ptrace: introduce PTRACE_SET_SYSCALL_INFO API

These functions are going to be needed on all HAVE_ARCH_TRACEHOOK architectures to implement PTRACE_SET_SYSCALL_INFO API.

This partially reverts commit 7962c2eddbfe ("arch: remove unused function syscall_set_arguments()") by reusing some of old syscall_set_arguments() implementations.

Signed-off-by Dmitry V. Levin <[email protected]>

Tested-by Charlie Jenkins <[email protected]>

Reviewed-by Charlie Jenkins <[email protected]>

---
  arch/arc/include/asm/syscall.h        | 14 +++++++++++
  arch/arm/include/asm/syscall.h        | 13 ++++++++++
  arch/arm64/include/asm/syscall.h      | 13 ++++++++++
  arch/csky/include/asm/syscall.h       | 13 ++++++++++
  arch/hexagon/include/asm/syscall.h    | 14 +++++++++++
  arch/loongarch/include/asm/syscall.h  |  8 ++++++
  arch/mips/include/asm/syscall.h       | 32 ++++++++++++++++++++++++
  arch/nios2/include/asm/syscall.h      | 11 ++++++++
  arch/openrisc/include/asm/syscall.h   |  7 ++++++
  arch/parisc/include/asm/syscall.h     | 12 +++++++++
  arch/powerpc/include/asm/syscall.h    | 10 ++++++++
  arch/riscv/include/asm/syscall.h      |  9 +++++++
  arch/s390/include/asm/syscall.h       | 12 +++++++++
  arch/sh/include/asm/syscall_32.h      | 12 +++++++++
  arch/sparc/include/asm/syscall.h      | 10 ++++++++
  arch/um/include/asm/syscall-generic.h | 14 +++++++++++
  arch/x86/include/asm/syscall.h        | 36 +++++++++++++++++++++++++++
  arch/xtensa/include/asm/syscall.h     | 11 ++++++++
  include/asm-generic/syscall.h         | 16 ++++++++++++
  19 files changed, 267 insertions(+)

arch/arc/include/asm/syscall.h +14 -0

index 9709256e31c8..89c1e1736356 100644
@@ -67,6 +67,20 @@ syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
  	}
  }
 
+static inline void
+syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
+		      unsigned long *args)
+{
+	unsigned long *inside_ptregs = &regs->r0;
+	unsigned int n = 6;
+	unsigned int i = 0;
+
+	while (n--) {
+		*inside_ptregs = args[i++];
+		inside_ptregs--;
+	}
+}
+
  static inline int
  syscall_get_arch(struct task_struct *task)
  {

arch/arm/include/asm/syscall.h +13 -0

index fe4326d938c1..21927fa0ae2b 100644
@@ -80,6 +80,19 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	memcpy(args, &regs->ARM_r0 + 1, 5 * sizeof(args[0]));
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+	memcpy(&regs->ARM_r0, args, 6 * sizeof(args[0]));
+	/*
+	 * Also copy the first argument into ARM_ORIG_r0
+	 * so that syscall_get_arguments() would return it
+	 * instead of the previous value.
+	 */
+	regs->ARM_ORIG_r0 = regs->ARM_r0;
+}
+
  static inline int syscall_get_arch(struct task_struct *task)
  {
  	/* ARM tasks don't change audit architectures on the fly. */

arch/arm64/include/asm/syscall.h +13 -0

index ab8e14b96f68..76020b66286b 100644
@@ -73,6 +73,19 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	memcpy(args, &regs->regs[1], 5 * sizeof(args[0]));
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+	memcpy(&regs->regs[0], args, 6 * sizeof(args[0]));
+	/*
+	 * Also copy the first argument into orig_x0
+	 * so that syscall_get_arguments() would return it
+	 * instead of the previous value.
+	 */
+	regs->orig_x0 = regs->regs[0];
+}
+
  /*
   * We don't care about endianness (__AUDIT_ARCH_LE bit) here because
   * AArch64 has the same system calls both on little- and big- endian.

