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Diffstat (limited to 'arch/s390/kernel/ftrace.c')
-rw-r--r--arch/s390/kernel/ftrace.c132
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