--- zzzz-none-000/linux-3.10.107/arch/s390/kernel/ftrace.c 2017-06-27 09:49:32.000000000 +0000 +++ scorpion-7490-727/linux-3.10.107/arch/s390/kernel/ftrace.c 2021-02-04 17:41:59.000000000 +0000 @@ -1,12 +1,13 @@ /* * Dynamic function tracer architecture backend. * - * Copyright IBM Corp. 2009 + * Copyright IBM Corp. 2009,2014 * * Author(s): Heiko Carstens , * Martin Schwidefsky */ +#include #include #include #include @@ -15,112 +16,149 @@ #include #include #include +#include +#include "entry.h" -#ifdef CONFIG_DYNAMIC_FTRACE - -void ftrace_disable_code(void); -void ftrace_enable_insn(void); - -#ifdef CONFIG_64BIT /* - * The 64-bit mcount code looks like this: + * The mcount code looks like this: * stg %r14,8(%r15) # offset 0 - * > larl %r1,<&counter> # offset 6 - * > brasl %r14,_mcount # offset 12 + * larl %r1,<&counter> # offset 6 + * brasl %r14,_mcount # offset 12 + * lg %r14,8(%r15) # offset 18 + * Total length is 24 bytes. Only the first instruction will be patched + * by ftrace_make_call / ftrace_make_nop. + * The enabled ftrace code block looks like this: + * > brasl %r0,ftrace_caller # offset 0 + * larl %r1,<&counter> # offset 6 + * brasl %r14,_mcount # offset 12 + * lg %r14,8(%r15) # offset 18 + * The ftrace function gets called with a non-standard C function call ABI + * where r0 contains the return address. It is also expected that the called + * function only clobbers r0 and r1, but restores r2-r15. + * For module code we can't directly jump to ftrace caller, but need a + * trampoline (ftrace_plt), which clobbers also r1. + * The return point of the ftrace function has offset 24, so execution + * continues behind the mcount block. + * The disabled ftrace code block looks like this: + * > jg .+24 # offset 0 + * larl %r1,<&counter> # offset 6 + * brasl %r14,_mcount # offset 12 * lg %r14,8(%r15) # offset 18 - * Total length is 24 bytes. The middle two instructions of the mcount - * block get overwritten by ftrace_make_nop / ftrace_make_call. - * The 64-bit enabled ftrace code block looks like this: - * stg %r14,8(%r15) # offset 0 - * > lg %r1,__LC_FTRACE_FUNC # offset 6 - * > lgr %r0,%r0 # offset 12 - * > basr %r14,%r1 # offset 16 - * lg %r14,8(%15) # offset 18 - * The return points of the mcount/ftrace function have the same offset 18. - * The 64-bit disable ftrace code block looks like this: - * stg %r14,8(%r15) # offset 0 - * > jg .+18 # offset 6 - * > lgr %r0,%r0 # offset 12 - * > basr %r14,%r1 # offset 16 - * lg %r14,8(%15) # offset 18 * The jg instruction branches to offset 24 to skip as many instructions * as possible. + * In case we use gcc's hotpatch feature the original and also the disabled + * function prologue contains only a single six byte instruction and looks + * like this: + * > brcl 0,0 # offset 0 + * To enable ftrace the code gets patched like above and afterwards looks + * like this: + * > brasl %r0,ftrace_caller # offset 0 */ -asm( - " .align 4\n" - "ftrace_disable_code:\n" - " jg 0f\n" - " lgr %r0,%r0\n" - " basr %r14,%r1\n" - "0:\n" - " .align 4\n" - "ftrace_enable_insn:\n" - " lg %r1,"__stringify(__LC_FTRACE_FUNC)"\n"); -#define FTRACE_INSN_SIZE 6 +unsigned long ftrace_plt; -#else /* CONFIG_64BIT */ -/* - * The 31-bit mcount code looks like this: - * st %r14,4(%r15) # offset 0 - * > bras %r1,0f # offset 4 - * > .long _mcount # offset 8 - * > .long <&counter> # offset 12 - * > 0: l %r14,0(%r1) # offset 16 - * > l %r1,4(%r1) # offset 20 - * basr %r14,%r14 # offset 24 - * l %r14,4(%r15) # offset 26 - * Total length is 30 bytes. The twenty bytes starting from offset 4 - * to offset 24 get overwritten by ftrace_make_nop / ftrace_make_call. - * The 31-bit enabled ftrace code block looks like this: - * st %r14,4(%r15) # offset 0 - * > l %r14,__LC_FTRACE_FUNC # offset 4 - * > j 0f # offset 8 - * > .fill 12,1,0x07 # offset 12 - * 0: basr %r14,%r14 # offset 24 - * l %r14,4(%r14) # offset 26 - * The return points of the mcount/ftrace function have the same offset 26. - * The 31-bit disabled ftrace code block looks like this: - * st %r14,4(%r15) # offset 0 - * > j .