self-modifying code support

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@163 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 301 insertions, 12 deletions

diff --git a/exec.c b/exec.c
index a917143..0ed49c6 100644
--- a/exec.c
+++ b/exec.c
@@ -1,5 +1,5 @@
 /*
- *  virtual page mapping
+ *  virtual page mapping and translated block handling
  * 
  *  Copyright (c) 2003 Fabrice Bellard
  *
@@ -24,13 +24,32 @@
 #include <errno.h>
 #include <unistd.h>
 #include <inttypes.h>
+#include <sys/mman.h>
 
 #include "cpu-i386.h"
 
+//#define DEBUG_TB_INVALIDATE
+#define DEBUG_FLUSH
+
+/* make various TB consistency checks */
+//#define DEBUG_TB_CHECK 
+
+/* threshold to flush the translated code buffer */
+#define CODE_GEN_BUFFER_MAX_SIZE (CODE_GEN_BUFFER_SIZE - CODE_GEN_MAX_SIZE)
+
+#define CODE_GEN_MAX_BLOCKS    (CODE_GEN_BUFFER_SIZE / 64)
+
+TranslationBlock tbs[CODE_GEN_MAX_BLOCKS];
+TranslationBlock *tb_hash[CODE_GEN_HASH_SIZE];
+int nb_tbs;
+
+uint8_t code_gen_buffer[CODE_GEN_BUFFER_SIZE];
+uint8_t *code_gen_ptr;
+
 /* XXX: pack the flags in the low bits of the pointer ? */
 typedef struct PageDesc {
-    struct TranslationBlock *first_tb;
     unsigned long flags;
+    TranslationBlock *first_tb;
 } PageDesc;
 
 #define L2_BITS 10
@@ -39,6 +58,8 @@ typedef struct PageDesc {
 #define L1_SIZE (1 << L1_BITS)
 #define L2_SIZE (1 << L2_BITS)
 
+static void tb_invalidate_page(unsigned long address);
+
 unsigned long real_host_page_size;
 unsigned long host_page_bits;
 unsigned long host_page_size;
@@ -104,36 +125,44 @@ void page_dump(FILE *f)
     }
 }
 
-
-static inline PageDesc *page_find_alloc(unsigned long address)
+static inline PageDesc *page_find_alloc(unsigned int index)
 {
-    unsigned int index;
     PageDesc **lp, *p;
 
-    index = address >> TARGET_PAGE_BITS;
     lp = &l1_map[index >> L2_BITS];
     p = *lp;
     if (!p) {
         /* allocate if not found */
         p = malloc(sizeof(PageDesc) * L2_SIZE);
-        memset(p, 0, sizeof(sizeof(PageDesc) * L2_SIZE));
+        memset(p, 0, sizeof(PageDesc) * L2_SIZE);
         *lp = p;
     }
     return p + (index & (L2_SIZE - 1));
 }
 
-int page_get_flags(unsigned long address)
+static inline PageDesc *page_find(unsigned int index)
 {
-    unsigned int index;
     PageDesc *p;
 
-    index = address >> TARGET_PAGE_BITS;
     p = l1_map[index >> L2_BITS];
     if (!p)
         return 0;
-    return p[index & (L2_SIZE - 1)].flags;
+    return p + (index & (L2_SIZE - 1));
+}
+
+int page_get_flags(unsigned long address)
+{
+    PageDesc *p;
+
+    p = page_find(address >> TARGET_PAGE_BITS);
+    if (!p)
+        return 0;
+    return p->flags;
 }
 
+/* modify the flags of a page and invalidate the code if
+   necessary. The flag PAGE_WRITE_ORG is positionned automatically
+   depending on PAGE_WRITE */
 void page_set_flags(unsigned long start, unsigned long end, int flags)
 {
     PageDesc *p;
@@ -141,8 +170,268 @@ void page_set_flags(unsigned long start, unsigned long end, int flags)
 
