Commit 4141c857 authored by Mark Rutland's avatar Mark Rutland Committed by Will Deacon

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: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 27d83e68
......@@ -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
......
......@@ -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
......
// SPDX-License-Identifier: GPL-2.0
#include <linux/errno.h>
#include <linux/nospec.h>
#include <linux/ptrace.h>
#include <linux/syscalls.h>
#include <asm/syscall.h>
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;
}
......@@ -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",
......
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