diff options
Diffstat (limited to 'arch/s390/kernel/ftrace.c')
| -rw-r--r-- | arch/s390/kernel/ftrace.c | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c new file mode 100644 index 00000000..78bdf0e5 --- /dev/null +++ b/arch/s390/kernel/ftrace.c @@ -0,0 +1,198 @@ +/* + * Dynamic function tracer architecture backend. + * + * Copyright IBM Corp. 2009 + * + * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>, + * Martin Schwidefsky <schwidefsky@de.ibm.com> + */ + +#include <linux/hardirq.h> +#include <linux/uaccess.h> +#include <linux/ftrace.h> +#include <linux/kernel.h> +#include <linux/types.h> +#include <linux/kprobes.h> +#include <trace/syscall.h> +#include <asm/asm-offsets.h> + +#ifdef CONFIG_64BIT +#define MCOUNT_OFFSET_RET 12 +#else +#define MCOUNT_OFFSET_RET 22 +#endif + +#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: + * 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 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. + */ +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 + +#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"); + +#define FTRACE_INSN_SIZE 4 + +#endif /* CONFIG_64BIT */ + + +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; + 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; + return 0; +} + +int ftrace_update_ftrace_func(ftrace_func_t func) +{ + return 0; +} + +int __init ftrace_dyn_arch_init(void *data) +{ + *(unsigned long *) data = 0; + return 0; +} + +#endif /* CONFIG_DYNAMIC_FTRACE */ + +#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) +{ + struct ftrace_graph_ent trace; + + if (unlikely(atomic_read(¤t->tracing_graph_pause))) + goto out; + if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY) + goto out; + trace.func = (ip & PSW_ADDR_INSN) - MCOUNT_OFFSET_RET; + /* Only trace if the calling function expects to. */ + if (!ftrace_graph_entry(&trace)) { + current->curr_ret_stack--; + goto out; + } + parent = (unsigned long) return_to_handler; +out: + return parent; +} + +#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. + */ +int ftrace_enable_ftrace_graph_caller(void) +{ + unsigned short offset; + + offset = ((void *) prepare_ftrace_return - + (void *) ftrace_graph_caller) / 2; + return probe_kernel_write(ftrace_graph_caller + 2, + &offset, sizeof(offset)); +} + +int ftrace_disable_ftrace_graph_caller(void) +{ + static unsigned short offset = 0x0002; + + return probe_kernel_write(ftrace_graph_caller + 2, + &offset, sizeof(offset)); +} + +#endif /* CONFIG_DYNAMIC_FTRACE */ +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |