generalize lgread_u32/lgwrite_u32.

Jes complains that page table code still uses lgread_u32 even though
it now uses general kernel pte types.  The best thing to do is to
generalize lgread_u32 and lgwrite_u32.

This means we lose the efficiency of getuser().  We could potentially
regain it if we used __copy_from_user instead of copy_from_user, but
I'm not certain that our range check is equivalent to access_ok() on
all platforms.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Jes Sorensen <jes@sgi.com>

7 files changed, 38 insertions, 46 deletions

diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c
index 3aec29ec7715..35d19ae58de7 100644
--- a/drivers/lguest/core.c
+++ b/drivers/lguest/core.c
@@ -145,33 +145,10 @@ int lguest_address_ok(const struct lguest *lg,
         return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr);
 }
 
-/* This is a convenient routine to get a 32-bit value from the Guest (a very
- * common operation).  Here we can see how useful the kill_lguest() routine we
- * met in the Launcher can be: we return a random value (0) instead of needing
- * to return an error. */
-u32 lgread_u32(struct lguest *lg, unsigned long addr)
-{
-        u32 val = 0;
-
-        /* Don't let them access lguest binary. */
-        if (!lguest_address_ok(lg, addr, sizeof(val))
-            || get_user(val, (u32 *)(lg->mem_base + addr)) != 0)
-                kill_guest(lg, "bad read address %#lx: pfn_limit=%u membase=%p", addr, lg->pfn_limit, lg->mem_base);
-        return val;
-}
-
-/* Same thing for writing a value. */
-void lgwrite_u32(struct lguest *lg, unsigned long addr, u32 val)
-{
-        if (!lguest_address_ok(lg, addr, sizeof(val))
-            || put_user(val, (u32 *)(lg->mem_base + addr)) != 0)
-                kill_guest(lg, "bad write address %#lx", addr);
-}
-
-/* This routine is more generic, and copies a range of Guest bytes into a
- * buffer.  If the copy_from_user() fails, we fill the buffer with zeroes, so
- * the caller doesn't end up using uninitialized kernel memory. */
-void lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes)
+/* This routine copies memory from the Guest.  Here we can see how useful the
+ * kill_lguest() routine we met in the Launcher can be: we return a random
+ * value (all zeroes) instead of needing to return an error. */
+void __lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes)
 {
         if (!lguest_address_ok(lg, addr, bytes)
             || copy_from_user(b, lg->mem_base + addr, bytes) != 0) {
@@ -181,15 +158,15 @@ void lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes)
         }
 }
 
-/* Similarly, our generic routine to copy into a range of Guest bytes. */
-void lgwrite(struct lguest *lg, unsigned long addr, const void *b,
-             unsigned bytes)
+/* This is the write (copy into guest) version. */
+void __lgwrite(struct lguest *lg, unsigned long addr, const void *b,
+               unsigned bytes)
 {
         if (!lguest_address_ok(lg, addr, bytes)
             || copy_to_user(lg->mem_base + addr, b, bytes) != 0)
                 kill_guest(lg, "bad write address %#lx len %u", addr, bytes);
 }
-/* (end of memory access helper routines) :*/
+/*:*/
 
 /*H:030 Let's jump straight to the the main loop which runs the Guest.
  * Remember, this is called by the Launcher reading /dev/lguest, and we keep
diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c
index 3a53788ba450..9d5184c7c14a 100644
--- a/drivers/lguest/hypercalls.c
+++ b/drivers/lguest/hypercalls.c
@@ -47,7 +47,7 @@ static void do_hcall(struct lguest *lg, struct hcall_args *args)
                 char msg[128];
                 /* If the lgread fails, it will call kill_guest() itself; the
                  * kill_guest() with the message will be ignored. */
-                lgread(lg, msg, args->arg1, sizeof(msg));
+                __lgread(lg, msg, args->arg1, sizeof(msg));
                 msg[sizeof(msg)-1] = '\0';
                 kill_guest(lg, "CRASH: %s", msg);
                 break;
diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c
index 3271c0031a1b..82966982cb38 100644
--- a/drivers/lguest/interrupts_and_traps.c
+++ b/drivers/lguest/interrupts_and_traps.c
@@ -45,7 +45,7 @@ static void push_guest_stack(struct lguest *lg, unsigned long *gstack, u32 val)
 {
         /* Stack grows upwards: move stack then write value. */
         *gstack -= 4;
-        lgwrite_u32(lg, *gstack, val);
+        lgwrite(lg, *gstack, u32, val);
 }
 
 /*H:210 The set_guest_interrupt() routine actually delivers the interrupt or
diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h
index 4d45b7036e82..d9144beca82c 100644
--- a/drivers/lguest/lg.h
+++ b/drivers/lguest/lg.h
@@ -98,12 +98,27 @@ struct lguest
 extern struct mutex lguest_lock;
 
 /* core.c: */
-u32 lgread_u32(struct lguest *lg, unsigned long addr);
-void lgwrite_u32(struct lguest *lg, unsigned long addr, u32 val);
-void lgread(struct lguest *lg, void *buf, unsigned long addr, unsigned len);
-void lgwrite(struct lguest *lg, unsigned long, const void *buf, unsigned len);
 int lguest_address_ok(const struct lguest *lg,
                       unsigned long addr, unsigned long len);
+void __lgread(struct lguest *, void *, unsigned long, unsigned);
+void __lgwrite(struct lguest *, unsigned long, const void *, unsigned);
+
+/*L:306 Using memory-copy operations like that is usually inconvient, so we
+ * have the following helper macros which read and write a specific type (often
+ * an unsigned long).
+ *
+ * This reads into a variable of the given type then returns that. */
+#define lgread(lg, addr, type)                                          \
+        ({ type _v; __lgread((lg), &_v, (addr), sizeof(_v)); _v; })
+
+/* This checks that the variable is of the given type, then writes it out. */
+#define lgwrite(lg, addr, type, val)                            \
+        do {                                                    \
+                typecheck(type, val);                           \
+                __lgwrite((lg), (addr), &(val), sizeof(val));   \
+        } while(0)
+/* (end of memory access helper routines) :*/
+
 int run_guest(struct lguest *lg, unsigned long __user *user);
 
