diff options
Diffstat (limited to 'arch/s390/kernel/ftrace.c')
| -rw-r--r-- | arch/s390/kernel/ftrace.c | 139 |
1 files changed, 54 insertions, 85 deletions
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c index 54d6493c4a5..51d14fe5eb9 100644 --- a/arch/s390/kernel/ftrace.c +++ b/arch/s390/kernel/ftrace.c @@ -1,7 +1,7 @@ /* * Dynamic function tracer architecture backend. * - * Copyright IBM Corp. 2009 + * Copyright IBM Corp. 2009,2014 * * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>, * Martin Schwidefsky <schwidefsky@de.ibm.com> @@ -17,100 +17,76 @@ #include <asm/asm-offsets.h> #include "entry.h" -#ifdef CONFIG_DYNAMIC_FTRACE - +void mcount_replace_code(void); void ftrace_disable_code(void); void ftrace_enable_insn(void); -#ifdef CONFIG_64BIT /* - * The 64-bit mcount code looks like this: + * The mcount code looks like this: * stg %r14,8(%r15) # offset 0 - * > larl %r1,<&counter> # offset 6 - * > brasl %r14,_mcount # offset 12 + * 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 + * 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. + * The enabled ftrace code block looks like this: + * larl %r0,.+24 # 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 + * br %r1 # offset 12 + * brcl 0,0 # offset 14 + * brc 0,0 # offset 20 + * 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. + * 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 - * > lgr %r0,%r0 # offset 12 - * > basr %r14,%r1 # offset 16 - * lg %r14,8(%15) # offset 18 + * br %r1 # offset 12 + * brcl 0,0 # offset 14 + * brc 0,0 # offset 20 * 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" - " lgr %r0,%r0\n" - " basr %r14,%r1\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 -#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_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, + unsigned long addr) +{ + return 0; +} 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; + } if (probe_kernel_write((void *) rec->ip, ftrace_disable_code, MCOUNT_INSN_SIZE)) return -EPERM; @@ -135,8 +111,6 @@ int __init ftrace_dyn_arch_init(void) return 0; } -#endif /* CONFIG_DYNAMIC_FTRACE */ - #ifdef CONFIG_FUNCTION_GRAPH_TRACER /* * Hook the return address and push it in the stack of return addresses @@ -162,31 +136,26 @@ 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. + * there is branch relative on condition. To enable the ftrace graph code + * block, we simply patch the mask field of the instruction to zero and + * turn the instruction into a nop. + * To disable the ftrace graph code the mask field will be patched to + * all ones, which turns the instruction into an unconditional branch. */ int ftrace_enable_ftrace_graph_caller(void) { - unsigned short offset; + u8 op = 0x04; /* set mask field to zero */ - offset = ((void *) prepare_ftrace_return - - (void *) ftrace_graph_caller) / 2; - return probe_kernel_write((void *) ftrace_graph_caller + 2, - &offset, sizeof(offset)); + return probe_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op)); } int ftrace_disable_ftrace_graph_caller(void) { - static unsigned short offset = 0x0002; + u8 op = 0xf4; /* set mask field to all ones */ - return probe_kernel_write((void *) ftrace_graph_caller + 2, - &offset, sizeof(offset)); + return probe_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op)); } -#endif /* CONFIG_DYNAMIC_FTRACE */ #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |