[PATCH v3 07/12] fuzz/x86_emulate: Move all state into fuzz_state

[George Dunlap <george.dunlap@citrix.com>]

This is in preparation for adding the option for a more "compact"
interpretation of the fuzzing data, in which we only change select
bits of the state.

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
---
v3:
 - Move DATA_OFFSET inside the structure
 - Remove a stray blank line
v2: Port over previous changes

CC: Ian Jackson <ian.jackson@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Jan Beulich <jbeulich@suse.com>
---
 tools/fuzz/x86_instruction_emulator/fuzz-emul.c | 89 +++++++++++++------------
 1 file changed, 45 insertions(+), 44 deletions(-)

diff --git a/tools/fuzz/x86_instruction_emulator/fuzz-emul.c b/tools/fuzz/x86_instruction_emulator/fuzz-emul.c
index 8998f21fe1..20d52b33f8 100644
--- a/tools/fuzz/x86_instruction_emulator/fuzz-emul.c
+++ b/tools/fuzz/x86_instruction_emulator/fuzz-emul.c
@@ -24,14 +24,8 @@
 /* Layout of data expected as fuzzing input. */
 struct fuzz_corpus
 {
-    unsigned long cr[5];
-    uint64_t msr[MSR_INDEX_MAX];
-    struct cpu_user_regs regs;
-    struct segment_register segments[SEG_NUM];
-    unsigned long options;
     unsigned char data[4096];
 } input;
-#define DATA_OFFSET offsetof(struct fuzz_corpus, data)
 
 /*
  * Internal state of the fuzzing harness.  Calculated initially from the input
@@ -39,7 +33,14 @@ struct fuzz_corpus
  */
 struct fuzz_state
 {
+    unsigned long options;
+    unsigned long cr[5];
+    uint64_t msr[MSR_INDEX_MAX];
+    struct segment_register segments[SEG_NUM];
+    struct cpu_user_regs regs;
+
     /* Fuzzer's input data. */
+#define DATA_OFFSET offsetof(struct fuzz_state, corpus)
     struct fuzz_corpus *corpus;
 
     /* Real amount of data backing corpus->data[]. */
@@ -392,11 +393,10 @@ static int fuzz_read_segment(
     struct x86_emulate_ctxt *ctxt)
 {
     const struct fuzz_state *s = ctxt->data;
-    const struct fuzz_corpus *c = s->corpus;
 
     assert(is_x86_user_segment(seg) || is_x86_system_segment(seg));
 
-    *reg = c->segments[seg];
+    *reg = s->segments[seg];
 
     return X86EMUL_OKAY;
 }
@@ -407,7 +407,6 @@ static int fuzz_write_segment(
     struct x86_emulate_ctxt *ctxt)
 {
     struct fuzz_state *s = ctxt->data;
-    struct fuzz_corpus *c = s->corpus;
     int rc;
 
     assert(is_x86_user_segment(seg) || is_x86_system_segment(seg));
@@ -415,7 +414,7 @@ static int fuzz_write_segment(
     rc = maybe_fail(ctxt, "write_segment", true);
 
     if ( rc == X86EMUL_OKAY )
-        c->segments[seg] = *reg;
+        s->segments[seg] = *reg;
 
     return rc;
 }
@@ -426,12 +425,11 @@ static int fuzz_read_cr(
     struct x86_emulate_ctxt *ctxt)
 {
     const struct fuzz_state *s = ctxt->data;
-    const struct fuzz_corpus *c = s->corpus;
 
-    if ( reg >= ARRAY_SIZE(c->cr) )
+    if ( reg >= ARRAY_SIZE(s->cr) )
         return X86EMUL_UNHANDLEABLE;
 
-    *val = c->cr[reg];
+    *val = s->cr[reg];
 
     return X86EMUL_OKAY;
 }
@@ -442,17 +440,16 @@ static int fuzz_write_cr(
     struct x86_emulate_ctxt *ctxt)
 {
     struct fuzz_state *s = ctxt->data;
-    struct fuzz_corpus *c = s->corpus;
     int rc;
 
