ARM: add uprobes support

Using Rabin Vincent's ARM uprobes patches as a base, enable uprobes
support on ARM.

Caveats:

 - Thumb is not supported

Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: David A. Long <dave.long@linaro.org>

5 files changed, 484 insertions, 0 deletions

diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index bb739f28dd80..a766bcbaf8ad 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_DYNAMIC_FTRACE)	+= ftrace.o insn.o
 obj-$(CONFIG_FUNCTION_GRAPH_TRACER)     += ftrace.o insn.o
 obj-$(CONFIG_JUMP_LABEL)        += jump_label.o insn.o patch.o
 obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o
+obj-$(CONFIG_UPROBES)           += probes.o probes-arm.o uprobes.o uprobes-arm.o
 obj-$(CONFIG_KPROBES)           += probes.o kprobes.o kprobes-common.o patch.o
 ifdef CONFIG_THUMB2_KERNEL
 obj-$(CONFIG_KPROBES)           += kprobes-thumb.o probes-thumb.o
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 04d63880037f..bd1983437205 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -13,6 +13,7 @@
 #include <linux/personality.h>
 #include <linux/uaccess.h>
 #include <linux/tracehook.h>
+#include <linux/uprobes.h>
 
 #include <asm/elf.h>
 #include <asm/cacheflush.h>
@@ -590,6 +591,9 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
                                         return restart;
                                 }
                                 syscall = 0;
+                        } else if (thread_flags & _TIF_UPROBE) {
+                                clear_thread_flag(TIF_UPROBE);
+                                uprobe_notify_resume(regs);
                         } else {
                                 clear_thread_flag(TIF_NOTIFY_RESUME);
                                 tracehook_notify_resume(regs);
diff --git a/arch/arm/kernel/uprobes-arm.c b/arch/arm/kernel/uprobes-arm.c
new file mode 100644
index 000000000000..d3b655ff17da
--- /dev/null
+++ b/arch/arm/kernel/uprobes-arm.c
@@ -0,0 +1,234 @@
+/*
+ * Copyright (C) 2012 Rabin Vincent <rabin at rab.in>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/stddef.h>
+#include <linux/wait.h>
+#include <linux/uprobes.h>
+#include <linux/module.h>
+
+#include "probes.h"
+#include "probes-arm.h"
+#include "uprobes.h"
+
+static int uprobes_substitute_pc(unsigned long *pinsn, u32 oregs)
+{
+        probes_opcode_t insn = __mem_to_opcode_arm(*pinsn);
+        probes_opcode_t temp;
+        probes_opcode_t mask;
+        int freereg;
+        u32 free = 0xffff;
+        u32 regs;
+
+        for (regs = oregs; regs; regs >>= 4, insn >>= 4) {
+                if ((regs & 0xf) == REG_TYPE_NONE)
+                        continue;
+
+                free &= ~(1 << (insn & 0xf));
+        }
+
+        /* No PC, no problem */
+        if (free & (1 << 15))
+                return 15;
+
+        if (!free)
+                return -1;
+
+        /*
+         * fls instead of ffs ensures that for "ldrd r0, r1, [pc]" we would
+         * pick LR instead of R1.
+         */
+        freereg = free = fls(free) - 1;
+
+        temp = __mem_to_opcode_arm(*pinsn);
+        insn = temp;
+        regs = oregs;
+        mask = 0xf;
+
+        for (; regs; regs >>= 4, mask <<= 4, free <<= 4, temp >>= 4) {
+                if ((regs & 0xf) == REG_TYPE_NONE)
+                        continue;
+
+                if ((temp & 0xf) != 15)
+                        continue;
+
+                insn &= ~mask;
+                insn |= free & mask;
+        }
+
+        *pinsn = __opcode_to_mem_arm(insn);
+        return freereg;
+}
+
+static void uprobe_set_pc(struct arch_uprobe *auprobe,
+                          struct arch_uprobe_task *autask,
+                          struct pt_regs *regs)
+{
+        u32 pcreg = auprobe->pcreg;
+
+        autask->backup = regs->uregs[pcreg];
+        regs->uregs[pcreg] = regs->ARM_pc + 8;
+}
+
+static void uprobe_unset_pc(struct arch_uprobe *auprobe,
+                            struct arch_uprobe_task *autask,
+                            struct pt_regs *regs)
+{
+        /* PC will be taken care of by common code */
+        regs->uregs[auprobe->pcreg] = autask->backup;
+}
+
+static void uprobe_aluwrite_pc(struct arch_uprobe *auprobe,
