--- /dev/null
+/*
+ * User-space Probes (UProbes) for x86
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2008-2011
+ * Authors:
+ * Srikar Dronamraju
+ * Jim Keniston
+ */
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/ptrace.h>
+#include <linux/uprobes.h>
+#include <linux/uaccess.h>
+
+#include <linux/kdebug.h>
+#include <asm/processor.h>
+#include <asm/insn.h>
+
+/* Post-execution fixups. */
+
+/* Adjust IP back to vicinity of actual insn */
+#define UPROBE_FIX_IP 0x01
+
+/* Adjust the return address of a call insn */
+#define UPROBE_FIX_CALL 0x02
+
+/* Instruction will modify TF, don't change it */
+#define UPROBE_FIX_SETF 0x04
+
+#define UPROBE_FIX_RIP_SI 0x08
+#define UPROBE_FIX_RIP_DI 0x10
+#define UPROBE_FIX_RIP_BX 0x20
+#define UPROBE_FIX_RIP_MASK \
+ (UPROBE_FIX_RIP_SI | UPROBE_FIX_RIP_DI | UPROBE_FIX_RIP_BX)
+
+#define UPROBE_TRAP_NR UINT_MAX
+
+/* Adaptations for mhiramat x86 decoder v14. */
+#define OPCODE1(insn) ((insn)->opcode.bytes[0])
+#define OPCODE2(insn) ((insn)->opcode.bytes[1])
+#define OPCODE3(insn) ((insn)->opcode.bytes[2])
+#define MODRM_REG(insn) X86_MODRM_REG((insn)->modrm.value)
+
+#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
+ (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
+ (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
+ (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
+ (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
+ << (row % 32))
+
+/*
+ * Good-instruction tables for 32-bit apps. This is non-const and volatile
+ * to keep gcc from statically optimizing it out, as variable_test_bit makes
+ * some versions of gcc to think only *(unsigned long*) is used.
+ *
+ * Opcodes we'll probably never support:
+ * 6c-6f - ins,outs. SEGVs if used in userspace
+ * e4-e7 - in,out imm. SEGVs if used in userspace
+ * ec-ef - in,out acc. SEGVs if used in userspace
+ * cc - int3. SIGTRAP if used in userspace
+ * ce - into. Not used in userspace - no kernel support to make it useful. SEGVs
+ * (why we support bound (62) then? it's similar, and similarly unused...)
+ * f1 - int1. SIGTRAP if used in userspace
+ * f4 - hlt. SEGVs if used in userspace
+ * fa - cli. SEGVs if used in userspace
+ * fb - sti. SEGVs if used in userspace
+ *
+ * Opcodes which need some work to be supported:
+ * 07,17,1f - pop es/ss/ds
+ * Normally not used in userspace, but would execute if used.
+ * Can cause GP or stack exception if tries to load wrong segment descriptor.
+ * We hesitate to run them under single step since kernel's handling
+ * of userspace single-stepping (TF flag) is fragile.
+ * We can easily refuse to support push es/cs/ss/ds (06/0e/16/1e)
+ * on the same grounds that they are never used.
+ * cd - int N.
+ * Used by userspace for "int 80" syscall entry. (Other "int N"
+ * cause GP -> SEGV since their IDT gates don't allow calls from CPL 3).
+ * Not supported since kernel's handling of userspace single-stepping
+ * (TF flag) is fragile.
+ * cf - iret. Normally not used in userspace. Doesn't SEGV unless arguments are bad
+ */
+#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
+static volatile u32 good_insns_32[256 / 32] = {
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+ /* ---------------------------------------------- */
+ W(0x00, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* 00 */
+ W(0x10, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) , /* 10 */
+ W(0x20, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 20 */
+ W(0x30, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 30 */
+ W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
+ W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */
+ W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* 60 */
+ W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 70 */
+ W(0x80, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
+ W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
+ W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* a0 */
+ W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */
+ W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* c0 */
+ W(0xd0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
+ W(0xe0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* e0 */
+ W(0xf0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1) /* f0 */
+ /* ---------------------------------------------- */
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+};
+#else
+#define good_insns_32 NULL
+#endif
+
+/* Good-instruction tables for 64-bit apps.