-    if ( reg >= ARRAY_SIZE(c->cr) )
+    if ( reg >= ARRAY_SIZE(s->cr) )
         return X86EMUL_UNHANDLEABLE;
 
     rc = maybe_fail(ctxt, "write_cr", true);
     if ( rc != X86EMUL_OKAY )
         return rc;
 
-    c->cr[reg] = val;
+    s->cr[reg] = val;
 
     return X86EMUL_OKAY;
 }
@@ -487,7 +484,6 @@ static int fuzz_read_msr(
     struct x86_emulate_ctxt *ctxt)
 {
     const struct fuzz_state *s = ctxt->data;
-    const struct fuzz_corpus *c = s->corpus;
     unsigned int idx;
 
     switch ( reg )
@@ -501,10 +497,10 @@ static int fuzz_read_msr(
          */
         return data_read(ctxt, x86_seg_none, "read_msr", val, sizeof(*val));
     case MSR_EFER:
-        *val = c->msr[MSRI_EFER];
+        *val = s->msr[MSRI_EFER];
         *val &= ~EFER_LMA;
-        if ( (*val & EFER_LME) && (c->cr[4] & X86_CR4_PAE) &&
-             (c->cr[0] & X86_CR0_PG) )
+        if ( (*val & EFER_LME) && (s->cr[4] & X86_CR4_PAE) &&
+             (s->cr[0] & X86_CR0_PG) )
         {
             printf("Setting EFER_LMA\n");
             *val |= EFER_LMA;
@@ -516,7 +512,7 @@ static int fuzz_read_msr(
     {
         if ( msr_index[idx] == reg )
         {
-            *val = c->msr[idx];
+            *val = s->msr[idx];
             return X86EMUL_OKAY;
         }
     }
@@ -531,7 +527,6 @@ static int fuzz_write_msr(
     struct x86_emulate_ctxt *ctxt)
 {
     struct fuzz_state *s = ctxt->data;
-    struct fuzz_corpus *c = s->corpus;
     unsigned int idx;
     int rc;
 
@@ -550,7 +545,7 @@ static int fuzz_write_msr(
     {
         if ( msr_index[idx] == reg )
         {
-            c->msr[idx] = val;
+            s->msr[idx] = val;
             return X86EMUL_OKAY;
         }
     }
@@ -600,15 +595,14 @@ static void setup_fpu_exception_handler(void)
 static void dump_state(struct x86_emulate_ctxt *ctxt)
 {
     struct fuzz_state *s = ctxt->data;
-    const struct fuzz_corpus *c = s->corpus;
     struct cpu_user_regs *regs = ctxt->regs;
     uint64_t val = 0;
 
     printf(" -- State -- \n");
     printf("addr / sp size: %d / %d\n", ctxt->addr_size, ctxt->sp_size);
-    printf(" cr0: %lx\n", c->cr[0]);
-    printf(" cr3: %lx\n", c->cr[3]);
-    printf(" cr4: %lx\n", c->cr[4]);
+    printf(" cr0: %lx\n", s->cr[0]);
+    printf(" cr3: %lx\n", s->cr[3]);
+    printf(" cr4: %lx\n", s->cr[4]);
 
     printf(" rip: %"PRIx64"\n", regs->rip);
 
@@ -629,15 +623,13 @@ static bool long_mode_active(struct x86_emulate_ctxt *ctxt)
 static bool in_longmode(struct x86_emulate_ctxt *ctxt)
 {
     const struct fuzz_state *s = ctxt->data;
-    const struct fuzz_corpus *c = s->corpus;
 
-    return long_mode_active(ctxt) && c->segments[x86_seg_cs].l;
+    return long_mode_active(ctxt) && s->segments[x86_seg_cs].l;
 }
 
 static void set_sizes(struct x86_emulate_ctxt *ctxt)
 {
     struct fuzz_state *s = ctxt->data;
-    const struct fuzz_corpus *c = s->corpus;
 
     ctxt->lma = long_mode_active(ctxt);
 
