From 4141c857fd09dbed480f021b3eece4f46c653161 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Wed, 11 Jul 2018 14:56:43 +0100 Subject: [PATCH] arm64: convert raw syscall invocation to C As a first step towards invoking syscalls with a pt_regs argument, convert the raw syscall invocation logic to C. We end up with a bit more register shuffling, but the unified invocation logic means we can unify the tracing paths, too. Previously, assembly had to open-code calls to ni_sys() when the system call number was out-of-bounds for the relevant syscall table. This case is now handled by invoke_syscall(), and the assembly no longer need to handle this case explicitly. This allows the tracing paths to be simplified and unified, as we no longer need the __ni_sys_trace path and the __sys_trace_return label. This only converts the invocation of the syscall. The rest of the syscall triage and tracing is left in assembly for now, and will be converted in subsequent patches. Signed-off-by: Mark Rutland Reviewed-by: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon --- arch/arm64/kernel/Makefile | 3 ++- arch/arm64/kernel/entry.S | 36 ++++++++++------------------------ arch/arm64/kernel/syscall.c | 47 +++++++++++++++++++++++++++++++++++++++++++++ arch/arm64/kernel/traps.c | 16 --------------- 4 files changed, 59 insertions(+), 43 deletions(-) create mode 100644 arch/arm64/kernel/syscall.c diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 0025f869..4e24d224 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -18,7 +18,8 @@ arm64-obj-y := debug-monitors.o entry.o irq.o fpsimd.o \ hyp-stub.o psci.o cpu_ops.o insn.o \ return_address.o cpuinfo.o cpu_errata.o \ cpufeature.o alternative.o cacheinfo.o \ - smp.o smp_spin_table.o topology.o smccc-call.o + smp.o smp_spin_table.o topology.o smccc-call.o \ + syscall.o extra-$(CONFIG_EFI) := efi-entry.o diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 2018095..2045aec 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -903,7 +903,6 @@ ENDPROC(el0_error) */ ret_fast_syscall: disable_daif - str x0, [sp, #S_X0] // returned x0 #ifndef CONFIG_DEBUG_RSEQ ldr x1, [tsk, #TSK_TI_FLAGS] // re-check for syscall tracing and x2, x1, #_TIF_SYSCALL_WORK @@ -978,15 +977,11 @@ el0_svc_naked: // compat entry point tst x16, #_TIF_SYSCALL_WORK // check for syscall hooks b.ne __sys_trace - cmp wscno, wsc_nr // check upper syscall limit - b.hs ni_sys - mask_nospec64 xscno, xsc_nr, x19 // enforce bounds for syscall number - ldr x16, [stbl, xscno, lsl #3] // address in the syscall table - blr x16 // call sys_* routine - b ret_fast_syscall -ni_sys: mov x0, sp - bl do_ni_syscall + mov w1, wscno + mov w2, wsc_nr + mov x3, stbl + bl invoke_syscall b ret_fast_syscall ENDPROC(el0_svc) @@ -1003,29 +998,18 @@ __sys_trace: bl syscall_trace_enter cmp w0, #NO_SYSCALL // skip the syscall? b.eq __sys_trace_return_skipped - mov wscno, w0 // syscall number (possibly new) - mov x1, sp // pointer to regs - cmp wscno, wsc_nr // check upper syscall limit - b.hs __ni_sys_trace - ldp x0, x1, [sp] // restore the syscall args - ldp x2, x3, [sp, #S_X2] - ldp x4, x5, [sp, #S_X4] - ldp x6, x7, [sp, #S_X6] - ldr x16, [stbl, xscno, lsl #3] // address in the syscall table - blr x16 // call sys_* routine -__sys_trace_return: - str x0, [sp, #S_X0] // save returned x0 + mov x0, sp + mov w1, wscno + mov w2, wsc_nr + mov x3, stbl + bl invoke_syscall + __sys_trace_return_skipped: mov x0, sp bl syscall_trace_exit b ret_to_user -__ni_sys_trace: - mov x0, sp - bl do_ni_syscall - b __sys_trace_return - .popsection // .entry.text #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c new file mode 100644 index 0000000..93d36f2 --- /dev/null +++ b/arch/arm64/kernel/syscall.c @@ -0,0 +1,47 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include + +#include + +long compat_arm_syscall(struct pt_regs *regs); + +asmlinkage long do_ni_syscall(struct pt_regs *regs) +{ +#ifdef CONFIG_COMPAT + long ret; + if (is_compat_task()) { + ret = compat_arm_syscall(regs); + if (ret != -ENOSYS) + return ret; + } +#endif + + return sys_ni_syscall(); +} + +static long __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn) +{ + return syscall_fn(regs->regs[0], regs->regs[1], regs->regs[2], + regs->regs[3], regs->regs[4], regs->regs[5]); +} + +asmlinkage void invoke_syscall(struct pt_regs *regs, unsigned int scno, + unsigned int sc_nr, + const syscall_fn_t syscall_table[]) +{ + long ret; + + if (scno < sc_nr) { + syscall_fn_t syscall_fn; + syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)]; + ret = __invoke_syscall(regs, syscall_fn); + } else { + ret = do_ni_syscall(regs); + } + + regs->regs[0] = ret; +} diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index c272927..039e9ff 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -547,22 +547,6 @@ asmlinkage void __exception do_sysinstr(unsigned int esr, struct pt_regs *regs) do_undefinstr(regs); } -long compat_arm_syscall(struct pt_regs *regs); - -asmlinkage long do_ni_syscall(struct pt_regs *regs) -{ -#ifdef CONFIG_COMPAT - long ret; - if (is_compat_task()) { - ret = compat_arm_syscall(regs); - if (ret != -ENOSYS) - return ret; - } -#endif - - return sys_ni_syscall(); -} - static const char *esr_class_str[] = { [0 ... ESR_ELx_EC_MAX] = "UNRECOGNIZED EC", [ESR_ELx_EC_UNKNOWN] = "Unknown/Uncategorized", -- 2.7.4