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- // 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 /* 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 *)®s->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);
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