+ *
+ * Genuinely invalid opcodes:
+ * 06,07 - formerly push/pop es
+ * 0e - formerly push cs
+ * 16,17 - formerly push/pop ss
+ * 1e,1f - formerly push/pop ds
+ * 27,2f,37,3f - formerly daa/das/aaa/aas
+ * 60,61 - formerly pusha/popa
+ * 62 - formerly bound. EVEX prefix for AVX512 (not yet supported)
+ * 82 - formerly redundant encoding of Group1
+ * 9a - formerly call seg:ofs
+ * ce - formerly into
+ * d4,d5 - formerly aam/aad
+ * d6 - formerly undocumented salc
+ * ea - formerly jmp seg:ofs
+ *
+ * Opcodes we'll probably never support:
+ * 6c-6f - ins,outs. SEGVs if used in userspace
+ * e4-e7 - in,out imm. SEGVs if used in userspace
+ * ec-ef - in,out acc. SEGVs if used in userspace
+ * cc - int3. SIGTRAP if used in userspace
+ * f1 - int1. SIGTRAP if used in userspace
+ * f4 - hlt. SEGVs if used in userspace
+ * fa - cli. SEGVs if used in userspace
+ * fb - sti. SEGVs if used in userspace
+ *
+ * Opcodes which need some work to be supported:
+ * cd - int N.
+ * Used by userspace for "int 80" syscall entry. (Other "int N"
+ * cause GP -> SEGV since their IDT gates don't allow calls from CPL 3).
+ * Not supported since kernel's handling of userspace single-stepping
+ * (TF flag) is fragile.
+ * cf - iret. Normally not used in userspace. Doesn't SEGV unless arguments are bad
+ */
+#if defined(CONFIG_X86_64)
+static volatile u32 good_insns_64[256 / 32] = {
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+ /* ---------------------------------------------- */
+ W(0x00, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 1) | /* 00 */
+ W(0x10, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) , /* 10 */
+ W(0x20, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) | /* 20 */
+ W(0x30, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) , /* 30 */
+ W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
+ W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */
+ W(0x60, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* 60 */
+ W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 70 */
+ W(0x80, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
+ W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1) , /* 90 */
+ W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* a0 */
+ W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */
+ W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* c0 */
+ W(0xd0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
+ W(0xe0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0) | /* e0 */
+ W(0xf0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1) /* f0 */
+ /* ---------------------------------------------- */
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+};
+#else
+#define good_insns_64 NULL
+#endif
+
+/* Using this for both 64-bit and 32-bit apps.
+ * Opcodes we don't support:
+ * 0f 00 - SLDT/STR/LLDT/LTR/VERR/VERW/-/- group. System insns
+ * 0f 01 - SGDT/SIDT/LGDT/LIDT/SMSW/-/LMSW/INVLPG group.
+ * Also encodes tons of other system insns if mod=11.
+ * Some are in fact non-system: xend, xtest, rdtscp, maybe more
+ * 0f 05 - syscall
+ * 0f 06 - clts (CPL0 insn)
+ * 0f 07 - sysret
+ * 0f 08 - invd (CPL0 insn)
+ * 0f 09 - wbinvd (CPL0 insn)
+ * 0f 0b - ud2
+ * 0f 30 - wrmsr (CPL0 insn) (then why rdmsr is allowed, it's also CPL0 insn?)
+ * 0f 34 - sysenter
+ * 0f 35 - sysexit
+ * 0f 37 - getsec
+ * 0f 78 - vmread (Intel VMX. CPL0 insn)
+ * 0f 79 - vmwrite (Intel VMX. CPL0 insn)
+ * Note: with prefixes, these two opcodes are
+ * extrq/insertq/AVX512 convert vector ops.
+ * 0f ae - group15: [f]xsave,[f]xrstor,[v]{ld,st}mxcsr,clflush[opt],
+ * {rd,wr}{fs,gs}base,{s,l,m}fence.
+ * Why? They are all user-executable.
+ */
+static volatile u32 good_2byte_insns[256 / 32] = {
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+ /* ---------------------------------------------- */
+ W(0x00, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1) | /* 00 */
+ W(0x10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 10 */
+ W(0x20, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 20 */
+ W(0x30, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1) , /* 30 */
+ W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
+ W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */
+ W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 60 */
+ W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1) , /* 70 */
+ W(0x80, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
+ W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
+ W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1) | /* a0 */
+ W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */
+ W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
+ W(0xd0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
+ W(0xe0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* e0 */
+ W(0xf0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) /* f0 */
+ /* ---------------------------------------------- */
+ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
+};
+#undef W
+
+/*
+ * opcodes we may need to refine support for:
+ *
+ * 0f - 2-byte instructions: For many of these instructions, the validity
+ * depends on the prefix and/or the reg field. On such instructions, we
+ * just consider the opcode combination valid if it corresponds to any
+ * valid instruction.