 /* Helper macros to obtain the first 12 or the last 20 bits, this is only the
diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
index fe3c7575647b..2a45f0691c9b 100644
--- a/drivers/lguest/page_tables.c
+++ b/drivers/lguest/page_tables.c
@@ -209,7 +209,7 @@ int demand_page(struct lguest *lg, unsigned long vaddr, int errcode)
         pte_t *spte;
 
         /* First step: get the top-level Guest page table entry. */
-        gpgd = __pgd(lgread_u32(lg, gpgd_addr(lg, vaddr)));
+        gpgd = lgread(lg, gpgd_addr(lg, vaddr), pgd_t);
         /* Toplevel not present?  We can't map it in. */
         if (!(pgd_flags(gpgd) & _PAGE_PRESENT))
                 return 0;
@@ -235,7 +235,7 @@ int demand_page(struct lguest *lg, unsigned long vaddr, int errcode)
         /* OK, now we look at the lower level in the Guest page table: keep its
          * address, because we might update it later. */
         gpte_ptr = gpte_addr(lg, gpgd, vaddr);
-        gpte = __pte(lgread_u32(lg, gpte_ptr));
+        gpte = lgread(lg, gpte_ptr, pte_t);
 
         /* If this page isn't in the Guest page tables, we can't page it in. */
         if (!(pte_flags(gpte) & _PAGE_PRESENT))
@@ -278,7 +278,7 @@ int demand_page(struct lguest *lg, unsigned long vaddr, int errcode)
 
         /* Finally, we write the Guest PTE entry back: we've set the
          * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags. */
-        lgwrite_u32(lg, gpte_ptr, pte_val(gpte));
+        lgwrite(lg, gpte_ptr, pte_t, gpte);
 
         /* We succeeded in mapping the page! */
         return 1;
@@ -366,12 +366,12 @@ unsigned long guest_pa(struct lguest *lg, unsigned long vaddr)
         pte_t gpte;
 
         /* First step: get the top-level Guest page table entry. */
-        gpgd = __pgd(lgread_u32(lg, gpgd_addr(lg, vaddr)));
+        gpgd = lgread(lg, gpgd_addr(lg, vaddr), pgd_t);
         /* Toplevel not present?  We can't map it in. */
         if (!(pgd_flags(gpgd) & _PAGE_PRESENT))
                 kill_guest(lg, "Bad address %#lx", vaddr);
 
-        gpte = __pte(lgread_u32(lg, gpte_addr(lg, gpgd, vaddr)));
+        gpte = lgread(lg, gpte_addr(lg, gpgd, vaddr), pte_t);
         if (!(pte_flags(gpte) & _PAGE_PRESENT))
                 kill_guest(lg, "Bad address %#lx", vaddr);
 
diff --git a/drivers/lguest/segments.c b/drivers/lguest/segments.c
index 95eb9cf297bf..c2434ec99f7b 100644
--- a/drivers/lguest/segments.c
+++ b/drivers/lguest/segments.c
@@ -150,7 +150,7 @@ void load_guest_gdt(struct lguest *lg, unsigned long table, u32 num)
                 kill_guest(lg, "too many gdt entries %i", num);
 
         /* We read the whole thing in, then fix it up. */
-        lgread(lg, lg->arch.gdt, table, num * sizeof(lg->arch.gdt[0]));
+        __lgread(lg, lg->arch.gdt, table, num * sizeof(lg->arch.gdt[0]));
         fixup_gdt_table(lg, 0, ARRAY_SIZE(lg->arch.gdt));
         /* Mark that the GDT changed so the core knows it has to copy it again,
          * even if the Guest is run on the same CPU. */
@@ -161,7 +161,7 @@ void guest_load_tls(struct lguest *lg, unsigned long gtls)
 {
         struct desc_struct *tls = &lg->arch.gdt[GDT_ENTRY_TLS_MIN];
 
-        lgread(lg, tls, gtls, sizeof(*tls)*GDT_ENTRY_TLS_ENTRIES);
+        __lgread(lg, tls, gtls, sizeof(*tls)*GDT_ENTRY_TLS_ENTRIES);
         fixup_gdt_table(lg, GDT_ENTRY_TLS_MIN, GDT_ENTRY_TLS_MAX+1);
         lg->changed |= CHANGED_GDT_TLS;
 }
diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
index ef976ccb4192..9eed12d5a395 100644
--- a/drivers/lguest/x86/core.c
+++ b/drivers/lguest/x86/core.c
@@ -222,7 +222,7 @@ static int emulate_insn(struct lguest *lg)
                 return 0;
 
         /* Decoding x86 instructions is icky. */
-        lgread(lg, &insn, physaddr, 1);
+        insn = lgread(lg, physaddr, u8);
 
         /* 0x66 is an "operand prefix".  It means it's using the upper 16 bits
            of the eax register. */
@@ -230,7 +230,7 @@ static int emulate_insn(struct lguest *lg)
                 shift = 16;
                 /* The instruction is 1 byte so far, read the next byte. */
                 insnlen = 1;
-                lgread(lg, &insn, physaddr + insnlen, 1);
+                insn = lgread(lg, physaddr + insnlen, u8);
         }
 
         /* We can ignore the lower bit for the moment and decode the 4 opcodes