kernel/linux.git/arch/powerpc/include/asm/syscalls.h, branch v6.19.11

powerpc/32: fix syscall wrappers with 64-bit arguments

2022-10-31T23:24:09+00:00

With the introduction of syscall wrappers all wrappers for syscalls with 64-bit arguments must be handled specially, not only those that have unaligned 64-bit arguments. This left out the fallocate() and sync_file_range2() syscalls. Fixes: 7e92e01b7245 ("powerpc: Provide syscall wrapper") Fixes: e23750623835 ("powerpc/32: fix syscall wrappers with 64-bit arguments of unaligned register-pairs") Signed-off-by: Andreas Schwab Reviewed-by: Arnd Bergmann Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/87mt9cxd6g.fsf_-_@igel.home

powerpc/32: fix syscall wrappers with 64-bit arguments of unaligned register-pairs

2022-10-12T13:49:58+00:00

powerpc 32-bit system call (and function) calling convention for 64-bit arguments requires the next available odd-pair (two sequential registers with the first being odd-numbered) from the standard register argument allocation. The first argument register is r3, so a 64-bit argument that appears at an even position in the argument list must skip a register (unless there were preceding 64-bit arguments, which might throw things off). This requires non-standard compat definitions to deal with the holes in the argument register allocation. With pt_regs syscall wrappers which use a standard mapper to map pt_regs GPRs to function arguments, 32-bit kernels hit the same basic problem, the standard definitions don't cope with the unused argument registers. Fix this by having 32-bit kernels share those syscall definitions with compat. Thanks to Jason for spending a lot of time finding and bisecting this and developing a trivial reproducer. The perfect bug report. Reported-by: Jason A. Donenfeld Signed-off-by: Nicholas Piggin Fixes: 7e92e01b72452 ("powerpc: Provide syscall wrapper") Reviewed-by: Arnd Bergmann Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20221012035335.866440-1-npiggin@gmail.com

powerpc: Don't add __powerpc_ prefix to syscall entry points

2022-10-06T13:59:54+00:00

When using syscall wrappers the __SYSCALL_DEFINEx() and related macros add a "__powerpc_" prefix to all syscall entry points. So for example sys_mmap becomes __powerpc_sys_mmap. This risks breaking workflows and tools that expect the old naming scheme. At a minimum setting a breakpoint on eg. sys_mmap with gdb no longer works. There seems to be no compelling reason to add the "__powerpc_" prefix, other than that it follows what some other arches do (x86, arm64, s390). But unlike other arches powerpc doesn't always enable syscall wrappers, so the syscall entry points can change name depending on CONFIG options. For those reasons drop the "__powerpc_" prefix, reverting to the existing naming. Doing so reveals two prototypes in signal.h that have the incorrect type when syscall wrappers are enabled. There are already prototypes for both functions in syscalls.h, so drop the ones from signal.h. Fixes: 7e92e01b7245 ("powerpc: Provide syscall wrapper") Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20221006135940.1223988-1-mpe@ellerman.id.au

powerpc: Provide syscall wrapper

2022-09-28T09:22:09+00:00

Implement syscall wrapper as per s390, x86, arm64. When enabled cause handlers to accept parameters from a stack frame rather than from user scratch register state. This allows for user registers to be safely cleared in order to reduce caller influence on speculation within syscall routine. The wrapper is a macro that emits syscall handler symbols that call into the target handler, obtaining its parameters from a struct pt_regs on the stack. As registers are already saved to the stack prior to calling system_call_exception, it appears that this function is executed more efficiently with the new stack-pointer convention than with parameters passed by registers, avoiding the allocation of a stack frame for this method. On a 32-bit system, we see >20% performance increases on the null_syscall microbenchmark, and on a Power 8 the performance gains amortise the cost of clearing and restoring registers which is implemented at the end of this series, seeing final result of ~5.6% performance improvement on null_syscall. Syscalls are wrapped in this fashion on all platforms except for the Cell processor as this commit does not provide SPU support. This can be quickly fixed in a successive patch, but requires spu_sys_callback to allocate a pt_regs structure to satisfy the wrapped calling convention. Co-developed-by: Andrew Donnellan Signed-off-by: Andrew Donnellan Signed-off-by: Rohan McLure Reviewed-by: Nicholas Piggin [mpe: Make incompatible with COMPAT to retain clearing of high bits of args] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220921065605.1051927-22-rmclure@linux.ibm.com

