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linux-bl808/arch/arm/kernel/entry-common.S
Arnd Bergmann 4e57a4ddf6 ARM: 9107/1: syscall: always store thread_info->abi_syscall 
The system call number is used in a a couple of places, in particular
ptrace, seccomp and /proc/<pid>/syscall.

The last one apparently never worked reliably on ARM for tasks that are
not currently getting traced.

Storing the syscall number in the normal entry path makes it work,
as well as allowing us to see if the current system call is for OABI
compat mode, which is the next thing I want to hook into.

Since the thread_info->syscall field is not just the number any more, it
is now renamed to abi_syscall. In kernels that enable both OABI and EABI,
the upper bits of this field encode 0x900000 (__NR_OABI_SYSCALL_BASE)
for OABI tasks, while normal EABI tasks do not set the upper bits. This
makes it possible to implement the in_oabi_syscall() helper later.

All other users of thread_info->syscall go through the syscall_get_nr()
helper, which in turn filters out the ABI bits.

Note that the ABI information is lost with PTRACE_SET_SYSCALL, so one
cannot set the internal number to a particular version, but this was
already the case. We could change it to let gdb encode the ABI type along
with the syscall in a CONFIG_OABI_COMPAT-enabled kernel, but that itself
would be a (backwards-compatible) ABI change, so I don't do it here.

Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
2021-08-20 11:39:26 +01:00

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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* linux/arch/arm/kernel/entry-common.S
*
* Copyright (C) 2000 Russell King
*/
#include <asm/assembler.h>
#include <asm/unistd.h>
#include <asm/ftrace.h>
#include <asm/unwind.h>
#include <asm/memory.h>
#ifdef CONFIG_AEABI
#include <asm/unistd-oabi.h>
#endif
.equ NR_syscalls, __NR_syscalls
#ifdef CONFIG_NEED_RET_TO_USER
#include <mach/entry-macro.S>
#else
.macro arch_ret_to_user, tmp1, tmp2
.endm
#endif
#include "entry-header.S"
saved_psr .req r8
#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING)
saved_pc .req r9
#define TRACE(x...) x
#else
saved_pc .req lr
#define TRACE(x...)
#endif
.section .entry.text,"ax",%progbits
.align 5
#if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING) || \
IS_ENABLED(CONFIG_DEBUG_RSEQ))
/*
* This is the fast syscall return path. We do as little as possible here,
* such as avoiding writing r0 to the stack. We only use this path if we
* have tracing, context tracking and rseq debug disabled - the overheads
* from those features make this path too inefficient.
*/
ret_fast_syscall:
__ret_fast_syscall:
UNWIND(.fnstart )
UNWIND(.cantunwind )
disable_irq_notrace @ disable interrupts
ldr r2, [tsk, #TI_ADDR_LIMIT]
ldr r1, =TASK_SIZE
cmp r2, r1
blne addr_limit_check_failed
ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing
movs r1, r1, lsl #16
bne fast_work_pending
/* perform architecture specific actions before user return */
arch_ret_to_user r1, lr
restore_user_regs fast = 1, offset = S_OFF
UNWIND(.fnend )
ENDPROC(ret_fast_syscall)
/* Ok, we need to do extra processing, enter the slow path. */
fast_work_pending:
str r0, [sp, #S_R0+S_OFF]! @ returned r0
/* fall through to work_pending */
#else
/*
* The "replacement" ret_fast_syscall for when tracing, context tracking,
* or rseq debug is enabled. As we will need to call out to some C functions,
* we save r0 first to avoid needing to save registers around each C function
* call.
*/
ret_fast_syscall:
__ret_fast_syscall:
UNWIND(.fnstart )
UNWIND(.cantunwind )
str r0, [sp, #S_R0 + S_OFF]! @ save returned r0
#if IS_ENABLED(CONFIG_DEBUG_RSEQ)
/* do_rseq_syscall needs interrupts enabled. */
mov r0, sp @ 'regs'
bl do_rseq_syscall
#endif
disable_irq_notrace @ disable interrupts
ldr r2, [tsk, #TI_ADDR_LIMIT]
ldr r1, =TASK_SIZE
cmp r2, r1
blne addr_limit_check_failed
ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing
movs r1, r1, lsl #16
beq no_work_pending
UNWIND(.fnend )
ENDPROC(ret_fast_syscall)
/* Slower path - fall through to work_pending */
#endif
tst r1, #_TIF_SYSCALL_WORK
bne __sys_trace_return_nosave
slow_work_pending:
mov r0, sp @ 'regs'
mov r2, why @ 'syscall'
bl do_work_pending
cmp r0, #0
beq no_work_pending
movlt scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
ldmia sp, {r0 - r6} @ have to reload r0 - r6
b local_restart @ ... and off we go
ENDPROC(ret_fast_syscall)
/*
* "slow" syscall return path. "why" tells us if this was a real syscall.
* IRQs may be enabled here, so always disable them. Note that we use the
* "notrace" version to avoid calling into the tracing code unnecessarily.
* do_work_pending() will update this state if necessary.
*/
ENTRY(ret_to_user)
ret_slow_syscall:
#if IS_ENABLED(CONFIG_DEBUG_RSEQ)
/* do_rseq_syscall needs interrupts enabled. */
enable_irq_notrace @ enable interrupts
mov r0, sp @ 'regs'
bl do_rseq_syscall
#endif
disable_irq_notrace @ disable interrupts
ENTRY(ret_to_user_from_irq)
ldr r2, [tsk, #TI_ADDR_LIMIT]
ldr r1, =TASK_SIZE
cmp r2, r1
blne addr_limit_check_failed
ldr r1, [tsk, #TI_FLAGS]
movs r1, r1, lsl #16
bne slow_work_pending
no_work_pending:
asm_trace_hardirqs_on save = 0
/* perform architecture specific actions before user return */
arch_ret_to_user r1, lr
ct_user_enter save = 0
restore_user_regs fast = 0, offset = 0
ENDPROC(ret_to_user_from_irq)
ENDPROC(ret_to_user)
/*
* This is how we return from a fork.
*/
ENTRY(ret_from_fork)
bl schedule_tail
cmp r5, #0
movne r0, r4
badrne lr, 1f
retne r5
1: get_thread_info tsk
b ret_slow_syscall
ENDPROC(ret_from_fork)
/*=============================================================================
* SWI handler
*-----------------------------------------------------------------------------
*/
.align 5
ENTRY(vector_swi)
#ifdef CONFIG_CPU_V7M
v7m_exception_entry
#else
sub sp, sp, #PT_REGS_SIZE
stmia sp, {r0 - r12} @ Calling r0 - r12
ARM( add r8, sp, #S_PC )
ARM( stmdb r8, {sp, lr}^ ) @ Calling sp, lr
THUMB( mov r8, sp )
THUMB( store_user_sp_lr r8, r10, S_SP ) @ calling sp, lr
mrs saved_psr, spsr @ called from non-FIQ mode, so ok.
TRACE( mov saved_pc, lr )
str saved_pc, [sp, #S_PC] @ Save calling PC
str saved_psr, [sp, #S_PSR] @ Save CPSR
str r0, [sp, #S_OLD_R0] @ Save OLD_R0
#endif
zero_fp
alignment_trap r10, ip, __cr_alignment
asm_trace_hardirqs_on save=0
enable_irq_notrace
ct_user_exit save=0
/*
* Get the system call number.
*/
#if defined(CONFIG_OABI_COMPAT)
/*
* If we have CONFIG_OABI_COMPAT then we need to look at the swi
* value to determine if it is an EABI or an old ABI call.
*/
#ifdef CONFIG_ARM_THUMB
tst saved_psr, #PSR_T_BIT
movne r10, #0 @ no thumb OABI emulation
USER( ldreq r10, [saved_pc, #-4] ) @ get SWI instruction
#else
USER( ldr r10, [saved_pc, #-4] ) @ get SWI instruction
#endif
ARM_BE8(rev r10, r10) @ little endian instruction
#elif defined(CONFIG_AEABI)
/*
* Pure EABI user space always put syscall number into scno (r7).
*/
#elif defined(CONFIG_ARM_THUMB)
/* Legacy ABI only, possibly thumb mode. */
tst saved_psr, #PSR_T_BIT @ this is SPSR from save_user_regs
addne scno, r7, #__NR_SYSCALL_BASE @ put OS number in
USER( ldreq scno, [saved_pc, #-4] )
#else
/* Legacy ABI only. */
USER( ldr scno, [saved_pc, #-4] ) @ get SWI instruction
#endif
/* saved_psr and saved_pc are now dead */
uaccess_disable tbl
get_thread_info tsk
adr tbl, sys_call_table @ load syscall table pointer
#if defined(CONFIG_OABI_COMPAT)
/*
* If the swi argument is zero, this is an EABI call and we do nothing.
*
* If this is an old ABI call, get the syscall number into scno and
* get the old ABI syscall table address.
*/
bics r10, r10, #0xff000000
strne r10, [tsk, #TI_ABI_SYSCALL]
streq scno, [tsk, #TI_ABI_SYSCALL]
eorne scno, r10, #__NR_OABI_SYSCALL_BASE
ldrne tbl, =sys_oabi_call_table
#elif !defined(CONFIG_AEABI)
bic scno, scno, #0xff000000 @ mask off SWI op-code
str scno, [tsk, #TI_ABI_SYSCALL]
eor scno, scno, #__NR_SYSCALL_BASE @ check OS number
#else
str scno, [tsk, #TI_ABI_SYSCALL]
#endif
/*
* Reload the registers that may have been corrupted on entry to
* the syscall assembly (by tracing or context tracking.)
*/
TRACE( ldmia sp, {r0 - r3} )
local_restart:
ldr r10, [tsk, #TI_FLAGS] @ check for syscall tracing
stmdb sp!, {r4, r5} @ push fifth and sixth args
tst r10, #_TIF_SYSCALL_WORK @ are we tracing syscalls?
bne __sys_trace
invoke_syscall tbl, scno, r10, __ret_fast_syscall
add r1, sp, #S_OFF
2: cmp scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
eor r0, scno, #__NR_SYSCALL_BASE @ put OS number back
bcs arm_syscall
mov why, #0 @ no longer a real syscall
b sys_ni_syscall @ not private func
#if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)
/*
* We failed to handle a fault trying to access the page
* containing the swi instruction, but we're not really in a
* position to return -EFAULT. Instead, return back to the
* instruction and re-enter the user fault handling path trying
