Fix: bytecode interpreter: LOAD_FIELD: handle user fields

The instructions for recursive traversal through composed types
are used by the capture bytecode, and by filter expressions which
access fields nested within composed types.

Instructions BYTECODE_OP_LOAD_FIELD_STRING and
BYTECODE_OP_LOAD_FIELD_SEQUENCE were leaving the "user" attribute
uninitialized. Initialize those to 0.

The handling of userspace strings and integers is missing in LOAD_FIELD
instructions. Therefore, ensure that the specialization leaves the
generic LOAD_FIELD instruction in place for userspace input.

Add a "user" attribute to:
- struct bytecode_get_index_data elem field (produced by the
  specialization),
- struct vstack_load used by the specialization,
- struct load_ptr used by the interpreter.
- struct lttng_interpreter_output used by the event notification
  capture.

Use this "user" attribute in dynamic_load_field() for integer, string
and string_sequence object types to ensure that the proper
userspace-aware accesses are performed when loading those fields.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ib8d4db5b7da5064e5897ab3802ab47e063607036

diff --git a/include/lttng/lttng-bytecode.h b/include/lttng/lttng-bytecode.h
index cd0d8fbedc81542b55004e04826fbc29aaf5cda0..37c0e8a04fd9700cf881c2bd566c47bb966e2611 100644 (file)
--- a/include/lttng/lttng-bytecode.h
+++ b/include/lttng/lttng-bytecode.h
@@ -102,6 +102,7 @@ struct bytecode_get_index_data {
                size_t len;
                enum object_type type;
                bool rev_bo;    /* reverse byte order */
+               bool user;      /* from userspace */
        } elem;
 };
 
@@ -111,6 +112,7 @@ struct vstack_load {
        enum object_type object_type;
        const struct lttng_kernel_event_field *field;
        bool rev_bo;    /* reverse byte order */
+       bool user;      /* from userspace */
 };
 
 struct vstack_entry {
@@ -180,6 +182,7 @@ struct load_ptr {
        const void *ptr;
        size_t nr_elem;
        bool rev_bo;
+       bool user;      /* from userspace */
        /* Temporary place-holders for contexts. */
        union {
                int64_t s64;
@@ -199,7 +202,7 @@ struct estack_entry {
                        const char __user *user_str;
                        size_t seq_len;
                        enum estack_string_literal_type literal_type;
-                       int user;               /* is string from userspace ? */
+                       bool user;              /* is string from userspace ? */
                } s;
                struct load_ptr ptr;
        } u;
@@ -271,7 +274,9 @@ struct lttng_interpreter_output {
 
                struct {
                        const char *str;
+                       const char __user *user_str;
                        size_t len;
+                       bool user;              /* is string from userspace ? */
                } str;
                struct {
                        const void *ptr;

diff --git a/src/lttng-bytecode-interpreter.c b/src/lttng-bytecode-interpreter.c
index 4b100ab861761abb68993a93ad09f0a50004588d..4bb3a79ac6c4ef1fa7ea7f2bc5f9b3dff26ff655 100644 (file)
--- a/src/lttng-bytecode-interpreter.c
+++ b/src/lttng-bytecode-interpreter.c
@@ -16,6 +16,7 @@
 #include <lttng/lttng-bytecode.h>
 #include <lttng/string-utils.h>
 #include <lttng/events-internal.h>
+#include <lttng/probe-user.h>
 
 /*
  * get_char should be called with page fault handler disabled if it is expected
@@ -284,6 +285,9 @@ static int context_get_index(struct lttng_kernel_probe_ctx *lttng_probe_ctx,
 
