diff options
Diffstat (limited to 'arch/powerpc/lib/test_emulate_step_exec_instr.S')
| -rw-r--r-- | arch/powerpc/lib/test_emulate_step_exec_instr.S | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/arch/powerpc/lib/test_emulate_step_exec_instr.S b/arch/powerpc/lib/test_emulate_step_exec_instr.S new file mode 100644 index 000000000000..1580f34f4f4f --- /dev/null +++ b/arch/powerpc/lib/test_emulate_step_exec_instr.S @@ -0,0 +1,150 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Non-emulated single-stepping support (currently limited to basic integer + * computations) used to validate the instruction emulation infrastructure. + * + * Copyright (C) 2019 IBM Corporation + */ + +#include <asm/asm-offsets.h> +#include <asm/ppc_asm.h> +#include <asm/code-patching-asm.h> +#include <linux/errno.h> + +/* int exec_instr(struct pt_regs *regs) */ +_GLOBAL(exec_instr) + + /* + * Stack frame layout (INT_FRAME_SIZE bytes) + * In-memory pt_regs (SP + STACK_FRAME_OVERHEAD) + * Scratch space (SP + 8) + * Back chain (SP + 0) + */ + + /* + * Allocate a new stack frame with enough space to hold the register + * states in an in-memory pt_regs and also create the back chain to + * the caller's stack frame. + */ + stdu r1, -INT_FRAME_SIZE(r1) + + /* + * Save non-volatile GPRs on stack. This includes TOC pointer (GPR2) + * and local variables (GPR14 to GPR31). The register for the pt_regs + * parameter (GPR3) is saved additionally to ensure that the resulting + * register state can still be saved even if GPR3 gets overwritten + * when loading the initial register state for the test instruction. + * The stack pointer (GPR1) and the thread pointer (GPR13) are not + * saved as these should not be modified anyway. + */ + SAVE_2GPRS(2, r1) + SAVE_NVGPRS(r1) + + /* + * Save LR on stack to ensure that the return address is available + * even if it gets overwritten by the test instruction. + */ + mflr r0 + std r0, _LINK(r1) + + /* + * Save CR on stack. For simplicity, the entire register is saved + * even though only fields 2 to 4 are non-volatile. + */ + mfcr r0 + std r0, _CCR(r1) + + /* + * Load register state for the test instruction without touching the + * critical non-volatile registers. The register state is passed as a + * pointer to a pt_regs instance. + */ + subi r31, r3, GPR0 + + /* Load LR from pt_regs */ + ld r0, _LINK(r31) + mtlr r0 + + /* Load CR from pt_regs */ + ld r0, _CCR(r31) + mtcr r0 + + /* Load XER from pt_regs */ + ld r0, _XER(r31) + mtxer r0 + + /* Load GPRs from pt_regs */ + REST_GPR(0, r31) + REST_10GPRS(2, r31) + REST_GPR(12, r31) + REST_NVGPRS(r31) + + /* Placeholder for the test instruction */ +1: nop + patch_site 1b patch__exec_instr + + /* + * Since GPR3 is overwritten, temporarily restore it back to its + * original state, i.e. the pointer to pt_regs, to ensure that the + * resulting register state can be saved. Before doing this, a copy + * of it is created in the scratch space which is used later on to + * save it to pt_regs. + */ + std r3, 8(r1) + REST_GPR(3, r1) + + /* Save resulting GPR state to pt_regs */ + subi r3, r3, GPR0 + SAVE_GPR(0, r3) + SAVE_GPR(2, r3) + SAVE_8GPRS(4, r3) + SAVE_GPR(12, r3) + SAVE_NVGPRS(r3) + + /* Save resulting LR to pt_regs */ + mflr r0 + std r0, _LINK(r3) + + /* Save resulting CR to pt_regs */ + mfcr r0 + std r0, _CCR(r3) + + /* Save resulting XER to pt_regs */ + mfxer r0 + std r0, _XER(r3) + + /* Restore resulting GPR3 from scratch space and save it to pt_regs */ + ld r0, 8(r1) + std r0, GPR3(r3) + + /* Set return value to denote execution success */ + li r3, 0 + + /* Continue */ + b 3f + + /* Set return value to denote execution failure */ +2: li r3, -EFAULT + + /* Restore the non-volatile GPRs from stack */ +3: REST_GPR(2, r1) + REST_NVGPRS(r1) + + /* Restore LR from stack to be able to return */ + ld r0, _LINK(r1) + mtlr r0 + + /* Restore CR from stack */ + ld r0, _CCR(r1) + mtcr r0 + + /* Tear down stack frame */ + addi r1, r1, INT_FRAME_SIZE + + /* Return */ + blr + + /* Setup exception table */ + EX_TABLE(1b, 2b) + +_ASM_NOKPROBE_SYMBOL(exec_instr) |