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arm64: convert syscall trace logic to C

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Currently syscall tracing is a tricky assembly state machine, which can
be rather difficult to follow, and even harder to modify. Before we
start fiddling with it for pt_regs syscalls, let's convert it to C.

This is not intended to have any functional change.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@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 14:56:44 +01:00
committed by Will Deacon
parent 4141c857fd
commit f37099b699
2 changed files with 56 additions and 56 deletions
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55
arch/arm64/kernel/entry.S
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@@ -896,26 +896,6 @@ el0_error_naked:
b ret_to_user
ENDPROC(el0_error)
/*
* This is the fast syscall return path. We do as little as possible here,
* and this includes saving x0 back into the kernel stack.
*/
ret_fast_syscall:
disable_daif
#ifndef CONFIG_DEBUG_RSEQ
ldr x1, [tsk, #TSK_TI_FLAGS] // re-check for syscall tracing
and x2, x1, #_TIF_SYSCALL_WORK
cbnz x2, ret_fast_syscall_trace
and x2, x1, #_TIF_WORK_MASK
cbnz x2, work_pending
enable_step_tsk x1, x2
kernel_exit 0
#endif
ret_fast_syscall_trace:
enable_daif
b __sys_trace_return_skipped // we already saved x0
/*
* Ok, we need to do extra processing, enter the slow path.
*/
@@ -971,44 +951,13 @@ alternative_else_nop_endif
#endif
el0_svc_naked: // compat entry point
stp x0, xscno, [sp, #S_ORIG_X0] // save the original x0 and syscall number
enable_daif
ct_user_exit 1
tst x16, #_TIF_SYSCALL_WORK // check for syscall hooks
b.ne __sys_trace
mov x0, sp
mov w1, wscno
mov w2, wsc_nr
mov x3, stbl
bl invoke_syscall
b ret_fast_syscall
ENDPROC(el0_svc)
/*
* This is the really slow path. We're going to be doing context
* switches, and waiting for our parent to respond.
*/
__sys_trace:
cmp wscno, #NO_SYSCALL // user-issued syscall(-1)?
b.ne 1f
mov x0, #-ENOSYS // set default errno if so
str x0, [sp, #S_X0]
1: mov x0, sp
bl syscall_trace_enter
cmp w0, #NO_SYSCALL // skip the syscall?
b.eq __sys_trace_return_skipped
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
bl el0_svc_common
b ret_to_user
ENDPROC(el0_svc)
.popsection // .entry.text