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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
commit2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch)
tree848558de17fb3008cdf4d861b01ac7781903ce39 /arch/arm64/kernel/syscall.c
parentInitial commit. (diff)
downloadlinux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz
linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip
Adding upstream version 6.1.76.upstream/6.1.76
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'arch/arm64/kernel/syscall.c')
-rw-r--r--arch/arm64/kernel/syscall.c215
1 files changed, 215 insertions, 0 deletions
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
new file mode 100644
index 000000000..d72e8f234
--- /dev/null
+++ b/arch/arm64/kernel/syscall.c
@@ -0,0 +1,215 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/compiler.h>
+#include <linux/context_tracking.h>
+#include <linux/errno.h>
+#include <linux/nospec.h>
+#include <linux/ptrace.h>
+#include <linux/randomize_kstack.h>
+#include <linux/syscalls.h>
+
+#include <asm/daifflags.h>
+#include <asm/debug-monitors.h>
+#include <asm/exception.h>
+#include <asm/fpsimd.h>
+#include <asm/syscall.h>
+#include <asm/thread_info.h>
+#include <asm/unistd.h>
+
+long compat_arm_syscall(struct pt_regs *regs, int scno);
+long sys_ni_syscall(void);
+
+static long do_ni_syscall(struct pt_regs *regs, int scno)
+{
+#ifdef CONFIG_COMPAT
+ long ret;
+ if (is_compat_task()) {
+ ret = compat_arm_syscall(regs, scno);
+ 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);
+}
+
+static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
+ unsigned int sc_nr,
+ const syscall_fn_t syscall_table[])
+{
+ long ret;
+
+ add_random_kstack_offset();
+
+ 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, scno);
+ }
+
+ syscall_set_return_value(current, regs, 0, ret);
+
+ /*
+ * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
+ * but not enough for arm64 stack utilization comfort. To keep
+ * reasonable stack head room, reduce the maximum offset to 9 bits.
+ *
+ * The actual entropy will be further reduced by the compiler when
+ * applying stack alignment constraints: the AAPCS mandates a
+ * 16-byte (i.e. 4-bit) aligned SP at function boundaries.
+ *
+ * The resulting 5 bits of entropy is seen in SP[8:4].
+ */
+ choose_random_kstack_offset(get_random_u16() & 0x1FF);
+}
+
+static inline bool has_syscall_work(unsigned long flags)
+{
+ return unlikely(flags & _TIF_SYSCALL_WORK);
+}
+
+int syscall_trace_enter(struct pt_regs *regs);
+void syscall_trace_exit(struct pt_regs *regs);
+
+static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
+ const syscall_fn_t syscall_table[])
+{
+ unsigned long flags = read_thread_flags();
+
+ regs->orig_x0 = regs->regs[0];
+ regs->syscallno = scno;
+
+ /*
+ * BTI note:
+ * The architecture does not guarantee that SPSR.BTYPE is zero
+ * on taking an SVC, so we could return to userspace with a
+ * non-zero BTYPE after the syscall.
+ *
+ * This shouldn't matter except when userspace is explicitly
+ * doing something stupid, such as setting PROT_BTI on a page
+ * that lacks conforming BTI/PACIxSP instructions, falling
+ * through from one executable page to another with differing
+ * PROT_BTI, or messing with BTYPE via ptrace: in such cases,
+ * userspace should not be surprised if a SIGILL occurs on
+ * syscall return.
+ *
+ * So, don't touch regs->pstate & PSR_BTYPE_MASK here.
+ * (Similarly for HVC and SMC elsewhere.)
+ */
+
+ local_daif_restore(DAIF_PROCCTX);
+
+ if (flags & _TIF_MTE_ASYNC_FAULT) {
+ /*
+ * Process the asynchronous tag check fault before the actual
+ * syscall. do_notify_resume() will send a signal to userspace
+ * before the syscall is restarted.
+ */
+ syscall_set_return_value(current, regs, -ERESTARTNOINTR, 0);
+ return;
+ }
+
+ if (has_syscall_work(flags)) {
+ /*
+ * The de-facto standard way to skip a system call using ptrace
+ * is to set the system call to -1 (NO_SYSCALL) and set x0 to a
+ * suitable error code for consumption by userspace. However,
+ * this cannot be distinguished from a user-issued syscall(-1)
+ * and so we must set x0 to -ENOSYS here in case the tracer doesn't
+ * issue the skip and we fall into trace_exit with x0 preserved.
+ *
+ * This is slightly odd because it also means that if a tracer
+ * sets the system call number to -1 but does not initialise x0,
+ * then x0 will be preserved for all system calls apart from a
+ * user-issued syscall(-1). However, requesting a skip and not
+ * setting the return value is unlikely to do anything sensible
+ * anyway.
+ */
+ if (scno == NO_SYSCALL)
+ syscall_set_return_value(current, regs, -ENOSYS, 0);
+ scno = syscall_trace_enter(regs);
+ if (scno == NO_SYSCALL)
+ goto trace_exit;
+ }
+
+ invoke_syscall(regs, scno, sc_nr, syscall_table);
+
+ /*
+ * The tracing status may have changed under our feet, so we have to
+ * check again. However, if we were tracing entry, then we always trace
+ * exit regardless, as the old entry assembly did.
+ */
+ if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
+ local_daif_mask();
+ flags = read_thread_flags();
+ if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP))
+ return;
+ local_daif_restore(DAIF_PROCCTX);
+ }
+
+trace_exit:
+ syscall_trace_exit(regs);
+}
+
+/*
+ * As per the ABI exit SME streaming mode and clear the SVE state not
+ * shared with FPSIMD on syscall entry.
+ */
+static inline void fp_user_discard(void)
+{
+ /*
+ * If SME is active then exit streaming mode. If ZA is active
+ * then flush the SVE registers but leave userspace access to
+ * both SVE and SME enabled, otherwise disable SME for the
+ * task and fall through to disabling SVE too. This means
+ * that after a syscall we never have any streaming mode
+ * register state to track, if this changes the KVM code will
+ * need updating.
+ */
+ if (system_supports_sme() && test_thread_flag(TIF_SME)) {
+ u64 svcr = read_sysreg_s(SYS_SVCR);
+
+ if (svcr & SVCR_SM_MASK)
+ sme_smstop_sm();
+ }
+
+ if (!system_supports_sve())
+ return;
+
+ /*
+ * If SME is not active then disable SVE, the registers will
+ * be cleared when userspace next attempts to access them and
+ * we do not need to track the SVE register state until then.
+ */
+ clear_thread_flag(TIF_SVE);
+
+ /*
+ * task_fpsimd_load() won't be called to update CPACR_EL1 in
+ * ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only
+ * happens if a context switch or kernel_neon_begin() or context
+ * modification (sigreturn, ptrace) intervenes.
+ * So, ensure that CPACR_EL1 is already correct for the fast-path case.
+ */
+ sve_user_disable();
+}
+
+void do_el0_svc(struct pt_regs *regs)
+{
+ fp_user_discard();
+ el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table);
+}
+
+#ifdef CONFIG_COMPAT
+void do_el0_svc_compat(struct pt_regs *regs)
+{
+ el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls,
+ compat_sys_call_table);
+}
+#endif