        switch (field->type->type) {
        case lttng_kernel_type_integer:
+       {
+               const struct lttng_kernel_type_integer *integer_type = lttng_kernel_get_type_integer(field->type);
+
                ctx_field->get_value(ctx_field->priv, lttng_probe_ctx, &v);
                if (lttng_kernel_get_type_integer(field->type)->signedness) {
                        ptr->object_type = OBJECT_TYPE_S64;
@@ -294,8 +298,10 @@ static int context_get_index(struct lttng_kernel_probe_ctx *lttng_probe_ctx,
                        ptr->u.u64 = v.u.s64;   /* Cast. */
                        ptr->ptr = &ptr->u.u64;
                }
-               ptr->rev_bo = lttng_kernel_get_type_integer(field->type)->reverse_byte_order;
+               ptr->rev_bo = integer_type->reverse_byte_order;
+               ptr->user = integer_type->user;
                break;
+       }
        case lttng_kernel_type_enum:
        {
                const struct lttng_kernel_type_enum *enum_type = lttng_kernel_get_type_enum(field->type);
@@ -312,11 +318,13 @@ static int context_get_index(struct lttng_kernel_probe_ctx *lttng_probe_ctx,
                        ptr->ptr = &ptr->u.u64;
                }
                ptr->rev_bo = integer_type->reverse_byte_order;
+               ptr->user = integer_type->user;
                break;
        }
        case lttng_kernel_type_array:
        {
                const struct lttng_kernel_type_array *array_type = lttng_kernel_get_type_array(field->type);
+               const struct lttng_kernel_type_integer *integer_type;
 
                if (!lttng_kernel_type_is_bytewise_integer(array_type->elem_type)) {
                        printk(KERN_WARNING "LTTng: bytecode: Array nesting only supports integer types.\n");
@@ -326,7 +334,9 @@ static int context_get_index(struct lttng_kernel_probe_ctx *lttng_probe_ctx,
                        printk(KERN_WARNING "LTTng: bytecode: Only string arrays are supported for contexts.\n");
                        return -EINVAL;
                }
+               integer_type = lttng_kernel_get_type_integer(array_type->elem_type);
                ptr->object_type = OBJECT_TYPE_STRING;
+               ptr->user = integer_type->user;
                ctx_field->get_value(ctx_field->priv, lttng_probe_ctx, &v);
                ptr->ptr = v.u.str;
                break;
@@ -334,6 +344,7 @@ static int context_get_index(struct lttng_kernel_probe_ctx *lttng_probe_ctx,
        case lttng_kernel_type_sequence:
        {
                const struct lttng_kernel_type_sequence *sequence_type = lttng_kernel_get_type_sequence(field->type);
+               const struct lttng_kernel_type_integer *integer_type;
 
                if (!lttng_kernel_type_is_bytewise_integer(sequence_type->elem_type)) {
                        printk(KERN_WARNING "LTTng: bytecode: Sequence nesting only supports integer types.\n");
@@ -343,16 +354,23 @@ static int context_get_index(struct lttng_kernel_probe_ctx *lttng_probe_ctx,
                        printk(KERN_WARNING "LTTng: bytecode: Only string sequences are supported for contexts.\n");
                        return -EINVAL;
                }
+               integer_type = lttng_kernel_get_type_integer(sequence_type->elem_type);
                ptr->object_type = OBJECT_TYPE_STRING;
+               ptr->user = integer_type->user;
                ctx_field->get_value(ctx_field->priv, lttng_probe_ctx, &v);
                ptr->ptr = v.u.str;
                break;
        }
        case lttng_kernel_type_string:
+       {
+               const struct lttng_kernel_type_string *string_type = lttng_kernel_get_type_string(field->type);
+
                ptr->object_type = OBJECT_TYPE_STRING;
+               ptr->user = string_type->user;
                ctx_field->get_value(ctx_field->priv, lttng_probe_ctx, &v);
                ptr->ptr = v.u.str;
                break;
+       }
        case lttng_kernel_type_struct:
                printk(KERN_WARNING "LTTng: bytecode: Structure type cannot be loaded.\n");
                return -EINVAL;
@@ -388,6 +406,7 @@ static int dynamic_get_index(struct lttng_kernel_probe_ctx *lttng_probe_ctx,
                        stack_top->u.ptr.ptr = ptr;
                        stack_top->u.ptr.object_type = gid->elem.type;
                        stack_top->u.ptr.rev_bo = gid->elem.rev_bo;
+                       stack_top->u.ptr.user = gid->elem.user;
                        BUG_ON(stack_top->u.ptr.field->type->type != lttng_kernel_type_array);
                        stack_top->u.ptr.field = NULL;
                        break;
@@ -407,6 +426,7 @@ static int dynamic_get_index(struct lttng_kernel_probe_ctx *lttng_probe_ctx,
                        stack_top->u.ptr.ptr = ptr;
                        stack_top->u.ptr.object_type = gid->elem.type;
                        stack_top->u.ptr.rev_bo = gid->elem.rev_bo;
+                       stack_top->u.ptr.user = gid->elem.user;
                        BUG_ON(stack_top->u.ptr.field->type->type != lttng_kernel_type_sequence);
                        stack_top->u.ptr.field = NULL;
                        break;
@@ -443,6 +463,7 @@ static int dynamic_get_index(struct lttng_kernel_probe_ctx *lttng_probe_ctx,
                stack_top->u.ptr.type = LOAD_OBJECT;
                stack_top->u.ptr.field = gid->field;
                stack_top->u.ptr.rev_bo = gid->elem.rev_bo;
+               stack_top->u.ptr.user = gid->elem.user;
                break;
        }
 
