diff options
Diffstat (limited to 'arch/x86/kernel/mcount_64.S')
| -rw-r--r-- | arch/x86/kernel/mcount_64.S | 224 |
1 files changed, 172 insertions, 52 deletions
diff --git a/arch/x86/kernel/mcount_64.S b/arch/x86/kernel/mcount_64.S index c73aecf10d3..94ea120fa21 100644 --- a/arch/x86/kernel/mcount_64.S +++ b/arch/x86/kernel/mcount_64.S @@ -21,40 +21,159 @@ # define function_hook mcount #endif +/* All cases save the original rbp (8 bytes) */ +#ifdef CONFIG_FRAME_POINTER +# ifdef CC_USING_FENTRY +/* Save parent and function stack frames (rip and rbp) */ +# define MCOUNT_FRAME_SIZE (8+16*2) +# else +/* Save just function stack frame (rip and rbp) */ +# define MCOUNT_FRAME_SIZE (8+16) +# endif +#else +/* No need to save a stack frame */ +# define MCOUNT_FRAME_SIZE 8 +#endif /* CONFIG_FRAME_POINTER */ + +/* Size of stack used to save mcount regs in save_mcount_regs */ +#define MCOUNT_REG_SIZE (SS+8 + MCOUNT_FRAME_SIZE) + +/* + * gcc -pg option adds a call to 'mcount' in most functions. + * When -mfentry is used, the call is to 'fentry' and not 'mcount' + * and is done before the function's stack frame is set up. + * They both require a set of regs to be saved before calling + * any C code and restored before returning back to the function. + * + * On boot up, all these calls are converted into nops. When tracing + * is enabled, the call can jump to either ftrace_caller or + * ftrace_regs_caller. Callbacks (tracing functions) that require + * ftrace_regs_caller (like kprobes) need to have pt_regs passed to + * it. For this reason, the size of the pt_regs structure will be + * allocated on the stack and the required mcount registers will + * be saved in the locations that pt_regs has them in. + */ + +/* + * @added: the amount of stack added before calling this + * + * After this is called, the following registers contain: + * + * %rdi - holds the address that called the trampoline + * %rsi - holds the parent function (traced function's return address) + * %rdx - holds the original %rbp + */ +.macro save_mcount_regs added=0 + + /* Always save the original rbp */ + pushq %rbp + +#ifdef CONFIG_FRAME_POINTER + /* + * Stack traces will stop at the ftrace trampoline if the frame pointer + * is not set up properly. If fentry is used, we need to save a frame + * pointer for the parent as well as the function traced, because the + * fentry is called before the stack frame is set up, where as mcount + * is called afterward. + */ +#ifdef CC_USING_FENTRY + /* Save the parent pointer (skip orig rbp and our return address) */ + pushq \added+8*2(%rsp) + pushq %rbp + movq %rsp, %rbp + /* Save the return address (now skip orig rbp, rbp and parent) */ + pushq \added+8*3(%rsp) +#else + /* Can't assume that rip is before this (unless added was zero) */ + pushq \added+8(%rsp) +#endif + pushq %rbp + movq %rsp, %rbp +#endif /* CONFIG_FRAME_POINTER */ + + /* + * We add enough stack to save all regs. + */ + subq $(MCOUNT_REG_SIZE - MCOUNT_FRAME_SIZE), %rsp + movq %rax, RAX(%rsp) + movq %rcx, RCX(%rsp) + movq %rdx, RDX(%rsp) + movq %rsi, RSI(%rsp) + movq %rdi, RDI(%rsp) + movq %r8, R8(%rsp) + movq %r9, R9(%rsp) + /* + * Save the original RBP. Even though the mcount ABI does not + * require this, it helps out callers. + */ + movq MCOUNT_REG_SIZE-8(%rsp), %rdx + movq %rdx, RBP(%rsp) + + /* Copy the parent address into %rsi (second parameter) */ +#ifdef CC_USING_FENTRY + movq MCOUNT_REG_SIZE+8+\added(%rsp), %rsi +#else + /* %rdx contains original %rbp */ + movq 8(%rdx), %rsi +#endif + + /* Move RIP to its proper location */ + movq MCOUNT_REG_SIZE+\added(%rsp), %rdi + movq %rdi, RIP(%rsp) + + /* + * Now %rdi (the first parameter) has the return address of + * where ftrace_call returns. But the callbacks expect the + * address of the call itself. + */ + subq $MCOUNT_INSN_SIZE, %rdi + .endm + +.macro restore_mcount_regs + movq R9(%rsp), %r9 + movq R8(%rsp), %r8 + movq RDI(%rsp), %rdi + movq RSI(%rsp), %rsi + movq RDX(%rsp), %rdx + movq RCX(%rsp), %rcx + movq RAX(%rsp), %rax + + /* ftrace_regs_caller can modify %rbp */ + movq RBP(%rsp), %rbp + + addq $MCOUNT_REG_SIZE, %rsp + + .endm + #ifdef CONFIG_DYNAMIC_FTRACE