rethook: x86: Add rethook x86 implementation

Add rethook for x86 implementation. Most of the code has been copied from
kretprobes on x86.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164735286243.1084943.7477055110527046644.stgit@devnote2

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 9b356da..1270b65 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -221,6 +221,7 @@ 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 2a1f873..192df5b 100644 (file)
--- 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 6aef9ee..792a893 100644 (file)
--- 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 7d3a2e2..c993521 100644 (file)
--- 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 (file)
index 0000000..f0f2f06
--- /dev/null
+++ b/arch/x86/kernel/rethook.c
@@ -0,0 +1,119 @@
+// 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"
+
+__visible void arch_rethook_trampoline_callback(struct pt_regs *regs);
+
+/*
+ * 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);
+
+/*
+ * 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);
+
+/*
+ * 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;
+}
+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);