+ *
+ * 8f - Group 1 - only reg = 0 is OK
+ * c6-c7 - Group 11 - only reg = 0 is OK
+ * d9-df - fpu insns with some illegal encodings
+ * f2, f3 - repnz, repz prefixes. These are also the first byte for
+ * certain floating-point instructions, such as addsd.
+ *
+ * fe - Group 4 - only reg = 0 or 1 is OK
+ * ff - Group 5 - only reg = 0-6 is OK
+ *
+ * others -- Do we need to support these?
+ *
+ * 0f - (floating-point?) prefetch instructions
+ * 07, 17, 1f - pop es, pop ss, pop ds
+ * 26, 2e, 36, 3e - es:, cs:, ss:, ds: segment prefixes --
+ * but 64 and 65 (fs: and gs:) seem to be used, so we support them
+ * 67 - addr16 prefix
+ * ce - into
+ * f0 - lock prefix
+ */
+
+/*
+ * TODO:
+ * - Where necessary, examine the modrm byte and allow only valid instructions
+ * in the different Groups and fpu instructions.
+ */
+
+static bool is_prefix_bad(struct insn *insn)
+{
+ int i;
+
+ for (i = 0; i < insn->prefixes.nbytes; i++) {
+ switch (insn->prefixes.bytes[i]) {
+ case 0x26: /* INAT_PFX_ES */
+ case 0x2E: /* INAT_PFX_CS */
+ case 0x36: /* INAT_PFX_DS */
+ case 0x3E: /* INAT_PFX_SS */
+ case 0xF0: /* INAT_PFX_LOCK */
+ return true;
+ }
+ }
+ return false;
+}
+
+static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool x86_64)
+{
+ u32 volatile *good_insns;
+
+ insn_init(insn, auprobe->insn, sizeof(auprobe->insn), x86_64);
+ /* has the side-effect of processing the entire instruction */
+ insn_get_length(insn);
+ if (WARN_ON_ONCE(!insn_complete(insn)))
+ return -ENOEXEC;
+
+ if (is_prefix_bad(insn))
+ return -ENOTSUPP;
+
+ if (x86_64)
+ good_insns = good_insns_64;
+ else
+ good_insns = good_insns_32;
+
+ if (test_bit(OPCODE1(insn), (unsigned long *)good_insns))
+ return 0;
+
+ if (insn->opcode.nbytes == 2) {
+ if (test_bit(OPCODE2(insn), (unsigned long *)good_2byte_insns))
+ return 0;
+ }
+
+ return -ENOTSUPP;
+}
+
+#ifdef CONFIG_X86_64
+static inline bool is_64bit_mm(struct mm_struct *mm)
+{
+ return !config_enabled(CONFIG_IA32_EMULATION) ||
+ !(mm->context.ia32_compat == TIF_IA32);
+}
+/*
+ * If arch_uprobe->insn doesn't use rip-relative addressing, return
+ * immediately. Otherwise, rewrite the instruction so that it accesses
+ * its memory operand indirectly through a scratch register. Set
+ * defparam->fixups accordingly. (The contents of the scratch register
+ * will be saved before we single-step the modified instruction,
+ * and restored afterward).
+ *
+ * We do this because a rip-relative instruction can access only a
+ * relatively small area (+/- 2 GB from the instruction), and the XOL
+ * area typically lies beyond that area. At least for instructions
+ * that store to memory, we can't execute the original instruction
+ * and "fix things up" later, because the misdirected store could be
+ * disastrous.
+ *
+ * Some useful facts about rip-relative instructions:
+ *
+ * - There's always a modrm byte with bit layout "00 reg 101".
+ * - There's never a SIB byte.
+ * - The displacement is always 4 bytes.
+ * - REX.B=1 bit in REX prefix, which normally extends r/m field,
+ * has no effect on rip-relative mode. It doesn't make modrm byte
+ * with r/m=101 refer to register 1101 = R13.
+ */
+static void riprel_analyze(struct arch_uprobe *auprobe, struct insn *insn)
+{
+ u8 *cursor;
+ u8 reg;
+ u8 reg2;
+
+ if (!insn_rip_relative(insn))
+ return;
+
+ /*
+ * insn_rip_relative() would have decoded rex_prefix, vex_prefix, modrm.
+ * Clear REX.b bit (extension of MODRM.rm field):
+ * we want to encode low numbered reg, not r8+.
+ */
+ if (insn->rex_prefix.nbytes) {
+ cursor = auprobe->insn + insn_offset_rex_prefix(insn);
+ /* REX byte has 0100wrxb layout, clearing REX.b bit */
+ *cursor &= 0xfe;
+ }
+ /*
+ * Similar treatment for VEX3 prefix.
