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Commit ae30cc05 authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Michael Ellerman
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powerpc64/ftrace: Implement support for ftrace_regs_caller() 



With -mprofile-kernel, we always save the full register state in
ftrace_caller(). While this works, this is inefficient if we're not
interested in the register state, such as when we're using the function
tracer.

Rename the existing ftrace_caller() as ftrace_regs_caller() and provide
a simpler implementation for ftrace_caller() that is used when registers
are not required to be saved.

Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 9ef40423

arch/powerpc/include/asm/ftrace.h

+0 −2
Original line number Diff line number Diff line
@@ -49,8 +49,6 @@ 
extern void _mcount(void);



#ifdef CONFIG_DYNAMIC_FTRACE

# define FTRACE_ADDR ((unsigned long)ftrace_caller)

# define FTRACE_REGS_ADDR FTRACE_ADDR

static inline unsigned long ftrace_call_adjust(unsigned long addr)

{

       /* reloction of mcount call site is the same as the address */

arch/powerpc/include/asm/module.h

+3 −0
Original line number Diff line number Diff line
@@ -53,6 +53,9 @@ struct mod_arch_specific { 
#ifdef CONFIG_DYNAMIC_FTRACE

	unsigned long toc;

	unsigned long tramp;

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

	unsigned long tramp_regs;

#endif

#endif



	/* For module function descriptor dereference */

arch/powerpc/kernel/module_64.c

+21 −7
Original line number Diff line number Diff line
@@ -280,6 +280,10 @@ static unsigned long get_stubs_size(const Elf64_Ehdr *hdr, 
#ifdef CONFIG_DYNAMIC_FTRACE

	/* make the trampoline to the ftrace_caller */

	relocs++;

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

	/* an additional one for ftrace_regs_caller */

	relocs++;

#endif

#endif



	pr_debug("Looks like a total of %lu stubs, max\n", relocs);
@@ -765,7 +769,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, 
 * via the paca (in r13). The target (ftrace_caller()) is responsible for

 * saving and restoring the toc before returning.

 */

static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module *me)

static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs,

				struct module *me, unsigned long addr)

{

	struct ppc64_stub_entry *entry;

	unsigned int i, num_stubs;
@@ -792,9 +797,10 @@ static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module 
	memcpy(entry->jump, stub_insns, sizeof(stub_insns));



	/* Stub uses address relative to kernel toc (from the paca) */

	reladdr = (unsigned long)ftrace_caller - kernel_toc_addr();

	reladdr = addr - kernel_toc_addr();

	if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {

		pr_err("%s: Address of ftrace_caller out of range of kernel_toc.\n", me->name);

		pr_err("%s: Address of %ps out of range of kernel_toc.\n",

							me->name, (void *)addr);

		return 0;

	}
@@ -802,22 +808,30 @@ static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module 
	entry->jump[2] |= PPC_LO(reladdr);



	/* Eventhough we don't use funcdata in the stub, it's needed elsewhere. */

	entry->funcdata = func_desc((unsigned long)ftrace_caller);

	entry->funcdata = func_desc(addr);

	entry->magic = STUB_MAGIC;



	return (unsigned long)entry;

}

#else

static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module *me)

static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs,

				struct module *me, unsigned long addr)

{

	return stub_for_addr(sechdrs, (unsigned long)ftrace_caller, me);

	return stub_for_addr(sechdrs, addr, me);

}

#endif



int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)

{

	mod->arch.toc = my_r2(sechdrs, mod);

	mod->arch.tramp = create_ftrace_stub(sechdrs, mod);

	mod->arch.tramp = create_ftrace_stub(sechdrs, mod,

					(unsigned long)ftrace_caller);

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

	mod->arch.tramp_regs = create_ftrace_stub(sechdrs, mod,

					(unsigned long)ftrace_regs_caller);

	if (!mod->arch.tramp_regs)

		return -ENOENT;

#endif



	if (!mod->arch.tramp)

		return -ENOENT;

arch/powerpc/kernel/trace/ftrace.c

+172 −12
Original line number Diff line number Diff line
@@ -357,6 +357,8 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 
{

	unsigned int op[2];

	void *ip = (void *)rec->ip;

	unsigned long entry, ptr, tramp;

	struct module *mod = rec->arch.mod;



	/* read where this goes */

	if (probe_kernel_read(op, ip, sizeof(op)))
@@ -368,19 +370,44 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 
		return -EINVAL;

	}



	/* If we never set up a trampoline to ftrace_caller, then bail */

	if (!rec->arch.mod->arch.tramp) {

	/* If we never set up ftrace trampoline(s), then bail */

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

	if (!mod->arch.tramp || !mod->arch.tramp_regs) {

#else

	if (!mod->arch.tramp) {

#endif

		pr_err("No ftrace trampoline\n");

		return -EINVAL;

