[PATCH 2/3] [RFC] seccomp: give BPF x32 bit when restoring x32 filter

[Richard Guy Briggs]

Commit
	fca460f hpa at zytor.com 2012-02-19 07:56:26 -0800
	x32: Handle the x32 system call flag

provided a method to multiplex architecture with the syscall number for X32
calls.

Commit
	8b4b9f2 pmoore at redhat.com 2013-02-15 12:21:43 -0500
	x86: remove the x32 syscall bitmask from syscall_get_nr()

broke audit and potentially other users of syscall_get_nr() which depend on
that call as named.

Commit
	audit: add AUDIT_ARCH_X86_X32 arch definition

is required to provide the new ARCH definition AUDIT_ARCH_X86_X32 for
syscall_get_arch().

This patch along with reverting 8b4b9f2 should satisfy other regular users of
syscall_get_nr() without changing the seccomp interface to BPF.

Cc: Paul Moore <pmoore at redhat.com>
Cc: Eric Paris <eparis at redhat.com>
Cc: Al Viro <aviro at redhat.com>
Cc: Will Drewry <wad at chromium.org>
Cc: H. Peter Anvin <hpa at zytor.com>
Signed-off-by: Richard Guy Briggs <rgb at redhat.com>
Link: http://lkml.kernel.org/r/cover.1405023592.git.rgb@redhat.com
---
 arch/x86/include/asm/syscall.h |    4 ++++
 kernel/seccomp.c               |    6 ++++++
 2 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index d6a756a..d58b6be 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -236,6 +236,10 @@ static inline int syscall_get_arch(void)
 		return AUDIT_ARCH_I386;
 #endif
 	/* Both x32 and x86_64 are considered "64-bit". */
+#ifdef CONFIG_X86_X32_ABI
+	if (task_pt_regs(current)->orig_ax & __X32_SYSCALL_BIT)
+		return AUDIT_ARCH_X86_X32;
+#endif
 	return AUDIT_ARCH_X86_64;
 }
 #endif	/* CONFIG_X86_32 */
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index b35c215..bc18214 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -73,6 +73,12 @@ static void populate_seccomp_data(struct seccomp_data *sd)
 
 	sd->nr = syscall_get_nr(task, regs);
 	sd->arch = syscall_get_arch();
+#ifdef CONFIG_X86_X32_ABI
+	if (sd->arch == AUDIT_ARCH_X86_X32) {
+		sd->arch = AUDIT_ARCH_X86_64;
+		sd->nr |= __X32_SYSCALL_BIT;
+	}
+#endif
 	syscall_get_arguments(task, regs, 0, 6, args);
 	sd->args[0] = args[0];
 	sd->args[1] = args[1];
-- 
1.7.1