+ * TODO: add XOP/EVEX treatment when insn decoder supports them
+ */
+ if (insn->vex_prefix.nbytes == 3) {
+ /*
+ * vex2: c5 rvvvvLpp (has no b bit)
+ * vex3/xop: c4/8f rxbmmmmm wvvvvLpp
+ * evex: 62 rxbR00mm wvvvv1pp zllBVaaa
+ * (evex will need setting of both b and x since
+ * in non-sib encoding evex.x is 4th bit of MODRM.rm)
+ * Setting VEX3.b (setting because it has inverted meaning):
+ */
+ cursor = auprobe->insn + insn_offset_vex_prefix(insn) + 1;
+ *cursor |= 0x20;
+ }
+
+ /*
+ * Convert from rip-relative addressing to register-relative addressing
+ * via a scratch register.
+ *
+ * This is tricky since there are insns with modrm byte
+ * which also use registers not encoded in modrm byte:
+ * [i]div/[i]mul: implicitly use dx:ax
+ * shift ops: implicitly use cx
+ * cmpxchg: implicitly uses ax
+ * cmpxchg8/16b: implicitly uses dx:ax and bx:cx
+ * Encoding: 0f c7/1 modrm
+ * The code below thinks that reg=1 (cx), chooses si as scratch.
+ * mulx: implicitly uses dx: mulx r/m,r1,r2 does r1:r2 = dx * r/m.
+ * First appeared in Haswell (BMI2 insn). It is vex-encoded.
+ * Example where none of bx,cx,dx can be used as scratch reg:
+ * c4 e2 63 f6 0d disp32 mulx disp32(%rip),%ebx,%ecx
+ * [v]pcmpistri: implicitly uses cx, xmm0
+ * [v]pcmpistrm: implicitly uses xmm0
+ * [v]pcmpestri: implicitly uses ax, dx, cx, xmm0
+ * [v]pcmpestrm: implicitly uses ax, dx, xmm0
+ * Evil SSE4.2 string comparison ops from hell.
+ * maskmovq/[v]maskmovdqu: implicitly uses (ds:rdi) as destination.
+ * Encoding: 0f f7 modrm, 66 0f f7 modrm, vex-encoded: c5 f9 f7 modrm.
+ * Store op1, byte-masked by op2 msb's in each byte, to (ds:rdi).
+ * AMD says it has no 3-operand form (vex.vvvv must be 1111)
+ * and that it can have only register operands, not mem
+ * (its modrm byte must have mode=11).
+ * If these restrictions will ever be lifted,
+ * we'll need code to prevent selection of di as scratch reg!
+ *
+ * Summary: I don't know any insns with modrm byte which
+ * use SI register implicitly. DI register is used only
+ * by one insn (maskmovq) and BX register is used
+ * only by one too (cmpxchg8b).
+ * BP is stack-segment based (may be a problem?).
+ * AX, DX, CX are off-limits (many implicit users).
+ * SP is unusable (it's stack pointer - think about "pop mem";
+ * also, rsp+disp32 needs sib encoding -> insn length change).
+ */
+
+ reg = MODRM_REG(insn); /* Fetch modrm.reg */
+ reg2 = 0xff; /* Fetch vex.vvvv */
+ if (insn->vex_prefix.nbytes == 2)
+ reg2 = insn->vex_prefix.bytes[1];
+ else if (insn->vex_prefix.nbytes == 3)
+ reg2 = insn->vex_prefix.bytes[2];
+ /*
+ * TODO: add XOP, EXEV vvvv reading.
+ *
+ * vex.vvvv field is in bits 6-3, bits are inverted.
+ * But in 32-bit mode, high-order bit may be ignored.
+ * Therefore, let's consider only 3 low-order bits.
+ */
+ reg2 = ((reg2 >> 3) & 0x7) ^ 0x7;
+ /*
+ * Register numbering is ax,cx,dx,bx, sp,bp,si,di, r8..r15.
+ *
+ * Choose scratch reg. Order is important: must not select bx
+ * if we can use si (cmpxchg8b case!)
+ */
+ if (reg != 6 && reg2 != 6) {
+ reg2 = 6;
+ auprobe->defparam.fixups |= UPROBE_FIX_RIP_SI;
+ } else if (reg != 7 && reg2 != 7) {
+ reg2 = 7;
+ auprobe->defparam.fixups |= UPROBE_FIX_RIP_DI;
+ /* TODO (paranoia): force maskmovq to not use di */
+ } else {
+ reg2 = 3;
+ auprobe->defparam.fixups |= UPROBE_FIX_RIP_BX;
+ }
+ /*
+ * Point cursor at the modrm byte. The next 4 bytes are the
+ * displacement. Beyond the displacement, for some instructions,
+ * is the immediate operand.
