq	$0			/* pt_regs->ip = 0 (placeholder) */
+SYM_INNER_LABEL(entry_SYSENTER_compat_after_hwframe, SYM_L_GLOBAL)
+
+	/*
+	 * User tracing code (ptrace or signal handlers) might assume that
+	 * the saved RAX contains a 32-bit number when we're invoking a 32-bit
+	 * syscall.  Just in case the high bits are nonzero, zero-extend
+	 * the syscall number.  (This could almost certainly be deleted
+	 * with no ill effects.)
+	 */
+	movl	%eax, %eax
+
+	pushq	%rax			/* pt_regs->orig_ax */
+	PUSH_AND_CLEAR_REGS rax=$-ENOSYS
+	UNWIND_HINT_REGS
+
+	cld
+
+	IBRS_ENTER
+	UNTRAIN_RET
+
+	/*
+	 * SYSENTER doesn't filter flags, so we need to clear NT and AC
+	 * ourselves.  To save a few cycles, we can check whether
+	 * either was set instead of doing an unconditional popfq.
+	 * This needs to happen before enabling interrupts so that
+	 * we don't get preempted with NT set.
+	 *
+	 * If TF is set, we will single-step all the way to here -- do_debug
+	 * will ignore all the traps.  (Yes, this is slow, but so is
+	 * single-stepping in general.  This allows us to avoid having
+	 * a more complicated code to handle the case where a user program
+	 * forces us to single-step through the SYSENTER entry code.)
+	 *
+	 * NB.: .Lsysenter_fix_flags is a label with the code under it moved
+	 * out-of-line as an optimization: NT is unlikely to be set in the
+	 * majority of the cases and instead of polluting the I$ unnecessarily,
+	 * we're keeping that code behind a branch which will predict as
+	 * not-taken and therefore its instructions won't be fetched.
+	 */
+	testl	$X86_EFLAGS_NT|X86_EFLAGS_AC|X86_EFLAGS_TF, EFLAGS(%rsp)
+	jnz	.Lsysenter_fix_flags
+.Lsysenter_flags_fixed:
+
+	movq	%rsp, %rdi
+	call	do_SYSENTER_32
+	/* XEN PV guests always use IRET path */
+	ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \
+		    "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV
+	jmp	sysret32_from_system_call
+
+.Lsysenter_fix_flags:
+	pushq	$X86_EFLAGS_FIXED
+	popfq
+	jmp	.Lsysenter_flags_fixed
+SYM_INNER_LABEL(__end_entry_SYSENTER_compat, SYM_L_GLOBAL)
+	ANNOTATE_NOENDBR // is_sysenter_singlestep
+SYM_CODE_END(entry_SYSENTER_compat)
+
+/*
+ * 32-bit SYSCALL entry.
+ *
+ * 32-bit system calls through the vDSO's __kernel_vsyscall enter here
+ * on 64-bit kernels running on AMD CPUs.
+ *
+ * The SYSCALL instruction, in principle, should *only* occur in the
+ * vDSO.  In practice, it appears that this really is the case.
+ * As evidence:
+ *
+ *  - The calling convention for SYSCALL has changed several times without
+ *    anyone noticing.
+ *
+ *  - Prior to the in-kernel X86_BUG_SYSRET_SS_ATTRS fixup, anything
+ *    user task that did SYSCALL without immediately reloading SS
+ *    would randomly crash.
+ *
+ *  - Most programmers do not directly target AMD CPUs, and the 32-bit
+ *    SYSCALL instruction does not exist on Intel CPUs.  Even on AMD
+ *    CPUs, Linux disables the SYSCALL instruction on 32-bit kernels
+ *    because the SYSCALL instruction in legacy/native 32-bit mode (as
+ *    opposed to compat mode) is sufficiently poorly designed as to be
+ *    essentially unusable.
+ *
+ * 32-bit SYSCALL saves RIP to RCX, clears RFLAGS.RF, then saves
+ * RFLAGS to R11, then loads new SS, CS, and RIP from previously
+ * programmed MSRs.  RFLAGS gets masked by a value from another MSR
+ * (so CLD and CLAC are not needed).  SYSCALL does not save anything on
+ * the stack and does not change RSP.
+ *
+ * Note: RFLAGS saving+masking-with-MSR happens only in Long mode
+ * (in legacy 32-bit mode, IF, RF and VM bits are cleared and that's it).
+ * Don't get confused: RFLAGS saving+masking depends on Long Mode Active bit
+ * (EFER.LMA=1), NOT on bitness of userspace where SYSCALL executes
+ * or target CS descriptor's L bit (SYSCALL does not read segment descriptors).