+26 # offset 4 - * > j 0f # offset 8 - * > .fill 12,1,0x07 # offset 12 - * 0: basr %r14,%r14 # offset 24 - * l %r14,4(%r14) # offset 26 - * The j instruction branches to offset 30 to skip as many instructions - * as possible. - */ -asm( - " .align 4\n" - "ftrace_disable_code:\n" - " j 1f\n" - " j 0f\n" - " .fill 12,1,0x07\n" - "0: basr %r14,%r14\n" - "1:\n" - " .align 4\n" - "ftrace_enable_insn:\n" - " l %r14,"__stringify(__LC_FTRACE_FUNC)"\n"); +static inline void ftrace_generate_orig_insn(struct ftrace_insn *insn) +{ +#ifdef CC_USING_HOTPATCH + /* brcl 0,0 */ + insn->opc = 0xc004; + insn->disp = 0; +#else + /* stg r14,8(r15) */ + insn->opc = 0xe3e0; + insn->disp = 0xf0080024; +#endif +} + +static inline int is_kprobe_on_ftrace(struct ftrace_insn *insn) +{ +#ifdef CONFIG_KPROBES + if (insn->opc == BREAKPOINT_INSTRUCTION) + return 1; +#endif + return 0; +} -#define FTRACE_INSN_SIZE 4 +static inline void ftrace_generate_kprobe_nop_insn(struct ftrace_insn *insn) +{ +#ifdef CONFIG_KPROBES + insn->opc = BREAKPOINT_INSTRUCTION; + insn->disp = KPROBE_ON_FTRACE_NOP; +#endif +} -#endif /* CONFIG_64BIT */ +static inline void ftrace_generate_kprobe_call_insn(struct ftrace_insn *insn) +{ +#ifdef CONFIG_KPROBES + insn->opc = BREAKPOINT_INSTRUCTION; + insn->disp = KPROBE_ON_FTRACE_CALL; +#endif +} +int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, + unsigned long addr) +{ + return 0; +} int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { - if (probe_kernel_write((void *) rec->ip, ftrace_disable_code, - MCOUNT_INSN_SIZE)) - return -EPERM; + struct ftrace_insn orig, new, old; + + if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old))) + return -EFAULT; + if (addr == MCOUNT_ADDR) { + /* Initial code replacement */ + ftrace_generate_orig_insn(&orig); + ftrace_generate_nop_insn(&new); + } else if (is_kprobe_on_ftrace(&old)) { + /* + * If we find a breakpoint instruction, a kprobe has been + * placed at the beginning of the function. We write the + * constant KPROBE_ON_FTRACE_NOP into the remaining four + * bytes of the original instruction so that the kprobes + * handler can execute a nop, if it reaches this breakpoint. + */ + ftrace_generate_kprobe_call_insn(&orig); + ftrace_generate_kprobe_nop_insn(&new); + } else { + /* Replace ftrace call with a nop. */ + ftrace_generate_call_insn(&orig, rec->ip); + ftrace_generate_nop_insn(&new); + } + /* Verify that the to be replaced code matches what we expect. */ + if (memcmp(&orig, &old, sizeof(old))) + return -EINVAL; + s390_kernel_write((void *) rec->ip, &new, sizeof(new)); return 0; } int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { - if (probe_kernel_write((void *) rec->ip, ftrace_enable_insn, - FTRACE_INSN_SIZE)) - return -EPERM; + struct ftrace_insn orig, new, old; + + if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old))) + return -EFAULT; + if (is_kprobe_on_ftrace(&old)) { + /* + * If we find a breakpoint instruction, a kprobe has been + * placed at the beginning of the function. We write the + * constant KPROBE_ON_FTRACE_CALL into the remaining four + * bytes of the original