2009-06-12 16:26:44 +08:00
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/*
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* Dynamic function tracer architecture backend.
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*
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* Copyright IBM Corp. 2009
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*
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* Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
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2011-01-05 19:48:11 +08:00
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* Martin Schwidefsky <schwidefsky@de.ibm.com>
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2009-06-12 16:26:44 +08:00
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*/
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2009-06-12 16:26:46 +08:00
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#include <linux/hardirq.h>
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2009-06-12 16:26:44 +08:00
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#include <linux/uaccess.h>
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#include <linux/ftrace.h>
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#include <linux/kernel.h>
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#include <linux/types.h>
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2011-01-05 19:48:11 +08:00
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#include <linux/kprobes.h>
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2009-06-12 16:26:47 +08:00
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#include <trace/syscall.h>
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2010-02-27 05:37:43 +08:00
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#include <asm/asm-offsets.h>
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2009-06-12 16:26:44 +08:00
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2011-01-05 19:48:11 +08:00
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#ifdef CONFIG_64BIT
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#define MCOUNT_OFFSET_RET 12
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#else
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#define MCOUNT_OFFSET_RET 22
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#endif
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2009-06-12 16:26:46 +08:00
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#ifdef CONFIG_DYNAMIC_FTRACE
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2009-06-12 16:26:44 +08:00
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void ftrace_disable_code(void);
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2011-01-05 19:48:11 +08:00
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void ftrace_enable_insn(void);
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2009-06-12 16:26:44 +08:00
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#ifdef CONFIG_64BIT
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2011-01-05 19:48:11 +08:00
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/*
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* The 64-bit mcount code looks like this:
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* stg %r14,8(%r15) # offset 0
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* > larl %r1,<&counter> # offset 6
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* > brasl %r14,_mcount # offset 12
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* lg %r14,8(%r15) # offset 18
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* Total length is 24 bytes. The middle two instructions of the mcount
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* block get overwritten by ftrace_make_nop / ftrace_make_call.
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* The 64-bit enabled ftrace code block looks like this:
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* stg %r14,8(%r15) # offset 0
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* > lg %r1,__LC_FTRACE_FUNC # offset 6
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* > lgr %r0,%r0 # offset 12
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* > basr %r14,%r1 # offset 16
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* lg %r14,8(%15) # offset 18
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* The return points of the mcount/ftrace function have the same offset 18.
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* The 64-bit disable ftrace code block looks like this:
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* stg %r14,8(%r15) # offset 0
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* > jg .+18 # offset 6
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* > lgr %r0,%r0 # offset 12
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* > basr %r14,%r1 # offset 16
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* lg %r14,8(%15) # offset 18
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* The jg instruction branches to offset 24 to skip as many instructions
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* as possible.
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*/
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2009-06-12 16:26:44 +08:00
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asm(
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" .align 4\n"
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"ftrace_disable_code:\n"
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2011-01-05 19:48:11 +08:00
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" jg 0f\n"
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2009-06-12 16:26:44 +08:00
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" lgr %r0,%r0\n"
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2011-01-05 19:48:11 +08:00
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" basr %r14,%r1\n"
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"0:\n"
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2009-06-12 16:26:44 +08:00
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" .align 4\n"
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2011-01-05 19:48:11 +08:00
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"ftrace_enable_insn:\n"
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" lg %r1,"__stringify(__LC_FTRACE_FUNC)"\n");
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2009-06-12 16:26:44 +08:00
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2011-01-05 19:48:11 +08:00
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#define FTRACE_INSN_SIZE 6
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2009-06-12 16:26:44 +08:00
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#else /* CONFIG_64BIT */
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2011-01-05 19:48:11 +08:00
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/*
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* The 31-bit mcount code looks like this:
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* st %r14,4(%r15) # offset 0
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* > bras %r1,0f # offset 4
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* > .long _mcount # offset 8
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* > .long <&counter> # offset 12
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* > 0: l %r14,0(%r1) # offset 16
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* > l %r1,4(%r1) # offset 20
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* basr %r14,%r14 # offset 24
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* l %r14,4(%r15) # offset 26
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* Total length is 30 bytes. The twenty bytes starting from offset 4
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* to offset 24 get overwritten by ftrace_make_nop / ftrace_make_call.
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* The 31-bit enabled ftrace code block looks like this:
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* st %r14,4(%r15) # offset 0
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* > l %r14,__LC_FTRACE_FUNC # offset 4
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* > j 0f # offset 8
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* > .fill 12,1,0x07 # offset 12
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* 0: basr %r14,%r14 # offset 24
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* l %r14,4(%r14) # offset 26
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* The return points of the mcount/ftrace function have the same offset 26.
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* The 31-bit disabled ftrace code block looks like this:
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* st %r14,4(%r15) # offset 0
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* > j .+26 # offset 4
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* > j 0f # offset 8
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* > .fill 12,1,0x07 # offset 12
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* 0: basr %r14,%r14 # offset 24
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* l %r14,4(%r14) # offset 26
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* The j instruction branches to offset 30 to skip as many instructions
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* as possible.
