cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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rethook.c (3740B)

      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/*
      3 * x86 implementation of rethook. Mostly copied from arch/x86/kernel/kprobes/core.c.
      4 */
      5#include <linux/bug.h>
      6#include <linux/rethook.h>
      7#include <linux/kprobes.h>
      8#include <linux/objtool.h>
      9
     10#include "kprobes/common.h"
     11
     12__visible void arch_rethook_trampoline_callback(struct pt_regs *regs);
     13
     14#ifndef ANNOTATE_NOENDBR
     15#define ANNOTATE_NOENDBR
     16#endif
     17
     18/*
     19 * When a target function returns, this code saves registers and calls
     20 * arch_rethook_trampoline_callback(), which calls the rethook handler.
     21 */
     22asm(
     23	".text\n"
     24	".global arch_rethook_trampoline\n"
     25	".type arch_rethook_trampoline, @function\n"
     26	"arch_rethook_trampoline:\n"
     27#ifdef CONFIG_X86_64
     28	ANNOTATE_NOENDBR	/* This is only jumped from ret instruction */
     29	/* Push a fake return address to tell the unwinder it's a rethook. */
     30	"	pushq $arch_rethook_trampoline\n"
     31	UNWIND_HINT_FUNC
     32	"       pushq $" __stringify(__KERNEL_DS) "\n"
     33	/* Save the 'sp - 16', this will be fixed later. */
     34	"	pushq %rsp\n"
     35	"	pushfq\n"
     36	SAVE_REGS_STRING
     37	"	movq %rsp, %rdi\n"
     38	"	call arch_rethook_trampoline_callback\n"
     39	RESTORE_REGS_STRING
     40	/* In the callback function, 'regs->flags' is copied to 'regs->ss'. */
     41	"	addq $16, %rsp\n"
     42	"	popfq\n"
     43#else
     44	/* Push a fake return address to tell the unwinder it's a rethook. */
     45	"	pushl $arch_rethook_trampoline\n"
     46	UNWIND_HINT_FUNC
     47	"	pushl %ss\n"
     48	/* Save the 'sp - 8', this will be fixed later. */
     49	"	pushl %esp\n"
     50	"	pushfl\n"
     51	SAVE_REGS_STRING
     52	"	movl %esp, %eax\n"
     53	"	call arch_rethook_trampoline_callback\n"
     54	RESTORE_REGS_STRING
     55	/* In the callback function, 'regs->flags' is copied to 'regs->ss'. */
     56	"	addl $8, %esp\n"
     57	"	popfl\n"
     58#endif
     59	ASM_RET
     60	".size arch_rethook_trampoline, .-arch_rethook_trampoline\n"
     61);
     62NOKPROBE_SYMBOL(arch_rethook_trampoline);
     63
     64/*
     65 * Called from arch_rethook_trampoline
     66 */
     67__used __visible void arch_rethook_trampoline_callback(struct pt_regs *regs)
     68{
     69	unsigned long *frame_pointer;
     70
     71	/* fixup registers */
     72	regs->cs = __KERNEL_CS;
     73#ifdef CONFIG_X86_32
     74	regs->gs = 0;
     75#endif
     76	regs->ip = (unsigned long)&arch_rethook_trampoline;
     77	regs->orig_ax = ~0UL;
     78	regs->sp += 2*sizeof(long);
     79	frame_pointer = (long *)(regs + 1);
     80
     81	/*
     82	 * The return address at 'frame_pointer' is recovered by the
     83	 * arch_rethook_fixup_return() which called from this
     84	 * rethook_trampoline_handler().
     85	 */
     86	rethook_trampoline_handler(regs, (unsigned long)frame_pointer);
     87
     88	/*
     89	 * Copy FLAGS to 'pt_regs::ss' so that arch_rethook_trapmoline()
     90	 * can do RET right after POPF.
     91	 */
     92	*(unsigned long *)&regs->ss = regs->flags;
     93}
     94NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
     95
     96/*
     97 * arch_rethook_trampoline() skips updating frame pointer. The frame pointer
     98 * saved in arch_rethook_trampoline_callback() points to the real caller
     99 * function's frame pointer. Thus the arch_rethook_trampoline() doesn't have
    100 * a standard stack frame with CONFIG_FRAME_POINTER=y.
    101 * Let's mark it non-standard function. Anyway, FP unwinder can correctly
    102 * unwind without the hint.
    103 */
    104STACK_FRAME_NON_STANDARD_FP(arch_rethook_trampoline);
    105
    106/* This is called from rethook_trampoline_handler(). */
    107void arch_rethook_fixup_return(struct pt_regs *regs,
    108			       unsigned long correct_ret_addr)
    109{
    110	unsigned long *frame_pointer = (void *)(regs + 1);
    111
    112	/* Replace fake return address with real one. */
    113	*frame_pointer = correct_ret_addr;
    114}
    115NOKPROBE_SYMBOL(arch_rethook_fixup_return);
    116
    117void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
    118{
    119	unsigned long *stack = (unsigned long *)regs->sp;
    120
    121	rh->ret_addr = stack[0];
    122	rh->frame = regs->sp;
    123
    124	/* Replace the return addr with trampoline addr */
    125	stack[0] = (unsigned long) arch_rethook_trampoline;
    126}
    127NOKPROBE_SYMBOL(arch_rethook_prepare);