diff options
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kernel/ftrace.c | 195 | ||||
| -rw-r--r-- | arch/x86/kernel/mcount_64.S | 25 |
2 files changed, 210 insertions, 10 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 3386dc9aa333..e4d48f6cad86 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -17,6 +17,7 @@ #include <linux/ftrace.h> #include <linux/percpu.h> #include <linux/sched.h> +#include <linux/slab.h> #include <linux/init.h> #include <linux/list.h> #include <linux/module.h> @@ -644,13 +645,8 @@ int __init ftrace_dyn_arch_init(void) { return 0; } -#endif - -#ifdef CONFIG_FUNCTION_GRAPH_TRACER - -#ifdef CONFIG_DYNAMIC_FTRACE -extern void ftrace_graph_call(void); +#if defined(CONFIG_X86_64) || defined(CONFIG_FUNCTION_GRAPH_TRACER) static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr) { static union ftrace_code_union calc; @@ -664,6 +660,193 @@ static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr) */ return calc.code; } +#endif + +/* Currently only x86_64 supports dynamic trampolines */ +#ifdef CONFIG_X86_64 + +#ifdef CONFIG_MODULES +#include <linux/moduleloader.h> +/* Module allocation simplifies allocating memory for code */ +static inline void *alloc_tramp(unsigned long size) +{ + return module_alloc(size); +} +static inline void tramp_free(void *tramp) +{ + module_free(NULL, tramp); +} +#else +/* Trampolines can only be created if modules are supported */ +static inline void *alloc_tramp(unsigned long size) +{ + return NULL; +} +static inline void tramp_free(void *tramp) { } +#endif + +/* Defined as markers to the end of the ftrace default trampolines */ +extern void ftrace_caller_end(void); +extern void ftrace_regs_caller_end(void); +extern void ftrace_return(void); +extern void ftrace_caller_op_ptr(void); +extern void ftrace_regs_caller_op_ptr(void); + +/* movq function_trace_op(%rip), %rdx */ +/* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */ +#define OP_REF_SIZE 7 + +/* + * The ftrace_ops is passed to the function callback. Since the + * trampoline only services a single ftrace_ops, we can pass in + * that ops directly. + * + * The ftrace_op_code_union is used to create a pointer to the + * ftrace_ops that will be passed to the callback function. + */ +union ftrace_op_code_union { + char code[OP_REF_SIZE]; + struct { + char op[3]; + int offset; + } __attribute__((packed)); +}; + +static unsigned long create_trampoline(struct ftrace_ops *ops) +{ + unsigned const char *jmp; + unsigned long start_offset; + unsigned long end_offset; + unsigned long op_offset; + unsigned long offset; + unsigned long size; + unsigned long ip; + unsigned long *ptr; + void *trampoline; + /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */ + unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 }; + union ftrace_op_code_union op_ptr; + int ret; + + if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { + start_offset = (unsigned long)ftrace_regs_caller; + end_offset = (unsigned long)ftrace_regs_caller_end; + op_offset = (unsigned long)ftrace_regs_caller_op_ptr; + } else { + start_offset = (unsigned long)ftrace_caller; + end_offset = (unsigned long)ftrace_caller_end; + op_offset = (unsigned long)ftrace_caller_op_ptr; + } + + size = end_offset - start_offset; + + /* + * Allocate enough size to store the ftrace_caller code, + * the jmp to ftrace_return, as well as the address of + * the ftrace_ops this trampoline is used for. + */ + trampoline = alloc_tramp(size + MCOUNT_INSN_SIZE + sizeof(void *)); + if (!trampoline) + return 0; + + /* Copy ftrace_caller onto the trampoline memory */ + ret = probe_kernel_read(trampoline, (void *)start_offset, size); + if (WARN_ON(ret < 0)) { + tramp_free(trampoline); + return 0; + } + + ip = (unsigned long)trampoline + size; + + /* The trampoline ends with a jmp to ftrace_return */ + jmp = ftrace_jmp_replace(ip, (unsigned long)ftrace_return); + memcpy(trampoline + size, jmp, MCOUNT_INSN_SIZE); + + /* + * The address of the ftrace_ops that is