+ */
+ cursor = auprobe->insn + insn_offset_modrm(insn);
+ /*
+ * Change modrm from "00 reg 101" to "10 reg reg2". Example:
+ * 89 05 disp32 mov %eax,disp32(%rip) becomes
+ * 89 86 disp32 mov %eax,disp32(%rsi)
+ */
+ *cursor = 0x80 | (reg << 3) | reg2;
+}
+
+static inline unsigned long *
+scratch_reg(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ if (auprobe->defparam.fixups & UPROBE_FIX_RIP_SI)
+ return ®s->si;
+ if (auprobe->defparam.fixups & UPROBE_FIX_RIP_DI)
+ return ®s->di;
+ return ®s->bx;
+}
+
+/*
+ * If we're emulating a rip-relative instruction, save the contents
+ * of the scratch register and store the target address in that register.
+ */
+static void riprel_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ if (auprobe->defparam.fixups & UPROBE_FIX_RIP_MASK) {
+ struct uprobe_task *utask = current->utask;
+ unsigned long *sr = scratch_reg(auprobe, regs);
+
+ utask->autask.saved_scratch_register = *sr;
+ *sr = utask->vaddr + auprobe->defparam.ilen;
+ }
+}
+
+static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ if (auprobe->defparam.fixups & UPROBE_FIX_RIP_MASK) {
+ struct uprobe_task *utask = current->utask;
+ unsigned long *sr = scratch_reg(auprobe, regs);
+
+ *sr = utask->autask.saved_scratch_register;
+ }
+}
+#else /* 32-bit: */
+static inline bool is_64bit_mm(struct mm_struct *mm)
+{
+ return false;
+}
+/*
+ * No RIP-relative addressing on 32-bit
+ */
+static void riprel_analyze(struct arch_uprobe *auprobe, struct insn *insn)
+{
+}
+static void riprel_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+}
+static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+}
+#endif /* CONFIG_X86_64 */
+
+struct uprobe_xol_ops {
+ bool (*emulate)(struct arch_uprobe *, struct pt_regs *);
+ int (*pre_xol)(struct arch_uprobe *, struct pt_regs *);
+ int (*post_xol)(struct arch_uprobe *, struct pt_regs *);
+ void (*abort)(struct arch_uprobe *, struct pt_regs *);
+};
+
+static inline int sizeof_long(void)
+{
+ return is_ia32_task() ? 4 : 8;
+}
+
+static int default_pre_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ riprel_pre_xol(auprobe, regs);
+ return 0;
+}
+
+static int push_ret_address(struct pt_regs *regs, unsigned long ip)
+{
+ unsigned long new_sp = regs->sp - sizeof_long();
+
+ if (copy_to_user((void __user *)new_sp, &ip, sizeof_long()))
+ return -EFAULT;
+
+ regs->sp = new_sp;
+ return 0;
+}
+
+/*
+ * We have to fix things up as follows:
+ *
+ * Typically, the new ip is relative to the copied instruction. We need
+ * to make it relative to the original instruction (FIX_IP). Exceptions
+ * are return instructions and absolute or indirect jump or call instructions.
+ *
+ * If the single-stepped instruction was a call, the return address that
+ * is atop the stack is the address following the copied instruction. We
+ * need to make it the address following the original instruction (FIX_CALL).
+ *
+ * If the original instruction was a rip-relative instruction such as
+ * "movl %edx,0xnnnn(%rip)", we have instead executed an equivalent
+ * instruction using a scratch register -- e.g., "movl %edx,0xnnnn(%rsi)".
+ * We need to restore the contents of the scratch register
+ * (FIX_RIP_reg).
