pm24.git/arch/arm64/kernel/sys.c, branch v5.1

arm64: implement syscall wrappers

2018-07-12T13:49:48Z

To minimize the risk of userspace-controlled values being used under speculation, this patch adds pt_regs based syscall wrappers for arm64, which pass the minimum set of required userspace values to syscall implementations. For each syscall, a wrapper which takes a pt_regs argument is automatically generated, and this extracts the arguments before calling the "real" syscall implementation. Each syscall has three functions generated: * __do_sys_ is the "real" syscall implementation, with the expected prototype. * __se_sys_ is the sign-extension/narrowing wrapper, inherited from common code. This takes a series of long parameters, casting each to the requisite types required by the "real" syscall implementation in __do_sys_. This wrapper *may* not be necessary on arm64 given the AAPCS rules on unused register bits, but it seemed safer to keep the wrapper for now. * __arm64__sys_ takes a struct pt_regs pointer, and extracts *only* the relevant register values, passing these on to the __se_sys_ wrapper. The syscall invocation code is updated to handle the calling convention required by __arm64__sys_, and passes a single struct pt_regs pointer. The compiler can fold the syscall implementation and its wrappers, such that the overhead of this approach is minimized. Note that we play games with sys_ni_syscall(). It can't be defined with SYSCALL_DEFINE0() because we must avoid the possibility of error injection. Additionally, there are a couple of locations where we need to call it from C code, and we don't (currently) have a ksys_ni_syscall(). While it has no wrapper, passing in a redundant pt_regs pointer is benign per the AAPCS. When ARCH_HAS_SYSCALL_WRAPPER is selected, no prototype is defines for sys_ni_syscall(). Since we need to treat it differently for in-kernel calls and the syscall tables, the prototype is defined as-required. The wrappers are largely the same as their x86 counterparts, but simplified as we don't have a variety of compat calling conventions that require separate stubs. Unlike x86, we have some zero-argument compat syscalls, and must define COMPAT_SYSCALL_DEFINE0() to ensure that these are also given an __arm64_compat_sys_ prefix. Signed-off-by: Mark Rutland Reviewed-by: Dominik Brodowski Reviewed-by: Catalin Marinas Cc: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon

arm64: use SYSCALL_DEFINE6() for mmap

2018-07-12T13:49:48Z

We don't currently annotate our mmap implementation as a syscall, as we need to do to use pt_regs syscall wrappers. Let's mark it as a real syscall. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland Reviewed-by: Dominik Brodowski Acked-by: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon

arm64: remove in-kernel call to sys_personality()

2018-07-12T13:49:48Z

With pt_regs syscall wrappers, the calling convention for sys_personality() will change. Use ksys_personality(), which is functionally equivalent. Signed-off-by: Mark Rutland Acked-by: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon

arm64: drop alignment from syscall tables

2018-07-12T13:49:48Z

Our syscall tables are aligned to 4096 bytes, which allowed their addresses to be generated with a single adrp in entry.S. This has the unfortunate property of wasting space in .rodata for the necessary padding. Now that the address is generated by C code, we can rely on the compiler to do the right thing, and drop the alignemnt. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon

arm64: introduce syscall_fn_t

2018-07-12T13:40:39Z

In preparation for invoking arbitrary syscalls from C code, let's define a type for an arbitrary syscall, matching the parameter passing rules of the AAPCS. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon

arm64: remove sigreturn wrappers

2018-07-12T13:40:39Z

The arm64 sigreturn* syscall handlers are non-standard. Rather than taking a number of user parameters in registers as per the AAPCS, they expect the pt_regs as their sole argument. To make this work, we override the syscall definitions to invoke wrappers written in assembly, which mov the SP into x0, and branch to their respective C functions. On other architectures (such as x86), the sigreturn* functions take no argument and instead use current_pt_regs() to acquire the user registers. This requires less boilerplate code, and allows for other features such as interposing C code in this path. This patch takes the same approach for arm64. Signed-off-by: Mark Rutland Tentatively-reviewed-by: Dave Martin Reviewed-by: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon

mm: add ksys_mmap_pgoff() helper; remove in-kernel calls to sys_mmap_pgoff()

2018-04-02T18:16:11Z

Using this helper allows us to avoid the in-kernel calls to the sys_mmap_pgoff() syscall. The ksys_ prefix denotes that this function is meant as a drop-in replacement for the syscall. In particular, it uses the same calling convention as sys_mmap_pgoff(). This patch is part of a series which removes in-kernel calls to syscalls. On this basis, the syscall entry path can be streamlined. For details, see http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net Cc: Andrew Morton Cc: linux-mm@kvack.org Signed-off-by: Dominik Brodowski

arm64: compat: Check for AArch32 state

2016-04-20T11:22:42Z

Make sure we have AArch32 state available for running COMPAT binaries and also for switching the personality to PER_LINUX32. Signed-off-by: Yury Norov [ Added cap bit, checks for HWCAP, personality ] Signed-off-by: Suzuki K Poulose Tested-by: Yury Norov Signed-off-by: Will Deacon

arm64: make sys_call_table const

2015-01-27T09:38:08Z

As with x86, mark the sys_call_table const such that it will be placed in the .rodata section. This will cause attempts to modify the table (accidental or deliberate) to fail when strict page permissions are in place. In the absence of strict page permissions, there should be no functional change. Signed-off-by: Mark Rutland Acked-by: Will Deacon Signed-off-by: Catalin Marinas

arm64: Remove asm/syscalls.h

2015-01-27T09:38:08Z

This patch moves the sys_rt_sigreturn_wrapper prototype to arch/arm64/kernel/sys.c and removes the asm/syscalls.h header. Signed-off-by: Catalin Marinas