arch/csky/include/asm/syscall.h +13 -0

index 0de5734950bf..30403f7a0487 100644
@@ -59,6 +59,19 @@ syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
  	memcpy(args, &regs->a1, 5 * sizeof(args[0]));
  }
 
+static inline void
+syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
+		      const unsigned long *args)
+{
+	memcpy(&regs->a0, args, 6 * sizeof(regs->a0));
+	/*
+	 * Also copy the first argument into orig_x0
+	 * so that syscall_get_arguments() would return it
+	 * instead of the previous value.
+	 */
+	regs->orig_a0 = regs->a0;
+}
+
  static inline int
  syscall_get_arch(struct task_struct *task)
  {

arch/hexagon/include/asm/syscall.h +14 -0

index f6e454f18038..1024a6548d78 100644
@@ -33,6 +33,13 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	memcpy(args, &(&regs->r00)[0], 6 * sizeof(args[0]));
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 unsigned long *args)
+{
+	memcpy(&(&regs->r00)[0], args, 6 * sizeof(args[0]));
+}
+
  static inline long syscall_get_error(struct task_struct *task,
  				     struct pt_regs *regs)
  {

@@ -45,6 +52,13 @@ static inline long syscall_get_return_value(struct task_struct *task,
  	return regs->r00;
  }
 
+static inline void syscall_set_return_value(struct task_struct *task,
+					    struct pt_regs *regs,
+					    int error, long val)
+{
+	regs->r00 = (long) error ?: val;
+}
+
  static inline int syscall_get_arch(struct task_struct *task)
  {
  	return AUDIT_ARCH_HEXAGON;

arch/loongarch/include/asm/syscall.h +8 -0

index e286dc58476e..ff415b3c0a8e 100644
@@ -61,6 +61,14 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	memcpy(&args[1], &regs->regs[5], 5 * sizeof(long));
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 unsigned long *args)
+{
+	regs->orig_a0 = args[0];
+	memcpy(&regs->regs[5], &args[1], 5 * sizeof(long));
+}
+
  static inline int syscall_get_arch(struct task_struct *task)
  {
  	return AUDIT_ARCH_LOONGARCH64;

arch/mips/include/asm/syscall.h +32 -0

index b3f00ede8bb3..2dcc1d01b405 100644
@@ -74,6 +74,23 @@ static inline void mips_get_syscall_arg(unsigned long *arg,
  #endif
  }
 
+static inline void mips_set_syscall_arg(unsigned long *arg,
+	struct task_struct *task, struct pt_regs *regs, unsigned int n)
+{
+#ifdef CONFIG_32BIT
+	switch (n) {
+	case 0: case 1: case 2: case 3:
+		regs->regs[4 + n] = *arg;
+		return;
+	case 4: case 5: case 6: case 7:
+		*arg = regs->pad0[n] = *arg;
+		return;
+	}
+#else
+	regs->regs[4 + n] = *arg;
+#endif
+}
+
  static inline long syscall_get_error(struct task_struct *task,
  				     struct pt_regs *regs)
  {

@@ -120,6 +137,21 @@ static inline void syscall_get_arguments(struct task_struct *task,
  		mips_get_syscall_arg(args++, task, regs, i++);
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 unsigned long *args)
+{
+	unsigned int i = 0;
+	unsigned int n = 6;
+
+	/* O32 ABI syscall() */
+	if (mips_syscall_is_indirect(task, regs))
+		i++;
+
+	while (n--)
+		mips_set_syscall_arg(args++, task, regs, i++);
+}
+
  extern const unsigned long sys_call_table[];
  extern const unsigned long sys32_call_table[];
  extern const unsigned long sysn32_call_table[];

arch/nios2/include/asm/syscall.h +11 -0

index fff52205fb65..526449edd768 100644
@@ -58,6 +58,17 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	*args   = regs->r9;
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+	struct pt_regs *regs, const unsigned long *args)
+{
+	regs->r4 = *args++;
+	regs->r5 = *args++;
+	regs->r6 = *args++;
+	regs->r7 = *args++;
+	regs->r8 = *args++;
+	regs->r9 = *args;
+}
+
  static inline int syscall_get_arch(struct task_struct *task)
  {
  	return AUDIT_ARCH_NIOS2;

arch/openrisc/include/asm/syscall.h +7 -0

index 903ed882bdec..e6383be2a195 100644
@@ -57,6 +57,13 @@ syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
  	memcpy(args, &regs->gpr[3], 6 * sizeof(args[0]));
  }
 
