Le 14/12/2025 à 14:02, Mukesh Kumar Chaurasiya a écrit :
From: Mukesh Kumar Chaurasiya <[email protected]>
Convert the PowerPC syscall entry and exit paths to use the generic
entry/exit framework by selecting GENERIC_ENTRY and integrating with
the common syscall handling routines.
This change transitions PowerPC away from its custom syscall entry and
exit code to use the generic helpers such as:
- syscall_enter_from_user_mode()
- syscall_exit_to_user_mode()
As part of this migration:
- The architecture now selects GENERIC_ENTRY in Kconfig.
- Old tracing, seccomp, and audit handling in ptrace.c is removed in
favor of generic entry infrastructure.
- interrupt.c and syscall.c are simplified to delegate context
management and user exit handling to the generic entry path.
- The new pt_regs field `exit_flags` introduced earlier is now used
to carry per-syscall exit state flags (e.g. _TIF_RESTOREALL).
This aligns PowerPC with the common entry code used by other
architectures and reduces duplicated logic around syscall tracing,
context tracking, and signal handling.
The performance benchmarks from perf bench basic syscall are below:
perf bench syscall usec/op
| Test | With Patch | Without Patch | % Change |
| --------------- | ---------- | ------------- | -------- |
| getppid usec/op | 0.207795 | 0.210373 | -1.22% |
| getpgid usec/op | 0.206282 | 0.211676 | -2.55% |
| fork usec/op | 833.986 | 814.809 | +2.35% |
| execve usec/op | 360.939 | 365.168 | -1.16% |
perf bench syscall ops/sec
| Test | With Patch | Without Patch | % Change |
| --------------- | ---------- | ------------- | -------- |
| getppid ops/sec | 48,12,433 | 47,53,459 | +1.24% |
| getpgid ops/sec | 48,47,744 | 47,24,192 | +2.61% |
| fork ops/sec | 1,199 | 1,227 | -2.28% |
| execve ops/sec | 2,770 | 2,738 | +1.16% |
IPI latency benchmark
| Metric | With Patch | Without Patch | % Change |
| ----------------------- | ---------------- | ---------------- | -------- |
| Dry-run (ns) | 206,675.81 | 206,719.36 | -0.02% |
| Self-IPI avg (ns) | 1,939,991.00 | 1,976,116.15 | -1.83% |
| Self-IPI max (ns) | 3,533,718.93 | 3,582,650.33 | -1.37% |
| Normal IPI avg (ns) | 111,110,034.23 | 110,513,373.51 | +0.54% |
| Normal IPI max (ns) | 150,393,442.64 | 149,669,477.89 | +0.48% |
| Broadcast IPI max (ns) | 3,978,231,022.96 | 4,359,916,859.46 | -8.73% |
| Broadcast lock max (ns) | 4,025,425,714.49 | 4,384,956,730.83 | -8.20% |
Thats very close to performance earlier with arch specific handling.
Signed-off-by: Mukesh Kumar Chaurasiya <[email protected]>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/entry-common.h | 5 +-
arch/powerpc/kernel/interrupt.c | 139 +++++++----------------
arch/powerpc/kernel/ptrace/ptrace.c | 141 ------------------------
arch/powerpc/kernel/signal.c | 10 +-
arch/powerpc/kernel/syscall.c | 119 +-------------------
6 files changed, 49 insertions(+), 366 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index b0c602c3bbe1..a4330775b254 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -203,6 +203,7 @@ config PPC
select GENERIC_CPU_AUTOPROBE
select GENERIC_CPU_VULNERABILITIES if PPC_BARRIER_NOSPEC
select GENERIC_EARLY_IOREMAP
+ select GENERIC_ENTRY
select GENERIC_GETTIMEOFDAY
select GENERIC_IDLE_POLL_SETUP
select GENERIC_IOREMAP
diff --git a/arch/powerpc/include/asm/entry-common.h
b/arch/powerpc/include/asm/entry-common.h
index e2ae7416dee1..77129174f882 100644
--- a/arch/powerpc/include/asm/entry-common.h
+++ b/arch/powerpc/include/asm/entry-common.h
@@ -3,7 +3,7 @@
#ifndef _ASM_PPC_ENTRY_COMMON_H
#define _ASM_PPC_ENTRY_COMMON_H
-#ifdef CONFIG_GENERIC_IRQ_ENTRY
+#ifdef CONFIG_GENERIC_ENTRY
Powerpc now selected this inconditionaly. Why is this #ifdef needed ?
