// SPDX-License-Identifier: GPL-2.0-or-later/* * x86 implementation of rethook. Mostly copied from arch/x86/kernel/kprobes/core.c. */#include <linux/bug.h>#include <linux/rethook.h>#include <linux/kprobes.h>#include <linux/objtool.h> #include "kprobes/common.h" __visible void arch_rethook_trampoline_callback(struct pt_regs *regs); #ifndef ANNOTATE_NOENDBR#define ANNOTATE_NOENDBR#endif /* * When a target function returns, this code saves registers and calls * arch_rethook_trampoline_callback(), which calls the rethook handler. */asm(	".text\n"	".global arch_rethook_trampoline\n"	".type arch_rethook_trampoline, @function\n"	"arch_rethook_trampoline:\n"#ifdef CONFIG_X86_64	ANNOTATE_NOENDBR "\n"	/* This is only jumped from ret instruction */	/* Push a fake return address to tell the unwinder it's a rethook. */	"	pushq $arch_rethook_trampoline\n"	UNWIND_HINT_FUNC	"       pushq $" __stringify(__KERNEL_DS) "\n"	/* Save the 'sp - 16', this will be fixed later. */	"	pushq %rsp\n"	"	pushfq\n"	SAVE_REGS_STRING	"	movq %rsp, %rdi\n"	"	call arch_rethook_trampoline_callback\n"	RESTORE_REGS_STRING	/* In the callback function, 'regs->flags' is copied to 'regs->ss'. */	"	addq $16, %rsp\n"	"	popfq\n"#else	/* Push a fake return address to tell the unwinder it's a rethook. */	"	pushl $arch_rethook_trampoline\n"	UNWIND_HINT_FUNC	"	pushl %ss\n"	/* Save the 'sp - 8', this will be fixed later. */	"	pushl %esp\n"	"	pushfl\n"	SAVE_REGS_STRING	"	movl %esp, %eax\n"	"	call arch_rethook_trampoline_callback\n"	RESTORE_REGS_STRING	/* In the callback function, 'regs->flags' is copied to 'regs->ss'. */	"	addl $8, %esp\n"	"	popfl\n"#endif	ASM_RET	".size arch_rethook_trampoline, .-arch_rethook_trampoline\n");NOKPROBE_SYMBOL(arch_rethook_trampoline); /* * Called from arch_rethook_trampoline */__used __visible void arch_rethook_trampoline_callback(struct pt_regs *regs){	unsigned long *frame_pointer; 	/* fixup registers */	regs->cs = __KERNEL_CS;#ifdef CONFIG_X86_32	regs->gs = 0;#endif	regs->ip = (unsigned long)&arch_rethook_trampoline;	regs->orig_ax = ~0UL;	regs->sp += 2*sizeof(long);	frame_pointer = (long *)(regs + 1); 	/*	 * The return address at 'frame_pointer' is recovered by the	 * arch_rethook_fixup_return() which called from this	 * rethook_trampoline_handler().	 */	rethook_trampoline_handler(regs, (unsigned long)frame_pointer); 	/*	 * Copy FLAGS to 'pt_regs::ss' so that arch_rethook_trapmoline()	 * can do RET right after POPF.	 */	*(unsigned long *)&regs->ss = regs->flags;}NOKPROBE_SYMBOL(arch_rethook_trampoline_callback); /* * arch_rethook_trampoline() skips updating frame pointer. The frame pointer * saved in arch_rethook_trampoline_callback() points to the real caller * function's frame pointer. Thus the arch_rethook_trampoline() doesn't have * a standard stack frame with CONFIG_FRAME_POINTER=y. * Let's mark it non-standard function. Anyway, FP unwinder can correctly * unwind without the hint. */STACK_FRAME_NON_STANDARD_FP(arch_rethook_trampoline); /* This is called from rethook_trampoline_handler(). */void arch_rethook_fixup_return(struct pt_regs *regs,			       unsigned long correct_ret_addr){	unsigned long *frame_pointer = (void *)(regs + 1); 	/* Replace fake return address with real one. */	*frame_pointer = correct_ret_addr;}NOKPROBE_SYMBOL(arch_rethook_fixup_return); void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount){	unsigned long *stack = (unsigned long *)regs->sp; 	rh->ret_addr = stack[0];	rh->frame = regs->sp; 	/* Replace the return addr with trampoline addr */	stack[0] = (unsigned long) arch_rethook_trampoline;}NOKPROBE_SYMBOL(arch_rethook_prepare);