[PATCH] samples/seccomp: fix endianness bug in LO_ARG define

From: Heiko Carstens
Date: Tue Jul 31 2012 - 10:15:36 EST


From: Heiko Carstens <heiko.carstens@xxxxxxxxxx>

The LO_ARG define needs to consider endianness also for 32 bit builds.

The "bpf_fancy" test case didn't work on s390 in 32 bit and compat mode
because the LO_ARG define resulted in a BPF program which read the upper
halve of the 64 bit system call arguments instead of the lower halves.

Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
---
samples/seccomp/bpf-helper.h | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/samples/seccomp/bpf-helper.h b/samples/seccomp/bpf-helper.h
index 643279d..38ee70f 100644
--- a/samples/seccomp/bpf-helper.h
+++ b/samples/seccomp/bpf-helper.h
@@ -59,6 +59,16 @@ void seccomp_bpf_print(struct sock_filter *filter, size_t count);
#define FIND_LABEL(labels, label) seccomp_bpf_label((labels), #label)

#define EXPAND(...) __VA_ARGS__
+
+/* Ensure that we load the logically correct offset. */
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
+#elif __BYTE_ORDER == __BIG_ENDIAN
+#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32)
+#else
+#error "Unknown endianness"
+#endif
+
/* Map all width-sensitive operations */
#if __BITS_PER_LONG == 32

@@ -70,21 +80,16 @@ void seccomp_bpf_print(struct sock_filter *filter, size_t count);
#define JLE(x, jt) JLE32(x, EXPAND(jt))
#define JA(x, jt) JA32(x, EXPAND(jt))
#define ARG(i) ARG_32(i)
-#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)])

#elif __BITS_PER_LONG == 64

/* Ensure that we load the logically correct offset. */
#if __BYTE_ORDER == __LITTLE_ENDIAN
#define ENDIAN(_lo, _hi) _lo, _hi
-#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32)
#elif __BYTE_ORDER == __BIG_ENDIAN
#define ENDIAN(_lo, _hi) _hi, _lo
-#define LO_ARG(idx) offsetof(struct seccomp_data, args[(idx)]) + sizeof(__u32)
#define HI_ARG(idx) offsetof(struct seccomp_data, args[(idx)])
-#else
-#error "Unknown endianness"
#endif

union arg64 {
--
1.7.11.4

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