+ */
+static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ struct uprobe_task *utask = current->utask;
+
+ riprel_post_xol(auprobe, regs);
+ if (auprobe->defparam.fixups & UPROBE_FIX_IP) {
+ long correction = utask->vaddr - utask->xol_vaddr;
+ regs->ip += correction;
+ } else if (auprobe->defparam.fixups & UPROBE_FIX_CALL) {
+ regs->sp += sizeof_long(); /* Pop incorrect return address */
+ if (push_ret_address(regs, utask->vaddr + auprobe->defparam.ilen))
+ return -ERESTART;
+ }
+ /* popf; tell the caller to not touch TF */
+ if (auprobe->defparam.fixups & UPROBE_FIX_SETF)
+ utask->autask.saved_tf = true;
+
+ return 0;
+}
+
+static void default_abort_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ riprel_post_xol(auprobe, regs);
+}
+
+static struct uprobe_xol_ops default_xol_ops = {
+ .pre_xol = default_pre_xol_op,
+ .post_xol = default_post_xol_op,
+ .abort = default_abort_op,
+};
+
+static bool branch_is_call(struct arch_uprobe *auprobe)
+{
+ return auprobe->branch.opc1 == 0xe8;
+}
+
+#define CASE_COND \
+ COND(70, 71, XF(OF)) \
+ COND(72, 73, XF(CF)) \
+ COND(74, 75, XF(ZF)) \
+ COND(78, 79, XF(SF)) \
+ COND(7a, 7b, XF(PF)) \
+ COND(76, 77, XF(CF) || XF(ZF)) \
+ COND(7c, 7d, XF(SF) != XF(OF)) \
+ COND(7e, 7f, XF(ZF) || XF(SF) != XF(OF))
+
+#define COND(op_y, op_n, expr) \
+ case 0x ## op_y: DO((expr) != 0) \
+ case 0x ## op_n: DO((expr) == 0)
+
+#define XF(xf) (!!(flags & X86_EFLAGS_ ## xf))
+
+static bool is_cond_jmp_opcode(u8 opcode)
+{
+ switch (opcode) {
+ #define DO(expr) \
+ return true;
+ CASE_COND
+ #undef DO
+
+ default:
+ return false;
+ }
+}
+
+static bool check_jmp_cond(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ unsigned long flags = regs->flags;
+
+ switch (auprobe->branch.opc1) {
+ #define DO(expr) \
+ return expr;
+ CASE_COND
+ #undef DO
+
+ default: /* not a conditional jmp */
+ return true;
+ }
+}
+
+#undef XF
+#undef COND
+#undef CASE_COND
+
+static bool branch_emulate_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ unsigned long new_ip = regs->ip += auprobe->branch.ilen;
+ unsigned long offs = (long)auprobe->branch.offs;
+
+ if (branch_is_call(auprobe)) {
+ /*
+ * If it fails we execute this (mangled, see the comment in
+ * branch_clear_offset) insn out-of-line. In the likely case
+ * this should trigger the trap, and the probed application
+ * should die or restart the same insn after it handles the
+ * signal, arch_uprobe_post_xol() won't be even called.
+ *
+ * But there is corner case, see the comment in ->post_xol().
+ */
+ if (push_ret_address(regs, new_ip))
+ return false;
+ } else if (!check_jmp_cond(auprobe, regs)) {
+ offs = 0;
+ }
+
+ regs->ip = new_ip + offs;
+ return true;
+}
+
+static int branch_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ BUG_ON(!branch_is_call(auprobe));
+ /*
+ * We can only get here if branch_emulate_op() failed to push the ret
+ * address _and_ another thread expanded our stack before the (mangled)
+ * "call" insn was executed out-of-line. Just restore ->sp and restart.
+ * We could also restore ->ip and try to call branch_emulate_op() again.
+ */
+ regs->sp += sizeof_long();
+ return -ERESTART;
+}
+
+static void branch_clear_offset(struct arch_uprobe *auprobe, struct insn *insn)
+{
+ /*
+ * Turn this insn into "call 1f; 1:", this is what we will execute
+ * out-of-line if ->emulate() fails. We only need this to generate
+ * a trap, so that the probed task receives the correct signal with
+ * the properly filled siginfo.
+ *
+ * But see the comment in ->post_xol(), in the unlikely case it can
+ * succeed. So we need to ensure that the new ->ip can not fall into
+ * the non-canonical area and trigger #GP.
+ *
+ * We could turn it into (say) "pushf", but then we would need to
+ * divorce ->insn[] and ->ixol[]. We need to preserve the 1st byte
+ * of ->insn[] for set_orig_insn().
+ */
+ memset(auprobe->insn + insn_offset_immediate(insn),
+ 0, insn->immediate.nbytes);
+}
+
+static struct uprobe_xol_ops branch_xol_ops = {
+ .emulate = branch_emulate_op,
+ .post_xol = branch_post_xol_op,
+};
+
+/* Returns -ENOSYS if branch_xol_ops doesn't handle this insn */
+static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
+{
+ u8 opc1 = OPCODE1(insn);
+ int i;
+
+ switch (opc1) {
+ case 0xeb: /* jmp 8 */
+ case 0xe9: /* jmp 32 */
+ case 0x90: /* prefix* + nop; same as jmp with .offs = 0 */
+ break;
+
+ case 0xe8: /* call relative */
+ branch_clear_offset(auprobe, insn);
+ break;
+
+ case 0x0f:
+ if (insn->opcode.nbytes != 2)
+ return -ENOSYS;
+ /*
+ * If it is a "near" conditional jmp, OPCODE2() - 0x10 matches
+ * OPCODE1() of the "short" jmp which checks the same condition.