@@ -645,11 +637,20 @@ static void set_sizes(struct x86_emulate_ctxt *ctxt)
         ctxt->addr_size = ctxt->sp_size = 64;
     else
     {
-        ctxt->addr_size = c->segments[x86_seg_cs].db ? 32 : 16;
-        ctxt->sp_size   = c->segments[x86_seg_ss].db ? 32 : 16;
+        ctxt->addr_size = s->segments[x86_seg_cs].db ? 32 : 16;
+        ctxt->sp_size   = s->segments[x86_seg_ss].db ? 32 : 16;
     }
 }
 
+static void setup_state(struct x86_emulate_ctxt *ctxt)
+{
+    struct fuzz_state *s = ctxt->data;
+
+    /* Fuzz all of the state in one go */
+    if (!input_read(s, s, DATA_OFFSET))
+        exit(-1);
+}
+
 #define CANONICALIZE(x)                                   \
     do {                                                  \
         uint64_t _y = (x);                                \
@@ -709,8 +710,7 @@ enum {
 static void disable_hooks(struct x86_emulate_ctxt *ctxt)
 {
     struct fuzz_state *s = ctxt->data;
-    const struct fuzz_corpus *c = s->corpus;
-    unsigned long bitmap = c->options;
+    unsigned long bitmap = s->options;
 
     /* See also sanitize_input, some hooks can't be disabled. */
     MAYBE_DISABLE_HOOK(read);
@@ -760,12 +760,11 @@ static void disable_hooks(struct x86_emulate_ctxt *ctxt)
 static void sanitize_input(struct x86_emulate_ctxt *ctxt)
 {
     struct fuzz_state *s = ctxt->data;
-    struct fuzz_corpus *c = s->corpus;
-    struct cpu_user_regs *regs = &c->regs;
-    unsigned long bitmap = c->options;
+    struct cpu_user_regs *regs = ctxt->regs;
+    unsigned long bitmap = s->options;
 
     /* Some hooks can't be disabled. */
-    c->options &= ~((1<<HOOK_read)|(1<<HOOK_insn_fetch));
+    s->options &= ~((1<<HOOK_read)|(1<<HOOK_insn_fetch));
 
     /* Zero 'private' entries */
     regs->error_code = 0;
@@ -779,8 +778,8 @@ static void sanitize_input(struct x86_emulate_ctxt *ctxt)
      * CR0.PG can't be set if CR0.PE isn't set.  Set is more interesting, so
      * set PE if PG is set.
      */
-    if ( c->cr[0] & X86_CR0_PG )
-        c->cr[0] |= X86_CR0_PE;
+    if ( s->cr[0] & X86_CR0_PG )
+        s->cr[0] |= X86_CR0_PE;
 
     /* EFLAGS.VM not available in long mode */
     if ( long_mode_active(ctxt) )
@@ -789,8 +788,8 @@ static void sanitize_input(struct x86_emulate_ctxt *ctxt)
     /* EFLAGS.VM implies 16-bit mode */
     if ( regs->rflags & X86_EFLAGS_VM )
     {
-        c->segments[x86_seg_cs].db = 0;
-        c->segments[x86_seg_ss].db = 0;
+        s->segments[x86_seg_cs].db = 0;
+        s->segments[x86_seg_ss].db = 0;
     }
 }
 
@@ -812,7 +811,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data_p, size_t size)
     };
     struct x86_emulate_ctxt ctxt = {
         .data = &state,
-        .regs = &input.regs,
+        .regs = &state.regs,
         .addr_size = 8 * sizeof(void *),
         .sp_size = 8 * sizeof(void *),
     };
@@ -836,7 +835,9 @@ int LLVMFuzzerTestOneInput(const uint8_t *data_p, size_t size)
     memcpy(&input, data_p, size);
 
     state.corpus = &input;
-    state.data_num = size - DATA_OFFSET;
+    state.data_num = size;
+
+    setup_state(&ctxt);
 
     sanitize_input(&ctxt);
 
-- 
2.14.2


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