instruction so that the kprobes + * handler can execute a brasl if it reaches this breakpoint. + */ + ftrace_generate_kprobe_nop_insn(&orig); + ftrace_generate_kprobe_call_insn(&new); + } else { + /* Replace nop with an ftrace call. */ + ftrace_generate_nop_insn(&orig); + ftrace_generate_call_insn(&new, rec->ip); + } + /* Verify that the to be replaced code matches what we expect. */ + if (memcmp(&orig, &old, sizeof(old))) + return -EINVAL; + s390_kernel_write((void *) rec->ip, &new, sizeof(new)); return 0; } @@ -129,65 +167,78 @@ return 0; } -int __init ftrace_dyn_arch_init(void *data) +int __init ftrace_dyn_arch_init(void) { - *(unsigned long *) data = 0; return 0; } -#endif /* CONFIG_DYNAMIC_FTRACE */ +static int __init ftrace_plt_init(void) +{ + unsigned int *ip; + + ftrace_plt = (unsigned long) module_alloc(PAGE_SIZE); + if (!ftrace_plt) + panic("cannot allocate ftrace plt\n"); + ip = (unsigned int *) ftrace_plt; + ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */ + ip[1] = 0x100a0004; + ip[2] = 0x07f10000; + ip[3] = FTRACE_ADDR >> 32; + ip[4] = FTRACE_ADDR & 0xffffffff; + set_memory_ro(ftrace_plt, 1); + return 0; +} +device_initcall(ftrace_plt_init); #ifdef CONFIG_FUNCTION_GRAPH_TRACER /* * Hook the return address and push it in the stack of return addresses * in current thread info. */ -unsigned long __kprobes prepare_ftrace_return(unsigned long parent, - unsigned long ip) +unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip) { struct ftrace_graph_ent trace; + if (unlikely(ftrace_graph_is_dead())) + goto out; if (unlikely(atomic_read(¤t->tracing_graph_pause))) goto out; ip = (ip & PSW_ADDR_INSN) - MCOUNT_INSN_SIZE; - if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY) - goto out; trace.func = ip; + trace.depth = current->curr_ret_stack + 1; /* Only trace if the calling function expects to. */ - if (!ftrace_graph_entry(&trace)) { - current->curr_ret_stack--; + if (!ftrace_graph_entry(&trace)) + goto out; + if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY) goto out; - } parent = (unsigned long) return_to_handler; out: return parent; } +NOKPROBE_SYMBOL(prepare_ftrace_return); -#ifdef CONFIG_DYNAMIC_FTRACE /* * Patch the kernel code at ftrace_graph_caller location. The instruction - * there is branch relative and save to prepare_ftrace_return. To disable - * the call to prepare_ftrace_return we patch the bras offset to point - * directly after the instructions. To enable the call we calculate - * the original offset to prepare_ftrace_return and put it back. + * there is branch relative on condition. To enable the ftrace graph code + * block, we simply patch the mask field of the instruction to zero and + * turn the instruction into a nop. + * To disable the ftrace graph code the mask field will be patched to + * all ones, which turns the instruction into an unconditional branch. */ int ftrace_enable_ftrace_graph_caller(void) { - unsigned short offset; + u8 op = 0x04; /* set mask field to zero */ - offset = ((void *) prepare_ftrace_return - - (void *) ftrace_graph_caller) / 2; - return probe_kernel_write(ftrace_graph_caller + 2, - &offset, sizeof(offset)); + s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op)); + return 0; } int ftrace_disable_ftrace_graph_caller(void) { - static unsigned short offset = 0x0002; + u8 op = 0xf4; /* set mask field to all ones */ - return probe_kernel_write(ftrace_graph_caller + 2, - &offset, sizeof(offset)); + s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op)); + return 0; } -#endif /* CONFIG_DYNAMIC_FTRACE */ #endif /* CONFIG_FUNCTION_GRAPH_TRACER */