[PATCH v2 4/7] syscall.h: introduce syscall_set_nr()

Dmitry V. Levin
2025-01-13T17:11:58Z

Similar to syscall_set_arguments() that complements
syscall_get_arguments(), introduce syscall_set_nr()
that complements syscall_get_nr().

syscall_set_nr() is going to be needed along with
syscall_set_arguments() on all HAVE_ARCH_TRACEHOOK
architectures to implement PTRACE_SET_SYSCALL_INFO API.

Signed-off-by: Dmitry V. Levin <ldv@strace.io>
---
arch/arc/include/asm/syscall.h | 11 +++++++++++
arch/arm/include/asm/syscall.h | 24 ++++++++++++++++++++++++
arch/arm64/include/asm/syscall.h | 16 ++++++++++++++++
arch/hexagon/include/asm/syscall.h | 7 +++++++
arch/loongarch/include/asm/syscall.h | 7 +++++++
arch/m68k/include/asm/syscall.h | 7 +++++++
arch/microblaze/include/asm/syscall.h | 7 +++++++
arch/mips/include/asm/syscall.h | 14 ++++++++++++++
arch/nios2/include/asm/syscall.h | 5 +++++
arch/openrisc/include/asm/syscall.h | 6 ++++++
arch/parisc/include/asm/syscall.h | 7 +++++++
arch/powerpc/include/asm/syscall.h | 10 ++++++++++
arch/riscv/include/asm/syscall.h | 7 +++++++
arch/s390/include/asm/syscall.h | 12 ++++++++++++
arch/sh/include/asm/syscall_32.h | 12 ++++++++++++
arch/sparc/include/asm/syscall.h | 12 ++++++++++++
arch/um/include/asm/syscall-generic.h | 5 +++++
arch/x86/include/asm/syscall.h | 7 +++++++
arch/xtensa/include/asm/syscall.h | 7 +++++++
include/asm-generic/syscall.h | 14 ++++++++++++++
20 files changed, 197 insertions(+)

diff --git a/arch/arc/include/asm/syscall.h b/arch/arc/include/asm/syscall.h
index 89c1e1736356..728d625a10f1 100644
--- a/arch/arc/include/asm/syscall.h
+++ b/arch/arc/include/asm/syscall.h
@@ -23,6 +23,17 @@ syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
return -1;
}

+static inline void
+syscall_set_nr(struct task_struct *task, struct pt_regs *regs, int nr)
+{
+ /*
+ * Unlike syscall_get_nr(), syscall_set_nr() can be called only when
+ * the target task is stopped for tracing on entering syscall, so
+ * there is no need to have the same check syscall_get_nr() has.
+ */
+ regs->r8 = nr;
+}
+
static inline void
syscall_rollback(struct task_struct *task, struct pt_regs *regs)
{
diff --git a/arch/arm/include/asm/syscall.h b/arch/arm/include/asm/syscall.h
index 21927fa0ae2b..18b102a30741 100644
--- a/arch/arm/include/asm/syscall.h
+++ b/arch/arm/include/asm/syscall.h
@@ -68,6 +68,30 @@ static inline void syscall_set_return_value(struct task_struct *task,
regs->ARM_r0 = (long) error ? error : val;
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ if (nr == -1) {
+ task_thread_info(task)->abi_syscall = -1;
+ /*
+ * When the syscall number is set to -1, the syscall will be
+ * skipped. In this case the syscall return value has to be
+ * set explicitly, otherwise the first syscall argument is
+ * returned as the syscall return value.
+ */
+ syscall_set_return_value(task, regs, -ENOSYS, 0);
+ return;
+ }
+ if ((IS_ENABLED(CONFIG_AEABI) && !IS_ENABLED(CONFIG_OABI_COMPAT))) {
+ task_thread_info(task)->abi_syscall = nr;
+ return;
+ }
+ task_thread_info(task)->abi_syscall =
+ (task_thread_info(task)->abi_syscall & ~__NR_SYSCALL_MASK) |
+ (nr & __NR_SYSCALL_MASK);
+}
+
#define SYSCALL_MAX_ARGS 7

static inline void syscall_get_arguments(struct task_struct *task,
diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
index 76020b66286b..712daa90e643 100644
--- a/arch/arm64/include/asm/syscall.h
+++ b/arch/arm64/include/asm/syscall.h
@@ -61,6 +61,22 @@ static inline void syscall_set_return_value(struct task_struct *task,
regs->regs[0] = val;
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ regs->syscallno = nr;
+ if (nr == -1) {
+ /*
+ * When the syscall number is set to -1, the syscall will be
+ * skipped. In this case the syscall return value has to be
+ * set explicitly, otherwise the first syscall argument is
+ * returned as the syscall return value.
+ */
+ syscall_set_return_value(task, regs, -ENOSYS, 0);
+ }
+}
+
#define SYSCALL_MAX_ARGS 6