+ */
+ opc1 = OPCODE2(insn) - 0x10;
+ default:
+ if (!is_cond_jmp_opcode(opc1))
+ return -ENOSYS;
+ }
+
+ /*
+ * 16-bit overrides such as CALLW (66 e8 nn nn) are not supported.
+ * Intel and AMD behavior differ in 64-bit mode: Intel ignores 66 prefix.
+ * No one uses these insns, reject any branch insns with such prefix.
+ */
+ for (i = 0; i < insn->prefixes.nbytes; i++) {
+ if (insn->prefixes.bytes[i] == 0x66)
+ return -ENOTSUPP;
+ }
+
+ auprobe->branch.opc1 = opc1;
+ auprobe->branch.ilen = insn->length;
+ auprobe->branch.offs = insn->immediate.value;
+
+ auprobe->ops = &branch_xol_ops;
+ return 0;
+}
+
+/**
+ * arch_uprobe_analyze_insn - instruction analysis including validity and fixups.
+ * @mm: the probed address space.
+ * @arch_uprobe: the probepoint information.
+ * @addr: virtual address at which to install the probepoint
+ * Return 0 on success or a -ve number on error.
+ */
+int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long addr)
+{
+ struct insn insn;
+ u8 fix_ip_or_call = UPROBE_FIX_IP;
+ int ret;
+
+ ret = uprobe_init_insn(auprobe, &insn, is_64bit_mm(mm));
+ if (ret)
+ return ret;
+
+ ret = branch_setup_xol_ops(auprobe, &insn);
+ if (ret != -ENOSYS)
+ return ret;
+
+ /*
+ * Figure out which fixups default_post_xol_op() will need to perform,
+ * and annotate defparam->fixups accordingly.
+ */
+ switch (OPCODE1(&insn)) {
+ case 0x9d: /* popf */
+ auprobe->defparam.fixups |= UPROBE_FIX_SETF;
+ break;
+ case 0xc3: /* ret or lret -- ip is correct */
+ case 0xcb:
+ case 0xc2:
+ case 0xca:
+ case 0xea: /* jmp absolute -- ip is correct */
+ fix_ip_or_call = 0;
+ break;
+ case 0x9a: /* call absolute - Fix return addr, not ip */
+ fix_ip_or_call = UPROBE_FIX_CALL;
+ break;
+ case 0xff:
+ switch (MODRM_REG(&insn)) {
+ case 2: case 3: /* call or lcall, indirect */
+ fix_ip_or_call = UPROBE_FIX_CALL;
+ break;
+ case 4: case 5: /* jmp or ljmp, indirect */
+ fix_ip_or_call = 0;
+ break;
+ }
+ /* fall through */
+ default:
+ riprel_analyze(auprobe, &insn);
+ }
+
+ auprobe->defparam.ilen = insn.length;
+ auprobe->defparam.fixups |= fix_ip_or_call;
+
+ auprobe->ops = &default_xol_ops;
+ return 0;
+}
+
+/*
+ * arch_uprobe_pre_xol - prepare to execute out of line.
+ * @auprobe: the probepoint information.
+ * @regs: reflects the saved user state of current task.
+ */
+int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ struct uprobe_task *utask = current->utask;
+
+ if (auprobe->ops->pre_xol) {
+ int err = auprobe->ops->pre_xol(auprobe, regs);
+ if (err)
+ return err;
+ }
+
+ regs->ip = utask->xol_vaddr;
+ utask->autask.saved_trap_nr = current->thread.trap_nr;
+ current->thread.trap_nr = UPROBE_TRAP_NR;
+
+ utask->autask.saved_tf = !!(regs->flags & X86_EFLAGS_TF);
+ regs->flags |= X86_EFLAGS_TF;
+ if (test_tsk_thread_flag(current, TIF_BLOCKSTEP))
+ set_task_blockstep(current, false);
+
+ return 0;
+}
+
+/*
+ * If xol insn itself traps and generates a signal(Say,
+ * SIGILL/SIGSEGV/etc), then detect the case where a singlestepped
+ * instruction jumps back to its own address. It is assumed that anything
+ * like do_page_fault/do_trap/etc sets thread.trap_nr != -1.
