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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>
This commit is contained in:
Mark Rutland 2018-07-11 14:56:45 +01:00 committed by Will Deacon
parent f37099b699
commit 3b7142752e
3 changed files with 43 additions and 40 deletions
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4
arch/arm64/include/asm/syscall.h
View File

@ -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)
{

42
arch/arm64/kernel/entry.S
View File

@ -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)

37
arch/arm64/kernel/syscall.c
View File

@ -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