arm64: convert native/compat syscall entry to C

Now that the syscall invocation logic is in C, we can migrate the rest
of the syscall entry logic over, so that the entry assembly needn't look
at the register values at all.

The SVE reset across syscall logic now unconditionally clears TIF_SVE,
but sve_user_disable() will only write back to CPACR_EL1 when SVE is
actually enabled.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
index 50841cb..b83d0e6 100644 (file)
--- a/arch/arm64/include/asm/syscall.h
+++ b/arch/arm64/include/asm/syscall.h
@@ -26,6 +26,10 @@ typedef long (*syscall_fn_t)(unsigned long, unsigned long,
 
 extern const syscall_fn_t sys_call_table[];
 
+#ifdef CONFIG_COMPAT
+extern const syscall_fn_t compat_sys_call_table[];
+#endif
+
 static inline int syscall_get_nr(struct task_struct *task,
                                 struct pt_regs *regs)
 {

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 05b9f03..156c4e3 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -720,14 +720,9 @@ el0_sync_compat:
        b.ge    el0_dbg
        b       el0_inv
 el0_svc_compat:
-       /*
-        * AArch32 syscall handling
-        */
-       ldr     x16, [tsk, #TSK_TI_FLAGS]       // load thread flags
-       adrp    stbl, compat_sys_call_table     // load compat syscall table pointer
-       mov     wscno, w7                       // syscall number in w7 (r7)
-       mov     wsc_nr, #__NR_compat_syscalls
-       b       el0_svc_naked
+       mov     x0, sp
+       bl      el0_svc_compat_handler
+       b       ret_to_user
 
        .align  6
 el0_irq_compat:
@@ -925,37 +920,8 @@ ENDPROC(ret_to_user)
  */
        .align  6
 el0_svc:
-       ldr     x16, [tsk, #TSK_TI_FLAGS]       // load thread flags
-       adrp    stbl, sys_call_table            // load syscall table pointer
-       mov     wscno, w8                       // syscall number in w8
-       mov     wsc_nr, #__NR_syscalls
-
-#ifdef CONFIG_ARM64_SVE
-alternative_if_not ARM64_SVE
-       b       el0_svc_naked
-alternative_else_nop_endif
-       tbz     x16, #TIF_SVE, el0_svc_naked    // Skip unless TIF_SVE set:
-       bic     x16, x16, #_TIF_SVE             // discard SVE state
-       str     x16, [tsk, #TSK_TI_FLAGS]
-
-       /*
-        * 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:
-        */
-       mrs     x9, cpacr_el1
-       bic     x9, x9, #CPACR_EL1_ZEN_EL0EN    // disable SVE for el0
-       msr     cpacr_el1, x9                   // synchronised by eret to el0
-#endif
-
-el0_svc_naked:                                 // compat entry point
        mov     x0, sp
-       mov     w1, wscno
-       mov     w2, wsc_nr
-       mov     x3, stbl
-       bl      el0_svc_common
+       bl      el0_svc_handler
        b       ret_to_user
 ENDPROC(el0_svc)
 

diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index 82098e6..7ff2d7b 100644 (file)
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -8,8 +8,10 @@
 #include <linux/syscalls.h>
 
 #include <asm/daifflags.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);
 
@@ -58,8 +60,8 @@ static inline bool has_syscall_work(unsigned long flags)
 int syscall_trace_enter(struct pt_regs *regs);
 void syscall_trace_exit(struct pt_regs *regs);
 
-asmlinkage void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
-                              const syscall_fn_t syscall_table[])
+static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
+                          const syscall_fn_t syscall_table[])
 {
        unsigned long flags = current_thread_info()->flags;
 
@@ -96,3 +98,34 @@ asmlinkage void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 trace_exit:
        syscall_trace_exit(regs);
 }
+
+static inline void sve_user_discard(void)
+{
+       if (!system_supports_sve())
+               return;
+
+       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();
+}
+
+asmlinkage void el0_svc_handler(struct pt_regs *regs)
+{
+       sve_user_discard();
+       el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table);
+}
+
+#ifdef CONFIG_COMPAT
+asmlinkage void el0_svc_compat_handler(struct pt_regs *regs)
+{
+       el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls,
+                      compat_sys_call_table);
+}
+#endif