@@ -472,7 +493,12 @@ static int dynamic_load_field(struct estack_entry *stack_top)
        switch (stack_top->u.ptr.object_type) {
        case OBJECT_TYPE_S8:
                dbg_printk("op load field s8\n");
-               stack_top->u.v = *(int8_t *) stack_top->u.ptr.ptr;
+               if (stack_top->u.ptr.user) {
+                       if (lttng_copy_from_user_check_nofault(&stack_top->u.v, (int8_t __user *) stack_top->u.ptr.ptr, sizeof(int8_t)))
+                               stack_top->u.v = 0;
+               } else {
+                       stack_top->u.v = *(int8_t *) stack_top->u.ptr.ptr;
+               }
                stack_top->type = REG_S64;
                break;
        case OBJECT_TYPE_S16:
@@ -480,7 +506,12 @@ static int dynamic_load_field(struct estack_entry *stack_top)
                int16_t tmp;
 
                dbg_printk("op load field s16\n");
-               tmp = *(int16_t *) stack_top->u.ptr.ptr;
+               if (stack_top->u.ptr.user) {
+                       if (lttng_copy_from_user_check_nofault(&tmp, (int16_t __user *) stack_top->u.ptr.ptr, sizeof(int16_t)))
+                               tmp = 0;
+               } else {
+                       tmp = *(int16_t *) stack_top->u.ptr.ptr;
+               }
                if (stack_top->u.ptr.rev_bo)
                        __swab16s(&tmp);
                stack_top->u.v = tmp;
@@ -492,7 +523,12 @@ static int dynamic_load_field(struct estack_entry *stack_top)
                int32_t tmp;
 
                dbg_printk("op load field s32\n");
-               tmp = *(int32_t *) stack_top->u.ptr.ptr;
+               if (stack_top->u.ptr.user) {
+                       if (lttng_copy_from_user_check_nofault(&tmp, (int32_t __user *) stack_top->u.ptr.ptr, sizeof(int32_t)))
+                               tmp = 0;
+               } else {
+                       tmp = *(int32_t *) stack_top->u.ptr.ptr;
+               }
                if (stack_top->u.ptr.rev_bo)
                        __swab32s(&tmp);
                stack_top->u.v = tmp;
@@ -504,7 +540,12 @@ static int dynamic_load_field(struct estack_entry *stack_top)
                int64_t tmp;
 
                dbg_printk("op load field s64\n");
-               tmp = *(int64_t *) stack_top->u.ptr.ptr;
+               if (stack_top->u.ptr.user) {
+                       if (lttng_copy_from_user_check_nofault(&tmp, (int64_t __user *) stack_top->u.ptr.ptr, sizeof(int64_t)))
+                               tmp = 0;
+               } else {
+                       tmp = *(int64_t *) stack_top->u.ptr.ptr;
+               }
                if (stack_top->u.ptr.rev_bo)
                        __swab64s(&tmp);
                stack_top->u.v = tmp;
@@ -516,6 +557,11 @@ static int dynamic_load_field(struct estack_entry *stack_top)
                int64_t tmp;
 
                dbg_printk("op load field signed enumeration\n");
+               if (stack_top->u.ptr.user) {
+                       dbg_printk("Bytecode warning: user enum unsupported.\n");
+                       ret = -EINVAL;
+                       goto end;
+               }
                tmp = *(int64_t *) stack_top->u.ptr.ptr;
                if (stack_top->u.ptr.rev_bo)
                        __swab64s(&tmp);
@@ -525,7 +571,12 @@ static int dynamic_load_field(struct estack_entry *stack_top)
        }
        case OBJECT_TYPE_U8:
                dbg_printk("op load field u8\n");
-               stack_top->u.v = *(uint8_t *) stack_top->u.ptr.ptr;
+               if (stack_top->u.ptr.user) {
+                       if (lttng_copy_from_user_check_nofault(&stack_top->u.v, (uint8_t __user *) stack_top->u.ptr.ptr, sizeof(uint8_t)))
+                               stack_top->u.v = 0;
+               } else {
+                       stack_top->u.v = *(uint8_t *) stack_top->u.ptr.ptr;
+               }
                stack_top->type = REG_U64;
                break;
        case OBJECT_TYPE_U16:
@@ -533,7 +584,12 @@ static int dynamic_load_field(struct estack_entry *stack_top)
                uint16_t tmp;
 
                dbg_printk("op load field u16\n");
-               tmp = *(uint16_t *) stack_top->u.ptr.ptr;
+               if (stack_top->u.ptr.user) {
+                       if (lttng_copy_from_user_check_nofault(&tmp, (uint16_t __user *) stack_top->u.ptr.ptr, sizeof(uint16_t)))
+                               tmp = 0;
+               } else {
+                       tmp = *(uint16_t *) stack_top->u.ptr.ptr;
+               }
                if (stack_top->u.ptr.rev_bo)
                        __swab16s(&tmp);
                stack_top->u.v = tmp;
@@ -545,7 +601,12 @@ static int dynamic_load_field(struct estack_entry *stack_top)
                uint32_t tmp;
 
                dbg_printk("op load field u32\n");
-               tmp = *(uint32_t *) stack_top->u.ptr.ptr;
+               if (stack_top->u.ptr.user) {
+                       if (lttng_copy_from_user_check_nofault(&tmp, (uint32_t __user *) stack_top->u.ptr.ptr, sizeof(uint32_t)))
+                               tmp = 0;
+               } else {
+                       tmp = *(uint32_t *) stack_top->u.ptr.ptr;
+               }
                if (stack_top->u.ptr.rev_bo)
                        __swab32s(&tmp);
                stack_top->u.v = tmp;
@@ -557,7 +618,12 @@ static int dynamic_load_field(struct estack_entry *stack_top)
                uint64_t tmp;
 
                dbg_printk("op load field u64\n");
-               tmp = *(uint64_t *) stack_top->u.ptr.ptr;
+               if (stack_top->u.ptr.user) {
+                       if (lttng_copy_from_user_check_nofault(&tmp, (uint64_t __user *) stack_top->u.ptr.ptr, sizeof(uint64_t)))
+                               tmp = 0;
+               } else {
+                       tmp = *(uint64_t *) stack_top->u.ptr.ptr;
+               }
                if (stack_top->u.ptr.rev_bo)
                        __swab64s(&tmp);
                stack_top->u.v = tmp;
@@ -569,6 +635,11 @@ static int dynamic_load_field(struct estack_entry *stack_top)
                uint64_t tmp;
 
                dbg_printk("op load field unsigned enumeration\n");
+               if (stack_top->u.ptr.user) {
+                       dbg_printk("Bytecode warning: user enum unsupported.\n");
+                       ret = -EINVAL;
+                       goto end;
+               }
                tmp = *(uint64_t *) stack_top->u.ptr.ptr;
                if (stack_top->u.ptr.rev_bo)
                        __swab64s(&tmp);
@@ -578,19 +649,30 @@ static int dynamic_load_field(struct estack_entry *stack_top)
        }
        case OBJECT_TYPE_STRING:
        {
-               const char *str;
+               dbg_printk("op load field string: user=%d\n", stack_top->u.ptr.user);
+               if (stack_top->u.ptr.user) {
+                       const char __user *user_str = (const char __user *) stack_top->u.ptr.ptr;
 
-               dbg_printk("op load field string\n");
-               str = (const char *) stack_top->u.ptr.ptr;
-               stack_top->u.s.str = str;
-               if (unlikely(!stack_top->u.s.str)) {
-                       dbg_printk("Bytecode warning: loading a NULL string.\n");
-                       ret = -EINVAL;
-                       goto end;
+                       stack_top->u.s.user_str = user_str;
+                       if (unlikely(!stack_top->u.s.user_str)) {
+                               dbg_printk("Bytecode warning: loading a NULL user string.\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       stack_top->u.s.user = 1;
+               } else {
+                       const char *str = (const char *) stack_top->u.ptr.ptr;
+
+                       stack_top->u.s.str = str;
+                       if (unlikely(!stack_top->u.s.str)) {
+                               dbg_printk("Bytecode warning: loading a NULL string.\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       stack_top->u.s.user = 0;
                }
                stack_top->u.s.seq_len = LTTNG_SIZE_MAX;
-               stack_top->u.s.literal_type =
-                       ESTACK_STRING_LITERAL_TYPE_NONE;
+               stack_top->u.s.literal_type = ESTACK_STRING_LITERAL_TYPE_NONE;
                stack_top->type = REG_STRING;
                break;
        }
@@ -598,17 +680,27 @@ static int dynamic_load_field(struct estack_entry *stack_top)
        {
                const char *ptr;
 
-               dbg_printk("op load field string sequence\n");
+               dbg_printk("op load field string sequence: user=%d\n", stack_top->u.ptr.user);
                ptr = stack_top->u.ptr.ptr;
                stack_top->u.s.seq_len = *(unsigned long *) ptr;
-               stack_top->u.s.str = *(const char **) (ptr + sizeof(unsigned long));
-               if (unlikely(!stack_top->u.s.str)) {
-                       dbg_printk("Bytecode warning: loading a NULL sequence.\n");
-                       ret = -EINVAL;
-                       goto end;
+               if (stack_top->u.ptr.user) {
+                       stack_top->u.s.user_str = *(const char __user **) (ptr + sizeof(unsigned long));
+                       if (unlikely(!stack_top->u.s.user_str)) {
+                               dbg_printk("Bytecode warning: loading a NULL user sequence.\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       stack_top->u.s.user = 1;
+               } else {
+                       stack_top->u.s.str = *(const char **) (ptr + sizeof(unsigned long));
+                       if (unlikely(!stack_top->u.s.str)) {
+                               dbg_printk("Bytecode warning: loading a NULL sequence.\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       stack_top->u.s.user = 0;
                }
-               stack_top->u.s.literal_type =
-                       ESTACK_STRING_LITERAL_TYPE_NONE;
+               stack_top->u.s.literal_type = ESTACK_STRING_LITERAL_TYPE_NONE;
                stack_top->type = REG_STRING;
                break;
        }
@@ -654,8 +746,13 @@ again:
                break;
        case REG_STRING:
                output->type = LTTNG_INTERPRETER_TYPE_STRING;
-               output->u.str.str = ax->u.s.str;
                output->u.str.len = ax->u.s.seq_len;
+               output->u.str.user = ax->u.s.user;
+               if (ax->u.s.user) {
+                       output->u.str.user_str = ax->u.s.user_str;
+               } else {
+                       output->u.str.str = ax->u.s.str;
+               }
                break;
        case REG_PTR:
                switch (ax->u.ptr.object_type) {
@@ -1791,6 +1888,7 @@ int lttng_bytecode_interpret(struct lttng_kernel_bytecode_runtime *kernel_byteco
                        estack_ax(stack, top)->u.s.literal_type =
                                ESTACK_STRING_LITERAL_TYPE_NONE;
                        estack_ax(stack, top)->type = REG_STRING;
+                       estack_ax(stack, top)->u.s.user = 0;
                        next_pc += sizeof(struct load_op);
                        PO;
                }
@@ -1811,6 +1909,7 @@ int lttng_bytecode_interpret(struct lttng_kernel_bytecode_runtime *kernel_byteco
                        estack_ax(stack, top)->u.s.literal_type =
                                ESTACK_STRING_LITERAL_TYPE_NONE;
                        estack_ax(stack, top)->type = REG_STRING;
+                       estack_ax(stack, top)->u.s.user = 0;
                        next_pc += sizeof(struct load_op);
                        PO;
                }

