From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752942AbcBJRoo (ORCPT ); Wed, 10 Feb 2016 12:44:44 -0500 Received: from verein.lst.de ([213.95.11.211]:43196 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752185AbcBJRol (ORCPT ); Wed, 10 Feb 2016 12:44:41 -0500 In-Reply-To: <20160210174221.EBBEC692C8@newverein.lst.de> References: <20160210174221.EBBEC692C8@newverein.lst.de> From: Torsten Duwe Date: Wed, 10 Feb 2016 17:22:10 +0100 Subject: [PATCH v8 2/8] ppc64le FTRACE_WITH_REGS implementation To: Michael Ellerman Cc: Jiri Kosina , Miroslav Benes , Petr Mladek , Jessica Yu , Steven Rostedt , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org Message-Id: <20160210174440.27A48692CE@newverein.lst.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Implement FTRACE_WITH_REGS for powerpc64, on ELF ABI v2. Initial work started by Vojtech Pavlik, used with permission. * arch/powerpc/kernel/entry_64.S: - Implement an effective ftrace_caller that works from within the kernel binary as well as from modules. * arch/powerpc/kernel/ftrace.c: - be prepared to deal with ppc64 ELF ABI v2, especially calls to _mcount that result from gcc -mprofile-kernel - a little more error verbosity * arch/powerpc/kernel/module_64.c: - do not save the TOC pointer on the trampoline when the destination is ftrace_caller. This trampoline jump happens from a function prologue before a new stack frame is set up, so bad things may happen otherwise... - relax is_module_trampoline() to recognise the modified trampoline. Signed-off-by: Torsten Duwe --- arch/powerpc/include/asm/ftrace.h | 5 +++ arch/powerpc/kernel/entry_64.S | 78 +++++++++++++++++++++++++++++++++++++++ arch/powerpc/kernel/ftrace.c | 64 +++++++++++++++++++++++++++++--- arch/powerpc/kernel/module_64.c | 25 ++++++++++++- 4 files changed, 165 insertions(+), 7 deletions(-) diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h index ef89b14..50ca758 100644 --- a/arch/powerpc/include/asm/ftrace.h +++ b/arch/powerpc/include/asm/ftrace.h @@ -46,6 +46,8 @@ 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 */ @@ -58,6 +60,9 @@ struct dyn_arch_ftrace { #endif /* CONFIG_DYNAMIC_FTRACE */ #endif /* __ASSEMBLY__ */ +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS +#define ARCH_SUPPORTS_FTRACE_OPS 1 +#endif #endif #if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64) && !defined(__ASSEMBLY__) diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 2a7313c..c063564 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -1148,6 +1148,7 @@ _GLOBAL(_mcount) mtlr r0 bctr +#ifndef CC_USING_MPROFILE_KERNEL _GLOBAL_TOC(ftrace_caller) /* Taken from output of objdump from lib64/glibc */ mflr r3 @@ -1169,6 +1170,83 @@ _GLOBAL(ftrace_graph_stub) ld r0, 128(r1) mtlr r0 addi r1, r1, 112 +#else +_GLOBAL(ftrace_caller) + std r0,LRSAVE(r1) +#if defined(_CALL_ELF) && _CALL_ELF == 2 + mflr r0 + bl 2f +2: mflr r12 + mtlr r0 + mr r0,r2 /* save callee's TOC */ + addis r2,r12,(.TOC.-ftrace_caller-12)@ha + addi r2,r2,(.TOC.-ftrace_caller-12)@l +#else + mr r0,r2 +#endif + ld r12,LRSAVE(r1) /* get caller's address */ + + stdu r1,-SWITCH_FRAME_SIZE(r1) + + std r12, _LINK(r1) + SAVE_8GPRS(0,r1) + std r0, 24(r1) /* save TOC */ + SAVE_8GPRS(8,r1) + SAVE_8GPRS(16,r1) + SAVE_8GPRS(24,r1) + + addis r3,r2,function_trace_op@toc@ha + addi r3,r3,function_trace_op@toc@l + ld r5,0(r3) + + mflr r3 + std r3, _NIP(r1) + std r3, 16(r1) + subi r3, r3, MCOUNT_INSN_SIZE + mfmsr r4 + std r4, _MSR(r1) + mfctr r4 + std r4, _CTR(r1) + mfxer r4 + std r4, _XER(r1) + mr r4, r12 + addi r6, r1 ,STACK_FRAME_OVERHEAD + +.globl ftrace_call +ftrace_call: + bl ftrace_stub + nop + + ld r3, _NIP(r1) + mtlr r3 + + REST_8GPRS(0,r1) + REST_8GPRS(8,r1) + REST_8GPRS(16,r1) + REST_8GPRS(24,r1) + + addi r1, r1, SWITCH_FRAME_SIZE + + ld r12, LRSAVE(r1) /* get caller's address */ + mtlr r12 + mr r2,r0 /* restore callee's TOC */ + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + stdu r1, -112(r1) +.globl ftrace_graph_call +ftrace_graph_call: + b ftrace_graph_stub +_GLOBAL(ftrace_graph_stub) + addi r1, r1, 112 +#endif + + mflr r0 /* move this LR to CTR */ + mtctr r0 + + ld r0,LRSAVE(r1) /* restore callee's lr at _mcount site */ + mtlr r0 + bctr /* jump after _mcount site */ +#endif /* CC_USING_MPROFILE_KERNEL */ _GLOBAL(ftrace_stub) blr #else diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c index 