diff options
Diffstat (limited to 'arch/powerpc/kernel/trace/ftrace.c')
| -rw-r--r-- | arch/powerpc/kernel/trace/ftrace.c | 261 |
1 files changed, 257 insertions, 4 deletions
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c index 4bfbb54dee517..4bf051d3e21e7 100644 --- a/arch/powerpc/kernel/trace/ftrace.c +++ b/arch/powerpc/kernel/trace/ftrace.c @@ -30,6 +30,16 @@ #ifdef CONFIG_DYNAMIC_FTRACE + +/* + * We generally only have a single long_branch tramp and at most 2 or 3 plt + * tramps generated. But, we don't use the plt tramps currently. We also allot + * 2 tramps after .text and .init.text. So, we only end up with around 3 usable + * tramps in total. Set aside 8 just to be sure. + */ +#define NUM_FTRACE_TRAMPS 8 +static unsigned long ftrace_tramps[NUM_FTRACE_TRAMPS]; + static unsigned int ftrace_call_replace(unsigned long ip, unsigned long addr, int link) { @@ -85,13 +95,16 @@ static int test_24bit_addr(unsigned long ip, unsigned long addr) return create_branch((unsigned int *)ip, addr, 0); } -#ifdef CONFIG_MODULES - static int is_bl_op(unsigned int op) { return (op & 0xfc000003) == 0x48000001; } +static int is_b_op(unsigned int op) +{ + return (op & 0xfc000003) == 0x48000000; +} + static unsigned long find_bl_target(unsigned long ip, unsigned int op) { static int offset; @@ -104,6 +117,7 @@ static unsigned long find_bl_target(unsigned long ip, unsigned int op) return ip + (long)offset; } +#ifdef CONFIG_MODULES #ifdef CONFIG_PPC64 static int __ftrace_make_nop(struct module *mod, @@ -270,6 +284,146 @@ __ftrace_make_nop(struct module *mod, #endif /* PPC64 */ #endif /* CONFIG_MODULES */ +static unsigned long find_ftrace_tramp(unsigned long ip) +{ + int i; + + /* + * We have the compiler generated long_branch tramps at the end + * and we prefer those + */ + for (i = NUM_FTRACE_TRAMPS - 1; i >= 0; i--) + if (!ftrace_tramps[i]) + continue; + else if (create_branch((void *)ip, ftrace_tramps[i], 0)) + return ftrace_tramps[i]; + + return 0; +} + +static int add_ftrace_tramp(unsigned long tramp) +{ + int i; + + for (i = 0; i < NUM_FTRACE_TRAMPS; i++) + if (!ftrace_tramps[i]) { + ftrace_tramps[i] = tramp; + return 0; + } + + return -1; +} + +/* + * If this is a compiler generated long_branch trampoline (essentially, a + * trampoline that has a branch to _mcount()), we re-write the branch to + * instead go to ftrace_[regs_]caller() and note down the location of this + * trampoline. + */ +static int setup_mcount_compiler_tramp(unsigned long tramp) +{ + int i, op; + unsigned long ptr; + static unsigned long ftrace_plt_tramps[NUM_FTRACE_TRAMPS]; + + /* Is this a known long jump tramp? */ + for (i = 0; i < NUM_FTRACE_TRAMPS; i++) + if (!ftrace_tramps[i]) + break; + else if (ftrace_tramps[i] == tramp) + return 0; + + /* Is this a known plt tramp? */ + for (i = 0; i < NUM_FTRACE_TRAMPS; i++) + if (!ftrace_plt_tramps[i]) + break; + else if (ftrace_plt_tramps[i] == tramp) + return -1; + + /* New trampoline -- read where this goes */ + if (probe_kernel_read(&op, (void *)tramp, sizeof(int))) { + pr_debug("Fetching opcode failed.\n"); + return -1; + } + + /* Is this a 24 bit branch? */ + if (!is_b_op(op)) { + pr_debug("Trampoline is not a long branch tramp.\n"); + return -1; + } + + /* lets find where the pointer goes */ + ptr = find_bl_target(tramp, op); + + if (ptr != ppc_global_function_entry((void *)_mcount)) { + pr_debug("Trampoline target %p is not _mcount\n", (void *)ptr); + return -1; + } + + /* Let's re-write the tramp to go to ftrace_[regs_]caller */ +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS + ptr = ppc_global_function_entry((void *)ftrace_regs_caller); +#else + ptr = ppc_global_function_entry((void *)ftrace_caller); +#endif + if (!create_branch((void *)tramp, ptr, 0)) { + pr_debug("%ps is not reachable from existing mcount tramp\n", + (void *)ptr); + return -1; + } + + if (patch_branch((unsigned int *)tramp, ptr, 0)) { + pr_debug("REL24 out of range!