static inline void syscall_get_arguments(struct task_struct *task,
diff --git a/arch/hexagon/include/asm/syscall.h b/arch/hexagon/include/asm/syscall.h
index 1024a6548d78..70637261817a 100644
--- a/arch/hexagon/include/asm/syscall.h
+++ b/arch/hexagon/include/asm/syscall.h
@@ -26,6 +26,13 @@ static inline long syscall_get_nr(struct task_struct *task,
return regs->r06;
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ regs->r06 = nr;
+}
+
static inline void syscall_get_arguments(struct task_struct *task,
struct pt_regs *regs,
unsigned long *args)
diff --git a/arch/loongarch/include/asm/syscall.h b/arch/loongarch/include/asm/syscall.h
index ff415b3c0a8e..81d2733f7b94 100644
--- a/arch/loongarch/include/asm/syscall.h
+++ b/arch/loongarch/include/asm/syscall.h
@@ -26,6 +26,13 @@ static inline long syscall_get_nr(struct task_struct *task,
return regs->regs[11];
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ regs->regs[11] = nr;
+}
+
static inline void syscall_rollback(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/m68k/include/asm/syscall.h b/arch/m68k/include/asm/syscall.h
index d1453e850cdd..bf84b160c2eb 100644
--- a/arch/m68k/include/asm/syscall.h
+++ b/arch/m68k/include/asm/syscall.h
@@ -14,6 +14,13 @@ static inline int syscall_get_nr(struct task_struct *task,
return regs->orig_d0;
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ regs->orig_d0 = nr;
+}
+
static inline void syscall_rollback(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/microblaze/include/asm/syscall.h b/arch/microblaze/include/asm/syscall.h
index 5eb3f624cc59..b5b6b91fae3e 100644
--- a/arch/microblaze/include/asm/syscall.h
+++ b/arch/microblaze/include/asm/syscall.h
@@ -14,6 +14,13 @@ static inline long syscall_get_nr(struct task_struct *task,
return regs->r12;
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ regs->r12 = nr;
+}
+
static inline void syscall_rollback(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/mips/include/asm/syscall.h b/arch/mips/include/asm/syscall.h
index 3163d1506fae..58d68205fd2c 100644
--- a/arch/mips/include/asm/syscall.h
+++ b/arch/mips/include/asm/syscall.h
@@ -41,6 +41,20 @@ static inline long syscall_get_nr(struct task_struct *task,
return task_thread_info(task)->syscall;
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ /*
+ * New syscall number has to be assigned to regs[2] because
+ * syscall_trace_entry() loads it from there unconditionally.
+ *
+ * Consequently, if the syscall was indirect and nr != __NR_syscall,
+ * then after this assignment the syscall will cease to be indirect.
+ */
+ task_thread_info(task)->syscall = regs->regs[2] = nr;
+}
+
static inline void mips_syscall_update_nr(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/nios2/include/asm/syscall.h b/arch/nios2/include/asm/syscall.h
index 526449edd768..8e3eb1d689bb 100644
--- a/arch/nios2/include/asm/syscall.h
+++ b/arch/nios2/include/asm/syscall.h
@@ -15,6 +15,11 @@ static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
return regs->r2;
}

+static inline void syscall_set_nr(struct task_struct *task, struct pt_regs *regs, int nr)
+{
+ regs->r2 = nr;
+}
+
static inline void syscall_rollback(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/openrisc/include/asm/syscall.h b/arch/openrisc/include/asm/syscall.h
index e6383be2a195..5e037d9659c5 100644
--- a/arch/openrisc/include/asm/syscall.h
+++ b/arch/openrisc/include/asm/syscall.h
@@ -25,6 +25,12 @@ syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
return regs->orig_gpr11;
}

+static inline void
+syscall_set_nr(struct task_struct *task, struct pt_regs *regs, int nr)
+{
+ regs->orig_gpr11 = nr;
+}
+
static inline void
syscall_rollback(struct task_struct *task, struct pt_regs *regs)
{
diff --git a/arch/parisc/include/asm/syscall.h b/arch/parisc/include/asm/syscall.h
index b146d0ae4c77..c11222798ab2 100644
--- a/arch/parisc/include/asm/syscall.h
+++ b/arch/parisc/include/asm/syscall.h
@@ -17,6 +17,13 @@ static inline long syscall_get_nr(struct task_struct *tsk,
return regs->gr[20];
}

+static inline void syscall_set_nr(struct task_struct *tsk,
+ struct pt_regs *regs,
+ int nr)
+{
+ regs->gr[20] = nr;
+}
+
static inline void syscall_get_arguments(struct task_struct *tsk,
struct pt_regs *regs,
unsigned long *args)
diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index 521f279e6b33..7505dcfed247 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -39,6 +39,16 @@ static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
return -1;
}

