* 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/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_disable_return(void);
-void ftrace_call_code(void);
-void ftrace_nop_code(void);
-
-#define FTRACE_INSN_SIZE 4
+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"
- " j 0f\n"
- " .word 0x0024\n"
- " lg %r1,"__stringify(__LC_FTRACE_FUNC)"\n"
- " basr %r14,%r1\n"
- "ftrace_disable_return:\n"
- " lg %r14,8(15)\n"
+ " jg 0f\n"
" lgr %r0,%r0\n"
- "0:\n");
-
-asm(
+ " basr %r14,%r1\n"
+ "0:\n"
" .align 4\n"
- "ftrace_nop_code:\n"
- " j .+"__stringify(MCOUNT_INSN_SIZE)"\n");
+ "ftrace_enable_insn:\n"
+ " lg %r1,"__stringify(__LC_FTRACE_FUNC)"\n");
-asm(
- " .align 4\n"
- "ftrace_call_code:\n"
- " stg %r14,8(%r15)\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"
- " l %r1,"__stringify(__LC_FTRACE_FUNC)"\n"
- " basr %r14,%r1\n"
- "ftrace_disable_return:\n"
- " l %r14,4(%r15)\n"
- " j 0f\n"
- " bcr 0,%r7\n"
- " bcr 0,%r7\n"
- " bcr 0,%r7\n"
- " bcr 0,%r7\n"
- " bcr 0,%r7\n"
- " bcr 0,%r7\n"
- "0:\n");
-
-asm(
+ " .fill 12,1,0x07\n"
+ "0: basr %r14,%r14\n"
+ "1:\n"
" .align 4\n"
- "ftrace_nop_code:\n"
- " j .+"__stringify(MCOUNT_INSN_SIZE)"\n");
+ "ftrace_enable_insn:\n"
+ " l %r14,"__stringify(__LC_FTRACE_FUNC)"\n");
-asm(
- " .align 4\n"
- "ftrace_call_code:\n"
- " st %r14,4(%r15)\n");
+#define FTRACE_INSN_SIZE 4
#endif /* CONFIG_64BIT */
-static int ftrace_modify_code(unsigned long ip,
- void *old_code, int old_size,
- void *new_code, int new_size)
-{
- unsigned char replaced[MCOUNT_INSN_SIZE];
-
- /*
- * Note: Due to modules code can disappear and change.
- * We need to protect against faulting as well as code
- * changing. We do this by using the probe_kernel_*
- * functions.
- * This however is just a simple sanity check.
- */
- if (probe_kernel_read(replaced, (void *)ip, old_size))
- return -EFAULT;
- if (memcmp(replaced, old_code, old_size) != 0)
- return -EINVAL;
- if (probe_kernel_write((void *)ip, new_code, new_size))
- return -EPERM;
- return 0;
-}
-
-static int ftrace_make_initial_nop(struct module *mod, struct dyn_ftrace *rec,
- unsigned long addr)
-{
- return ftrace_modify_code(rec->ip,
- ftrace_call_code, FTRACE_INSN_SIZE,
- ftrace_disable_code, MCOUNT_INSN_SIZE);
-}
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
- if (addr == MCOUNT_ADDR)
- return ftrace_make_initial_nop(mod, rec, addr);
- return ftrace_modify_code(rec->ip,
- ftrace_call_code, FTRACE_INSN_SIZE,
- ftrace_nop_code, FTRACE_INSN_SIZE);
+ 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)
{
- return ftrace_modify_code(rec->ip,
- ftrace_nop_code, FTRACE_INSN_SIZE,
- ftrace_call_code, FTRACE_INSN_SIZE);
+ 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)
{
- ftrace_dyn_func = (unsigned long)func;
return 0;
}
int __init ftrace_dyn_arch_init(void *data)
{
- *(unsigned long *)data = 0;
+ *(unsigned long *) data = 0;
return 0;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-#ifdef CONFIG_DYNAMIC_FTRACE
-/*
- * Patch the kernel code at ftrace_graph_caller location:
- * The instruction there is branch relative on condition. The condition mask
- * is either all ones (always branch aka disable ftrace_graph_caller) or all
- * zeroes (nop aka enable ftrace_graph_caller).
- * Instruction format for brc is a7m4xxxx where m is the condition mask.
- */
-int ftrace_enable_ftrace_graph_caller(void)
-{
- unsigned short opcode = 0xa704;
-
- return probe_kernel_write(ftrace_graph_caller, &opcode, sizeof(opcode));
-}
-
-int ftrace_disable_ftrace_graph_caller(void)
-{
- unsigned short opcode = 0xa7f4;
-
- return probe_kernel_write(ftrace_graph_caller, &opcode, sizeof(opcode));
-}
-
-static inline unsigned long ftrace_mcount_call_adjust(unsigned long addr)
-{
- return addr - (ftrace_disable_return - ftrace_disable_code);
-}
-
-#else /* CONFIG_DYNAMIC_FTRACE */
-
-static inline unsigned long ftrace_mcount_call_adjust(unsigned long addr)
-{
- return addr - MCOUNT_OFFSET_RET;
-}
-
-#endif /* CONFIG_DYNAMIC_FTRACE */
-
/*
* Hook the return address and push it in the stack of return addresses
* in current thread info.
*/
-unsigned long prepare_ftrace_return(unsigned long ip, unsigned long parent)
+unsigned long __kprobes prepare_ftrace_return(unsigned long parent,
+ unsigned long ip)
{
struct ftrace_graph_ent trace;
goto out;
if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY)
goto out;
- trace.func = ftrace_mcount_call_adjust(ip) & PSW_ADDR_INSN;
+ 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;
+ 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 */
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