diff --git a/src/lttng-bytecode-specialize.c b/src/lttng-bytecode-specialize.c
index f8b5f19dcdc5d1629a9a9977631446f3c28a6483..936e342db786b86f1d5624eaa1a26b8add7f18b3 100644 (file)
--- a/src/lttng-bytecode-specialize.c
+++ b/src/lttng-bytecode-specialize.c
@@ -77,57 +77,68 @@ static int specialize_load_field(struct vstack_entry *stack_top,
        case OBJECT_TYPE_S8:
                dbg_printk("op load field s8\n");
                stack_top->type = REG_S64;
-               if (!stack_top->load.rev_bo)
+               if (!stack_top->load.user)
                        insn->op = BYTECODE_OP_LOAD_FIELD_S8;
                break;
        case OBJECT_TYPE_S16:
                dbg_printk("op load field s16\n");
                stack_top->type = REG_S64;
-               if (!stack_top->load.rev_bo)
+               if (!stack_top->load.rev_bo && !stack_top->load.user)
                        insn->op = BYTECODE_OP_LOAD_FIELD_S16;
                break;
        case OBJECT_TYPE_S32:
                dbg_printk("op load field s32\n");
                stack_top->type = REG_S64;
-               if (!stack_top->load.rev_bo)
+               if (!stack_top->load.rev_bo && !stack_top->load.user)
                        insn->op = BYTECODE_OP_LOAD_FIELD_S32;
                break;
        case OBJECT_TYPE_S64:
                dbg_printk("op load field s64\n");
                stack_top->type = REG_S64;
-               if (!stack_top->load.rev_bo)
+               if (!stack_top->load.rev_bo && !stack_top->load.user)
                        insn->op = BYTECODE_OP_LOAD_FIELD_S64;
                break;
        case OBJECT_TYPE_SIGNED_ENUM:
                dbg_printk("op load field signed enumeration\n");
-               stack_top->type = REG_PTR;
+               if (stack_top->load.user) {
+                       printk(KERN_WARNING "LTTng: bytecode: user enum unsupported\n");
+                       ret = -EINVAL;
+                       goto end;
+               }
+               stack_top->type = REG_S64;
                break;
        case OBJECT_TYPE_U8:
                dbg_printk("op load field u8\n");
                stack_top->type = REG_S64;
-               insn->op = BYTECODE_OP_LOAD_FIELD_U8;
+               if (!stack_top->load.user)
+                       insn->op = BYTECODE_OP_LOAD_FIELD_U8;
                break;
        case OBJECT_TYPE_U16:
                dbg_printk("op load field u16\n");
                stack_top->type = REG_S64;
-               if (!stack_top->load.rev_bo)
+               if (!stack_top->load.rev_bo && !stack_top->load.user)
                        insn->op = BYTECODE_OP_LOAD_FIELD_U16;
                break;
        case OBJECT_TYPE_U32:
                dbg_printk("op load field u32\n");
                stack_top->type = REG_S64;
-               if (!stack_top->load.rev_bo)
+               if (!stack_top->load.rev_bo && !stack_top->load.user)
                        insn->op = BYTECODE_OP_LOAD_FIELD_U32;
                break;
        case OBJECT_TYPE_U64:
                dbg_printk("op load field u64\n");
                stack_top->type = REG_S64;
-               if (!stack_top->load.rev_bo)
+               if (!stack_top->load.rev_bo && !stack_top->load.user)
                        insn->op = BYTECODE_OP_LOAD_FIELD_U64;
                break;
        case OBJECT_TYPE_UNSIGNED_ENUM:
                dbg_printk("op load field unsigned enumeration\n");
-               stack_top->type = REG_PTR;
+               if (stack_top->load.user) {
+                       printk(KERN_WARNING "LTTng: bytecode: user enum unsupported\n");
+                       ret = -EINVAL;
+                       goto end;
+               }
+               stack_top->type = REG_U64;
                break;
        case OBJECT_TYPE_DOUBLE:
                printk(KERN_WARNING "LTTng: bytecode: Double type unsupported\n\n");
@@ -136,12 +147,14 @@ static int specialize_load_field(struct vstack_entry *stack_top,
        case OBJECT_TYPE_STRING:
                dbg_printk("op load field string\n");
                stack_top->type = REG_STRING;
-               insn->op = BYTECODE_OP_LOAD_FIELD_STRING;
+               if (!stack_top->load.user)
+                       insn->op = BYTECODE_OP_LOAD_FIELD_STRING;
                break;
        case OBJECT_TYPE_STRING_SEQUENCE:
                dbg_printk("op load field string sequence\n");
                stack_top->type = REG_STRING;
-               insn->op = BYTECODE_OP_LOAD_FIELD_SEQUENCE;
+               if (!stack_top->load.user)
+                       insn->op = BYTECODE_OP_LOAD_FIELD_SEQUENCE;
                break;
        case OBJECT_TYPE_DYNAMIC:
                ret = -EINVAL;
@@ -237,9 +250,8 @@ static int specialize_get_index(struct bytecode_runtime *runtime,
                        gid.array_len = num_elems * (elem_len / CHAR_BIT);
                        gid.elem.type = stack_top->load.object_type;
                        gid.elem.len = elem_len;
-                       if (integer_type->reverse_byte_order)
-                               gid.elem.rev_bo = true;
-                       stack_top->load.rev_bo = gid.elem.rev_bo;
+                       stack_top->load.rev_bo = gid.elem.rev_bo = integer_type->reverse_byte_order;
+                       stack_top->load.user = gid.elem.user = integer_type->user;
                        break;
                }
                case OBJECT_TYPE_SEQUENCE:
@@ -266,9 +278,8 @@ static int specialize_get_index(struct bytecode_runtime *runtime,
                        gid.offset = index * (elem_len / CHAR_BIT);
                        gid.elem.type = stack_top->load.object_type;
                        gid.elem.len = elem_len;
-                       if (integer_type->reverse_byte_order)
-                               gid.elem.rev_bo = true;
-                       stack_top->load.rev_bo = gid.elem.rev_bo;
+                       stack_top->load.rev_bo = gid.elem.rev_bo = integer_type->reverse_byte_order;
+                       stack_top->load.user = gid.elem.user = integer_type->user;
                        break;
                }
                case OBJECT_TYPE_STRUCT:
@@ -332,12 +343,17 @@ static int specialize_load_object(const struct lttng_kernel_event_field *field,
 