#include <asm/cputime.h>
#include <asm/interrupt.h>
@@ -217,9 +217,6 @@ static inline void arch_interrupt_enter_prepare(struct
pt_regs *regs)
if (user_mode(regs)) {
kuap_lock();
- CT_WARN_ON(ct_state() != CT_STATE_USER);
- user_exit_irqoff();
-
account_cpu_user_entry();
account_stolen_time();
} else {
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 7f67f0b9d627..7d5cd4b5a610 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -1,6 +1,7 @@
// SPDX-License-Identifier: GPL-2.0-or-later
#include <linux/context_tracking.h>
+#include <linux/entry-common.h>
#include <linux/err.h>
#include <linux/compat.h>
#include <linux/rseq.h>
@@ -73,79 +74,6 @@ static notrace __always_inline bool
prep_irq_for_enabled_exit(bool restartable)
return true;
}
-static notrace unsigned long
-interrupt_exit_user_prepare_main(unsigned long ret, struct pt_regs *regs)
-{
- unsigned long ti_flags;
-
-again:
- ti_flags = read_thread_flags();
- while (unlikely(ti_flags & (_TIF_USER_WORK_MASK & ~_TIF_RESTORE_TM))) {
- local_irq_enable();
- if (ti_flags & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) {
- schedule();
- } else {
- /*
- * SIGPENDING must restore signal handler function
- * argument GPRs, and some non-volatiles (e.g., r1).
- * Restore all for now. This could be made lighter.
- */
- if (ti_flags & _TIF_SIGPENDING)
- ret |= _TIF_RESTOREALL;
- do_notify_resume(regs, ti_flags);
do_notify_resume() has no caller anymore, should be removed from
arch/powerpc/include/asm/signal.h and arch/powerpc/kernel/signal.c
- }
- local_irq_disable();
- ti_flags = read_thread_flags();
- }
-
- if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && IS_ENABLED(CONFIG_PPC_FPU)) {
- if (IS_ENABLED(CONFIG_PPC_TRANSACTIONAL_MEM) &&
- unlikely((ti_flags & _TIF_RESTORE_TM))) {
- restore_tm_state(regs);
- } else {
- unsigned long mathflags = MSR_FP;
-
- if (cpu_has_feature(CPU_FTR_VSX))
- mathflags |= MSR_VEC | MSR_VSX;
- else if (cpu_has_feature(CPU_FTR_ALTIVEC))
- mathflags |= MSR_VEC;
-
- /*
- * If userspace MSR has all available FP bits set,
- * then they are live and no need to restore. If not,
- * it means the regs were given up and restore_math
- * may decide to restore them (to avoid taking an FP
- * fault).
- */
- if ((regs->msr & mathflags) != mathflags)
- restore_math(regs);
- }
- }
-
- check_return_regs_valid(regs);
-
- user_enter_irqoff();
- if (!prep_irq_for_enabled_exit(true)) {
- user_exit_irqoff();
- local_irq_enable();
- local_irq_disable();
- goto again;
- }
-
-#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
- local_paca->tm_scratch = regs->msr;
-#endif
-
- booke_load_dbcr0();
-
- account_cpu_user_exit();
-
- /* Restore user access locks last */
- kuap_user_restore(regs);
-
- return ret;
-}
-
/*
* This should be called after a syscall returns, with r3 the return value
* from the syscall. If this function returns non-zero, the system call
@@ -160,17 +88,12 @@ notrace unsigned long syscall_exit_prepare(unsigned long
r3,
long scv)
{
unsigned long ti_flags;
- unsigned long ret = 0;
bool is_not_scv = !IS_ENABLED(CONFIG_PPC_BOOK3S_64) || !scv;
- CT_WARN_ON(ct_state() == CT_STATE_USER);
-
kuap_assert_locked();
regs->result = r3;
-
- /* Check whether the syscall is issued inside a restartable sequence */
- rseq_syscall(regs);
+ regs->exit_flags = 0;
ti_flags = read_thread_flags();
@@ -183,7 +106,7 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
if (unlikely(ti_flags & _TIF_PERSYSCALL_MASK)) {
if (ti_flags & _TIF_RESTOREALL)
- ret = _TIF_RESTOREALL;
+ regs->exit_flags = _TIF_RESTOREALL;
else
regs->gpr[3] = r3;
clear_bits(_TIF_PERSYSCALL_MASK, ¤t_thread_info()->flags);
@@ -192,18 +115,28 @@ notrace unsigned long syscall_exit_prepare(unsigned long
r3,
}
if (unlikely(ti_flags & _TIF_SYSCALL_DOTRACE)) {
- do_syscall_trace_leave(regs);
- ret |= _TIF_RESTOREALL;
+ regs->exit_flags |= _TIF_RESTOREALL;
}
- local_irq_disable();
- ret = interrupt_exit_user_prepare_main(ret, regs);