+static inline void syscall_set_nr(struct task_struct *task, struct pt_regs *regs, int nr)
+{
+ /*
+ * Unlike syscall_get_nr(), syscall_set_nr() can be called only when
+ * the target task is stopped for tracing on entering syscall, so
+ * there is no need to have the same check syscall_get_nr() has.
+ */
+ regs->gpr[0] = nr;
+}
+
static inline void syscall_rollback(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/riscv/include/asm/syscall.h b/arch/riscv/include/asm/syscall.h
index 8d389ba995c8..a5281cdf2b10 100644
--- a/arch/riscv/include/asm/syscall.h
+++ b/arch/riscv/include/asm/syscall.h
@@ -30,6 +30,13 @@ static inline int syscall_get_nr(struct task_struct *task,
return regs->a7;
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ regs->a7 = nr;
+}
+
static inline void syscall_rollback(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/s390/include/asm/syscall.h b/arch/s390/include/asm/syscall.h
index b3dd883699e7..12cd0c60c07b 100644
--- a/arch/s390/include/asm/syscall.h
+++ b/arch/s390/include/asm/syscall.h
@@ -24,6 +24,18 @@ static inline long syscall_get_nr(struct task_struct *task,
(regs->int_code & 0xffff) : -1;
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ /*
+ * Unlike syscall_get_nr(), syscall_set_nr() can be called only when
+ * the target task is stopped for tracing on entering syscall, so
+ * there is no need to have the same check syscall_get_nr() has.
+ */
+ regs->int_code = (regs->int_code & ~0xffff) | (nr & 0xffff);
+}
+
static inline void syscall_rollback(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/sh/include/asm/syscall_32.h b/arch/sh/include/asm/syscall_32.h
index cb51a7528384..7027d87d901d 100644
--- a/arch/sh/include/asm/syscall_32.h
+++ b/arch/sh/include/asm/syscall_32.h
@@ -15,6 +15,18 @@ static inline long syscall_get_nr(struct task_struct *task,
return (regs->tra >= 0) ? regs->regs[3] : -1L;
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ /*
+ * Unlike syscall_get_nr(), syscall_set_nr() can be called only when
+ * the target task is stopped for tracing on entering syscall, so
+ * there is no need to have the same check syscall_get_nr() has.
+ */
+ regs->regs[3] = nr;
+}
+
static inline void syscall_rollback(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/sparc/include/asm/syscall.h b/arch/sparc/include/asm/syscall.h
index 62a5a78804c4..b0233924d323 100644
--- a/arch/sparc/include/asm/syscall.h
+++ b/arch/sparc/include/asm/syscall.h
@@ -25,6 +25,18 @@ static inline long syscall_get_nr(struct task_struct *task,
return (syscall_p ? regs->u_regs[UREG_G1] : -1L);
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ /*
+ * Unlike syscall_get_nr(), syscall_set_nr() can be called only when
+ * the target task is stopped for tracing on entering syscall, so
+ * there is no need to have the same check syscall_get_nr() has.
+ */
+ regs->u_regs[UREG_G1] = nr;
+}
+
static inline void syscall_rollback(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/um/include/asm/syscall-generic.h b/arch/um/include/asm/syscall-generic.h
index 2984feb9d576..bcd73bcfe577 100644
--- a/arch/um/include/asm/syscall-generic.h
+++ b/arch/um/include/asm/syscall-generic.h
@@ -21,6 +21,11 @@ static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
return PT_REGS_SYSCALL_NR(regs);
}

+static inline void syscall_set_nr(struct task_struct *task, struct pt_regs *regs, int nr)
+{
+ PT_REGS_SYSCALL_NR(regs) = nr;
+}
+
static inline void syscall_rollback(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index b9c249dd9e3d..c10dbb74cd00 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -38,6 +38,13 @@ static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
return regs->orig_ax;
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ regs->orig_ax = nr;
+}
+
static inline void syscall_rollback(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/arch/xtensa/include/asm/syscall.h b/arch/xtensa/include/asm/syscall.h
index f9a671cbf933..7db3b489c8ad 100644
--- a/arch/xtensa/include/asm/syscall.h
+++ b/arch/xtensa/include/asm/syscall.h
@@ -28,6 +28,13 @@ static inline long syscall_get_nr(struct task_struct *task,
return regs->syscall;
}

+static inline void syscall_set_nr(struct task_struct *task,
+ struct pt_regs *regs,
+ int nr)
+{
+ regs->syscall = nr;
+}
+
static inline void syscall_rollback(struct task_struct *task,
struct pt_regs *regs)
{
diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h
index 0f7b9a493de7..e33fd4e783c1 100644
--- a/include/asm-generic/syscall.h
+++ b/include/asm-generic/syscall.h
@@ -37,6 +37,20 @@ struct pt_regs;
*/
int syscall_get_nr(struct task_struct *task, struct pt_regs *regs);

+/**
+ * syscall_set_nr - change the system call a task is executing
+ * @task: task of interest, must be blocked
+ * @regs: task_pt_regs() of @task
+ * @nr: system call number
+ *
+ * Changes the system call number @task is about to execute.
+ *
+ * It's only valid to call this when @task is stopped for tracing on
+ * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or
+ * %SYSCALL_WORK_SYSCALL_AUDIT.
+ */
+void syscall_set_nr(struct task_struct *task, struct pt_regs *regs, int nr);
+
/**
* syscall_rollback - roll back registers after an aborted system call
* @task: task of interest, must be in system call exit tracing
--
ldv