        switch (field->type->type) {
        case lttng_kernel_type_integer:
-               if (lttng_kernel_get_type_integer(field->type)->signedness)
+       {
+               const struct lttng_kernel_type_integer *integer_type = lttng_kernel_get_type_integer(field->type);
+
+               if (integer_type->signedness)
                        load->object_type = OBJECT_TYPE_S64;
                else
                        load->object_type = OBJECT_TYPE_U64;
-               load->rev_bo = false;
+               load->rev_bo = integer_type->reverse_byte_order;
+               load->user = integer_type->user;
                break;
+       }
        case lttng_kernel_type_enum:
        {
                const struct lttng_kernel_type_enum *enum_type = lttng_kernel_get_type_enum(field->type);
@@ -347,25 +363,30 @@ static int specialize_load_object(const struct lttng_kernel_event_field *field,
                        load->object_type = OBJECT_TYPE_SIGNED_ENUM;
                else
                        load->object_type = OBJECT_TYPE_UNSIGNED_ENUM;
-               load->rev_bo = false;
+               load->rev_bo = integer_type->reverse_byte_order;
+               load->user = integer_type->user;
                break;
        }
        case lttng_kernel_type_array:
        {
                const struct lttng_kernel_type_array *array_type = lttng_kernel_get_type_array(field->type);
+               const struct lttng_kernel_type_integer *integer_type;
 
