Commit 7dfbfb87 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/ftrace: Activate HAVE_DYNAMIC_FTRACE_WITH_REGS on PPC32 



Unlike PPC64, PPC32 doesn't require any special compiler option
to get _mcount() call not clobbering registers.

Provide ftrace_regs_caller() and ftrace_regs_call() and activate
HAVE_DYNAMIC_FTRACE_WITH_REGS.

That's heavily copied from ftrace_64_mprofile.S

For the time being leave livepatching aside, it will come with
following patch.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1862dc7719855cc2a4eec80920d94c955877557e.1635423081.git.christophe.leroy@csgroup.eu
parent c93d4f6e

arch/powerpc/Kconfig

+2 −2
Original line number Diff line number Diff line
@@ -206,7 +206,7 @@ config PPC 
	select HAVE_DEBUG_KMEMLEAK

	select HAVE_DEBUG_STACKOVERFLOW

	select HAVE_DYNAMIC_FTRACE

	select HAVE_DYNAMIC_FTRACE_WITH_REGS	if MPROFILE_KERNEL

	select HAVE_DYNAMIC_FTRACE_WITH_REGS	if MPROFILE_KERNEL || PPC32

	select HAVE_EBPF_JIT

	select HAVE_EFFICIENT_UNALIGNED_ACCESS	if !(CPU_LITTLE_ENDIAN && POWER7_CPU)

	select HAVE_FAST_GUP
@@ -230,7 +230,7 @@ config PPC 
	select HAVE_KPROBES_ON_FTRACE

	select HAVE_KRETPROBES

	select HAVE_LD_DEAD_CODE_DATA_ELIMINATION

	select HAVE_LIVEPATCH			if HAVE_DYNAMIC_FTRACE_WITH_REGS

	select HAVE_LIVEPATCH			if HAVE_DYNAMIC_FTRACE_WITH_REGS && PPC64

	select HAVE_MOD_ARCH_SPECIFIC

	select HAVE_NMI				if PERF_EVENTS || (PPC64 && PPC_BOOK3S)

	select HAVE_OPTPROBES

arch/powerpc/kernel/module_32.c

+8 −0
Original line number Diff line number Diff line
@@ -306,6 +306,14 @@ int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs) 
	if (!module->arch.tramp)

		return -ENOENT;



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS

	module->arch.tramp_regs = do_plt_call(module->core_layout.base,

					      (unsigned long)ftrace_regs_caller,

					      sechdrs, module);

	if (!module->arch.tramp_regs)

		return -ENOENT;

#endif



	return 0;

}

#endif

arch/powerpc/kernel/trace/ftrace.c

+14 −2
Original line number Diff line number Diff line
@@ -561,6 +561,8 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 
	int err;

	struct ppc_inst op;

	u32 *ip = (u32 *)rec->ip;

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

	unsigned long tramp;



	/* read where this goes */

	if (copy_inst_from_kernel_nofault(&op, ip))
@@ -573,13 +575,23 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 
	}



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

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

#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;

	/* create the branch to the trampoline */

	err = create_branch(&op, ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK);

	err = create_branch(&op, ip, tramp, BRANCH_SET_LINK);

	if (err) {

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

		return -EINVAL;

arch/powerpc/kernel/trace/ftrace_32.S

+101 −8
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 
#include <asm/asm-offsets.h>

#include <asm/ftrace.h>

#include <asm/export.h>

#include <asm/ptrace.h>



_GLOBAL(mcount)

_GLOBAL(_mcount)
@@ -29,17 +30,21 @@ _GLOBAL(ftrace_caller) 
	MCOUNT_SAVE_FRAME

	/* r3 ends up with link register */

	subi	r3, r3, MCOUNT_INSN_SIZE

	lis	r5,function_trace_op@ha

	lwz	r5,function_trace_op@l(r5)

	li	r6, 0

.globl ftrace_call

ftrace_call:

	bl	ftrace_stub

	nop

	MCOUNT_RESTORE_FRAME

ftrace_caller_common:

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

.globl ftrace_graph_call

ftrace_graph_call:

	b	ftrace_graph_stub

_GLOBAL(ftrace_graph_stub)

#endif

	MCOUNT_RESTORE_FRAME

	/* old link register ends up in ctr reg */

	bctr
@@ -47,16 +52,92 @@ _GLOBAL(ftrace_graph_stub) 
_GLOBAL(ftrace_stub)

	blr



_GLOBAL(ftrace_regs_caller)

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

	stw	r0,LRSAVE(r1)



	/* Create our stack frame + pt_regs */

	stwu	r1,-INT_FRAME_SIZE(r1)



	/* Save all gprs to pt_regs */

	stw	r0, GPR0(r1)

	stmw	r2, GPR2(r1)



	/* Save previous stack pointer (r1) */

	addi	r8, r1, INT_FRAME_SIZE

	stw	r8, GPR1(r1)



	/* Load special regs for save below */

	mfmsr   r8

	mfctr   r9

	mfxer   r10

	mfcr	r11



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

	mflr	r7

	/* Save it as pt_regs->nip */

	stw     r7, _NIP(r1)

	/* Save the read LR in pt_regs->link */

	stw     r0, _LINK(r1)



	lis	r3,function_trace_op@ha

	lwz	r5,function_trace_op@l(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



	/* Save special regs */

	stw     r8, _MSR(r1)

	stw     r9, _CTR(r1)

	stw     r10, _XER(r1)

	stw     r11, _CCR(r1)



	/* Load &pt_regs in r6 for call below */

	addi    r6, r1, STACK_FRAME_OVERHEAD



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

.globl ftrace_regs_call

ftrace_regs_call:

	bl	ftrace_stub

	nop



	/* Load ctr with the possibly modified NIP */

	lwz	r3, _NIP(r1)

	mtctr	r3



	/* Restore gprs */

	lmw	r2, GPR2(r1)



	/* Restore possibly modified LR */

	lwz	r0, _LINK(r1)

	mtlr	r0



	/* Pop our stack frame */

	addi r1, r1, INT_FRAME_SIZE



	b	ftrace_caller_common



#ifdef CONFIG_FUNCTION_GRAPH_TRACER

_GLOBAL(ftrace_graph_caller)

	stwu	r1,-48(r1)

	stw	r3, 12(r1)

	stw	r4, 16(r1)

	stw	r5, 20(r1)

	stw	r6, 24(r1)

	stw	r7, 28(r1)

	stw	r8, 32(r1)

	stw	r9, 36(r1)

	stw	r10,40(r1)



	addi	r5, r1, 48

	/* load r4 with local address */

	lwz	r4, 44(r1)

	mfctr	r4		/* ftrace_caller has moved local addr here */

	stw	r4, 44(r1)

	mflr	r3		/* ftrace_caller has restored LR from stack */

	subi	r4, r4, MCOUNT_INSN_SIZE



	/* Grab the LR out of the caller stack frame */

	lwz	r3,52(r1)



	bl	prepare_ftrace_return

	nop
@@ -65,9 +146,21 @@ _GLOBAL(ftrace_graph_caller) 
         * Change the LR in the callers stack frame to this.

         */

	stw	r3,52(r1)

	mtlr	r3

	lwz	r0,44(r1)

	mtctr	r0



	lwz	r3, 12(r1)

	lwz	r4, 16(r1)

	lwz	r5, 20(r1)

	lwz	r6, 24(r1)

	lwz	r7, 28(r1)

	lwz	r8, 32(r1)

	lwz	r9, 36(r1)

	lwz	r10,40(r1)



	addi	r1, r1, 48



	MCOUNT_RESTORE_FRAME

	/* old link register ends up in ctr reg */

	bctr



_GLOBAL(return_to_handler)