diff options
Diffstat (limited to 'arch/arm64/kernel/entry-ftrace.S')
| -rw-r--r-- | arch/arm64/kernel/entry-ftrace.S | 353 |
1 files changed, 353 insertions, 0 deletions
diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S new file mode 100644 index 000000000..f0c16640e --- /dev/null +++ b/arch/arm64/kernel/entry-ftrace.S @@ -0,0 +1,353 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * arch/arm64/kernel/entry-ftrace.S + * + * Copyright (C) 2013 Linaro Limited + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> + */ + +#include <linux/linkage.h> +#include <linux/cfi_types.h> +#include <asm/asm-offsets.h> +#include <asm/assembler.h> +#include <asm/ftrace.h> +#include <asm/insn.h> + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS +/* + * Due to -fpatchable-function-entry=2, the compiler has placed two NOPs before + * the regular function prologue. For an enabled callsite, ftrace_init_nop() and + * ftrace_make_call() have patched those NOPs to: + * + * MOV X9, LR + * BL ftrace_caller + * + * Each instrumented function follows the AAPCS, so here x0-x8 and x18-x30 are + * live (x18 holds the Shadow Call Stack pointer), and x9-x17 are safe to + * clobber. + * + * We save the callsite's context into a struct ftrace_regs before invoking any + * ftrace callbacks. So that we can get a sensible backtrace, we create frame + * records for the callsite and the ftrace entry assembly. This is not + * sufficient for reliable stacktrace: until we create the callsite stack + * record, its caller is missing from the LR and existing chain of frame + * records. + */ +SYM_CODE_START(ftrace_caller) + bti c + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS + /* + * The literal pointer to the ops is at an 8-byte aligned boundary + * which is either 12 or 16 bytes before the BL instruction in the call + * site. See ftrace_call_adjust() for details. + * + * Therefore here the LR points at `literal + 16` or `literal + 20`, + * and we can find the address of the literal in either case by + * aligning to an 8-byte boundary and subtracting 16. We do the + * alignment first as this allows us to fold the subtraction into the + * LDR. + */ + bic x11, x30, 0x7 + ldr x11, [x11, #-(4 * AARCH64_INSN_SIZE)] // op + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS + /* + * If the op has a direct call, handle it immediately without + * saving/restoring registers. + */ + ldr x17, [x11, #FTRACE_OPS_DIRECT_CALL] // op->direct_call + cbnz x17, ftrace_caller_direct +#endif +#endif + + /* Save original SP */ + mov x10, sp + + /* Make room for ftrace regs, plus two frame records */ + sub sp, sp, #(FREGS_SIZE + 32) + + /* Save function arguments */ + stp x0, x1, [sp, #FREGS_X0] + stp x2, x3, [sp, #FREGS_X2] + stp x4, x5, [sp, #FREGS_X4] + stp x6, x7, [sp, #FREGS_X6] + str x8, [sp, #FREGS_X8] + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS + str xzr, [sp, #FREGS_DIRECT_TRAMP] +#endif + + /* Save the callsite's FP, LR, SP */ + str x29, [sp, #FREGS_FP] + str x9, [sp, #FREGS_LR] + str x10, [sp, #FREGS_SP] + + /* Save the PC after the ftrace callsite */ + str x30, [sp, #FREGS_PC] + + /* Create a frame record for the callsite above the ftrace regs */ + stp x29, x9, [sp, #FREGS_SIZE + 16] + add x29, sp, #FREGS_SIZE + 16 + + /* Create our frame record above the ftrace regs */ + stp x29, x30, [sp, #FREGS_SIZE] + add x29, sp, #FREGS_SIZE + + /* Prepare arguments for the the tracer func */ + sub x0, x30, #AARCH64_INSN_SIZE // ip (callsite's BL insn) + mov x1, x9 // parent_ip (callsite's LR) + mov x3, sp // regs + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS + mov x2, x11 // op + ldr x4, [x2, #FTRACE_OPS_FUNC] // op->func + blr x4 // op->func(ip, parent_ip, op, regs) + +#else + ldr_l x2, function_trace_op // op + +SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) + bl ftrace_stub // func(ip, parent_ip, op, regs) +#endif + +/* + * At the callsite x0-x8 and x19-x30 were live. Any C code will have preserved + * x19-x29 per the AAPCS, and we created frame records upon entry, so we need + * to restore x0-x8, x29, and x30. + */ + /* Restore function arguments */ + ldp x0, x1, [sp, #FREGS_X0] + ldp x2, x3, [sp, #FREGS_X2] + ldp x4, x5, [sp, #FREGS_X4] + ldp x6, x7, [sp, #FREGS_X6] + ldr x8, [sp, #FREGS_X8] + + /* Restore the callsite's FP */ + ldr x29, [sp, #FREGS_FP] + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS + ldr x17, [sp, #FREGS_DIRECT_TRAMP] + cbnz x17, ftrace_caller_direct_late +#endif + + /* Restore the callsite's LR and PC */ + ldr x30, [sp, #FREGS_LR] + ldr x9, [sp, #FREGS_PC] + + /* Restore the callsite's SP */ + add sp, sp, #FREGS_SIZE + 32 + + ret x9 + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS +SYM_INNER_LABEL(ftrace_caller_direct_late, SYM_L_LOCAL) + /* + * Head to a direct trampoline in x17 after having run other tracers. + * The ftrace_regs are live, and x0-x8 and FP have been restored. The + * LR, PC, and SP have not been restored. + */ + + /* + * Restore the callsite's LR and PC matching the trampoline calling + * convention. + */ + ldr x9, [sp, #FREGS_LR] + ldr x30, [sp, #FREGS_PC] + + /* Restore the callsite's SP */ + add sp, sp, #FREGS_SIZE + 32 + +SYM_INNER_LABEL(ftrace_caller_direct, SYM_L_LOCAL) + /* + * Head to a direct trampoline in x17. + * + * We use `BR X17` as this can safely land on a `BTI C` or `PACIASP` in + * the trampoline, and will not unbalance any return stack. + */ + br x17 +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ +SYM_CODE_END(ftrace_caller) + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS +SYM_CODE_START(ftrace_stub_direct_tramp) + bti c + mov x10, x30 + mov x30, x9 + ret x10 +SYM_CODE_END(ftrace_stub_direct_tramp) +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ + +#else /* CONFIG_DYNAMIC_FTRACE_WITH_ARGS */ + +/* + * Gcc with -pg will put the following code in the beginning of each function: + * mov x0, x30 + * bl _mcount + * [function's body ...] + * "bl _mcount" may be replaced to "bl ftrace_caller" or NOP if dynamic + * ftrace is enabled. + * + * Please note that x0 as an argument will not be used here because we can + * get lr(x30) of instrumented function at any time by winding up call stack + * as long as the kernel is compiled without -fomit-frame-pointer. + * (or CONFIG_FRAME_POINTER, this is forced on arm64) + * + * stack layout after mcount_enter in _mcount(): + * + * current sp/fp => 0:+-----+ + * in _mcount() | x29 | -> instrumented function's fp + * +-----+ + * | x30 | -> _mcount()'s lr (= instrumented function's pc) + * old sp => +16:+-----+ + * when instrumented | | + * function calls | ... | + * _mcount() | | + * | | + * instrumented => +xx:+-----+ + * function's fp | x29 | -> parent's fp + * +-----+ + * | x30 | -> instrumented function's lr (= parent's pc) + * +-----+ + * | ... | + */ + + .macro mcount_enter + stp x29, x30, [sp, #-16]! + mov x29, sp + .endm + + .macro mcount_exit + ldp x29, x30, [sp], #16 + ret + .endm + + .macro mcount_adjust_addr rd, rn + sub \rd, \rn, #AARCH64_INSN_SIZE + .endm + + /* for instrumented