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ARM: rethook: Add rethook arm implementation

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Add rethook arm implementation. Most of the code has been copied from
kretprobes on arm.
Since the arm's ftrace implementation is a bit special, this needs a
special care using from fprobe.

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/164735289643.1084943.15184590256680485720.stgit@devnote2
This commit is contained in:
Masami Hiramatsu 2022-03-15 23:01:36 +09:00 committed by Alexei Starovoitov
parent 02752bd99d
commit 515a49173b
5 changed files with 113 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/arm/Kconfig
View File

@ -107,6 +107,7 @@ config ARM
select HAVE_MOD_ARCH_SPECIFIC
select HAVE_NMI
select HAVE_OPTPROBES if !THUMB2_KERNEL
select HAVE_RETHOOK
select HAVE_PERF_EVENTS
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP

4
arch/arm/include/asm/stacktrace.h
View File

@ -14,7 +14,7 @@ struct stackframe {
unsigned long sp;
unsigned long lr;
unsigned long pc;
#ifdef CONFIG_KRETPROBES
#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)
struct llist_node *kr_cur;
struct task_struct *tsk;
#endif
@ -27,7 +27,7 @@ void arm_get_current_stackframe(struct pt_regs *regs, struct stackframe *frame)
frame->sp = regs->ARM_sp;
frame->lr = regs->ARM_lr;
frame->pc = regs->ARM_pc;
#ifdef CONFIG_KRETPROBES
#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)
frame->kr_cur = NULL;
frame->tsk = current;
#endif

6
arch/arm/kernel/stacktrace.c
View File

@ -1,6 +1,7 @@
// SPDX-License-Identifier: GPL-2.0-only
#include <linux/export.h>
#include <linux/kprobes.h>
#include <linux/rethook.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/stacktrace.h>
@ -66,6 +67,11 @@ int notrace unwind_frame(struct stackframe *frame)
frame->sp = *(unsigned long *)(fp - 8);
frame->pc = *(unsigned long *)(fp - 4);
#endif
#ifdef CONFIG_RETHOOK
if (is_rethook_trampoline(frame->pc))
frame->pc = rethook_find_ret_addr(frame->tsk, frame->fp,
&frame->kr_cur);
#endif
#ifdef CONFIG_KRETPROBES
if (is_kretprobe_trampoline(frame->pc))
frame->pc = kretprobe_find_ret_addr(frame->tsk,

1
arch/arm/probes/Makefile
View File

@ -6,3 +6,4 @@ obj-$(CONFIG_KPROBES) += decode-thumb.o
else
obj-$(CONFIG_KPROBES) += decode-arm.o
endif
obj-$(CONFIG_RETHOOK) += rethook.o

103
arch/arm/probes/rethook.c Normal file
View File

@ -0,0 +1,103 @@
// SPDX-License-Identifier: GPL-2.0-only
/*
* arm implementation of rethook. Mostly copied from arch/arm/probes/kprobes/core.c
*/
#include <linux/kprobes.h>
#include <linux/rethook.h>
/* Called from arch_rethook_trampoline */
static __used unsigned long arch_rethook_trampoline_callback(struct pt_regs *regs)
{
return rethook_trampoline_handler(regs, regs->ARM_fp);
}
NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
/*
* When a rethook'ed function returns, it returns to arch_rethook_trampoline
* which calls rethook callback. We construct a struct pt_regs to
* give a view of registers r0-r11, sp, lr, and pc to the user
* return-handler. This is not a complete pt_regs structure, but that
* should be enough for stacktrace from the return handler with or
* without pt_regs.
*/
asm(
".text\n"
".global arch_rethook_trampoline\n"
".type arch_rethook_trampoline, %function\n"
"arch_rethook_trampoline:\n"
#ifdef CONFIG_FRAME_POINTER
"ldr lr, =arch_rethook_trampoline \n\t"
/* this makes a framepointer on pt_regs. */
#ifdef CONFIG_CC_IS_CLANG
"stmdb sp, {sp, lr, pc} \n\t"
"sub sp, sp, #12 \n\t"
/* In clang case, pt_regs->ip = lr. */
"stmdb sp!, {r0 - r11, lr} \n\t"
/* fp points regs->r11 (fp) */
"add fp, sp, #44 \n\t"
#else /* !CONFIG_CC_IS_CLANG */
/* In gcc case, pt_regs->ip = fp. */
"stmdb sp, {fp, sp, lr, pc} \n\t"
"sub sp, sp, #16 \n\t"
"stmdb sp!, {r0 - r11} \n\t"
/* fp points regs->r15 (pc) */
"add fp, sp, #60 \n\t"
#endif /* CONFIG_CC_IS_CLANG */
#else /* !CONFIG_FRAME_POINTER */
"sub sp, sp, #16 \n\t"
"stmdb sp!, {r0 - r11} \n\t"
#endif /* CONFIG_FRAME_POINTER */
"mov r0, sp \n\t"
"bl arch_rethook_trampoline_callback \n\t"
"mov lr, r0 \n\t"
"ldmia sp!, {r0 - r11} \n\t"
"add sp, sp, #16 \n\t"
#ifdef CONFIG_THUMB2_KERNEL
"bx lr \n\t"
#else
"mov pc, lr \n\t"
#endif
".size arch_rethook_trampoline, .-arch_rethook_trampoline\n"
);
NOKPROBE_SYMBOL(arch_rethook_trampoline);
/*
* At the entry of function with mcount. The stack and registers are prepared
* for the mcount function as below.
*
* mov ip, sp
* push {fp, ip, lr, pc}
* sub fp, ip, #4 ; FP[0] = PC, FP[-4] = LR, and FP[-12] = call-site FP.
* push {lr}
* bl <__gnu_mcount_nc> ; call ftrace
*
* And when returning from the function, call-site FP, SP and PC are restored
* from stack as below;
*
* ldm sp, {fp, sp, pc}
*
* Thus, if the arch_rethook_prepare() is called from real function entry,
* it must change the LR and save FP in pt_regs. But if it is called via
* mcount context (ftrace), it must change the LR on stack, which is next
* to the PC (= FP[-4]), and save the FP value at FP[-12].
*/
void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
{
unsigned long *ret_addr, *frame;
if (mcount) {
ret_addr = (unsigned long *)(regs->ARM_fp - 4);
frame = (unsigned long *)(regs->ARM_fp - 12);
} else {
ret_addr = &regs->ARM_lr;
frame = &regs->ARM_fp;
}
rh->ret_addr = *ret_addr;
rh->frame = *frame;
/* Replace the return addr with trampoline addr. */
*ret_addr = (unsigned long)arch_rethook_trampoline;
}
NOKPROBE_SYMBOL(arch_rethook_prepare);