ENTRY(function_hook) retq END(function_hook) -/* skip is set if stack has been adjusted */ -.macro ftrace_caller_setup skip=0 - MCOUNT_SAVE_FRAME \skip +ENTRY(ftrace_caller) + /* save_mcount_regs fills in first two parameters */ + save_mcount_regs +GLOBAL(ftrace_caller_op_ptr) /* Load the ftrace_ops into the 3rd parameter */ movq function_trace_op(%rip), %rdx - /* Load ip into the first parameter */ - movq RIP(%rsp), %rdi - subq $MCOUNT_INSN_SIZE, %rdi - /* Load the parent_ip into the second parameter */ -#ifdef CC_USING_FENTRY - movq SS+16(%rsp), %rsi -#else - movq 8(%rbp), %rsi -#endif -.endm - -ENTRY(ftrace_caller) - ftrace_caller_setup /* regs go into 4th parameter (but make it NULL) */ movq $0, %rcx GLOBAL(ftrace_call) call ftrace_stub - MCOUNT_RESTORE_FRAME -ftrace_return: + restore_mcount_regs + + /* + * 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) @@ -66,11 +185,16 @@ GLOBAL(ftrace_stub) END(ftrace_caller) ENTRY(ftrace_regs_caller) - /* Save the current flags before compare (in SS location)*/ + /* Save the current flags before any operations that can change them */ pushfq - /* skip=8 to skip flags saved in SS */ - ftrace_caller_setup 8 + /* added 8 bytes to save flags */ + save_mcount_regs 8 + /* save_mcount_regs fills in first two parameters */ + +GLOBAL(ftrace_regs_caller_op_ptr) + /* Load the ftrace_ops into the 3rd parameter */ + movq function_trace_op(%rip), %rdx /* Save the rest of pt_regs */ movq %r15, R15(%rsp) @@ -79,18 +203,17 @@ ENTRY(ftrace_regs_caller) movq %r12, R12(%rsp) movq %r11, R11(%rsp) movq %r10, R10(%rsp) - movq %rbp, RBP(%rsp) movq %rbx, RBX(%rsp) /* Copy saved flags */ - movq SS(%rsp), %rcx + movq MCOUNT_REG_SIZE(%rsp), %rcx movq %rcx, EFLAGS(%rsp) /* Kernel segments */ movq $__KERNEL_DS, %rcx movq %rcx, SS(%rsp) movq $__KERNEL_CS, %rcx movq %rcx, CS(%rsp) - /* Stack - skipping return address */ - leaq SS+16(%rsp), %rcx + /* Stack - skipping return address and flags */ + leaq MCOUNT_REG_SIZE+8*2(%rsp), %rcx movq %rcx, RSP(%rsp) /* regs go into 4th parameter */ @@ -101,11 +224,11 @@ GLOBAL(ftrace_regs_call) /* Copy flags back to SS, to restore them */ movq EFLAGS(%rsp), %rax - movq %rax, SS(%rsp) + movq %rax, MCOUNT_REG_SIZE(%rsp) /* Handlers can change the RIP */ movq RIP(%rsp), %rax - movq %rax, SS+8(%rsp) + movq %rax, MCOUNT_REG_SIZE+8(%rsp) /* restore the rest of pt_regs */ movq R15(%rsp), %r15 @@ -113,19 +236,22 @@ GLOBAL(ftrace_regs_call) movq R13(%rsp), %r13 movq R12(%rsp), %r12 movq R10(%rsp), %r10 - movq RBP(%rsp), %rbp movq RBX(%rsp), %rbx - /* skip=8 to skip flags saved in SS */ - MCOUNT_RESTORE_FRAME 8 + restore_mcount_regs /* Restore flags */ popfq - jmp ftrace_return + /* + * 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) - popfq - jmp ftrace_stub + jmp ftrace_return END(ftrace_regs_caller) @@ -136,6 +262,7 @@ ENTRY(function_hook) cmpq $ftrace_stub, ftrace_trace_function jnz trace +fgraph_trace: #ifdef CONFIG_FUNCTION_GRAPH_TRACER cmpq $ftrace_stub, ftrace_graph_return jnz ftrace_graph_caller @@ -148,42 +275,35 @@ GLOBAL(ftrace_stub) retq trace: - MCOUNT_SAVE_FRAME - - movq RIP(%rsp), %rdi -#ifdef CC_USING_FENTRY - movq SS+16(%rsp), %rsi -#else - movq 8(%rbp), %rsi -#endif - subq $MCOUNT_INSN_SIZE, %rdi + /* save_mcount_regs fills in first two parameters */ + save_mcount_regs call *ftrace_trace_function - MCOUNT_RESTORE_FRAME + restore_mcount_regs - jmp ftrace_stub + jmp fgraph_trace END(function_hook) #endif /* CONFIG_DYNAMIC_FTRACE */ #endif /* CONFIG_FUNCTION_TRACER */ #ifdef CONFIG_FUNCTION_GRAPH_TRACER ENTRY(ftrace_graph_caller) - MCOUNT_SAVE_FRAME + /* Saves rbp into %rdx and fills first parameter */ + save_mcount_regs #ifdef CC_USING_FENTRY - leaq SS+16(%rsp), %rdi + leaq MCOUNT_REG_SIZE+8(%rsp), %rsi movq $0, %rdx /* No framepointers needed */ #else - leaq 8(%rbp), %rdi - movq (%rbp), %rdx + /* Save address of the return address of traced function */ + leaq 8(%rdx), %rsi + /* ftrace does sanity checks against frame pointers */ + movq (%rdx), %rdx #endif - movq RIP(%rsp), %rsi - subq $MCOUNT_INSN_SIZE, %rsi - call prepare_ftrace_return - MCOUNT_RESTORE_FRAME + restore_mcount_regs retq END(ftrace_graph_caller) |