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Message-Id: <20250107-arm-generic-entry-v3-10-4e5f3c15db2d@linaro.org>
Date: Tue, 07 Jan 2025 10:41:26 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Dmitry Vyukov <dvyukov@...gle.com>, Oleg Nesterov <oleg@...hat.com>,
Russell King <linux@...linux.org.uk>, Kees Cook <kees@...nel.org>,
Andy Lutomirski <luto@...capital.net>, Will Drewry <wad@...omium.org>,
Frederic Weisbecker <frederic@...nel.org>,
"Paul E. McKenney" <paulmck@...nel.org>,
Jinjie Ruan <ruanjinjie@...wei.com>, Arnd Bergmann <arnd@...db.de>,
Ard Biesheuvel <ardb@...nel.org>, Al Viro <viro@...iv.linux.org.uk>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH RFC v3 10/30] ARM: entry: move all tracing invocation to C
The traced invocation of syscall is rewritten in C, moving
over also the call to syscall_trace_exit() to C.
To do this we cannot have invoke_syscall_trace_asm() be a
leaf call, which is the mechanism we hithereto relied on
to make sure the stack is pulled back to the state we were
at before we called out to the code written in C.
Push the registers potentially used by C on the stack, and
make a copy of the two stack-pushed syscall arguments
on the top of the stack before invoking the syscall and
then drop these copied arguments and pop back the
registers before returning from invoke_syscall_trace_asm().
As we are now calling from and returning to C, we no
longer need to pass the regs pointer around so drop it.
Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
---
arch/arm/include/asm/syscall.h | 2 +-
arch/arm/kernel/entry-common.S | 32 +++++++++++++++-----------------
arch/arm/kernel/ptrace.c | 2 +-
arch/arm/kernel/syscall.c | 30 +++++++++++++++++++++---------
4 files changed, 38 insertions(+), 28 deletions(-)
diff --git a/arch/arm/include/asm/syscall.h b/arch/arm/include/asm/syscall.h
index 66067d165ba3fbbe0f840a89ae396eb1a311bacc..cb0073c4151bf70a82d15e17a95b6b6f48b245d6 100644
--- a/arch/arm/include/asm/syscall.h
+++ b/arch/arm/include/asm/syscall.h
@@ -20,7 +20,7 @@
extern const unsigned long sys_call_table[];
int invoke_syscall(void *table, struct pt_regs *regs, int scno, void *retp);
-int invoke_syscall_trace(void *table, struct pt_regs *regs, void *retp);
+void invoke_syscall_trace(void *table, struct pt_regs *regs);
static inline int syscall_get_nr(struct task_struct *task,
struct pt_regs *regs)
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 8baab7f97f59c434396f30b08ddd3029c5f9c0e5..dbc947d301ec11bb13007cb4bb161c035ede5c10 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -296,22 +296,11 @@ ENDPROC(vector_swi)
__sys_trace:
add r1, sp, #S_R0 + S_OFF @ pointer to regs
mov r0, tbl
- badr r2, __sys_trace_return
bl invoke_syscall_trace
- cmp r0, #-1
- bne __sys_trace_return
- add sp, sp, #S_OFF @ restore stack
-
-__sys_trace_return_nosave:
- enable_irq_notrace
- mov r0, sp
- bl syscall_trace_exit
+ add sp, sp, #S_OFF @ restore stack pointer
b ret_to_user
-__sys_trace_return:
- str r0, [sp, #S_R0 + S_OFF]! @ save returned r0
- mov r0, sp
- bl syscall_trace_exit
+__sys_trace_return_nosave:
b ret_to_user
.macro syscall_table_start, sym
@@ -437,18 +426,27 @@ SYM_FUNC_END(invoke_syscall_asm)
* r0: syscall table
* r1: regs
* r2: syscall number
- * r3: pointer to return function
*/
SYM_TYPED_FUNC_START(invoke_syscall_trace_asm)
#ifdef CONFIG_CPU_SPECTRE
csdb
#endif
+ /* Save registers because we are being called from C */
+ push {r4 - r10, lr}
mov tbl, r0
+ /* Make space to copy the two syscall stack arguments */
+ sub sp, sp, #S_OFF
mov scno, r2
- mov lr, r3 @ return address
- ldmia r1, {r0 - r6} @ reload r0-r6
- stmia sp, {r4, r5} @ update stack arguments
+ badr lr, __invoke_syscall_trace_ret @ return right here
+ ldmia r1, {r0 - r6} @ reload r0-r6 from regs
+ stmia sp, {r4, r5} @ copy stack arguments
ldr pc, [tbl, scno, lsl #2] @ call sys_* routine
+__invoke_syscall_trace_ret:
+ /* Drop the copied stack arguments */
+ add sp, sp, #S_OFF
+ pop {r4 - r10, lr}
+ ARM( mov pc, lr )
+ THUMB( bx lr )
SYM_FUNC_END(invoke_syscall_trace_asm)
#ifdef CONFIG_OABI_COMPAT
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index 07b0daf47441f1f76a8af416acc74fa5ed770403..ac7b98ae47249b4a00fc1cb871bb2d309bfd8c88 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -888,7 +888,7 @@ asmlinkage int syscall_trace_enter(struct pt_regs *regs)
return scno;
}
-asmlinkage void syscall_trace_exit(struct pt_regs *regs)
+void syscall_trace_exit(struct pt_regs *regs)
{
/*
* Audit the syscall before anything else, as a debugger may
diff --git a/arch/arm/kernel/syscall.c b/arch/arm/kernel/syscall.c
index 377e16c8c53c8e809e3f8b157a889ef115d5c043..e90f04f35b3485968a1e9046cf0889f56cca92e5 100644
--- a/arch/arm/kernel/syscall.c
+++ b/arch/arm/kernel/syscall.c
@@ -18,23 +18,35 @@ __visible int invoke_syscall(void *table, struct pt_regs *regs, int scno, void *
return sys_ni_syscall();
}
-int invoke_syscall_trace_asm(void *table, struct pt_regs *regs, int scno, void *retp);
+int invoke_syscall_trace_asm(void *table, struct pt_regs *regs, int scno);
__ADDRESSABLE(invoke_syscall_trace_asm);
-__visible int invoke_syscall_trace(void *table, struct pt_regs *regs, void *retp)
+__visible void invoke_syscall_trace(void *table, struct pt_regs *regs)
{
int scno;
+ int ret;
scno = syscall_trace_enter(regs);
if (scno == -1)
- return -1;
+ goto trace_exit_nosave;
- if (scno < NR_syscalls)
- /* Doing this with return makes sure the stack gets pop:ed */
- return invoke_syscall_trace_asm(table, regs, scno, retp);
+ if (scno < NR_syscalls) {
+ ret = invoke_syscall_trace_asm(table, regs, scno);
+ goto trace_exit_save;
+ }
- if (scno >= __ARM_NR_BASE)
- return arm_syscall(scno, regs);
+ if (scno >= __ARM_NR_BASE) {
+ ret = arm_syscall(scno, regs);
+ goto trace_exit_save;
+ }
- return sys_ni_syscall();
+ ret = sys_ni_syscall();
+
+trace_exit_save:
+ /* Save return value from syscall */
+ regs->ARM_r0 = ret;
+
+trace_exit_nosave:
+ local_irq_enable();
+ syscall_trace_exit(regs);
}
--
2.47.1
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