     start = start & TARGET_PAGE_MASK;
     end = TARGET_PAGE_ALIGN(end);
+    if (flags & PAGE_WRITE)
+        flags |= PAGE_WRITE_ORG;
     for(addr = start; addr < end; addr += TARGET_PAGE_SIZE) {
-        p = page_find_alloc(addr);
+        p = page_find_alloc(addr >> TARGET_PAGE_BITS);
+        /* if the write protection is set, then we invalidate the code
+           inside */
+        if (!(p->flags & PAGE_WRITE) && 
+            (flags & PAGE_WRITE) &&
+            p->first_tb) {
+            tb_invalidate_page(addr);
+        }
         p->flags = flags;
     }
 }
+
+void cpu_x86_tblocks_init(void)
+{
+    if (!code_gen_ptr) {
+        code_gen_ptr = code_gen_buffer;
+    }
+}
+
+/* set to NULL all the 'first_tb' fields in all PageDescs */
+static void page_flush_tb(void)
+{
+    int i, j;
+    PageDesc *p;
+
+    for(i = 0; i < L1_SIZE; i++) {
+        p = l1_map[i];
+        if (p) {
+            for(j = 0; j < L2_SIZE; j++)
+                p[j].first_tb = NULL;
+        }
+    }
+}
+
+/* flush all the translation blocks */
+void tb_flush(void)
+{
+    int i;
+#ifdef DEBUG_FLUSH
+    printf("qemu: flush code_size=%d nb_tbs=%d avg_tb_size=%d\n", 
+           code_gen_ptr - code_gen_buffer, 
+           nb_tbs, 
+           (code_gen_ptr - code_gen_buffer) / nb_tbs);
+#endif
+    nb_tbs = 0;
+    for(i = 0;i < CODE_GEN_HASH_SIZE; i++)
+        tb_hash[i] = NULL;
+    page_flush_tb();
+    code_gen_ptr = code_gen_buffer;
+    /* XXX: flush processor icache at this point */
+}
+
+#ifdef DEBUG_TB_CHECK
+
+static void tb_invalidate_check(unsigned long address)
+{
+    TranslationBlock *tb;
+    int i;
+    address &= TARGET_PAGE_MASK;
+    for(i = 0;i < CODE_GEN_HASH_SIZE; i++) {
+        for(tb = tb_hash[i]; tb != NULL; tb = tb->hash_next) {
+            if (!(address + TARGET_PAGE_SIZE <= tb->pc ||
+                  address >= tb->pc + tb->size)) {
+                printf("ERROR invalidate: address=%08lx PC=%08lx size=%04x\n",
+                       address, tb->pc, tb->size);
+            }
+        }
+    }
+}
+
+/* verify that all the pages have correct rights for code */
+static void tb_page_check(void)
+{
+    TranslationBlock *tb;
+    int i, flags1, flags2;
+    
+    for(i = 0;i < CODE_GEN_HASH_SIZE; i++) {
+        for(tb = tb_hash[i]; tb != NULL; tb = tb->hash_next) {
+            flags1 = page_get_flags(tb->pc);
+            flags2 = page_get_flags(tb->pc + tb->size - 1);
+            if ((flags1 & PAGE_WRITE) || (flags2 & PAGE_WRITE)) {
+                printf("ERROR page flags: PC=%08lx size=%04x f1=%x f2=%x\n",
+                       tb->pc, tb->size, flags1, flags2);
+            }
+        }
+    }
+}
+
+#endif
+
+/* invalidate one TB */
+static inline void tb_remove(TranslationBlock **ptb, TranslationBlock *tb,
+                             int next_offset)
+{
+    TranslationBlock *tb1;
+    for(;;) {
+        tb1 = *ptb;
+        if (tb1 == tb) {
+            *ptb = *(TranslationBlock **)((char *)tb1 + next_offset);
+            break;
+        }
+        ptb = (TranslationBlock **)((char *)tb1 + next_offset);
+    }
+}
+
+static inline void tb_invalidate(TranslationBlock *tb, int parity)
+{
+    PageDesc *p;
+    unsigned int page_index1, page_index2;
+    unsigned int h;
+
+    /* remove the TB from the hash list */
+    h = tb_hash_func(tb->pc);
+    tb_remove(&tb_hash[h], tb, 
+              offsetof(TranslationBlock, hash_next));
+    /* remove the TB from the page list */
+    page_index1 = tb->pc >> TARGET_PAGE_BITS;
+    if ((page_index1 & 1) == parity) {
+        p = page_find(page_index1);
+        tb_remove(&p->first_tb, tb, 
+                  offsetof(TranslationBlock, page_next[page_index1 & 1]));
+    }
+    page_index2 = (tb->pc + tb->size - 1) >> TARGET_PAGE_BITS;
+    if ((page_index2 & 1) == parity) {
+        p = page_find(page_index2);
+        tb_remove(&p->first_tb, tb, 
+                  offsetof(TranslationBlock, page_next[page_index2 & 1]));
+    }
+}
+
+/* invalidate all TBs which intersect with the target page starting at addr */
+static void tb_invalidate_page(unsigned long address)
