Messages in this thread | | | Date | Sun, 15 May 2022 17:47:04 +0800 | Subject | Re: [PATCH V10 13/22] LoongArch: Add system call support | From | WANG Xuerui <> |
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On 5/14/22 22:39, Huacai Chen wrote:
> Hi, Xuerui, > > On Sat, May 14, 2022 at 9:53 PM WANG Xuerui <kernel@xen0n.name> wrote: >> Hi, >> >> On 5/14/22 16:03, Huacai Chen wrote: >>> Add system call support and related uaccess.h for LoongArch. >>> >>> Q: Why keep _ARCH_WANT_SYS_CLONE definition while there is clone3: >>> A: The latest glibc release (2.35) has some basic support for clone3 but >>> it isn't complete. E.g., pthread_create() and spawni() have converted >>> to use clone3 but fork() will still use clone. Moreover, some seccomp >>> related applications can still not work perfectly with clone3. E.g., >>> Chromium sandbox cannot work at all and there is no solution for it, >>> which is more terrible than the fork() story [1]. >>> >>> [1] https://chromium-review.googlesource.com/c/chromium/src/+/2936184 >>> >>> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> >>> --- >>> arch/loongarch/include/asm/seccomp.h | 20 ++ >>> arch/loongarch/include/asm/syscall.h | 74 +++++++ >>> arch/loongarch/include/asm/uaccess.h | 269 +++++++++++++++++++++++ >>> arch/loongarch/include/asm/unistd.h | 11 + >>> arch/loongarch/include/uapi/asm/unistd.h | 5 + >>> arch/loongarch/kernel/entry.S | 89 ++++++++ >>> arch/loongarch/kernel/syscall.c | 63 ++++++ >>> 7 files changed, 531 insertions(+) >>> create mode 100644 arch/loongarch/include/asm/seccomp.h >>> create mode 100644 arch/loongarch/include/asm/syscall.h >>> create mode 100644 arch/loongarch/include/asm/uaccess.h >>> create mode 100644 arch/loongarch/include/asm/unistd.h >>> create mode 100644 arch/loongarch/include/uapi/asm/unistd.h >>> create mode 100644 arch/loongarch/kernel/entry.S >>> create mode 100644 arch/loongarch/kernel/syscall.c >>> >>> diff --git a/arch/loongarch/include/asm/seccomp.h b/arch/loongarch/include/asm/seccomp.h >>> new file mode 100644 >>> index 000000000000..31d6ab42e43e >>> --- /dev/null >>> +++ b/arch/loongarch/include/asm/seccomp.h >>> @@ -0,0 +1,20 @@ >>> +/* SPDX-License-Identifier: GPL-2.0 */ >>> + >>> +#ifndef _ASM_SECCOMP_H >>> +#define _ASM_SECCOMP_H >>> + >>> +#include <asm/unistd.h> >>> + >>> +#include <asm-generic/seccomp.h> >>> + >>> +#ifdef CONFIG_32BIT >>> +# define SECCOMP_ARCH_NATIVE AUDIT_ARCH_LOONGARCH32 >>> +# define SECCOMP_ARCH_NATIVE_NR NR_syscalls >>> +# define SECCOMP_ARCH_NATIVE_NAME "loongarch32" >>> +#else >>> +# define SECCOMP_ARCH_NATIVE AUDIT_ARCH_LOONGARCH64 >>> +# define SECCOMP_ARCH_NATIVE_NR NR_syscalls >>> +# define SECCOMP_ARCH_NATIVE_NAME "loongarch64" >>> +#endif >>> + >>> +#endif /* _ASM_SECCOMP_H */ >>> diff --git a/arch/loongarch/include/asm/syscall.h b/arch/loongarch/include/asm/syscall.h >>> new file mode 100644 >>> index 000000000000..e286dc58476e >>> --- /dev/null >>> +++ b/arch/loongarch/include/asm/syscall.h >>> @@ -0,0 +1,74 @@ >>> +/* SPDX-License-Identifier: GPL-2.0+ */ >>> +/* >>> + * Author: Hanlu Li <lihanlu@loongson.cn> >>> + * Huacai Chen <chenhuacai@loongson.cn> >>> + * >>> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited >>> + */ >>> + >>> +#ifndef __ASM_LOONGARCH_SYSCALL_H >>> +#define __ASM_LOONGARCH_SYSCALL_H >>> + >>> +#include <linux/compiler.h> >>> +#include <uapi/linux/audit.h> >>> +#include <linux/elf-em.h> >>> +#include <linux/kernel.h> >>> +#include <linux/sched.h> >>> +#include <linux/uaccess.h> >>> +#include <asm/ptrace.h> >>> +#include <asm/unistd.h> >>> + >>> +extern void *sys_call_table[]; >>> + >>> +static inline long syscall_get_nr(struct task_struct *task, >>> + struct pt_regs *regs) >>> +{ >>> + return regs->regs[11]; >> It may be better readability-wise to somehow change this 11 to something >> resembling A7, but it's okay as-is. > OK, keep it as is. > >>> +} >>> + >>> +static inline void syscall_rollback(struct task_struct *task, >>> + struct pt_regs *regs) >>> +{ >>> + regs->regs[4] = regs->orig_a0; >>> +} >>> + >>> +static inline long syscall_get_error(struct task_struct *task, >>> + struct pt_regs *regs) >>> +{ >>> + unsigned long error = regs->regs[4]; >>> + >>> + return IS_ERR_VALUE(error) ? error : 0; >>> +} >>> + >>> +static inline long syscall_get_return_value(struct task_struct *task, >>> + struct pt_regs *regs) >>> +{ >>> + return regs->regs[4]; >>> +} >>> + >>> +static inline void syscall_set_return_value(struct task_struct *task, >>> + struct pt_regs *regs, >>> + int error, long val) >>> +{ >>> + regs->regs[4] = (long) error ? error : val; >>> +} >>> + >>> +static inline void syscall_get_arguments(struct task_struct *task, >>> + struct pt_regs *regs, >>> + unsigned long *args) >>> +{ >>> + args[0] = regs->orig_a0; >>> + memcpy(&args[1], ®s->regs[5], 5 * sizeof(long)); >>> +} >>> + >>> +static inline int syscall_get_arch(struct task_struct *task) >>> +{ >>> + return AUDIT_ARCH_LOONGARCH64; >>> +} >>> + >>> +static inline bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs) >>> +{ >>> + return false; >>> +} >>> + >>> +#endif /* __ASM_LOONGARCH_SYSCALL_H */ >>> diff --git a/arch/loongarch/include/asm/uaccess.h b/arch/loongarch/include/asm/uaccess.h >>> new file mode 100644 >>> index 000000000000..217c6a3727b1 >>> --- /dev/null >>> +++ b/arch/loongarch/include/asm/uaccess.h >>> @@ -0,0 +1,269 @@ >>> +/* SPDX-License-Identifier: GPL-2.0 */ >>> +/* >>> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited >>> + * >>> + * Derived from MIPS: >>> + * Copyright (C) 1996, 1997, 1998, 1999, 2000, 03, 04 by Ralf Baechle >>> + * Copyright (C) 1999, 2000 Silicon Graphics, Inc. >>> + * Copyright (C) 2007 Maciej W. Rozycki >>> + * Copyright (C) 2014, Imagination Technologies Ltd. >>> + */ >>> +#ifndef _ASM_UACCESS_H >>> +#define _ASM_UACCESS_H >>> + >>> +#include <linux/kernel.h> >>> +#include <linux/string.h> >>> +#include <linux/extable.h> >>> +#include <asm/pgtable.h> >>> +#include <asm-generic/extable.h> >>> +#include <asm-generic/access_ok.h> >>> + >>> +extern u64 __ua_limit; >>> + >>> +#define __UA_ADDR ".dword" >>> +#define __UA_LA "la.abs" >>> +#define __UA_LIMIT __ua_limit >>> + >>> +/* >>> + * get_user: - Get a simple variable from user space. >>> + * @x: Variable to store result. >>> + * @ptr: Source address, in user space. >>> + * >>> + * Context: User context only. This function may sleep if pagefaults are >>> + * enabled. >>> + * >>> + * This macro copies a single simple variable from user space to kernel >>> + * space. It supports simple types like char and int, but not larger >>> + * data types like structures or arrays. >>> + * >>> + * @ptr must have pointer-to-simple-variable type, and the result of >>> + * dereferencing @ptr must be assignable to @x without a cast. >>> + * >>> + * Returns zero on success, or -EFAULT on error. >>> + * On error, the variable @x is set to zero. >>> + */ >>> +#define get_user(x, ptr) \ >>> +({ \ >>> + const __typeof__(*(ptr)) __user *__p = (ptr); \ >>> + \ >>> + might_fault(); \ >>> + access_ok(__p, sizeof(*__p)) ? __get_user((x), __p) : \ >>> + ((x) = 0, -EFAULT); \ >>> +}) >>> + >>> +/* >>> + * put_user: - Write a simple value into user space. >>> + * @x: Value to copy to user space. >>> + * @ptr: Destination address, in user space. >>> + * >>> + * Context: User context only. This function may sleep if pagefaults are >>> + * enabled. >>> + * >>> + * This macro copies a single simple value from kernel space to user >>> + * space. It supports simple types like char and int, but not larger >>> + * data types like structures or arrays. >>> + * >>> + * @ptr must have pointer-to-simple-variable type, and @x must be assignable >>> + * to the result of dereferencing @ptr. >>> + * >>> + * Returns zero on success, or -EFAULT on error. >>> + */ >>> +#define put_user(x, ptr) \ >>> +({ \ >>> + __typeof__(*(ptr)) __user *__p = (ptr); \ >>> + \ >>> + might_fault(); \ >>> + access_ok(__p, sizeof(*__p)) ? __put_user((x), __p) : -EFAULT; \ >>> +}) >>> + >>> +/* >>> + * __get_user: - Get a simple variable from user space, with less checking. >>> + * @x: Variable to store result. >>> + * @ptr: Source address, in user space. >>> + * >>> + * Context: User context only. This function may sleep if pagefaults are >>> + * enabled. >>> + * >>> + * This macro copies a single simple variable from user space to kernel >>> + * space. It supports simple types like char and int, but not larger >>> + * data types like structures or arrays. >>> + * >>> + * @ptr must have pointer-to-simple-variable type, and the result of >>> + * dereferencing @ptr must be assignable to @x without a cast. >>> + * >>> + * Caller must check the pointer with access_ok() before calling this >>> + * function. >>> + * >>> + * Returns zero on success, or -EFAULT on error. >>> + * On error, the variable @x is set to zero. >>> + */ >>> +#define __get_user(x, ptr) \ >>> +({ \ >>> + int __gu_err = 0; \ >>> + \ >>> + __chk_user_ptr(ptr); \ >>> + __get_user_common((x), sizeof(*(ptr)), ptr); \ >>> + __gu_err; \ >>> +}) >>> + >>> +/* >>> + * __put_user: - Write a simple value into user space, with less checking. >>> + * @x: Value to copy to user space. >>> + * @ptr: Destination address, in user space. >>> + * >>> + * Context: User context only. This function may sleep if pagefaults are >>> + * enabled. >>> + * >>> + * This macro copies a single simple value from kernel space to user >>> + * space. It supports simple types like char and int, but not larger >>> + * data types like structures or arrays. >>> + * >>> + * @ptr must have pointer-to-simple-variable type, and @x must be assignable >>> + * to the result of dereferencing @ptr. >>> + * >>> + * Caller must check the pointer with access_ok() before calling this >>> + * function. >>> + * >>> + * Returns zero on success, or -EFAULT on error. >>> + */ >>> +#define __put_user(x, ptr) \ >>> +({ \ >>> + int __pu_err = 0; \ >>> + __typeof__(*(ptr)) __pu_val; \ >>> + \ >>> + __pu_val = (x); \ >>> + __chk_user_ptr(ptr); \ >>> + __put_user_common(ptr, sizeof(*(ptr))); \ >>> + __pu_err; \ >>> +}) >>> + >>> +struct __large_struct { unsigned long buf[100]; }; >>> +#define __m(x) (*(struct __large_struct __user *)(x)) >>> + >>> +#define __get_user_common(val, size, ptr) \ >>> +do { \ >>> + switch (size) { \ >>> + case 1: __get_data_asm(val, "ld.b", ptr); break; \ >>> + case 2: __get_data_asm(val, "ld.h", ptr); break; \ >>> + case 4: __get_data_asm(val, "ld.w", ptr); break; \ >>> + case 8: __get_data_asm(val, "ld.d", ptr); break; \ >>> + default: BUILD_BUG(); break; \ >>> + } \ >>> +} while (0) >>> + >>> +#define __get_kernel_common(val, size, ptr) __get_user_common(val, size, ptr) >>> + >>> +#define __get_data_asm(val, insn, ptr) \ >>> +{ \ >>> + long __gu_tmp; \ >>> + \ >>> + __asm__ __volatile__( \ >>> + "1: " insn " %1, %2 \n" \ >>> + "2: \n" \ >>> + " .section .fixup,\"ax\" \n" \ >>> + "3: li.w %0, %3 \n" \ >>> + " or %1, $r0, $r0 \n" \ >>> + " b 2b \n" \ >>> + " .previous \n" \ >>> + " .section __ex_table,\"a\" \n" \ >>> + " "__UA_ADDR "\t1b, 3b \n" \ >>> + " .previous \n" \ >>> + : "+r" (__gu_err), "=r" (__gu_tmp) \ >>> + : "m" (__m(ptr)), "i" (-EFAULT)); \ >>> + \ >>> + (val) = (__typeof__(*(ptr))) __gu_tmp; \ >>> +} >>> + >>> +#define __put_user_common(ptr, size) \ >>> +do { \ >>> + switch (size) { \ >>> + case 1: __put_data_asm("st.b", ptr); break; \ >>> + case 2: __put_data_asm("st.h", ptr); break; \ >>> + case 4: __put_data_asm("st.w", ptr); break; \ >>> + case 8: __put_data_asm("st.d", ptr); break; \ >>> + default: BUILD_BUG(); break; \ >>> + } \ >>> +} while (0) >>> + >>> +#define __put_kernel_common(ptr, size) __put_user_common(ptr, size) >>> + >>> +#define __put_data_asm(insn, ptr) \ >>> +{ \ >>> + __asm__ __volatile__( \ >>> + "1: " insn " %z2, %1 # __put_user_asm\n" \ >>> + "2: \n" \ >>> + " .section .fixup,\"ax\" \n" \ >>> + "3: li.w %0, %3 \n" \ >>> + " b 2b \n" \ >>> + " .previous \n" \ >>> + " .section __ex_table,\"a\" \n" \ >>> + " " __UA_ADDR " 1b, 3b \n" \ >>> + " .previous \n" \ >>> + : "+r" (__pu_err), "=m" (__m(ptr)) \ >>> + : "Jr" (__pu_val), "i" (-EFAULT)); \ >>> +} >>> + >>> +#define __get_kernel_nofault(dst, src, type, err_label) \ >>> +do { \ >>> + int __gu_err = 0; \ >>> + \ >>> + __get_kernel_common(*((type *)(dst)), sizeof(type), \ >>> + (__force type *)(src)); \ >>> + if (unlikely(__gu_err)) \ >>> + goto err_label; \ >>> +} while (0) >>> + >>> +#define __put_kernel_nofault(dst, src, type, err_label) \ >>> +do { \ >>> + type __pu_val; \ >>> + int __pu_err = 0; \ >>> + \ >>> + __pu_val = *(__force type *)(src); \ >>> + __put_kernel_common(((type *)(dst)), sizeof(type)); \ >>> + if (unlikely(__pu_err)) \ >>> + goto err_label; \ >>> +} while (0) >>> + >>> +extern unsigned long __copy_user(void *to, const void *from, __kernel_size_t n); >>> + >>> +static inline unsigned long __must_check >>> +raw_copy_from_user(void *to, const void __user *from, unsigned long n) >>> +{ >>> + return __copy_user(to, from, n); >>> +} >>> + >>> +static inline unsigned long __must_check >>> +raw_copy_to_user(void __user *to, const void *from, unsigned long n) >>> +{ >>> + return __copy_user(to, from, n); >>> +} >>> + >>> +#define INLINE_COPY_FROM_USER >>> +#define INLINE_COPY_TO_USER >>> + >>> +/* >>> + * __clear_user: - Zero a block of memory in user space, with less checking. >>> + * @addr: Destination address, in user space. >>> + * @size: Number of bytes to zero. >>> + * >>> + * Zero a block of memory in user space. Caller must check >>> + * the specified block with access_ok() before calling this function. >>> + * >>> + * Returns number of bytes that could not be cleared. >>> + * On success, this will be zero. >>> + */ >>> +extern unsigned long __clear_user(void __user *addr, __kernel_size_t size); >>> + >>> +#define clear_user(addr, n) \ >>> +({ \ >>> + void __user *__cl_addr = (addr); \ >>> + unsigned long __cl_size = (n); \ >>> + if (__cl_size && access_ok(__cl_addr, __cl_size)) \ >>> + __cl_size = __clear_user(__cl_addr, __cl_size); \ >>> + __cl_size; \ >>> +}) >>> + >>> +extern long strncpy_from_user(char *to, const char __user *from, long n); >>> +extern long strnlen_user(const char __user *str, long n); >>> + >>> +#endif /* _ASM_UACCESS_H */ >>> diff --git a/arch/loongarch/include/asm/unistd.h b/arch/loongarch/include/asm/unistd.h >>> new file mode 100644 >>> index 000000000000..cfddb0116a8c >>> --- /dev/null >>> +++ b/arch/loongarch/include/asm/unistd.h >>> @@ -0,0 +1,11 @@ >>> +/* SPDX-License-Identifier: GPL-2.0+ */ >>> +/* >>> + * Author: Hanlu Li <lihanlu@loongson.cn> >>> + * Huacai Chen <chenhuacai@loongson.cn> >>> + * >>> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited >>> + */ >>> + >>> +#include <uapi/asm/unistd.h> >>> + >>> +#define NR_syscalls (__NR_syscalls) >>> diff --git a/arch/loongarch/include/uapi/asm/unistd.h b/arch/loongarch/include/uapi/asm/unistd.h >>> new file mode 100644 >>> index 000000000000..fcb668984f03 >>> --- /dev/null >>> +++ b/arch/loongarch/include/uapi/asm/unistd.h >>> @@ -0,0 +1,5 @@ >>> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ >>> +#define __ARCH_WANT_SYS_CLONE >>> +#define __ARCH_WANT_SYS_CLONE3 >> Having read the discussion in v9 regarding the sandbox scenario, I agree >> leaving clone alone would probably be the better choice. It's relieving >> seeing the stat cruft dropped... World rebuilds of new-world distros >> pending on the horizon. :-D > clone3() is not just a beautiful version of clone(), it has some new > features such as pidfd, so we need both clone() and clone3(). Apologizes if I didn't make it clear, but to clear any confusion: I'm not saying we don't want clone3, and we should keep both clone (for not breaking end user workflows involving sandboxed processes such as browsers) and clone3 (the path forward). > >>> + >>> +#include <asm-generic/unistd.h> >>> diff --git a/arch/loongarch/kernel/entry.S b/arch/loongarch/kernel/entry.S >>> new file mode 100644 >>> index 000000000000..d5b3dbcf5425 >>> --- /dev/null >>> +++ b/arch/loongarch/kernel/entry.S >>> @@ -0,0 +1,89 @@ >>> +/* SPDX-License-Identifier: GPL-2.0 */ >>> +/* >>> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited >>> + * >>> + * Derived from MIPS: >>> + * Copyright (C) 1994 - 2000, 2001, 2003 Ralf Baechle >>> + * Copyright (C) 1999, 2000 Silicon Graphics, Inc. >>> + * Copyright (C) 2001 MIPS Technologies, Inc. >>> + */ >>> + >>> +#include <asm/asm.h> >>> +#include <asm/asmmacro.h> >>> +#include <asm/loongarch.h> >>> +#include <asm/regdef.h> >>> +#include <asm/stackframe.h> >>> +#include <asm/thread_info.h> >>> + >>> + .text >>> + .cfi_sections .debug_frame >>> + .align 5 >>> +SYM_FUNC_START(handle_syscall) >>> + csrrd t0, PERCPU_BASE_KS >>> + la.abs t1, kernelsp >>> + add.d t1, t1, t0 >>> + move t2, sp >>> + ld.d sp, t1, 0 >>> + >>> + addi.d sp, sp, -PT_SIZE >>> + cfi_st t2, PT_R3 >>> + cfi_rel_offset sp, PT_R3 >>> + st.d zero, sp, PT_R0 >>> + csrrd t2, LOONGARCH_CSR_PRMD >>> + st.d t2, sp, PT_PRMD >>> + csrrd t2, LOONGARCH_CSR_CRMD >>> + st.d t2, sp, PT_CRMD >>> + csrrd t2, LOONGARCH_CSR_EUEN >>> + st.d t2, sp, PT_EUEN >>> + csrrd t2, LOONGARCH_CSR_ECFG >>> + st.d t2, sp, PT_ECFG >>> + csrrd t2, LOONGARCH_CSR_ESTAT >>> + st.d t2, sp, PT_ESTAT >>> + cfi_st ra, PT_R1 >>> + cfi_st a0, PT_R4 >>> + cfi_st a1, PT_R5 >>> + cfi_st a2, PT_R6 >>> + cfi_st a3, PT_R7 >>> + cfi_st a4, PT_R8 >>> + cfi_st a5, PT_R9 >>> + cfi_st a6, PT_R10 >>> + cfi_st a7, PT_R11 >>> + csrrd ra, LOONGARCH_CSR_ERA >>> + st.d ra, sp, PT_ERA >>> + cfi_rel_offset ra, PT_ERA >>> + >>> + cfi_st tp, PT_R2 >>> + cfi_st u0, PT_R21 >>> + cfi_st fp, PT_R22 >>> + >>> + SAVE_STATIC >>> + >>> + move u0, t0 >>> + li.d tp, ~_THREAD_MASK >>> + and tp, tp, sp >>> + >>> + move a0, sp >>> + bl do_syscall >>> + >>> + RESTORE_ALL_AND_RET >>> +SYM_FUNC_END(handle_syscall) >>> + >>> +SYM_CODE_START(ret_from_fork) >>> + bl schedule_tail # a0 = struct task_struct *prev >>> + move a0, sp >>> + bl syscall_exit_to_user_mode >>> + RESTORE_STATIC >>> + RESTORE_SOME >>> + RESTORE_SP_AND_RET >>> +SYM_CODE_END(ret_from_fork) >>> + >>> +SYM_CODE_START(ret_from_kernel_thread) >>> + bl schedule_tail # a0 = struct task_struct *prev >>> + move a0, s1 >>> + jirl ra, s0, 0 >>> + move a0, sp >>> + bl syscall_exit_to_user_mode >>> + RESTORE_STATIC >>> + RESTORE_SOME >>> + RESTORE_SP_AND_RET >>> +SYM_CODE_END(ret_from_kernel_thread) >>> diff --git a/arch/loongarch/kernel/syscall.c b/arch/loongarch/kernel/syscall.c >>> new file mode 100644 >>> index 000000000000..3fc4211db989 >>> --- /dev/null >>> +++ b/arch/loongarch/kernel/syscall.c >>> @@ -0,0 +1,63 @@ >>> +// SPDX-License-Identifier: GPL-2.0+ >>> +/* >>> + * Author: Hanlu Li <lihanlu@loongson.cn> >>> + * Huacai Chen <chenhuacai@loongson.cn> >>> + * >>> + * Copyright (C) 2020-2022 Loongson Technology Corporation Limited >>> + */ >>> +#include <linux/capability.h> >>> +#include <linux/entry-common.h> >>> +#include <linux/errno.h> >>> +#include <linux/linkage.h> >>> +#include <linux/syscalls.h> >>> +#include <linux/unistd.h> >>> + >>> +#include <asm/asm.h> >>> +#include <asm/signal.h> >>> +#include <asm/switch_to.h> >>> +#include <asm-generic/syscalls.h> >>> + >>> +#undef __SYSCALL >>> +#define __SYSCALL(nr, call) [nr] = (call), >>> + >>> +SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len, unsigned long, >>> + prot, unsigned long, flags, unsigned long, fd, off_t, offset) >>> +{ >>> + if (offset & ~PAGE_MASK) >>> + return -EINVAL; >>> + >>> + return ksys_mmap_pgoff(addr, len, prot, flags, fd, offset >> PAGE_SHIFT); >>> +} >>> + >>> +void *sys_call_table[__NR_syscalls] = { >>> + [0 ... __NR_syscalls - 1] = sys_ni_syscall, >>> +#include <asm/unistd.h> >>> +}; >>> + >>> +typedef long (*sys_call_fn)(unsigned long, unsigned long, >>> + unsigned long, unsigned long, unsigned long, unsigned long); >>> + >>> +void noinstr do_syscall(struct pt_regs *regs) >>> +{ >>> + unsigned long nr; >>> + sys_call_fn syscall_fn; >>> + >>> + nr = regs->regs[11]; >>> + /* Set for syscall restarting */ >>> + if (nr < NR_syscalls) >>> + regs->regs[0] = nr + 1; >>> + >>> + regs->csr_era += 4; >>> + regs->orig_a0 = regs->regs[4]; >>> + regs->regs[4] = -ENOSYS; >>> + >>> + nr = syscall_enter_from_user_mode(regs, nr); >>> + >>> + if (nr < NR_syscalls) { >> I saw in the manual that there's the BADI (出错指令) CSR that records the >> faulting instruction word for exceptions other than INT, GCHC and MERR; >> this implies we can read the trapping syscall insn word from this CSR, >> to inspect its immediate field, so we can reserve non-zero immediates on >> the syscall insn for future use. >> >> This would take 3 insns to complete: csrrd, bitfield extraction, and >> bail if non-zero; this should be an acceptable tradeoff for a lot of >> extensibility and scalability? > This need much efforts, we can optimize it in future.
Fair point. No one has used syscall insns with non-zero immediates, at least from what I've seen during the year porting software and reviewing others' patches, so we could add the check later and breakage should only be theoretical.
> > Huacai >>> + syscall_fn = sys_call_table[nr]; >>> + regs->regs[4] = syscall_fn(regs->orig_a0, regs->regs[5], regs->regs[6], >>> + regs->regs[7], regs->regs[8], regs->regs[9]); >>> + } >>> + >>> + syscall_exit_to_user_mode(regs); >>> +}
Now that we've gone through every point:
Reviewed-by: WANG Xuerui <git@xen0n.name>
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