Optimize sys_old_mmap
* mem.c (sys_old_mmap): For Ia64 and 32-bit personality of x86-64,
copy narrow parameters from userspace by single umove, not by six
separate ones; then assign them to long u_arg[i]. For SH[64],
avoid copying of tcp->u_arg.
(sys_mmap): Add FIXME comment - SH64 and i386 seem to be handled
differently for no apparent reason.
* test/mmap_offset_decode.c: New test program, illustrates FIXME.
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
diff --git a/mem.c b/mem.c
index de9b6bb..7ae8b5c 100644
--- a/mem.c
+++ b/mem.c
@@ -265,46 +265,44 @@
#ifdef LINUX
int sys_old_mmap(struct tcb *tcp)
{
- long u_arg[6];
-
#if defined(IA64)
- int i, v;
/*
- * IA64 processes never call this routine, they only use the
- * new `sys_mmap' interface. This code converts the integer
- * arguments that the IA32 process pushed onto the stack into
- * longs.
+ * IA64 processes never call this routine, they only use the
+ * new `sys_mmap' interface.
+ * For IA32 processes, this code converts the integer arguments
+ * that they pushed onto the stack, into longs.
*
- * Note that addresses with bit 31 set will be sign extended.
- * Fortunately, those addresses are not currently being generated
- * for IA32 processes so it's not a problem.
+ * Note that addresses with bit 31 set will be sign extended.
+ * Fortunately, those addresses are not currently being generated
+ * for IA32 processes so it's not a problem.
*/
+ int i;
+ long u_arg[6];
+ int narrow_arg[6];
+ if (umoven(tcp, tcp->u_arg[0], sizeof(narrow_arg), (char *) narrow_arg) == -1)
+ return 0;
for (i = 0; i < 6; i++)
- if (umove(tcp, tcp->u_arg[0] + (i * sizeof(int)), &v) == -1)
- return 0;
- else
- u_arg[i] = v;
+ u_arg[i] = narrow_arg[i];
#elif defined(SH) || defined(SH64)
/* SH has always passed the args in registers */
- int i;
- for (i = 0; i < 6; i++)
- u_arg[i] = tcp->u_arg[i];
+ long *u_arg = tcp->u_arg;
#else
+ long u_arg[6];
# if defined(X86_64)
if (current_personality == 1) {
int i;
- for (i = 0; i < 6; ++i) {
- unsigned int val;
- if (umove(tcp, tcp->u_arg[0] + i * 4, &val) == -1)
- return 0;
- u_arg[i] = val;
- }
+ unsigned narrow_arg[6];
+ if (umoven(tcp, tcp->u_arg[0], sizeof(narrow_arg), (char *) narrow_arg) == -1)
+ return 0;
+ for (i = 0; i < 6; ++i)
+ u_arg[i] = narrow_arg[i];
}
else
# endif
- if (umoven(tcp, tcp->u_arg[0], sizeof u_arg, (char *) u_arg) == -1)
+ if (umoven(tcp, tcp->u_arg[0], sizeof(u_arg), (char *) u_arg) == -1)
return 0;
-#endif /* !IA64 && !SH[64] */
+#endif /* other architectures */
+
return print_mmap(tcp, u_arg, u_arg[5]);
}
#endif /* LINUX */
@@ -314,6 +312,11 @@
{
long long offset = tcp->u_arg[5];
+ /* FIXME: why only SH64? i386 mmap2 syscall ends up
+ * in this function, but does not convert offset
+ * from pages to bytes. See test/mmap_offset_decode.c
+ * Why SH64 and i386 are handled differently?
+ */
#if defined(LINUX) && defined(SH64)
/*
* Old mmap differs from new mmap in specifying the