	}



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

	if (rec->flags & FTRACE_FL_REGS)

		tramp = mod->arch.tramp_regs;

	else

#endif

		tramp = mod->arch.tramp;



	if (module_trampoline_target(mod, tramp, &ptr)) {

		pr_err("Failed to get trampoline target\n");

		return -EFAULT;

	}



	pr_devel("trampoline target %lx", ptr);



	entry = ppc_global_function_entry((void *)addr);

	/* This should match what was called */

	if (ptr != entry) {

		pr_err("addr %lx does not match expected %lx\n", ptr, entry);

		return -EINVAL;

	}



	/* Ensure branch is within 24 bits */

	if (!create_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {

	if (!create_branch(ip, tramp, BRANCH_SET_LINK)) {

		pr_err("Branch out of range\n");

		return -EINVAL;

	}



	if (patch_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {

	if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {

		pr_err("REL24 out of range!\n");

		return -EINVAL;

	}
@@ -388,14 +415,6 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 
	return 0;

}



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,

			unsigned long addr)

{

	return ftrace_make_call(rec, addr);

}

#endif



#else  /* !CONFIG_PPC64: */

static int

__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
@@ -472,6 +491,137 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 
#endif /* CONFIG_MODULES */

}



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

#ifdef CONFIG_MODULES

static int

__ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,

					unsigned long addr)

{

	unsigned int op;

	unsigned long ip = rec->ip;

	unsigned long entry, ptr, tramp;

	struct module *mod = rec->arch.mod;



	/* If we never set up ftrace trampolines, then bail */

	if (!mod->arch.tramp || !mod->arch.tramp_regs) {

		pr_err("No ftrace trampoline\n");

		return -EINVAL;

	}



	/* read where this goes */

	if (probe_kernel_read(&op, (void *)ip, sizeof(int))) {

		pr_err("Fetching opcode failed.\n");

		return -EFAULT;

	}



	/* Make sure that that this is still a 24bit jump */

	if (!is_bl_op(op)) {

		pr_err("Not expected bl: opcode is %x\n", op);

		return -EINVAL;

	}



	/* lets find where the pointer goes */

	tramp = find_bl_target(ip, op);

	entry = ppc_global_function_entry((void *)old_addr);



	pr_devel("ip:%lx jumps to %lx", ip, tramp);



	if (tramp != entry) {

		/* old_addr is not within range, so we must have used a trampoline */

		if (module_trampoline_target(mod, tramp, &ptr)) {

			pr_err("Failed to get trampoline target\n");

			return -EFAULT;

		}



		pr_devel("trampoline target %lx", ptr);



		/* This should match what was called */

		if (ptr != entry) {

			pr_err("addr %lx does not match expected %lx\n", ptr, entry);

			return -EINVAL;

		}

	}



	/* The new target may be within range */

	if (test_24bit_addr(ip, addr)) {

		/* within range */

		if (patch_branch((unsigned int *)ip, addr, BRANCH_SET_LINK)) {

			pr_err("REL24 out of range!\n");

			return -EINVAL;

		}



		return 0;

	}



	if (rec->flags & FTRACE_FL_REGS)

		tramp = mod->arch.tramp_regs;

	else

		tramp = mod->arch.tramp;



	if (module_trampoline_target(mod, tramp, &ptr)) {

		pr_err("Failed to get trampoline target\n");

		return -EFAULT;

	}



	pr_devel("trampoline target %lx", ptr);



	entry = ppc_global_function_entry((void *)addr);

	/* This should match what was called */

	if (ptr != entry) {

		pr_err("addr %lx does not match expected %lx\n", ptr, entry);

		return -EINVAL;

	}



	/* Ensure branch is within 24 bits */

	if (!create_branch((unsigned int *)ip, tramp, BRANCH_SET_LINK)) {

		pr_err("Branch out of range\n");

		return -EINVAL;

	}



	if (patch_branch((unsigned int *)ip, tramp, BRANCH_SET_LINK)) {

		pr_err("REL24 out of range!\n");

		return -EINVAL;

	}



	return 0;

}

#endif



int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,

			unsigned long addr)

{

	unsigned long ip = rec->ip;

	unsigned int old, new;



	/*

	 * If the calling address is more that 24 bits away,

	 * then we had to use a trampoline to make the call.

	 * Otherwise just update the call site.

	 */

	if (test_24bit_addr(ip, addr) && test_24bit_addr(ip, old_addr)) {

		/* within range */

		old = ftrace_call_replace(ip, old_addr, 1);

		new = ftrace_call_replace(ip, addr, 1);

		return ftrace_modify_code(ip, old, new);

	}



#ifdef CONFIG_MODULES

	/*

	 * Out of range jumps are called from modules.