powerpc: Use common syscall handler type

2022-09-28T09:22:09+00:00

Cause syscall handlers to be typed as follows when called indirectly throughout the kernel. This is to allow for better type checking. typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long); Since both 32 and 64-bit abis allow for at least the first six machine-word length parameters to a function to be passed by registers, even handlers which admit fewer than six parameters may be viewed as having the above type. Coercing syscalls to syscall_fn requires a cast to void* to avoid -Wcast-function-type. Fixup comparisons in VDSO to avoid pointer-integer comparison. Introduce explicit cast on systems with SPUs. Signed-off-by: Rohan McLure Reviewed-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220921065605.1051927-19-rmclure@linux.ibm.com

powerpc: Include all arch-specific syscall prototypes

2022-09-28T09:22:08+00:00

Forward declare all syscall handler prototypes where a generic prototype is not provided in either linux/syscalls.h or linux/compat.h in asm/syscalls.h. This is required for compile-time type-checking for syscall handlers, which is implemented later in this series. 32-bit compatibility syscall handlers are expressed in terms of types in ppc32.h. Expose this header globally. Signed-off-by: Rohan McLure Acked-by: Nicholas Piggin [mpe: Use standard include guard naming for syscalls_32.h] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220921065605.1051927-17-rmclure@linux.ibm.com

powerpc: Adopt SYSCALL_DEFINE for arch-specific syscall handlers

2022-09-28T09:22:08+00:00

Arch-specific implementations of syscall handlers are currently used over generic implementations for the following reasons: 1. Semantics unique to powerpc 2. Compatibility syscalls require 'argument padding' to comply with 64-bit argument convention in ELF32 abi. 3. Parameter types or order is different in other architectures. These syscall handlers have been defined prior to this patch series without invoking the SYSCALL_DEFINE or COMPAT_SYSCALL_DEFINE macros with custom input and output types. We remove every such direct definition in favour of the aforementioned macros. Also update syscalls.tbl in order to refer to the symbol names generated by each of these macros. Since ppc64_personality can be called by both 64 bit and 32 bit binaries through compatibility, we must generate both both compat_sys_ and sys_ symbols for this handler. As an aside: A number of architectures including arm and powerpc agree on an alternative argument order and numbering for most of these arch-specific handlers. A future patch series may allow for asm/unistd.h to signal through its defines that a generic implementation of these syscall handlers with the correct calling convention be emitted, through the __ARCH_WANT_COMPAT_SYS_... convention. Signed-off-by: Rohan McLure Reviewed-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220921065605.1051927-16-rmclure@linux.ibm.com

powerpc: Remove direct call to mmap2 syscall handlers

2022-09-28T09:21:26+00:00

Syscall handlers should not be invoked internally by their symbol names, as these symbols defined by the architecture-defined SYSCALL_DEFINE macro. Move the compatibility syscall definition for mmap2 to syscalls.c, so that all mmap implementations can share a helper function. Remove 'inline' on static mmap helper. Signed-off-by: Rohan McLure Reviewed-by: Nicholas Piggin [mpe: Fix compat_sys_mmap2() prototype and offset handling] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220921065605.1051927-14-rmclure@linux.ibm.com

powerpc/32: Remove powerpc select specialisation

2022-09-26T13:00:15+00:00

Syscall #82 has been implemented for 32-bit platforms in a unique way on powerpc systems. This hack will in effect guess whether the caller is expecting new select semantics or old select semantics. It does so via a guess, based off the first parameter. In new select, this parameter represents the length of a user-memory array of file descriptors, and in old select this is a pointer to an arguments structure. The heuristic simply interprets sufficiently large values of its first parameter as being a call to old select. The following is a discussion on how this syscall should be handled. As discussed in this thread, the existence of such a hack suggests that for whatever powerpc binaries may predate glibc, it is most likely that they would have taken use of the old select semantics. x86 and arm64 both implement this syscall with oldselect semantics. Remove the powerpc implementation, and update syscall.tbl to refer to emit a reference to sys_old_select and compat_sys_old_select for 32-bit binaries, in keeping with how other architectures support syscall #82. Signed-off-by: Rohan McLure Reviewed-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/lkml/13737de5-0eb7-e881-9af0-163b0d29a1a0@csgroup.eu/ Link: https://lore.kernel.org/r/20220921065605.1051927-12-rmclure@linux.ibm.com

powerpc: Use generic fallocate compatibility syscall

2022-09-26T13:00:15+00:00

The powerpc fallocate compat syscall handler is identical to the generic implementation provided by commit 59c10c52f573f ("riscv: compat: syscall: Add compat_sys_call_table implementation"), and as such can be removed in favour of the generic implementation. A future patch series will replace more architecture-defined syscall handlers with generic implementations, dependent on introducing generic implementations that are compatible with powerpc and arm's parameter reorderings. Reported-by: Arnd Bergmann Signed-off-by: Rohan McLure Reviewed-by: Arnd Bergmann Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220921065605.1051927-11-rmclure@linux.ibm.com