+                               struct arch_uprobe_task *autask,
+                               struct pt_regs *regs)
+{
+        u32 pcreg = auprobe->pcreg;
+
+        alu_write_pc(regs->uregs[pcreg], regs);
+        regs->uregs[pcreg] = autask->backup;
+}
+
+static void uprobe_write_pc(struct arch_uprobe *auprobe,
+                            struct arch_uprobe_task *autask,
+                            struct pt_regs *regs)
+{
+        u32 pcreg = auprobe->pcreg;
+
+        load_write_pc(regs->uregs[pcreg], regs);
+        regs->uregs[pcreg] = autask->backup;
+}
+
+enum probes_insn
+decode_pc_ro(probes_opcode_t insn, struct arch_probes_insn *asi,
+             const struct decode_header *d)
+{
+        struct arch_uprobe *auprobe = container_of(asi, struct arch_uprobe,
+                                                   asi);
+        struct decode_emulate *decode = (struct decode_emulate *) d;
+        u32 regs = decode->header.type_regs.bits >> DECODE_TYPE_BITS;
+        int reg;
+
+        reg = uprobes_substitute_pc(&auprobe->ixol[0], regs);
+        if (reg == 15)
+                return INSN_GOOD;
+
+        if (reg == -1)
+                return INSN_REJECTED;
+
+        auprobe->pcreg = reg;
+        auprobe->prehandler = uprobe_set_pc;
+        auprobe->posthandler = uprobe_unset_pc;
+
+        return INSN_GOOD;
+}
+
+enum probes_insn
+decode_wb_pc(probes_opcode_t insn, struct arch_probes_insn *asi,
+             const struct decode_header *d, bool alu)
+{
+        struct arch_uprobe *auprobe = container_of(asi, struct arch_uprobe,
+                                                   asi);
+        enum probes_insn ret = decode_pc_ro(insn, asi, d);
+
+        if (((insn >> 12) & 0xf) == 15)
+                auprobe->posthandler = alu ? uprobe_aluwrite_pc
+                                           : uprobe_write_pc;
+
+        return ret;
+}
+
+enum probes_insn
+decode_rd12rn16rm0rs8_rwflags(probes_opcode_t insn,
+                              struct arch_probes_insn *asi,
+                              const struct decode_header *d)
+{
+        return decode_wb_pc(insn, asi, d, true);
+}
+
+enum probes_insn
+decode_ldr(probes_opcode_t insn, struct arch_probes_insn *asi,
+           const struct decode_header *d)
+{
+        return decode_wb_pc(insn, asi, d, false);
+}
+
+enum probes_insn
+uprobe_decode_ldmstm(probes_opcode_t insn,
+                     struct arch_probes_insn *asi,
+                     const struct decode_header *d)
+{
+        struct arch_uprobe *auprobe = container_of(asi, struct arch_uprobe,
+                                                   asi);
+        unsigned reglist = insn & 0xffff;
+        int rn = (insn >> 16) & 0xf;
+        int lbit = insn & (1 << 20);
+        unsigned used = reglist | (1 << rn);
+
+        if (rn == 15)
+                return INSN_REJECTED;
+
+        if (!(used & (1 << 15)))
+                return INSN_GOOD;
+
+        if (used & (1 << 14))
+                return INSN_REJECTED;
+
+        /* Use LR instead of PC */
+        insn ^= 0xc000;
+
+        auprobe->pcreg = 14;
+        auprobe->ixol[0] = __opcode_to_mem_arm(insn);
+
+        auprobe->prehandler = uprobe_set_pc;
+        if (lbit)
+                auprobe->posthandler = uprobe_write_pc;
+        else
+                auprobe->posthandler = uprobe_unset_pc;
+
+        return INSN_GOOD;
+}
+
+const union decode_action uprobes_probes_actions[] = {
+        [PROBES_EMULATE_NONE] = {.handler = probes_simulate_nop},
+        [PROBES_SIMULATE_NOP] = {.handler = probes_simulate_nop},
+        [PROBES_PRELOAD_IMM] = {.handler = probes_simulate_nop},
+        [PROBES_PRELOAD_REG] = {.handler = probes_simulate_nop},
+        [PROBES_BRANCH_IMM] = {.handler = simulate_blx1},
+        [PROBES_MRS] = {.handler = simulate_mrs},
+        [PROBES_BRANCH_REG] = {.handler = simulate_blx2bx},
+        [PROBES_CLZ] = {.handler = probes_simulate_nop},
+        [PROBES_SATURATING_ARITHMETIC] = {.handler = probes_simulate_nop},
+        [PROBES_MUL1] = {.handler = probes_simulate_nop},
+        [PROBES_MUL2] = {.handler = probes_simulate_nop},
+        [PROBES_SWP] = {.handler = probes_simulate_nop},
+        [PROBES_LDRSTRD] = {.decoder = decode_pc_ro},
