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ARM: rethook: Add rethook arm implementation
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 <[email protected]> Signed-off-by: Steven Rostedt (Google) <[email protected]> Tested-by: Steven Rostedt (Google) <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/bpf/164735289643.1084943.15184590256680485720.stgit@devnote2
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -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 = ®s->ARM_lr; | ||
| frame = ®s->ARM_fp; | ||
| } | ||
|
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| rh->ret_addr = *ret_addr; | ||
| rh->frame = *frame; | ||
|
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| /* Replace the return addr with trampoline addr. */ | ||
| *ret_addr = (unsigned long)arch_rethook_trampoline; | ||
| } | ||
| NOKPROBE_SYMBOL(arch_rethook_prepare); |