function's parent */ + .macro mcount_get_parent_fp reg + ldr \reg, [x29] + ldr \reg, [\reg] + .endm + + /* for instrumented function */ + .macro mcount_get_pc0 reg + mcount_adjust_addr \reg, x30 + .endm + + .macro mcount_get_pc reg + ldr \reg, [x29, #8] + mcount_adjust_addr \reg, \reg + .endm + + .macro mcount_get_lr reg + ldr \reg, [x29] + ldr \reg, [\reg, #8] + .endm + + .macro mcount_get_lr_addr reg + ldr \reg, [x29] + add \reg, \reg, #8 + .endm + +/* + * _mcount() is used to build the kernel with -pg option, but all the branch + * instructions to _mcount() are replaced to NOP initially at kernel start up, + * and later on, NOP to branch to ftrace_caller() when enabled or branch to + * NOP when disabled per-function base. + */ +SYM_FUNC_START(_mcount) + ret +SYM_FUNC_END(_mcount) +EXPORT_SYMBOL(_mcount) +NOKPROBE(_mcount) + +/* + * void ftrace_caller(unsigned long return_address) + * @return_address: return address to instrumented function + * + * This function is a counterpart of _mcount() in 'static' ftrace, and + * makes calls to: + * - tracer function to probe instrumented function's entry, + * - ftrace_graph_caller to set up an exit hook + */ +SYM_FUNC_START(ftrace_caller) + mcount_enter + + mcount_get_pc0 x0 // function's pc + mcount_get_lr x1 // function's lr + +SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) // tracer(pc, lr); + nop // This will be replaced with "bl xxx" + // where xxx can be any kind of tracer. + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) // ftrace_graph_caller(); + nop // If enabled, this will be replaced + // "b ftrace_graph_caller" +#endif + + mcount_exit +SYM_FUNC_END(ftrace_caller) + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +/* + * void ftrace_graph_caller(void) + * + * Called from _mcount() or ftrace_caller() when function_graph tracer is + * selected. + * This function w/ prepare_ftrace_return() fakes link register's value on + * the call stack in order to intercept instrumented function's return path + * and run return_to_handler() later on its exit. + */ +SYM_FUNC_START(ftrace_graph_caller) + mcount_get_pc x0 // function's pc + mcount_get_lr_addr x1 // pointer to function's saved lr + mcount_get_parent_fp x2 // parent's fp + bl prepare_ftrace_return // prepare_ftrace_return(pc, &lr, fp) + + mcount_exit +SYM_FUNC_END(ftrace_graph_caller) +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_ARGS */ + +SYM_TYPED_FUNC_START(ftrace_stub) + ret +SYM_FUNC_END(ftrace_stub) + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +SYM_TYPED_FUNC_START(ftrace_stub_graph) + ret +SYM_FUNC_END(ftrace_stub_graph) + +/* + * void return_to_handler(void) + * + * Run ftrace_return_to_handler() before going back to parent. + * @fp is checked against the value passed by ftrace_graph_caller(). + */ +SYM_CODE_START(return_to_handler) + /* save return value regs */ + sub sp, sp, #FGRET_REGS_SIZE + stp x0, x1, [sp, #FGRET_REGS_X0] + stp x2, x3, [sp, #FGRET_REGS_X2] + stp x4, x5, [sp, #FGRET_REGS_X4] + stp x6, x7, [sp, #FGRET_REGS_X6] + str x29, [sp, #FGRET_REGS_FP] // parent's fp + + mov x0, sp + bl ftrace_return_to_handler // addr = ftrace_return_to_hander(regs); + mov x30, x0 // restore the original return address + + /* restore return value regs */ + ldp x0, x1, [sp, #FGRET_REGS_X0] + ldp x2, x3, [sp, #FGRET_REGS_X2] + ldp x4, x5, [sp, #FGRET_REGS_X4] + ldp x6, x7, [sp, #FGRET_REGS_X6] + add sp, sp, #FGRET_REGS_SIZE + + ret +SYM_CODE_END(return_to_handler) +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |