0ef6f5c093
Currently arch_rethook_trampoline() generates an almost complete pt_regs on-stack, everything except regs->ss that is, that currently points to the fake return address, which is not a valid segment descriptor. Since interpretation of regs->[sb]p should be done in the context of regs->ss, and we have code actually doing that (see arch/x86/lib/insn-eval.c for instance), complete the job by also pushing ss. This ensures that anybody who does do look at regs->ss doesn't mysteriously malfunction, avoiding much future pain. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Link: https://lore.kernel.org/bpf/164826164851.2455864.17272661073069737350.stgit@devnote2
128 lines
3.7 KiB
C
128 lines
3.7 KiB
C
// 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);
|