+{
+    TranslationBlock *tb_next, *tb;
+    unsigned int page_index;
+    int parity1, parity2;
+    PageDesc *p;
+#ifdef DEBUG_TB_INVALIDATE
+    printf("tb_invalidate_page: %lx\n", address);
+#endif
+
+    page_index = address >> TARGET_PAGE_BITS;
+    p = page_find(page_index);
+    if (!p)
+        return;
+    tb = p->first_tb;
+    parity1 = page_index & 1;
+    parity2 = parity1 ^ 1;
+    while (tb != NULL) {
+        tb_next = tb->page_next[parity1];
+        tb_invalidate(tb, parity2);
+        tb = tb_next;
+    }
+    p->first_tb = NULL;
+}
+
+/* add the tb in the target page and protect it if necessary */
+static inline void tb_alloc_page(TranslationBlock *tb, unsigned int page_index)
+{
+    PageDesc *p;
+    unsigned long host_start, host_end, addr, page_addr;
+    int prot;
+
+    p = page_find_alloc(page_index);
+    tb->page_next[page_index & 1] = p->first_tb;
+    p->first_tb = tb;
+    if (p->flags & PAGE_WRITE) {
+        /* force the host page as non writable (writes will have a
+           page fault + mprotect overhead) */
+        page_addr = (page_index << TARGET_PAGE_BITS);
+        host_start = page_addr & host_page_mask;
+        host_end = host_start + host_page_size;
+        prot = 0;
+        for(addr = host_start; addr < host_end; addr += TARGET_PAGE_SIZE)
+            prot |= page_get_flags(addr);
+        mprotect((void *)host_start, host_page_size, 
+                 (prot & PAGE_BITS) & ~PAGE_WRITE);
+#ifdef DEBUG_TB_INVALIDATE
+        printf("protecting code page: 0x%08lx\n", 
+               host_start);
+#endif
+        p->flags &= ~PAGE_WRITE;
+#ifdef DEBUG_TB_CHECK
+        tb_page_check();
+#endif
+    }
+}
+
+/* Allocate a new translation block. Flush the translation buffer if
+   too many translation blocks or too much generated code. */
+TranslationBlock *tb_alloc(unsigned long pc, 
+                           unsigned long size)
+{
+    TranslationBlock *tb;
+    unsigned int page_index1, page_index2;
+
+    if (nb_tbs >= CODE_GEN_MAX_BLOCKS || 
+        (code_gen_ptr - code_gen_buffer) >= CODE_GEN_BUFFER_MAX_SIZE)
+        tb_flush();
+    tb = &tbs[nb_tbs++];
+    tb->pc = pc;
+    tb->size = size;
+
+    /* add in the page list */
+    page_index1 = pc >> TARGET_PAGE_BITS;
+    tb_alloc_page(tb, page_index1);
+    page_index2 = (pc + size - 1) >> TARGET_PAGE_BITS;
+    if (page_index2 != page_index1) {
+        tb_alloc_page(tb, page_index2);
+    }
+    return tb;
+}
+
+/* called from signal handler: invalidate the code and unprotect the
+   page. Return TRUE if the fault was succesfully handled. */
+int page_unprotect(unsigned long address)
+{
+    unsigned int page_index, prot;
+    PageDesc *p;
+    unsigned long host_start, host_end, addr;
+
+    page_index = address >> TARGET_PAGE_BITS;
+    p = page_find(page_index);
+    if (!p)
+        return 0;
+    if ((p->flags & (PAGE_WRITE_ORG | PAGE_WRITE)) == PAGE_WRITE_ORG) {
+        /* if the page was really writable, then we change its
+           protection back to writable */
+        host_start = address & host_page_mask;
+        host_end = host_start + host_page_size;
+        prot = 0;
+        for(addr = host_start; addr < host_end; addr += TARGET_PAGE_SIZE)
+            prot |= page_get_flags(addr);
+        mprotect((void *)host_start, host_page_size, 
+                 (prot & PAGE_BITS) | PAGE_WRITE);
+        p->flags |= PAGE_WRITE;
+
+        /* and since the content will be modified, we must invalidate
+           the corresponding translated code. */
+        tb_invalidate_page(address);
+#ifdef DEBUG_TB_CHECK
+        tb_invalidate_check(address);
+#endif
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+/* call this function when system calls directly modify a memory area */
+void page_unprotect_range(uint8_t *data, unsigned long data_size)
+{
+    unsigned long start, end, addr;
+
+    start = (unsigned long)data;
+    end = start + data_size;
+    start &= TARGET_PAGE_MASK;
+    end = TARGET_PAGE_ALIGN(end);
+    for(addr = start; addr < end; addr += TARGET_PAGE_SIZE) {
+        page_unprotect(addr);
+    }
+}