+ *
+ * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr,
+ * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to
+ * UPROBE_TRAP_NR == -1 set by arch_uprobe_pre_xol().
+ */
+bool arch_uprobe_xol_was_trapped(struct task_struct *t)
+{
+ if (t->thread.trap_nr != UPROBE_TRAP_NR)
+ return true;
+
+ return false;
+}
+
+/*
+ * Called after single-stepping. To avoid the SMP problems that can
+ * occur when we temporarily put back the original opcode to
+ * single-step, we single-stepped a copy of the instruction.
+ *
+ * This function prepares to resume execution after the single-step.
+ */
+int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ struct uprobe_task *utask = current->utask;
+ bool send_sigtrap = utask->autask.saved_tf;
+ int err = 0;
+
+ WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
+ current->thread.trap_nr = utask->autask.saved_trap_nr;
+
+ if (auprobe->ops->post_xol) {
+ err = auprobe->ops->post_xol(auprobe, regs);
+ if (err) {
+ /*
+ * Restore ->ip for restart or post mortem analysis.
+ * ->post_xol() must not return -ERESTART unless this
+ * is really possible.
+ */
+ regs->ip = utask->vaddr;
+ if (err == -ERESTART)
+ err = 0;
+ send_sigtrap = false;
+ }
+ }
+ /*
+ * arch_uprobe_pre_xol() doesn't save the state of TIF_BLOCKSTEP
+ * so we can get an extra SIGTRAP if we do not clear TF. We need
+ * to examine the opcode to make it right.
+ */
+ if (send_sigtrap)
+ send_sig(SIGTRAP, current, 0);
+
+ if (!utask->autask.saved_tf)
+ regs->flags &= ~X86_EFLAGS_TF;
+
+ return err;
+}
+
+/* callback routine for handling exceptions. */
+int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data)
+{
+ struct die_args *args = data;
+ struct pt_regs *regs = args->regs;
+ int ret = NOTIFY_DONE;
+
+ /* We are only interested in userspace traps */
+ if (regs && !user_mode(regs))
+ return NOTIFY_DONE;
+
+ switch (val) {
+ case DIE_INT3:
+ if (uprobe_pre_sstep_notifier(regs))
+ ret = NOTIFY_STOP;
+
+ break;
+
+ case DIE_DEBUG:
+ if (uprobe_post_sstep_notifier(regs))
+ ret = NOTIFY_STOP;
+
+ default:
+ break;
+ }
+
+ return ret;
+}
+
+/*
+ * This function gets called when XOL instruction either gets trapped or
+ * the thread has a fatal signal. Reset the instruction pointer to its
+ * probed address for the potential restart or for post mortem analysis.
+ */
+void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ struct uprobe_task *utask = current->utask;
+
+ if (auprobe->ops->abort)
+ auprobe->ops->abort(auprobe, regs);
+
+ current->thread.trap_nr = utask->autask.saved_trap_nr;
+ regs->ip = utask->vaddr;
+ /* clear TF if it was set by us in arch_uprobe_pre_xol() */
+ if (!utask->autask.saved_tf)
+ regs->flags &= ~X86_EFLAGS_TF;
+}
+
+static bool __skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ if (auprobe->ops->emulate)
+ return auprobe->ops->emulate(auprobe, regs);
+ return false;
+}
+
+bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ bool ret = __skip_sstep(auprobe, regs);
+ if (ret && (regs->flags & X86_EFLAGS_TF))
+ send_sig(SIGTRAP, current, 0);
+ return ret;
+}
+
+unsigned long
+arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs)
+{
+ int rasize = sizeof_long(), nleft;
+ unsigned long orig_ret_vaddr = 0; /* clear high bits for 32-bit apps */
+
+ if (copy_from_user(&orig_ret_vaddr, (void __user *)regs->sp, rasize))
+ return -1;
+
+ /* check whether address has been already hijacked */
+ if (orig_ret_vaddr == trampoline_vaddr)
+ return orig_ret_vaddr;
+
+ nleft = copy_to_user((void __user *)regs->sp, &trampoline_vaddr, rasize);
+ if (likely(!nleft))
+ return orig_ret_vaddr;
+
+ if (nleft != rasize) {
+ pr_err("uprobe: return address clobbered: pid=%d, %%sp=%#lx, "
+ "%%ip=%#lx\n", current->pid, regs->sp, regs->ip);
+
+ force_sig_info(SIGSEGV, SEND_SIG_FORCED, current);
+ }
+
+ return -1;
+}
Code Review / kvmfornfv.git / blobdiff