* to page it in. This will likely result in sending SEGV to the
* current task.
*/
9001:
sub lr, saved_pc, #4
str lr, [sp, #S_PC]
get_thread_info tsk
b ret_fast_syscall
#endif
ENDPROC(vector_swi)
/*
* This is the really slow path. We're going to be doing
* context switches, and waiting for our parent to respond.
*/
__sys_trace:
add r0, sp, #S_OFF
bl syscall_trace_enter
mov scno, r0
invoke_syscall tbl, scno, r10, __sys_trace_return, reload=1
cmp scno, #-1 @ skip the syscall?
bne 2b
add sp, sp, #S_OFF @ restore stack
__sys_trace_return_nosave:
enable_irq_notrace
mov r0, sp
bl syscall_trace_exit
b ret_slow_syscall
__sys_trace_return:
str r0, [sp, #S_R0 + S_OFF]! @ save returned r0
mov r0, sp
bl syscall_trace_exit
b ret_slow_syscall
.align 5
#ifdef CONFIG_ALIGNMENT_TRAP
.type __cr_alignment, #object
__cr_alignment:
.word cr_alignment
#endif
.ltorg
.macro syscall_table_start, sym
.equ __sys_nr, 0
.type \sym, #object
ENTRY(\sym)
.endm
.macro syscall, nr, func
.ifgt __sys_nr - \nr
.error "Duplicated/unorded system call entry"
.endif
.rept \nr - __sys_nr
.long sys_ni_syscall
.endr
.long \func
.equ __sys_nr, \nr + 1
.endm
.macro syscall_table_end, sym
.ifgt __sys_nr - __NR_syscalls
.error "System call table too big"
.endif
.rept __NR_syscalls - __sys_nr
.long sys_ni_syscall
.endr
.size \sym, . - \sym
.endm
#define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, native)
#define __SYSCALL(nr, func) syscall nr, func
/*
* This is the syscall table declaration for native ABI syscalls.
* With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
*/
syscall_table_start sys_call_table
#ifdef CONFIG_AEABI
#include <calls-eabi.S>
#else
#include <calls-oabi.S>
#endif
syscall_table_end sys_call_table
/*============================================================================
* Special system call wrappers
*/
@ r0 = syscall number
@ r8 = syscall table
sys_syscall:
bic scno, r0, #__NR_OABI_SYSCALL_BASE
cmp scno, #__NR_syscall - __NR_SYSCALL_BASE
cmpne scno, #NR_syscalls @ check range
#ifdef CONFIG_CPU_SPECTRE
movhs scno, #0
csdb
#endif
stmialo sp, {r5, r6} @ shuffle args
movlo r0, r1
movlo r1, r2
movlo r2, r3
movlo r3, r4
ldrlo pc, [tbl, scno, lsl #2]
b sys_ni_syscall
ENDPROC(sys_syscall)
sys_sigreturn_wrapper:
add r0, sp, #S_OFF
mov why, #0 @ prevent syscall restart handling
b sys_sigreturn
ENDPROC(sys_sigreturn_wrapper)
sys_rt_sigreturn_wrapper:
add r0, sp, #S_OFF
mov why, #0 @ prevent syscall restart handling
b sys_rt_sigreturn
ENDPROC(sys_rt_sigreturn_wrapper)
sys_statfs64_wrapper:
teq r1, #88
moveq r1, #84
b sys_statfs64
ENDPROC(sys_statfs64_wrapper)
sys_fstatfs64_wrapper:
teq r1, #88
moveq r1, #84
b sys_fstatfs64
ENDPROC(sys_fstatfs64_wrapper)
/*
* Note: off_4k (r5) is always units of 4K. If we can't do the requested
* offset, we return EINVAL.
*/
sys_mmap2:
str r5, [sp, #4]
b sys_mmap_pgoff
ENDPROC(sys_mmap2)
#ifdef CONFIG_OABI_COMPAT
/*
* These are syscalls with argument register differences
*/
sys_oabi_pread64:
stmia sp, {r3, r4}
b sys_pread64
ENDPROC(sys_oabi_pread64)
sys_oabi_pwrite64:
stmia sp, {r3, r4}
b sys_pwrite64
ENDPROC(sys_oabi_pwrite64)
sys_oabi_truncate64:
mov r3, r2
mov r2, r1
b sys_truncate64
ENDPROC(sys_oabi_truncate64)
sys_oabi_ftruncate64:
mov r3, r2
mov r2, r1
b sys_ftruncate64
ENDPROC(sys_oabi_ftruncate64)
sys_oabi_readahead:
str r3, [sp]
mov r3, r2
mov r2, r1
b sys_readahead
ENDPROC(sys_oabi_readahead)
/*
* Let's declare a second syscall table for old ABI binaries
* using the compatibility syscall entries.
*/
syscall_table_start sys_oabi_call_table
#undef __SYSCALL_WITH_COMPAT
#define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, compat)
#include <calls-oabi.S>
syscall_table_end sys_oabi_call_table
#endif
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