The exact CPU behaviour on i386 and x86_64 in the PASS case for the
icache-hygeine test depends on the details of the compiler's code
generation. Previously, we only tested for one of the possible
behaviours, meaning the test could SEGV depending on the exact
compiler version and options.
This patch makes the test cover the other case as well, making it much
more robust. It also adds some extra comments explaining more clearly
what happens in the PASS case.
Signed-off-by: David Gibson <[EMAIL PROTECTED]>
Index: libhugetlbfs/tests/icache-hygeine.c
===================================================================
--- libhugetlbfs.orig/tests/icache-hygeine.c 2007-03-07 15:31:28.000000000
+1100
+++ libhugetlbfs/tests/icache-hygeine.c 2007-03-07 15:43:51.000000000 +1100
@@ -30,6 +30,8 @@
* remap, or because the icache happens to get flushed in the interim.
*/
+#define _GNU_SOURCE
+
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@@ -37,6 +39,7 @@
#include <unistd.h>
#include <signal.h>
#include <sys/mman.h>
+#include <ucontext.h>
#include <hugetlbfs.h>
@@ -52,7 +55,6 @@
#endif
}
-
static void jumpfunc(int copy, void *p)
{
/* gcc bug workaround: if there is exactly one &&label
@@ -80,6 +82,10 @@
static void sig_handler(int signum, siginfo_t *si, void *uc)
{
+#if defined(__powerpc__) || defined(__powerpc64__)
+ /* On powerpc, 0 bytes are an illegal instruction, so, if the
+ * icache is cleared properly, we SIGILL as soon as we jump
+ * into the cleared page */
if (signum == SIGILL) {
verbose_printf("SIGILL at %p (sig_expected=%p)\n", si->si_addr,
sig_expected);
@@ -88,6 +94,19 @@
}
FAIL("SIGILL somewhere unexpected");
}
+#elif defined(__i386__) || defined(__x86_64__)
+ /* On x86, zero bytes form a valid instruction:
+ * add %al,(%eax) (i386)
+ * or add %al,(%rax) (x86_64)
+ *
+ * So, behaviour depends on the contents of [ER]AX, which in
+ * turn depends on the details of code generation. If [ER]AX
+ * contains a valid pointer, we will execute the instruction
+ * repeatedly until we run off that hugepage and get a SIGBUS
+ * on the second, truncated page. If [ER]AX does not contain
+ * a valid pointer, we will SEGV on the first instruction in
+ * the cleared page. We check for both possibilities
+ * below. */
if (signum == SIGBUS) {
verbose_printf("SIGBUS at %p (sig_expected=%p)\n", si->si_addr,
sig_expected);
@@ -98,6 +117,23 @@
}
FAIL("SIGBUS somewhere unexpected");
}
+ if (signum == SIGSEGV) {
+#ifdef __x86_64__
+ void *pc = (void *)((ucontext_t
*)uc)->uc_mcontext.gregs[REG_RIP];
+#else
+ void *pc = (void *)((ucontext_t
*)uc)->uc_mcontext.gregs[REG_EIP];
+#endif
+
+ verbose_printf("SIGSEGV at %p, PC=%p (sig_expected=%p)\n",
+ si->si_addr, pc, sig_expected);
+ if (sig_expected == pc) {
+ siglongjmp(sig_escape, 1);
+ }
+ FAIL("SIGSEGV somewhere unexpected");
+ }
+#else
+#error Need to setup signal conditions for this arch
+#endif
}
static void test_once(int fd)
@@ -133,7 +169,7 @@
q = p + hpage_size - COPY_SIZE;
sig_expected = q;
- jumpfunc(0, q); /* This should SIGILL */
+ jumpfunc(0, q); /* This should blow up */
FAIL("icache unclean");
}
@@ -159,6 +195,10 @@
if (err)
FAIL("Can't install SIGBUS handler");
+ err = sigaction(SIGSEGV, &sa, NULL);
+ if (err)
+ FAIL("Can't install SIGSEGV handler");
+
fd = hugetlbfs_unlinked_fd();
if (fd < 0)
CONFIG("Couldn't get hugepage fd");
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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