                if (!lttng_kernel_type_is_bytewise_integer(array_type->elem_type)) {
                        printk(KERN_WARNING "LTTng: bytecode: Array nesting only supports integer types.\n");
                        return -EINVAL;
                }
+               integer_type = lttng_kernel_get_type_integer(array_type->elem_type);
                if (is_context) {
                        load->object_type = OBJECT_TYPE_STRING;
+                       load->user = integer_type->user;
                } else {
                        if (array_type->encoding == lttng_kernel_string_encoding_none) {
                                load->object_type = OBJECT_TYPE_ARRAY;
                                load->field = field;
                        } else {
                                load->object_type = OBJECT_TYPE_STRING_SEQUENCE;
+                               load->user = integer_type->user;
                        }
                }
                break;
@@ -373,26 +394,35 @@ static int specialize_load_object(const struct lttng_kernel_event_field *field,
        case lttng_kernel_type_sequence:
        {
                const struct lttng_kernel_type_sequence *sequence_type = lttng_kernel_get_type_sequence(field->type);
+               const struct lttng_kernel_type_integer *integer_type;
 
                if (!lttng_kernel_type_is_bytewise_integer(sequence_type->elem_type)) {
                        printk(KERN_WARNING "LTTng: bytecode: Sequence nesting only supports integer types.\n");
                        return -EINVAL;
                }
+               integer_type = lttng_kernel_get_type_integer(sequence_type->elem_type);
                if (is_context) {
                        load->object_type = OBJECT_TYPE_STRING;
+                       load->user = integer_type->user;
                } else {
                        if (sequence_type->encoding == lttng_kernel_string_encoding_none) {
                                load->object_type = OBJECT_TYPE_SEQUENCE;
                                load->field = field;
                        } else {
                                load->object_type = OBJECT_TYPE_STRING_SEQUENCE;
+                               load->user = integer_type->user;
                        }
                }
                break;
        }
        case lttng_kernel_type_string:
+       {
+               const struct lttng_kernel_type_string *string_type = lttng_kernel_get_type_string(field->type);
+
                load->object_type = OBJECT_TYPE_STRING;
+               load->user = string_type->user;
                break;
+       }
        case lttng_kernel_type_struct:
                printk(KERN_WARNING "LTTng: bytecode: Structure type cannot be loaded.\n");
                return -EINVAL;
@@ -432,6 +462,7 @@ static int specialize_context_lookup(struct lttng_kernel_ctx *ctx,
        gid.ctx_index = idx;
        gid.elem.type = load->object_type;
        gid.elem.rev_bo = load->rev_bo;
+       gid.elem.user = load->user;
        gid.field = field;
        data_offset = bytecode_push_data(runtime, &gid,
                __alignof__(gid), sizeof(gid));
@@ -503,6 +534,7 @@ static int specialize_payload_lookup(const struct lttng_kernel_event_desc *event
        gid.offset = field_offset;
        gid.elem.type = load->object_type;
        gid.elem.rev_bo = load->rev_bo;
+       gid.elem.user = load->user;
        gid.field = field;
        data_offset = bytecode_push_data(runtime, &gid,
                __alignof__(gid), sizeof(gid));