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