used for this trampoline + * is stored at the end of the trampoline. This will be used to + * load the third parameter for the callback. Basically, that + * location at the end of the trampoline takes the place of + * the global function_trace_op variable. + */ + + ptr = (unsigned long *)(trampoline + size + MCOUNT_INSN_SIZE); + *ptr = (unsigned long)ops; + + op_offset -= start_offset; + memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE); + + /* Are we pointing to the reference? */ + if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0)) { + tramp_free(trampoline); + return 0; + } + + /* Load the contents of ptr into the callback parameter */ + offset = (unsigned long)ptr; + offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE; + + op_ptr.offset = offset; + + /* put in the new offset to the ftrace_ops */ + memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE); + + /* ALLOC_TRAMP flags lets us know we created it */ + ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP; + + return (unsigned long)trampoline; +} + +void arch_ftrace_update_trampoline(struct ftrace_ops *ops) +{ + ftrace_func_t func; + unsigned char *new; + unsigned long start_offset; + unsigned long call_offset; + unsigned long offset; + unsigned long ip; + int ret; + + if (ops->trampoline) { + /* + * The ftrace_ops caller may set up its own trampoline. + * In such a case, this code must not modify it. + */ + if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) + return; + } else { + ops->trampoline = create_trampoline(ops); + if (!ops->trampoline) + return; + } + + if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { + start_offset = (unsigned long)ftrace_regs_caller; + call_offset = (unsigned long)ftrace_regs_call; + } else { + start_offset = (unsigned long)ftrace_caller; + call_offset = (unsigned long)ftrace_call; + } + + offset = call_offset - start_offset; + ip = ops->trampoline + offset; + + func = ftrace_ops_get_func(ops); + + /* Do a safe modify in case the trampoline is executing */ + new = ftrace_call_replace(ip, (unsigned long)func); + ret = update_ftrace_func(ip, new); + + /* The update should never fail */ + WARN_ON(ret); +} +#endif /* CONFIG_X86_64 */ +#endif /* CONFIG_DYNAMIC_FTRACE */ + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + +#ifdef CONFIG_DYNAMIC_FTRACE +extern void ftrace_graph_call(void); static int ftrace_mod_jmp(unsigned long ip, void *func) { diff --git a/arch/x86/kernel/mcount_64.S b/arch/x86/kernel/mcount_64.S index c73aecf10d34..42f0cdd20baf 100644 --- a/arch/x86/kernel/mcount_64.S +++ b/arch/x86/kernel/mcount_64.S @@ -28,9 +28,11 @@ ENTRY(function_hook) END(function_hook) /* skip is set if stack has been adjusted */ -.macro ftrace_caller_setup skip=0 +.macro ftrace_caller_setup trace_label skip=0 MCOUNT_SAVE_FRAME \skip + /* Save this location */ +GLOBAL(\trace_label) /* Load the ftrace_ops into the 3rd parameter */ movq function_trace_op(%rip), %rdx @@ -46,7 +48,7 @@ END(function_hook) .endm ENTRY(ftrace_caller) - ftrace_caller_setup + ftrace_caller_setup ftrace_caller_op_ptr /* regs go into 4th parameter (but make it NULL) */ movq $0, %rcx @@ -54,7 +56,14 @@ GLOBAL(ftrace_call) call ftrace_stub MCOUNT_RESTORE_FRAME -ftrace_return: + + /* + * The copied trampoline must call ftrace_return as it + * still may need to call the function graph tracer. + */ +GLOBAL(ftrace_caller_end) + +GLOBAL(ftrace_return) #ifdef CONFIG_FUNCTION_GRAPH_TRACER GLOBAL(ftrace_graph_call) @@ -70,7 +79,7 @@ ENTRY(ftrace_regs_caller) pushfq /* skip=8 to skip flags saved in SS */ - ftrace_caller_setup 8 + ftrace_caller_setup ftrace_regs_caller_op_ptr 8 /* Save the rest of pt_regs */ movq %r15, R15(%rsp) @@ -122,6 +131,14 @@ GLOBAL(ftrace_regs_call) /* Restore flags */ popfq + /* + * As this jmp to ftrace_return can be a short jump + * it must not be copied into the trampoline. + * The trampoline will add the code to jump + * to the return. + */ +GLOBAL(ftrace_regs_caller_end) + jmp ftrace_return popfq |