diff options
Diffstat (limited to 'arch/s390/kernel/ftrace.c')
| -rw-r--r-- | arch/s390/kernel/ftrace.c | 132 |
1 files changed, 84 insertions, 48 deletions
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c index 51d14fe5eb9a..5744d25c1d33 100644 --- a/arch/s390/kernel/ftrace.c +++ b/arch/s390/kernel/ftrace.c @@ -7,6 +7,7 @@ * Martin Schwidefsky <schwidefsky@de.ibm.com> */ +#include <linux/moduleloader.h> #include <linux/hardirq.h> #include <linux/uaccess.h> #include <linux/ftrace.h> @@ -15,60 +16,39 @@ #include <linux/kprobes.h> #include <trace/syscall.h> #include <asm/asm-offsets.h> +#include <asm/cacheflush.h> #include "entry.h" -void mcount_replace_code(void); -void ftrace_disable_code(void); -void ftrace_enable_insn(void); - /* * The mcount code looks like this: * stg %r14,8(%r15) # offset 0 * larl %r1,<&counter> # offset 6 * brasl %r14,_mcount # offset 12 * lg %r14,8(%r15) # offset 18 - * Total length is 24 bytes. The complete mcount block initially gets replaced - * by ftrace_make_nop. Subsequent calls to ftrace_make_call / ftrace_make_nop - * only patch the jg/lg instruction within the block. - * Note: we do not patch the first instruction to an unconditional branch, - * since that would break kprobes/jprobes. It is easier to leave the larl - * instruction in and only modify the second instruction. + * 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: - * larl %r0,.+24 # offset 0 - * > lg %r1,__LC_FTRACE_FUNC # offset 6 - * br %r1 # offset 12 - * brcl 0,0 # offset 14 - * brc 0,0 # offset 20 + * > 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. - * larl %r0,.+24 # offset 0 - * > jg .+18 # offset 6 - * br %r1 # offset 12 - * brcl 0,0 # offset 14 - * brc 0,0 # offset 20 + * 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 * The jg instruction branches to offset 24 to skip as many instructions * as possible. */ -asm( - " .align 4\n" - "mcount_replace_code:\n" - " larl %r0,0f\n" - "ftrace_disable_code:\n" - " jg 0f\n" - " br %r1\n" - " brcl 0,0\n" - " brc 0,0\n" - "0:\n" - " .align 4\n" - "ftrace_enable_insn:\n" - " lg %r1,"__stringify(__LC_FTRACE_FUNC)"\n"); - -#define MCOUNT_BLOCK_SIZE 24 -#define MCOUNT_INSN_OFFSET 6 -#define FTRACE_INSN_SIZE 6 + +unsigned long ftrace_plt; int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr) @@ -79,24 +59,62 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { - /* Initial replacement of the whole mcount block */ - if (addr == MCOUNT_ADDR) { - if (probe_kernel_write((void *) rec->ip - MCOUNT_INSN_OFFSET, - mcount_replace_code, - MCOUNT_BLOCK_SIZE)) - return -EPERM; - return 0; + struct ftrace_insn insn; + unsigned short op; + void *from, *to; + size_t size; + + ftrace_generate_nop_insn(&insn); + size = sizeof(insn); + from = &insn; + to = (void *) rec->ip; + if (probe_kernel_read(&op, (void *) rec->ip, sizeof(op))) + return -EFAULT; + /* + * 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. + */ + if (op == BREAKPOINT_INSTRUCTION) { + size -= 2; + from += 2; + to += 2; + insn.disp = KPROBE_ON_FTRACE_NOP; } - if (probe_kernel_write((void *) rec->ip, ftrace_disable_code, - MCOUNT_INSN_SIZE)) + if (probe_kernel_write(to, from, size)) return -EPERM; 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)) + struct ftrace_insn insn; + unsigned short op; + void *from, *to; + size_t size; + + ftrace_generate_call_insn(&insn, rec->ip); + size = sizeof(insn); + from = &insn; + to = (void *) rec->ip; + if (probe_kernel_read(&op, (void *) rec->ip, sizeof(op))) + return -EFAULT; + /* + * 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. + */ + if (op == BREAKPOINT_INSTRUCTION) { + size -= 2; + from += 2; + to += 2; + insn.disp = KPROBE_ON_FTRACE_CALL; + } + if (probe_kernel_write(to, from, size)) return -EPERM; return 0; } @@ -111,6 +129,24 @@ int __init ftrace_dyn_arch_init(void) return 0; } +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 |