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    Subject[PATCH v5 4/9] rethook: x86: Add rethook x86 implementation
    Date
    Add rethook for x86 implementation. Most of the code
    has been copied from kretprobes on x86.

    Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
    ---
    Changes in v5:
    - Fix a build error if !CONFIG_KRETPROBES and !CONFIG_RETHOOK.
    Changes in v4:
    - fix stack backtrace as same as kretprobe does.
    ---
    arch/x86/Kconfig | 1
    arch/x86/include/asm/unwind.h | 8 ++-
    arch/x86/kernel/Makefile | 1
    arch/x86/kernel/kprobes/common.h | 1
    arch/x86/kernel/rethook.c | 115 ++++++++++++++++++++++++++++++++++++++
    5 files changed, 125 insertions(+), 1 deletion(-)
    create mode 100644 arch/x86/kernel/rethook.c

    diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    index 5c2ccb85f2ef..0a7d48a63787 100644
    --- a/arch/x86/Kconfig
    +++ b/arch/x86/Kconfig
    @@ -219,6 +219,7 @@ config X86
    select HAVE_KPROBES_ON_FTRACE
    select HAVE_FUNCTION_ERROR_INJECTION
    select HAVE_KRETPROBES
    + select HAVE_RETHOOK
    select HAVE_KVM
    select HAVE_LIVEPATCH if X86_64
    select HAVE_MIXED_BREAKPOINTS_REGS
    diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
    index 2a1f8734416d..192df5b2094d 100644
    --- a/arch/x86/include/asm/unwind.h
    +++ b/arch/x86/include/asm/unwind.h
    @@ -5,6 +5,7 @@
    #include <linux/sched.h>
    #include <linux/ftrace.h>
    #include <linux/kprobes.h>
    +#include <linux/rethook.h>
    #include <asm/ptrace.h>
    #include <asm/stacktrace.h>

    @@ -16,7 +17,7 @@ struct unwind_state {
    unsigned long stack_mask;
    struct task_struct *task;
    int graph_idx;
    -#ifdef CONFIG_KRETPROBES
    +#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)
    struct llist_node *kr_cur;
    #endif
    bool error;
    @@ -107,6 +108,11 @@ static inline
    unsigned long unwind_recover_kretprobe(struct unwind_state *state,
    unsigned long addr, unsigned long *addr_p)
    {
    +#ifdef CONFIG_RETHOOK
    + if (is_rethook_trampoline(addr))
    + return rethook_find_ret_addr(state->task, (unsigned long)addr_p,
    + &state->kr_cur);
    +#endif
    #ifdef CONFIG_KRETPROBES
    return is_kretprobe_trampoline(addr) ?
    kretprobe_find_ret_addr(state->task, addr_p, &state->kr_cur) :
    diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
    index 2ff3e600f426..66593d8c4d74 100644
    --- a/arch/x86/kernel/Makefile
    +++ b/arch/x86/kernel/Makefile
    @@ -106,6 +106,7 @@ obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
    obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.o
    obj-$(CONFIG_X86_TSC) += trace_clock.o
    obj-$(CONFIG_TRACING) += trace.o
    +obj-$(CONFIG_RETHOOK) += rethook.o
    obj-$(CONFIG_CRASH_CORE) += crash_core_$(BITS).o
    obj-$(CONFIG_KEXEC_CORE) += machine_kexec_$(BITS).o
    obj-$(CONFIG_KEXEC_CORE) += relocate_kernel_$(BITS).o crash.o
    diff --git a/arch/x86/kernel/kprobes/common.h b/arch/x86/kernel/kprobes/common.h
    index 7d3a2e2daf01..c993521d4933 100644
    --- a/arch/x86/kernel/kprobes/common.h
    +++ b/arch/x86/kernel/kprobes/common.h
    @@ -6,6 +6,7 @@

    #include <asm/asm.h>
    #include <asm/frame.h>
    +#include <asm/insn.h>

    #ifdef CONFIG_X86_64

    diff --git a/arch/x86/kernel/rethook.c b/arch/x86/kernel/rethook.c
    new file mode 100644
    index 000000000000..f2f3b9526e43
    --- /dev/null
    +++ b/arch/x86/kernel/rethook.c
    @@ -0,0 +1,115 @@
    +// 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 "kprobes/common.h"
    +
    +/*
    + * 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 += sizeof(long);
    + frame_pointer = &regs->sp + 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::sp' so that arch_rethook_trapmoline()
    + * can do RET right after POPF.
    + */
    + regs->sp = regs->flags;
    +}
    +NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
    +
    +/*
    + * 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
    + /* Push a fake return address to tell the unwinder it's a kretprobe. */
    + " pushq $arch_rethook_trampoline\n"
    + UNWIND_HINT_FUNC
    + /* Save the 'sp - 8', 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->sp'. */
    + " addq $8, %rsp\n"
    + " popfq\n"
    +#else
    + /* Push a fake return address to tell the unwinder it's a kretprobe. */
    + " pushl $arch_rethook_trampoline\n"
    + UNWIND_HINT_FUNC
    + /* Save the 'sp - 4', 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->sp'. */
    + " addl $4, %esp\n"
    + " popfl\n"
    +#endif
    + " ret\n"
    + ".size arch_rethook_trampoline, .-arch_rethook_trampoline\n"
    +);
    +NOKPROBE_SYMBOL(arch_rethook_trampoline);
    +/*
    + * 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 = &regs->sp + 1;
    +
    + /* Replace fake return address with real one. */
    + *frame_pointer = correct_ret_addr;
    +}
    +
    +void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs)
    +{
    + 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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