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*/
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2009-06-12 16:26:44 +08:00
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asm(
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" .align 4\n"
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"ftrace_disable_code:\n"
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2011-01-05 19:48:11 +08:00
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" j 1f\n"
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2009-06-12 16:26:44 +08:00
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" j 0f\n"
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2011-01-05 19:48:11 +08:00
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" .fill 12,1,0x07\n"
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"0: basr %r14,%r14\n"
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"1:\n"
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2009-06-12 16:26:44 +08:00
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" .align 4\n"
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2011-01-05 19:48:11 +08:00
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"ftrace_enable_insn:\n"
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" l %r14,"__stringify(__LC_FTRACE_FUNC)"\n");
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2009-06-12 16:26:44 +08:00
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2011-01-05 19:48:11 +08:00
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#define FTRACE_INSN_SIZE 4
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2009-06-12 16:26:44 +08:00
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#endif /* CONFIG_64BIT */
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int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
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unsigned long addr)
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{
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2011-01-05 19:48:11 +08:00
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if (probe_kernel_write((void *) rec->ip, ftrace_disable_code,
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MCOUNT_INSN_SIZE))
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return -EPERM;
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return 0;
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2009-06-12 16:26:44 +08:00
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}
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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2011-01-05 19:48:11 +08:00
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if (probe_kernel_write((void *) rec->ip, ftrace_enable_insn,
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FTRACE_INSN_SIZE))
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return -EPERM;
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return 0;
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2009-06-12 16:26:44 +08:00
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}
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int ftrace_update_ftrace_func(ftrace_func_t func)
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{
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return 0;
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}
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int __init ftrace_dyn_arch_init(void *data)
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{
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2011-01-05 19:48:11 +08:00
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*(unsigned long *) data = 0;
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2009-06-12 16:26:44 +08:00
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return 0;
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}
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2009-06-12 16:26:46 +08:00
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#endif /* CONFIG_DYNAMIC_FTRACE */
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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/*
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* Hook the return address and push it in the stack of return addresses
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* in current thread info.
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*/
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2011-01-05 19:48:11 +08:00
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unsigned long __kprobes prepare_ftrace_return(unsigned long parent,
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unsigned long ip)
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2009-06-12 16:26:46 +08:00
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{
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struct ftrace_graph_ent trace;
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if (unlikely(atomic_read(¤t->tracing_graph_pause)))
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goto out;
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function-graph: add stack frame test
In case gcc does something funny with the stack frames, or the return
from function code, we would like to detect that.
An arch may implement passing of a variable that is unique to the
function and can be saved on entering a function and can be tested
when exiting the function. Usually the frame pointer can be used for
this purpose.
This patch also implements this for x86. Where it passes in the stack
frame of the parent function, and will test that frame on exit.
There was a case in x86_32 with optimize for size (-Os) where, for a
few functions, gcc would align the stack frame and place a copy of the
return address into it. The function graph tracer modified the copy and
not the actual return address. On return from the funtion, it did not go
to the tracer hook, but returned to the parent. This broke the function
graph tracer, because the return of the parent (where gcc did not do
this funky manipulation) returned to the location that the child function
was suppose to. This caused strange kernel crashes.
This test detected the problem and pointed out where the issue was.
This modifies the parameters of one of the functions that the arch
specific code calls, so it includes changes to arch code to accommodate
the new prototype.
Note, I notice that the parsic arch implements its own push_return_trace.
This is now a generic function and the ftrace_push_return_trace should be
used instead. This patch does not touch that code.
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-06-19 00:45:08 +08:00
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if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY)
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2009-06-12 16:26:46 +08:00
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goto out;
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2011-01-05 19:48:11 +08:00
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trace.func = (ip & PSW_ADDR_INSN) - MCOUNT_OFFSET_RET;
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2009-06-12 16:26:46 +08:00
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/* Only trace if the calling function expects to. */
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if (!ftrace_graph_entry(&trace)) {
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current->curr_ret_stack--;
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goto out;
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}
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2011-01-05 19:48:11 +08:00
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parent = (unsigned long) return_to_handler;
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2009-06-12 16:26:46 +08:00
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out:
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return parent;
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}
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2011-01-05 19:48:11 +08:00
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#ifdef CONFIG_DYNAMIC_FTRACE
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/*
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* Patch the kernel code at ftrace_graph_caller location. The instruction
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* there is branch relative and save to prepare_ftrace_return. To disable
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* the call to prepare_ftrace_return we patch the bras offset to point
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* directly after the instructions. To enable the call we calculate
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* the original offset to prepare_ftrace_return and put it back.
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*/
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int ftrace_enable_ftrace_graph_caller(void)
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{
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unsigned short offset;
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offset = ((void *) prepare_ftrace_return -
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(void *) ftrace_graph_caller) / 2;
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return probe_kernel_write(ftrace_graph_caller + 2,
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&offset, sizeof(offset));
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}
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int ftrace_disable_ftrace_graph_caller(void)
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{
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static unsigned short offset = 0x0002;
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return probe_kernel_write(ftrace_graph_caller + 2,
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&offset, sizeof(offset));
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}
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#endif /* CONFIG_DYNAMIC_FTRACE */
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2009-06-12 16:26:46 +08:00
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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