diff options
| -rw-r--r-- | arch/x86/kernel/uprobes.c | 153 |
1 files changed, 134 insertions, 19 deletions
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c index 8b96a947021f..54e36248e9c0 100644 --- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -66,6 +66,49 @@ * 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. + * + * Prefixes. Most marked as "bad", but it doesn't matter, since insn decoder + * won't report *prefixes* as OPCODE1(insn). + * 0f - 2-byte opcode prefix + * 26,2e,36,3e - es:/cs:/ss:/ds: + * 64 - fs: (marked as "good", why?) + * 65 - gs: (marked as "good", why?) + * 66 - operand-size prefix + * 67 - address-size prefix + * f0 - lock prefix + * f2 - repnz (marked as "good", why?) + * f3 - rep/repz (marked as "good", why?) + * + * 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 + * + * Opcodes which can be enabled right away: + * 63 - arpl. This insn has no unusual exceptions (it's basically an arith op). + * d6 - salc. Undocumented "sign-extend carry flag to AL" insn */ #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) static volatile u32 good_insns_32[256 / 32] = { @@ -94,7 +137,55 @@ static volatile u32 good_insns_32[256 / 32] = { #define good_insns_32 NULL #endif -/* Good-instruction tables for 64-bit apps */ +/* Good-instruction tables for 64-bit apps. + * + * Prefixes. Most marked as "bad", but it doesn't matter, since insn decoder + * won't report *prefixes* as OPCODE1(insn). + * 0f - 2-byte opcode prefix + * 26,2e,36,3e - es:/cs:/ss:/ds: + * 40-4f - rex prefixes + * 64 - fs: (marked as "good", why?) + * 65 - gs: (marked as "good", why?) + * 66 - operand-size prefix + * 67 - address-size prefix + * f0 - lock prefix + * f2 - repnz (marked as "good", why?) + * f3 - rep/repz (marked as "good", why?) + * + * 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 + * 82 - formerly redundant encoding of Group1 + * 9a - formerly call seg:ofs (marked as "supported"???) + * c4,c5 - formerly les/lds. VEX prefixes for AVX + * ce - formerly into + * d4,d5 - formerly aam/aad + * d6 - formerly undocumented salc + * ea - formerly jmp seg:ofs (marked as "supported"???) + * + * 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 */ @@ -122,7 +213,48 @@ static volatile u32 good_insns_64[256 / 32] = { #define good_insns_64 NULL #endif -/* Using this for both 64-bit and 32-bit apps */ +/* 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 02 - lar (why? should be safe, it throws no exceptipons) + * 0f 03 - lsl (why? should be safe, it throws no exceptipons) + * 0f 04 - undefined + * 0f 05 - syscall + * 0f 06 - clts (CPL0 insn) + * 0f 07 - sysret + * 0f 08 - invd (CPL0 insn) + * 0f 09 - wbinvd (CPL0 insn) + * 0f 0a - undefined + * 0f 0b - ud2 + * 0f 0c - undefined + * 0f 0d - prefetchFOO (amd prefetch insns) + * 0f 18 - prefetchBAR (intel prefetch insns) + * 0f 24 - mov from test regs (perhaps entire 20-27 area can be disabled (special reg ops)) + * 0f 25 - undefined + * 0f 26 - mov to test regs + * 0f 27 - undefined + * 0f 30 - wrmsr (CPL0 insn) + * 0f 34 - sysenter + * 0f 35 - sysexit + * 0f 36 - undefined + * 0f 37 - getsec + * 0f 38-3f - 3-byte opcodes (why?? all look safe) + * 0f 78 - vmread + * 0f 79 - vmwrite + * 0f 7a - undefined + * 0f 7b - undefined + * 0f 7c - undefined + * 0f 7d - undefined + * 0f a6 - undefined + * 0f a7 - undefined + * 0f b8 - popcnt (why?? it's an ordinary ALU op) + * 0f d0 - undefined + * 0f f0 - lddqu (why?? it's an ordinary vector load op) + * 0f ff - undefined + */ static volatile u32 good_2byte_insns[256 / 32] = { /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ /* ---------------------------------------------- */ @@ -148,23 +280,6 @@ static volatile u32 good_2byte_insns[256 / 32] = { #undef W /* - * opcodes we'll probably never support: - * - * 6c-6d, e4-e5, ec-ed - in - * 6e-6f, e6-e7, ee-ef - out - * cc, cd - int3, int - * cf - iret - * d6 - illegal instruction - * f1 - int1/icebp - * f4 - hlt - * fa, fb - cli, sti - * 0f - lar, lsl, syscall, clts, sysret, sysenter, sysexit, invd, wbinvd, ud2 - * - * invalid opcodes in 64-bit mode: - * - * 06, 0e, 16, 1e, 27, 2f, 37, 3f, 60-62, 82, c4-c5, d4-d5 - * 63 - we support this opcode in x86_64 but not in i386. - * * opcodes we may need to refine support for: * * 0f - 2-byte instructions: For many of these instructions, the validity |