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Rao" To: Steven Rostedt , Michael Ellerman Subject: [RFC PATCH 10/14] powerpc/ftrace: Drop assumptions about ftrace trampoline target Date: Thu, 26 Nov 2020 23:38:47 +0530 Message-Id: <0ed4e63f6b3be1abdd59aa7b28a5dbdb99baeba1.1606412433.git.naveen.n.rao@linux.vnet.ibm.com> X-Mailer: git-send-email 2.25.4 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312, 18.0.737 definitions=2020-11-26_08:2020-11-26, 2020-11-26 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 mlxlogscore=999 clxscore=1015 spamscore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 mlxscore=0 adultscore=0 impostorscore=0 phishscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011260112 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" We currently assume that ftrace locations are patched to go to either ftrace_caller or ftrace_regs_caller. Drop this assumption in preparation for supporting ftrace direct calls. Signed-off-by: Naveen N. Rao --- arch/powerpc/kernel/trace/ftrace.c | 107 +++++++++++++++++++++++------ 1 file changed, 86 insertions(+), 21 deletions(-) diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c index 7ddb6e4b527c39..fcb21a9756e456 100644 --- a/arch/powerpc/kernel/trace/ftrace.c +++ b/arch/powerpc/kernel/trace/ftrace.c @@ -322,14 +322,15 @@ static int add_ftrace_tramp(unsigned long tramp, unsigned long target) */ static int setup_mcount_compiler_tramp(unsigned long tramp) { + int i; struct ppc_inst op; struct ppc_inst instr; struct ppc_ftrace_stub_data *stub; unsigned long ptr, ftrace_target = ppc_global_function_entry((void *)FTRACE_REGS_ADDR); - /* Is this a known long jump tramp? */ - hash_for_each_possible(ppc_ftrace_stubs, stub, hentry, ftrace_target) - if (stub->target == ftrace_target && stub->addr == tramp) + /* Is this a known tramp? */ + hash_for_each(ppc_ftrace_stubs, i, stub, hentry) + if (stub->addr == tramp) return 0; /* New trampoline -- read where this goes */ @@ -608,23 +609,16 @@ static int __ftrace_make_call_kernel(struct dyn_ftrace *rec, unsigned long addr) { struct ppc_inst op; void *ip = (void *)rec->ip; - unsigned long tramp, entry, ptr; + unsigned long tramp, ptr; - /* Make sure we're being asked to patch branch to a known ftrace addr */ - entry = ppc_global_function_entry((void *)ftrace_caller); ptr = ppc_global_function_entry((void *)addr); - if (ptr != entry) { #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS - entry = ppc_global_function_entry((void *)ftrace_regs_caller); - if (ptr != entry) { + /* Make sure we branch to ftrace_regs_caller since we only setup stubs for that */ + tramp = ppc_global_function_entry((void *)ftrace_caller); + if (ptr == tramp) + ptr = ppc_global_function_entry((void *)FTRACE_REGS_ADDR); #endif - pr_err("Unknown ftrace addr to patch: %ps\n", (void *)ptr); - return -EINVAL; -#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS - } -#endif - } /* Make sure we have a nop */ if (probe_kernel_read_inst(&op, ip)) { @@ -637,7 +631,7 @@ static int __ftrace_make_call_kernel(struct dyn_ftrace *rec, unsigned long addr) return -EINVAL; } - tramp = find_ftrace_tramp((unsigned long)ip, FTRACE_REGS_ADDR); + tramp = find_ftrace_tramp((unsigned long)ip, ptr); if (!tramp) { pr_err("No ftrace trampolines reachable from %ps\n", ip); return -EINVAL; @@ -783,6 +777,81 @@ __ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, } #endif +static int +__ftrace_modify_call_kernel(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr) +{ + struct ppc_inst op; + unsigned long ip = rec->ip; + unsigned long entry, ptr, tramp; + + /* read where this goes */ + if (probe_kernel_read_inst(&op, (void *)ip)) { + pr_err("Fetching opcode failed.\n"); + return -EFAULT; + } + + /* Make sure that this is still a 24bit jump */ + if (!is_bl_op(op)) { + pr_err("Not expected bl: opcode is %s\n", ppc_inst_as_str(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 */ + struct ppc_ftrace_stub_data *stub; + + hash_for_each_possible(ppc_ftrace_stubs, stub, hentry, entry) + if (stub->target == entry && stub->addr == tramp) + break; + + if (stub->target != entry || stub->addr != tramp) { + pr_err("we don't know about the tramp at %lx!\n", tramp); + return -EFAULT; + } + } + + /* The new target may be within range */ + if (test_24bit_addr(ip, addr)) { + /* within range */ + if (patch_branch((struct ppc_inst *)ip, addr, BRANCH_SET_LINK)) { + pr_err("REL24 out of range!\n"); + return -EINVAL; + } + + return 0; + } + + ptr = ppc_global_function_entry((void *)addr); + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS + /* Make sure we branch to ftrace_regs_caller since we only setup stubs for that */ + entry = ppc_global_function_entry((void *)ftrace_caller); + if (ptr == entry) + ptr = ppc_global_function_entry((void *)FTRACE_REGS_ADDR); +#endif + + tramp = find_ftrace_tramp(ip, ptr); + + if (!tramp) { + pr_err("Couldn't find a trampoline\n"); + return -EFAULT; + } + + pr_devel("trampoline %lx target %lx", tramp, ptr); + + if (patch_branch((struct ppc_inst *)ip, tramp, BRANCH_SET_LINK)) { + pr_err("REL24 out of range!\n"); + return -EINVAL; + } + + return 0; +} int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr) { @@ -800,11 +869,7 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, new = ftrace_call_replace(ip, addr, 1); return ftrace_modify_code(ip, old, new); } else if (core_kernel_text(ip)) { - /* - * We always patch out of range locations to go to the regs - * variant, so there is nothing to do here - */ - return 0; + return __ftrace_modify_call_kernel(rec, old_addr, addr); } #ifdef CONFIG_MODULES -- 2.25.4