+ syscall_exit_to_user_mode(regs);
+
+again:
+ user_enter_irqoff();
+ if (!prep_irq_for_enabled_exit(true)) {
+ user_exit_irqoff();
+ local_irq_enable();
+ local_irq_disable();
+ goto again;
+ }
+
+ /* Restore user access locks last */
+ kuap_user_restore(regs);
#ifdef CONFIG_PPC64
- regs->exit_result = ret;
+ regs->exit_result = regs->exit_flags;
#endif
- return ret;
+ return regs->exit_flags;
}
#ifdef CONFIG_PPC64
@@ -223,13 +156,16 @@ notrace unsigned long syscall_exit_restart(unsigned long
r3, struct pt_regs *reg
set_kuap(AMR_KUAP_BLOCKED);
#endif
- trace_hardirqs_off();
- user_exit_irqoff();
- account_cpu_user_entry();
-
- BUG_ON(!user_mode(regs));
+again:
+ user_enter_irqoff();
+ if (!prep_irq_for_enabled_exit(true)) {
+ user_exit_irqoff();
+ local_irq_enable();
+ local_irq_disable();
+ goto again;
+ }
- regs->exit_result = interrupt_exit_user_prepare_main(regs->exit_result, regs);
+ regs->exit_result |= regs->exit_flags;
return regs->exit_result;
}
@@ -241,7 +177,6 @@ notrace unsigned long interrupt_exit_user_prepare(struct
pt_regs *regs)
BUG_ON(regs_is_unrecoverable(regs));
BUG_ON(regs_irqs_disabled(regs));
- CT_WARN_ON(ct_state() == CT_STATE_USER);
/*
* We don't need to restore AMR on the way back to userspace for KUAP.
@@ -250,8 +185,21 @@ notrace unsigned long interrupt_exit_user_prepare(struct
pt_regs *regs)
kuap_assert_locked();
local_irq_disable();
+ regs->exit_flags = 0;
+again:
+ check_return_regs_valid(regs);
+ user_enter_irqoff();
+ if (!prep_irq_for_enabled_exit(true)) {
+ user_exit_irqoff();
+ local_irq_enable();
+ local_irq_disable();
+ goto again;
+ }
+
+ /* Restore user access locks last */
+ kuap_user_restore(regs);
- ret = interrupt_exit_user_prepare_main(0, regs);
+ ret = regs->exit_flags;
#ifdef CONFIG_PPC64
regs->exit_result = ret;
@@ -293,8 +241,6 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct
pt_regs *regs)
/* Returning to a kernel context with local irqs enabled. */
WARN_ON_ONCE(!(regs->msr & MSR_EE));
again:
- if (need_irq_preemption())
- irqentry_exit_cond_resched();
check_return_regs_valid(regs);
@@ -364,7 +310,6 @@ notrace unsigned long interrupt_exit_user_restart(struct pt_regs *regs)
#endif
trace_hardirqs_off();
- user_exit_irqoff();
account_cpu_user_entry();
BUG_ON(!user_mode(regs));
diff --git a/arch/powerpc/kernel/ptrace/ptrace.c
b/arch/powerpc/kernel/ptrace/ptrace.c
index 2134b6d155ff..316d4f5ead8e 100644
--- a/arch/powerpc/kernel/ptrace/ptrace.c
+++ b/arch/powerpc/kernel/ptrace/ptrace.c
@@ -21,9 +21,6 @@
#include <asm/switch_to.h>
#include <asm/debug.h>
-#define CREATE_TRACE_POINTS
-#include <trace/events/syscalls.h>
-
#include "ptrace-decl.h"
/*
@@ -195,144 +192,6 @@ long arch_ptrace(struct task_struct *child, long request,
return ret;
}
-#ifdef CONFIG_SECCOMP
-static int do_seccomp(struct pt_regs *regs)
-{
- if (!test_thread_flag(TIF_SECCOMP))
- return 0;
-
- /*
- * The ABI we present to seccomp tracers is that r3 contains
- * the syscall return value and orig_gpr3 contains the first
- * syscall parameter. This is different to the ptrace ABI where
- * both r3 and orig_gpr3 contain the first syscall parameter.
- */
- regs->gpr[3] = -ENOSYS;
-
- /*
- * We use the __ version here because we have already checked
- * TIF_SECCOMP. If this fails, there is nothing left to do, we
- * have already loaded -ENOSYS into r3, or seccomp has put
- * something else in r3 (via SECCOMP_RET_ERRNO/TRACE).
- */
- if (__secure_computing())
- return -1;
-
- /*
- * The syscall was allowed by seccomp, restore the register
- * state to what audit expects.
- * Note that we use orig_gpr3, which means a seccomp tracer can
- * modify the first syscall parameter (in orig_gpr3) and also
- * allow the syscall to proceed.
- */
- regs->gpr[3] = regs->orig_gpr3;
-
- return 0;
-}
-#else
-static inline int do_seccomp(struct pt_regs *regs) { return 0; }
-#endif /* CONFIG_SECCOMP */
-
-/**
- * do_syscall_trace_enter() - Do syscall tracing on kernel entry.
