Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 23c7d70d authored by Jean Pihet's avatar Jean Pihet Committed by Catalin Marinas
Browse files

ARM64: perf: add support for frame pointer unwinding in compat mode 



When profiling a 32-bit application, user space callchain unwinding
using the frame pointer is performed in compat mode. The code is taken
over from the AARCH32 code and adapted to work on AARCH64.

Signed-off-by: default avatarJean Pihet <jean.pihet@linaro.org>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 2ee0d7fd

arch/arm64/kernel/perf_event.c

+67 −8
Original line number Diff line number Diff line
@@ -1386,22 +1386,80 @@ user_backtrace(struct frame_tail __user *tail, 
	return buftail.fp;

}



/*

 * The registers we're interested in are at the end of the variable

 * length saved register structure. The fp points at the end of this

 * structure so the address of this struct is:

 * (struct compat_frame_tail *)(xxx->fp)-1

 *

 * This code has been adapted from the ARM OProfile support.

 */

struct compat_frame_tail {

	compat_uptr_t	fp; /* a (struct compat_frame_tail *) in compat mode */

	u32		sp;

	u32		lr;

} __attribute__((packed));



static struct compat_frame_tail __user *

compat_user_backtrace(struct compat_frame_tail __user *tail,

		      struct perf_callchain_entry *entry)

{

	struct compat_frame_tail buftail;

	unsigned long err;



	/* Also check accessibility of one struct frame_tail beyond */

	if (!access_ok(VERIFY_READ, tail, sizeof(buftail)))

		return NULL;



	pagefault_disable();

	err = __copy_from_user_inatomic(&buftail, tail, sizeof(buftail));

	pagefault_enable();



	if (err)

		return NULL;



	perf_callchain_store(entry, buftail.lr);



	/*

	 * Frame pointers should strictly progress back up the stack

	 * (towards higher addresses).

	 */

	if (tail + 1 >= (struct compat_frame_tail __user *)

			compat_ptr(buftail.fp))

		return NULL;



	return (struct compat_frame_tail __user *)compat_ptr(buftail.fp) - 1;

}



void perf_callchain_user(struct perf_callchain_entry *entry,

			 struct pt_regs *regs)

{

	struct frame_tail __user *tail;



	if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {

		/* We don't support guest os callchain now */

		return;

	}



	perf_callchain_store(entry, regs->pc);



	if (!compat_user_mode(regs)) {

		/* AARCH64 mode */

		struct frame_tail __user *tail;



		tail = (struct frame_tail __user *)regs->regs[29];



		while (entry->nr < PERF_MAX_STACK_DEPTH &&

		       tail && !((unsigned long)tail & 0xf))

			tail = user_backtrace(tail, entry);

	} else {

		/* AARCH32 compat mode */

		struct compat_frame_tail __user *tail;



		tail = (struct compat_frame_tail __user *)regs->compat_fp - 1;



		while ((entry->nr < PERF_MAX_STACK_DEPTH) &&

			tail && !((unsigned long)tail & 0x3))

			tail = compat_user_backtrace(tail, entry);

	}

}



/*
@@ -1429,6 +1487,7 @@ void perf_callchain_kernel(struct perf_callchain_entry *entry, 
	frame.fp = regs->regs[29];

	frame.sp = regs->sp;

	frame.pc = regs->pc;



	walk_stackframe(&frame, callchain_trace, entry);

}