	 */

	if (!rec->arch.mod) {

		pr_err("No module loaded\n");

		return -EINVAL;

	}



	return __ftrace_modify_call(rec, old_addr, addr);

#else

	/* We should not get here without modules */

	return -EINVAL;

#endif /* CONFIG_MODULES */

}

#endif



int ftrace_update_ftrace_func(ftrace_func_t func)

{

	unsigned long ip = (unsigned long)(&ftrace_call);
@@ -482,6 +632,16 @@ int ftrace_update_ftrace_func(ftrace_func_t func) 
	new = ftrace_call_replace(ip, (unsigned long)func, 1);

	ret = ftrace_modify_code(ip, old, new);



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

	/* Also update the regs callback function */

	if (!ret) {

		ip = (unsigned long)(&ftrace_regs_call);

		old = *(unsigned int *)&ftrace_regs_call;

		new = ftrace_call_replace(ip, (unsigned long)func, 1);

		ret = ftrace_modify_code(ip, old, new);

	}

#endif



	return ret;

}

arch/powerpc/kernel/trace/ftrace_64_mprofile.S

+66 −5
Original line number Diff line number Diff line
@@ -20,8 +20,8 @@ 
#ifdef CONFIG_DYNAMIC_FTRACE

/*

 *

 * ftrace_caller() is the function that replaces _mcount() when ftrace is

 * active.

 * ftrace_caller()/ftrace_regs_caller() is the function that replaces _mcount()

 * when ftrace is active.

 *

 * We arrive here after a function A calls function B, and we are the trace

 * function for B. When we enter r1 points to A's stack frame, B has not yet
@@ -37,7 +37,7 @@ 
 * Our job is to save the register state into a struct pt_regs (on the stack)

 * and then arrange for the ftrace function to be called.

 */

_GLOBAL(ftrace_caller)

_GLOBAL(ftrace_regs_caller)

	/* Save the original return address in A's stack frame */

	std	r0,LRSAVE(r1)
@@ -100,8 +100,8 @@ _GLOBAL(ftrace_caller) 
	addi    r6, r1 ,STACK_FRAME_OVERHEAD



	/* ftrace_call(r3, r4, r5, r6) */

.globl ftrace_call

ftrace_call:

.globl ftrace_regs_call

ftrace_regs_call:

	bl	ftrace_stub

	nop
@@ -162,6 +162,7 @@ ftrace_call: 
	bne-	livepatch_handler

#endif



ftrace_caller_common:

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

.globl ftrace_graph_call

ftrace_graph_call:
@@ -182,6 +183,66 @@ ftrace_no_trace: 
	mtlr	r0

	bctr



_GLOBAL(ftrace_caller)

	/* Save the original return address in A's stack frame */

	std	r0, LRSAVE(r1)



	/* Create our stack frame + pt_regs */

	stdu	r1, -SWITCH_FRAME_SIZE(r1)



	/* Save all gprs to pt_regs */

	SAVE_8GPRS(3, r1)



	lbz	r3, PACA_FTRACE_ENABLED(r13)

	cmpdi	r3, 0

	beq	ftrace_no_trace



	/* Get the _mcount() call site out of LR */

	mflr	r7

	std     r7, _NIP(r1)



	/* Save callee's TOC in the ABI compliant location */

	std	r2, 24(r1)

	ld	r2, PACATOC(r13)	/* get kernel TOC in r2 */



	addis	r3, r2, function_trace_op@toc@ha

	addi	r3, r3, function_trace_op@toc@l

	ld	r5, 0(r3)



	/* Calculate ip from nip-4 into r3 for call below */

	subi    r3, r7, MCOUNT_INSN_SIZE



	/* Put the original return address in r4 as parent_ip */

	mr	r4, r0



	/* Set pt_regs to NULL */

	li	r6, 0



	/* ftrace_call(r3, r4, r5, r6) */

.globl ftrace_call

ftrace_call:

	bl	ftrace_stub

	nop



	ld	r3, _NIP(r1)

	mtctr	r3



	/* Restore gprs */

	REST_8GPRS(3,r1)



	/* Restore callee's TOC */

	ld	r2, 24(r1)



	/* Pop our stack frame */

	addi	r1, r1, SWITCH_FRAME_SIZE



	/* Reload original LR */

	ld	r0, LRSAVE(r1)

	mtlr	r0



	/* Handle function_graph or go back */

	b	ftrace_caller_common



#ifdef CONFIG_LIVEPATCH

	/*

	 * This function runs in the mcount context, between two functions. As