\n"); + return -1; + } + + if (add_ftrace_tramp(tramp)) { + pr_debug("No tramp locations left\n"); + return -1; + } + + return 0; +} + +static int __ftrace_make_nop_kernel(struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned long tramp, ip = rec->ip; + unsigned int op; + + /* 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; + } + + /* Let's find where the pointer goes */ + tramp = find_bl_target(ip, op); + + pr_devel("ip:%lx jumps to %lx", ip, tramp); + + if (setup_mcount_compiler_tramp(tramp)) { + /* Are other trampolines reachable? */ + if (!find_ftrace_tramp(ip)) { + pr_err("No ftrace trampolines reachable from %ps\n", + (void *)ip); + return -EINVAL; + } + } + + if (patch_instruction((unsigned int *)ip, PPC_INST_NOP)) { + pr_err("Patching NOP failed.\n"); + return -EPERM; + } + + return 0; +} + int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { @@ -286,7 +440,8 @@ int ftrace_make_nop(struct module *mod, old = ftrace_call_replace(ip, addr, 1); new = PPC_INST_NOP; return ftrace_modify_code(ip, old, new); - } + } else if (core_kernel_text(ip)) + return __ftrace_make_nop_kernel(rec, addr); #ifdef CONFIG_MODULES /* @@ -456,6 +611,53 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) #endif /* CONFIG_PPC64 */ #endif /* CONFIG_MODULES */ +static int __ftrace_make_call_kernel(struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned int op; + void *ip = (void *)rec->ip; + unsigned long tramp, entry, 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) { +#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(&op, ip, sizeof(op))) { + pr_err("Unable to read ftrace location %p\n", ip); + return -EFAULT; + } + + if (op != PPC_INST_NOP) { + pr_err("Unexpected call sequence at %p: %x\n", ip, op); + return -EINVAL; + } + + tramp = find_ftrace_tramp((unsigned long)ip); + if (!tramp) { + pr_err("No ftrace trampolines reachable from %ps\n", ip); + return -EINVAL; + } + + if (patch_branch(ip, tramp, BRANCH_SET_LINK)) { + pr_err("Error patching branch to ftrace tramp!\n"); + return -EINVAL; + } + + return 0; +} + int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { unsigned long ip = rec->ip; @@ -471,7 +673,8 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) old = PPC_INST_NOP; new = ftrace_call_replace(ip, addr, 1); return ftrace_modify_code(ip, old, new); - } + } else if (core_kernel_text(ip)) + return __ftrace_make_call_kernel(rec, addr); #ifdef CONFIG_MODULES /* @@ -603,6 +806,12 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, old = ftrace_call_replace(ip, old_addr, 1); 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; } #ifdef CONFIG_MODULES @@ -654,10 +863,54 @@ void arch_ftrace_update_code(int command) ftrace_modify_all_code(command); } +#ifdef CONFIG_PPC64 +#define PACATOC offsetof(struct paca_struct, kernel_toc) + +#define PPC_LO(v) ((v) & 0xffff) +#define PPC_HI(v) (((v) >> 16) & 0xffff) +#define PPC_HA(v) PPC_HI ((v) + 0x8000) + +extern unsigned int ftrace_tramp_text[], ftrace_tramp_init[]; + +int __init ftrace_dyn_arch_init(void) +{ + int i; + unsigned int *tramp[] = { ftrace_tramp_text, ftrace_tramp_init }; + u32 stub_insns[] = { + 0xe98d0000 | PACATOC, /* ld r12,PACATOC(r13) */ + 0x3d8c0000, /* addis r12,r12,<high> */ + 0x398c0000, /* addi r12,r12,<low> */ + 0x7d8903a6, /* mtctr r12 */ + 0x4e800420, /* bctr */ + }; +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS + unsigned long addr = ppc_global_function_entry((void *)ftrace_regs_caller); +#else + unsigned long addr = ppc_global_function_entry((void *)ftrace_caller); +#endif + long reladdr = addr - kernel_toc_addr(); + + if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) { + pr_err("Address of %ps out of range of kernel_toc.\n", + (void *)addr); + return -1; + } + + for (i = 0; i < 2; i++) { + memcpy(tramp[i], stub_insns, sizeof(stub_insns)); + tramp[i][1] |= PPC_HA(reladdr); + tramp[i][2] |= PPC_LO(reladdr); + add_ftrace_tramp((unsigned long)tramp[i]); + } + + return 0; +} +#else int __init ftrace_dyn_arch_init(void) { return 0; } +#endif #endif /* CONFIG_DYNAMIC_FTRACE */ #ifdef CONFIG_FUNCTION_GRAPH_TRACER |