+ *
+ * Arguments:
+ * eax  system call number
+ * ecx  return address
+ * ebx  arg1
+ * ebp  arg2	(note: not saved in the stack frame, should not be touched)
+ * edx  arg3
+ * esi  arg4
+ * edi  arg5
+ * esp  user stack
+ * 0(%esp) arg6
+ */
+SYM_CODE_START(entry_SYSCALL_compat)
+	UNWIND_HINT_ENTRY
+	ENDBR
+	/* Interrupts are off on entry. */
+	swapgs
+
+	/* Stash user ESP */
+	movl	%esp, %r8d
+
+	/* Use %rsp as scratch reg. User ESP is stashed in r8 */
+	SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp
+
+	/* Switch to the kernel stack */
+	movq	PER_CPU_VAR(cpu_current_top_of_stack), %rsp
+
+SYM_INNER_LABEL(entry_SYSCALL_compat_safe_stack, SYM_L_GLOBAL)
+	ANNOTATE_NOENDBR
+
+	/* Construct struct pt_regs on stack */
+	pushq	$__USER32_DS		/* pt_regs->ss */
+	pushq	%r8			/* pt_regs->sp */
+	pushq	%r11			/* pt_regs->flags */
+	pushq	$__USER32_CS		/* pt_regs->cs */
+	pushq	%rcx			/* pt_regs->ip */
+SYM_INNER_LABEL(entry_SYSCALL_compat_after_hwframe, SYM_L_GLOBAL)
+	movl	%eax, %eax		/* discard orig_ax high bits */
+	pushq	%rax			/* pt_regs->orig_ax */
+	PUSH_AND_CLEAR_REGS rcx=%rbp rax=$-ENOSYS
+	UNWIND_HINT_REGS
+
+	IBRS_ENTER
+	UNTRAIN_RET
+
+	movq	%rsp, %rdi
+	call	do_fast_syscall_32
+	/* XEN PV guests always use IRET path */
+	ALTERNATIVE "testl %eax, %eax; jz swapgs_restore_regs_and_return_to_usermode", \
+		    "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV
+
+	/* Opportunistic SYSRET */
+sysret32_from_system_call:
+	/*
+	 * We are not going to return to userspace from the trampoline
+	 * stack. So let's erase the thread stack right now.
+	 */
+	STACKLEAK_ERASE
+
+	IBRS_EXIT
+
+	movq	RBX(%rsp), %rbx		/* pt_regs->rbx */
+	movq	RBP(%rsp), %rbp		/* pt_regs->rbp */
+	movq	EFLAGS(%rsp), %r11	/* pt_regs->flags (in r11) */
+	movq	RIP(%rsp), %rcx		/* pt_regs->ip (in rcx) */
+	addq	$RAX, %rsp		/* Skip r8-r15 */
+	popq	%rax			/* pt_regs->rax */
+	popq	%rdx			/* Skip pt_regs->cx */
+	popq	%rdx			/* pt_regs->dx */
+	popq	%rsi			/* pt_regs->si */
+	popq	%rdi			/* pt_regs->di */
+
+        /*
+         * USERGS_SYSRET32 does:
+         *  GSBASE = user's GS base
+         *  EIP = ECX
+         *  RFLAGS = R11
+         *  CS = __USER32_CS
+         *  SS = __USER_DS
+         *
+	 * ECX will not match pt_regs->cx, but we're returning to a vDSO
+	 * trampoline that will fix up RCX, so this is okay.
+	 *
+	 * R12-R15 are callee-saved, so they contain whatever was in them
+	 * when the system call started, which is already known to user
+	 * code.  We zero R8-R10 to avoid info leaks.
+         */
+	movq	RSP-ORIG_RAX(%rsp), %rsp
+SYM_INNER_LABEL(entry_SYSRETL_compat_unsafe_stack, SYM_L_GLOBAL)
+	ANNOTATE_NOENDBR
+
+	/*
+	 * The original userspace %rsp (RSP-ORIG_RAX(%rsp)) is stored
+	 * on the process stack which is not mapped to userspace and
+	 * not readable after we SWITCH_TO_USER_CR3.  Delay the CR3
+	 * switch until after after the last reference to the process
+	 * stack.
+	 *
+	 * %r8/%r9 are zeroed before the sysret, thus safe to clobber.
+	 */
+	SWITCH_TO_USER_CR3_NOSTACK scratch_reg=%r8 scratch_reg2=%r9
+
+	xorl	%r8d, %r8d
+	xorl	%r9d, %r9d
+	xorl	%r10d, %r10d
+	swapgs
+	sysretl
+SYM_INNER_LABEL(entry_SYSRETL_compat_end, SYM_L_GLOBAL)
+	ANNOTATE_NOENDBR
+	int3
+SYM_CODE_END(entry_SYSCALL_compat)