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arm64: Mirror arm for unimplemented compat syscalls

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Mirror arm behaviour for unimplemented syscalls: Below 2048 return
-ENOSYS, above 2048 raise SIGILL.

Signed-off-by: Michael Weiser <michael.weiser@gmx.de>
[will: Tweak die string to identify as compat syscall]
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Michael Weiser 2018-02-01 23:13:37 +01:00 committed by Will Deacon
parent 4a3928c6f8
commit 532826f371
1 changed files with 20 additions and 1 deletions
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21
arch/arm64/kernel/sys_compat.c
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@ -27,6 +27,7 @@
#include <linux/uaccess.h> #include <linux/uaccess.h>
#include <asm/cacheflush.h> #include <asm/cacheflush.h>
#include <asm/system_misc.h>
#include <asm/unistd.h> #include <asm/unistd.h>
static long static long
@ -67,6 +68,7 @@ do_compat_cache_op(unsigned long start, unsigned long end, int flags)
*/ */
long compat_arm_syscall(struct pt_regs *regs) long compat_arm_syscall(struct pt_regs *regs)
{ {
siginfo_t info;
unsigned int no = regs->regs[7]; unsigned int no = regs->regs[7];
switch (no) { switch (no) {
@ -99,6 +101,23 @@ long compat_arm_syscall(struct pt_regs *regs)
return 0; return 0;
default: default:
return -ENOSYS; /*
* Calls 9f00xx..9f07ff are defined to return -ENOSYS
* if not implemented, rather than raising SIGILL. This
* way the calling program can gracefully determine whether
* a feature is supported.
*/
if ((no & 0xffff) <= 0x7ff)
return -ENOSYS;
break;
} }
info.si_signo = SIGILL;
info.si_errno = 0;
info.si_code = ILL_ILLTRP;
info.si_addr = (void __user *)instruction_pointer(regs) -
(compat_thumb_mode(regs) ? 2 : 4);
arm64_notify_die("Oops - bad compat syscall(2)", regs, &info, no);
return 0;
} }