Commit cc93b923 authored by Naveen N Rao's avatar Naveen N Rao Committed by Michael Ellerman
Browse files

powerpc/ftrace: Add separate ftrace_init_nop() with additional validation 



Currently, we validate instructions around the ftrace location every
time we have to enable/disable ftrace. Introduce ftrace_init_nop() to
instead perform all the validation during ftrace initialization. This
allows us to simply patch the necessary instructions during
enabling/disabling ftrace.

Signed-off-by: default avatarNaveen N Rao <naveen@kernel.org>
Reviewed-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/f373684081e8e98be09b7f44d2d93069768324dc.1687166935.git.naveen@kernel.org
parent 33bb8a0b

arch/powerpc/include/asm/ftrace.h

+6 −0
Original line number Diff line number Diff line
@@ -29,11 +29,17 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr) 
unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,

				    unsigned long sp);



struct module;

struct dyn_ftrace;

struct dyn_arch_ftrace {

	struct module *mod;

};



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS

#define ftrace_need_init_nop()	(true)

int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);

#define ftrace_init_nop ftrace_init_nop



struct ftrace_regs {

	struct pt_regs regs;

};

arch/powerpc/kernel/trace/ftrace.c

+71 −0
Original line number Diff line number Diff line
@@ -31,6 +31,16 @@ 
#define	NUM_FTRACE_TRAMPS	2

static unsigned long ftrace_tramps[NUM_FTRACE_TRAMPS];



static ppc_inst_t ftrace_create_branch_inst(unsigned long ip, unsigned long addr, int link)

{

	ppc_inst_t op;



	WARN_ON(!is_offset_in_branch_range(addr - ip));

	create_branch(&op, (u32 *)ip, addr, link ? BRANCH_SET_LINK : 0);



	return op;

}



static ppc_inst_t

ftrace_call_replace(unsigned long ip, unsigned long addr, int link)

{
@@ -597,6 +607,67 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, 
}

#endif



int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)

{

	unsigned long addr, ip = rec->ip;

	ppc_inst_t old, new;

	int ret = 0;



	/* Verify instructions surrounding the ftrace location */

	if (IS_ENABLED(CONFIG_PPC32)) {

		/* Expected sequence: 'mflr r0', 'stw r0,4(r1)', 'bl _mcount' */

		ret = ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0)));

		if (!ret)

			ret = ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_STW(_R0, _R1, 4)));

	} else if (IS_ENABLED(CONFIG_MPROFILE_KERNEL)) {

		/* Expected sequence: 'mflr r0', ['std r0,16(r1)'], 'bl _mcount' */

		ret = ftrace_read_inst(ip - 4, &old);

		if (!ret && !ppc_inst_equal(old, ppc_inst(PPC_RAW_MFLR(_R0)))) {

			ret = ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0)));

			ret |= ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_STD(_R0, _R1, 16)));

		}

	} else {

		return -EINVAL;

	}



	if (ret)

		return ret;



	if (!core_kernel_text(ip)) {

		if (!mod) {

			pr_err("0x%lx: No module provided for non-kernel address\n", ip);

			return -EFAULT;

		}

		rec->arch.mod = mod;

	}



	/* Nop-out the ftrace location */

	new = ppc_inst(PPC_RAW_NOP());

	addr = MCOUNT_ADDR;

	if (is_offset_in_branch_range(addr - ip)) {

		/* Within range */

		old = ftrace_create_branch_inst(ip, addr, 1);

		ret = ftrace_modify_code(ip, old, new);

	} else if (core_kernel_text(ip) || (IS_ENABLED(CONFIG_MODULES) && mod)) {

		/*

		 * We would be branching to a linker-generated stub, or to the module _mcount

		 * stub. Let's just confirm we have a 'bl' here.

		 */

		ret = ftrace_read_inst(ip, &old);

		if (ret)

			return ret;

		if (!is_bl_op(old)) {

			pr_err("0x%lx: expected (bl) != found (%08lx)\n", ip, ppc_inst_as_ulong(old));

			return -EINVAL;

		}

		ret = patch_instruction((u32 *)ip, new);

	} else {

		return -EINVAL;

	}



	return ret;

}



int ftrace_update_ftrace_func(ftrace_func_t func)

{

	unsigned long ip = (unsigned long)(&ftrace_call);