+        [PROBES_LOAD_EXTRA] = {.decoder = decode_pc_ro},
+        [PROBES_LOAD] = {.decoder = decode_ldr},
+        [PROBES_STORE_EXTRA] = {.decoder = decode_pc_ro},
+        [PROBES_STORE] = {.decoder = decode_pc_ro},
+        [PROBES_MOV_IP_SP] = {.handler = simulate_mov_ipsp},
+        [PROBES_DATA_PROCESSING_REG] = {
+                .decoder = decode_rd12rn16rm0rs8_rwflags},
+        [PROBES_DATA_PROCESSING_IMM] = {
+                .decoder = decode_rd12rn16rm0rs8_rwflags},
+        [PROBES_MOV_HALFWORD] = {.handler = probes_simulate_nop},
+        [PROBES_SEV] = {.handler = probes_simulate_nop},
+        [PROBES_WFE] = {.handler = probes_simulate_nop},
+        [PROBES_SATURATE] = {.handler = probes_simulate_nop},
+        [PROBES_REV] = {.handler = probes_simulate_nop},
+        [PROBES_MMI] = {.handler = probes_simulate_nop},
+        [PROBES_PACK] = {.handler = probes_simulate_nop},
+        [PROBES_EXTEND] = {.handler = probes_simulate_nop},
+        [PROBES_EXTEND_ADD] = {.handler = probes_simulate_nop},
+        [PROBES_MUL_ADD_LONG] = {.handler = probes_simulate_nop},
+        [PROBES_MUL_ADD] = {.handler = probes_simulate_nop},
+        [PROBES_BITFIELD] = {.handler = probes_simulate_nop},
+        [PROBES_BRANCH] = {.handler = simulate_bbl},
+        [PROBES_LDMSTM] = {.decoder = uprobe_decode_ldmstm}
+};
diff --git a/arch/arm/kernel/uprobes.c b/arch/arm/kernel/uprobes.c
new file mode 100644
index 000000000000..f9bacee973bf
--- /dev/null
+++ b/arch/arm/kernel/uprobes.c
@@ -0,0 +1,210 @@
+/*
+ * Copyright (C) 2012 Rabin Vincent <rabin at rab.in>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/stddef.h>
+#include <linux/errno.h>
+#include <linux/highmem.h>
+#include <linux/sched.h>
+#include <linux/uprobes.h>
+#include <linux/notifier.h>
+
+#include <asm/opcodes.h>
+#include <asm/traps.h>
+
+#include "probes.h"
+#include "probes-arm.h"
+#include "uprobes.h"
+
+#define UPROBE_TRAP_NR  UINT_MAX
+
+bool is_swbp_insn(uprobe_opcode_t *insn)
+{
+        return (__mem_to_opcode_arm(*insn) & 0x0fffffff) ==
+                (UPROBE_SWBP_ARM_INSN & 0x0fffffff);
+}
+
+int set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm,
+             unsigned long vaddr)
+{
+        return uprobe_write_opcode(mm, vaddr,
+                   __opcode_to_mem_arm(auprobe->bpinsn));
+}
+
+bool arch_uprobe_ignore(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+        if (!auprobe->asi.insn_check_cc(regs->ARM_cpsr)) {
+                regs->ARM_pc += 4;
+                return true;
+        }
+
+        return false;
+}
+
+bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+        probes_opcode_t opcode;
+
+        if (!auprobe->simulate)
+                return false;
+
+        opcode = __mem_to_opcode_arm(*(unsigned int *) auprobe->insn);
+
+        auprobe->asi.insn_singlestep(opcode, &auprobe->asi, regs);
+
+        return true;
+}
+
+unsigned long
+arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
+                                  struct pt_regs *regs)
+{
+        unsigned long orig_ret_vaddr;
+
+        orig_ret_vaddr = regs->ARM_lr;
+        /* Replace the return addr with trampoline addr */
+        regs->ARM_lr = trampoline_vaddr;
+        return orig_ret_vaddr;
+}
+
+int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
+                             unsigned long addr)
+{
+        unsigned int insn;
+        unsigned int bpinsn;
+        enum probes_insn ret;
+
+        /* Thumb not yet support */
+        if (addr & 0x3)
+                return -EINVAL;
+
+        insn = __mem_to_opcode_arm(*(unsigned int *)auprobe->insn);
+        auprobe->ixol[0] = __opcode_to_mem_arm(insn);
+        auprobe->ixol[1] = __opcode_to_mem_arm(UPROBE_SS_ARM_INSN);
+
+        ret = arm_probes_decode_insn(insn, &auprobe->asi, false,
+                                     uprobes_probes_actions);
+        switch (ret) {
+        case INSN_REJECTED:
+                return -EINVAL;
+
+        case INSN_GOOD_NO_SLOT:
+                auprobe->simulate = true;
+                break;
+
+        case INSN_GOOD:
+        default:
+                break;
+        }
+
+        bpinsn = UPROBE_SWBP_ARM_INSN & 0x0fffffff;
+        if (insn >= 0xe0000000)