861af90..1fad1b3 100644 --- a/arch/powerpc/kernel/ftrace.c +++ b/arch/powerpc/kernel/ftrace.c @@ -61,8 +61,11 @@ ftrace_modify_code(unsigned long ip, unsigned int old, unsigned int new) return -EFAULT; /* Make sure it is what we expect it to be */ - if (replaced != old) + if (replaced != old) { + pr_err("%p: replaced (%#x) != old (%#x)", + (void *)ip, replaced, old); return -EINVAL; + } /* replace the text with the new text */ if (patch_instruction((unsigned int *)ip, new)) @@ -106,14 +109,16 @@ static int __ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { - unsigned int op; + unsigned int op, op0, op1, pop; unsigned long entry, ptr; unsigned long ip = rec->ip; void *tramp; /* read where this goes */ - if (probe_kernel_read(&op, (void *)ip, sizeof(int))) + 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)) { @@ -158,10 +163,49 @@ __ftrace_make_nop(struct module *mod, * * Use a b +8 to jump over the load. */ - op = 0x48000008; /* b +8 */ - if (patch_instruction((unsigned int *)ip, op)) + pop = PPC_INST_BRANCH | 8; /* b +8 */ + + /* + * Check what is in the next instruction. We can see ld r2,40(r1), but + * on first pass after boot we will see mflr r0. + */ + if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE)) { + pr_err("Fetching op failed.\n"); + return -EFAULT; + } + + if (op != PPC_INST_LD_TOC) + { + if (probe_kernel_read(&op0, (void *)(ip-8), MCOUNT_INSN_SIZE)) { + pr_err("Fetching op0 failed.\n"); + return -EFAULT; + } + + if (probe_kernel_read(&op1, (void *)(ip-4), MCOUNT_INSN_SIZE)) { + pr_err("Fetching op1 failed.\n"); + return -EFAULT; + } + + /* mflr r0 ; [ std r0,LRSAVE(r1) ]? */ + if ( (op0 != PPC_INST_MFLR || + op1 != PPC_INST_STD_LR) + && op1 != PPC_INST_MFLR ) + { + pr_err("Unexpected instructions around bl _mcount\n" + "when enabling dynamic ftrace!\t" + "(%08x,%08x,bl,%08x)\n", op0, op1, op); + return -EINVAL; + } + + /* When using -mkernel_profile there is no load to jump over */ + pop = PPC_INST_NOP; + } + + if (patch_instruction((unsigned int *)ip, pop)) { + pr_err("Patching NOP failed.\n"); return -EPERM; + } return 0; } @@ -287,6 +331,14 @@ int ftrace_make_nop(struct module *mod, #ifdef CONFIG_MODULES #ifdef CONFIG_PPC64 +#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 + /* Examine the existing instructions for __ftrace_make_call. * They should effectively be a NOP, and follow formal constraints, * depending on the ABI. Return false if they don't. @@ -354,7 +406,7 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) return 0; } -#else +#else /* !CONFIG_PPC64: */ static int __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c index 72a1a52..720e8fd 100644 --- a/arch/powerpc/kernel/module_64.c +++ b/arch/powerpc/kernel/module_64.c @@ -136,12 +136,25 @@ static u32 ppc64_stub_insns[] = { 0x4e800420 /* bctr */ }; +#ifdef CC_USING_MPROFILE_KERNEL +/* In case of _mcount calls or dynamic ftracing, Do not save the + * current callee's TOC (in R2) again into the original caller's stack + * frame during this trampoline hop. The stack frame already holds + * that of the original caller. _mcount and ftrace_caller will take + * care of this TOC value themselves. + */ +#define SQUASH_TOC_SAVE_INSN(trampoline_addr) \ + (((struct ppc64_stub_entry *)(trampoline_addr))->jump[2] = PPC_INST_NOP) +#else +#define SQUASH_TOC_SAVE_INSN(trampoline_addr) +#endif + #ifdef CONFIG_DYNAMIC_FTRACE static u32 ppc64_stub_mask[] = { 0xffff0000, 0xffff0000, - 0xffffffff, + 0x00000000, 0xffffffff, #if !defined(_CALL_ELF) || _CALL_ELF != 2 0xffffffff, @@ -168,6 +181,9 @@ bool is_module_trampoline(u32 *p) if ((insna & mask) != (insnb & mask)) return false; } + if (insns[2] != ppc64_stub_insns[2] && + insns[2] != PPC_INST_NOP) + return false; return true; } @@ -636,6 +652,9 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, return -ENOENT; if (!restore_r2((u32 *)location + 1, me)) return -ENOEXEC; + /* Squash the TOC saver for profiler calls */ + if (!strcmp("_mcount", strtab+sym->st_name)) + SQUASH_TOC_SAVE_INSN(value); } else value += local_entry_offset(sym); @@ -723,6 +742,10 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, me->arch.tramp = stub_for_addr(sechdrs, (unsigned long)ftrace_caller, me); + /* ftrace_caller will take care of the TOC; + * do not clobber original caller's value. + */ + SQUASH_TOC_SAVE_INSN(me->arch.tramp); #endif return 0; -- 1.8.5.6