- * @regs: the pt_regs of the task to trace (current)
- *
- * Performs various types of tracing on syscall entry. This includes seccomp,
- * ptrace, syscall tracepoints and audit.
- *
- * The pt_regs are potentially visible to userspace via ptrace, so their
- * contents is ABI.
- *
- * One or more of the tracers may modify the contents of pt_regs, in particular
- * to modify arguments or even the syscall number itself.
- *
- * It's also possible that a tracer can choose to reject the system call. In
- * that case this function will return an illegal syscall number, and will put
- * an appropriate return value in regs->r3.
- *
- * Return: the (possibly changed) syscall number.
- */
-long do_syscall_trace_enter(struct pt_regs *regs)
Remove prototype from arch/powerpc/include/asm/ptrace.h
-{
- u32 flags;
-
- flags = read_thread_flags() & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE);
-
- if (flags) {
- int rc = ptrace_report_syscall_entry(regs);
-
- if (unlikely(flags & _TIF_SYSCALL_EMU)) {
- /*
- * A nonzero return code from
- * ptrace_report_syscall_entry() tells us to prevent
- * the syscall execution, but we are not going to
- * execute it anyway.
- *
- * Returning -1 will skip the syscall execution. We want
- * to avoid clobbering any registers, so we don't goto
- * the skip label below.
- */
- return -1;
- }
-
- if (rc) {
- /*
- * The tracer decided to abort the syscall. Note that
- * the tracer may also just change regs->gpr[0] to an
- * invalid syscall number, that is handled below on the
- * exit path.
- */
- goto skip;
- }
- }
-
- /* Run seccomp after ptrace; allow it to set gpr[3]. */
- if (do_seccomp(regs))
- return -1;
-
- /* Avoid trace and audit when syscall is invalid. */
- if (regs->gpr[0] >= NR_syscalls)
- goto skip;
-
- if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
- trace_sys_enter(regs, regs->gpr[0]);
-
- if (!is_32bit_task())
- audit_syscall_entry(regs->gpr[0], regs->gpr[3], regs->gpr[4],
- regs->gpr[5], regs->gpr[6]);
- else
- audit_syscall_entry(regs->gpr[0],
- regs->gpr[3] & 0xffffffff,
- regs->gpr[4] & 0xffffffff,
- regs->gpr[5] & 0xffffffff,
- regs->gpr[6] & 0xffffffff);
-
- /* Return the possibly modified but valid syscall number */
- return regs->gpr[0];
-
-skip:
- /*
- * If we are aborting explicitly, or if the syscall number is
- * now invalid, set the return value to -ENOSYS.
- */
- regs->gpr[3] = -ENOSYS;
- return -1;
-}
-
-void do_syscall_trace_leave(struct pt_regs *regs)
-{
- int step;
-
- audit_syscall_exit(regs);
-
- if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
- trace_sys_exit(regs, regs->result);
-
- step = test_thread_flag(TIF_SINGLESTEP);
- if (step || test_thread_flag(TIF_SYSCALL_TRACE))
- ptrace_report_syscall_exit(regs, step);
-}
-
void __init pt_regs_check(void);
/*
diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
index 719930cf4ae1..9f1847b4742e 100644
--- a/arch/powerpc/kernel/signal.c
+++ b/arch/powerpc/kernel/signal.c
@@ -6,6 +6,7 @@
* Extracted from signal_32.c and signal_64.c
*/
+#include <linux/entry-common.h>
#include <linux/resume_user_mode.h>
#include <linux/signal.h>
#include <linux/uprobes.h>
@@ -22,11 +23,6 @@
#include "signal.h"
-/* This will be removed */
-#ifdef CONFIG_GENERIC_ENTRY
-#include <linux/entry-common.h>
-#endif /* CONFIG_GENERIC_ENTRY */
-
Until now CONFIG_GENERIC_ENTRY was not defined.
Now that it is defined, we remove the entire block ?
Then why has it been added at all ?
#ifdef CONFIG_VSX
unsigned long copy_fpr_to_user(void __user *to,
struct task_struct *task)
@@ -374,11 +370,9 @@ void signal_fault(struct task_struct *tsk, struct pt_regs
*regs,
task_pid_nr(tsk), where, ptr, regs->nip,
regs->link);
}
-#ifdef CONFIG_GENERIC_ENTRY
void arch_do_signal_or_restart(struct pt_regs *regs)
{
BUG_ON(regs != current->thread.regs);
- local_paca->generic_fw_flags |= GFW_RESTORE_ALL;
Why was that there ? I thought it was preparatory, then you remove it
before even using it ?
+ regs->exit_flags |= _TIF_RESTOREALL;
do_signal(current);
}
-#endif /* CONFIG_GENERIC_ENTRY */