+                bpinsn |= 0xe0000000;  /* Unconditional instruction */
+        else
+                bpinsn |= insn & 0xf0000000;  /* Copy condition from insn */
+
+        auprobe->bpinsn = bpinsn;
+
+        return 0;
+}
+
+int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+        struct uprobe_task *utask = current->utask;
+
+        if (auprobe->prehandler)
+                auprobe->prehandler(auprobe, &utask->autask, regs);
+
+        utask->autask.saved_trap_no = current->thread.trap_no;
+        current->thread.trap_no = UPROBE_TRAP_NR;
+        regs->ARM_pc = utask->xol_vaddr;
+
+        return 0;
+}
+
+int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+        struct uprobe_task *utask = current->utask;
+
+        WARN_ON_ONCE(current->thread.trap_no != UPROBE_TRAP_NR);
+
+        current->thread.trap_no = utask->autask.saved_trap_no;
+        regs->ARM_pc = utask->vaddr + 4;
+
+        if (auprobe->posthandler)
+                auprobe->posthandler(auprobe, &utask->autask, regs);
+
+        return 0;
+}
+
+bool arch_uprobe_xol_was_trapped(struct task_struct *t)
+{
+        if (t->thread.trap_no != UPROBE_TRAP_NR)
+                return true;
+
+        return false;
+}
+
+void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+        struct uprobe_task *utask = current->utask;
+
+        current->thread.trap_no = utask->autask.saved_trap_no;
+        instruction_pointer_set(regs, utask->vaddr);
+}
+
+int arch_uprobe_exception_notify(struct notifier_block *self,
+                                 unsigned long val, void *data)
+{
+        return NOTIFY_DONE;
+}
+
+static int uprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
+{
+        unsigned long flags;
+
+        local_irq_save(flags);
+        instr &= 0x0fffffff;
+        if (instr == (UPROBE_SWBP_ARM_INSN & 0x0fffffff))
+                uprobe_pre_sstep_notifier(regs);
+        else if (instr == (UPROBE_SS_ARM_INSN & 0x0fffffff))
+                uprobe_post_sstep_notifier(regs);
+        local_irq_restore(flags);
+
+        return 0;
+}
+
+unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
+{
+        return instruction_pointer(regs);
+}
+
+static struct undef_hook uprobes_arm_break_hook = {
+        .instr_mask     = 0x0fffffff,
+        .instr_val      = (UPROBE_SWBP_ARM_INSN & 0x0fffffff),
+        .cpsr_mask      = MODE_MASK,
+        .cpsr_val       = USR_MODE,
+        .fn             = uprobe_trap_handler,
+};
+
+static struct undef_hook uprobes_arm_ss_hook = {
+        .instr_mask     = 0x0fffffff,
+        .instr_val      = (UPROBE_SS_ARM_INSN & 0x0fffffff),
+        .cpsr_mask      = MODE_MASK,
+        .cpsr_val       = USR_MODE,
+        .fn             = uprobe_trap_handler,
+};
+
+static int arch_uprobes_init(void)
+{
+        register_undef_hook(&uprobes_arm_break_hook);
+        register_undef_hook(&uprobes_arm_ss_hook);
+
+        return 0;
+}
+device_initcall(arch_uprobes_init);
diff --git a/arch/arm/kernel/uprobes.h b/arch/arm/kernel/uprobes.h
new file mode 100644
index 000000000000..1d0c12dfbd03
--- /dev/null
+++ b/arch/arm/kernel/uprobes.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2012 Rabin Vincent <rabin at rab.in>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __ARM_KERNEL_UPROBES_H
+#define __ARM_KERNEL_UPROBES_H
+
+enum probes_insn uprobe_decode_ldmstm(probes_opcode_t insn,
+                                      struct arch_probes_insn *asi,
+                                      const struct decode_header *d);
+
+enum probes_insn decode_ldr(probes_opcode_t insn,
+                            struct arch_probes_insn *asi,
+                            const struct decode_header *d);
+
+enum probes_insn
+decode_rd12rn16rm0rs8_rwflags(probes_opcode_t insn,
+                              struct arch_probes_insn *asi,
+                              const struct decode_header *d);
+
+enum probes_insn
+decode_wb_pc(probes_opcode_t insn, struct arch_probes_insn *asi,
+             const struct decode_header *d, bool alu);
+
+enum probes_insn
+decode_pc_ro(probes_opcode_t insn, struct arch_probes_insn *asi,
+             const struct decode_header *d);
+
+extern const union decode_action uprobes_probes_actions[];
+
+#endif