+static inline void
+syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
+		      const unsigned long *args)
+{
+	memcpy(&regs->gpr[3], args, 6 * sizeof(args[0]));
+}
+
  static inline int syscall_get_arch(struct task_struct *task)
  {
  	return AUDIT_ARCH_OPENRISC;

arch/parisc/include/asm/syscall.h +12 -0

index 00b127a5e09b..b146d0ae4c77 100644
@@ -29,6 +29,18 @@ static inline void syscall_get_arguments(struct task_struct *tsk,
  	args[0] = regs->gr[26];
  }
 
+static inline void syscall_set_arguments(struct task_struct *tsk,
+					 struct pt_regs *regs,
+					 unsigned long *args)
+{
+	regs->gr[21] = args[5];
+	regs->gr[22] = args[4];
+	regs->gr[23] = args[3];
+	regs->gr[24] = args[2];
+	regs->gr[25] = args[1];
+	regs->gr[26] = args[0];
+}
+
  static inline long syscall_get_error(struct task_struct *task,
  				     struct pt_regs *regs)
  {

arch/powerpc/include/asm/syscall.h +10 -0

index 422d7735ace6..521f279e6b33 100644
@@ -114,6 +114,16 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	}
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+	memcpy(&regs->gpr[3], args, 6 * sizeof(args[0]));
+
+	/* Also copy the first argument into orig_gpr3 */
+	regs->orig_gpr3 = args[0];
+}
+
  static inline int syscall_get_arch(struct task_struct *task)
  {
  	if (is_tsk_32bit_task(task))

arch/riscv/include/asm/syscall.h +9 -0

index 121fff429dce..8d389ba995c8 100644
@@ -66,6 +66,15 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	memcpy(args, &regs->a1, 5 * sizeof(args[0]));
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+	regs->orig_a0 = args[0];
+	args++;
+	memcpy(&regs->a1, args, 5 * sizeof(regs->a1));
+}
+
  static inline int syscall_get_arch(struct task_struct *task)
  {
  #ifdef CONFIG_64BIT

arch/s390/include/asm/syscall.h +12 -0

index 27e3d804b311..b3dd883699e7 100644
@@ -78,6 +78,18 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	args[0] = regs->orig_gpr2 & mask;
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+	unsigned int n = 6;
+
+	while (n-- > 0)
+		if (n > 0)
+			regs->gprs[2 + n] = args[n];
+	regs->orig_gpr2 = args[0];
+}
+
  static inline int syscall_get_arch(struct task_struct *task)
  {
  #ifdef CONFIG_COMPAT

arch/sh/include/asm/syscall_32.h +12 -0

index d87738eebe30..cb51a7528384 100644
@@ -57,6 +57,18 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	args[0] = regs->regs[4];
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+	regs->regs[1] = args[5];
+	regs->regs[0] = args[4];
+	regs->regs[7] = args[3];
+	regs->regs[6] = args[2];
+	regs->regs[5] = args[1];
+	regs->regs[4] = args[0];
+}
+
  static inline int syscall_get_arch(struct task_struct *task)
  {
  	int arch = AUDIT_ARCH_SH;

arch/sparc/include/asm/syscall.h +10 -0

index 20c109ac8cc9..62a5a78804c4 100644
@@ -117,6 +117,16 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	}
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+	unsigned int i;
+
+	for (i = 0; i < 6; i++)
+		regs->u_regs[UREG_I0 + i] = args[i];
+}
+
  static inline int syscall_get_arch(struct task_struct *task)
  {
  #if defined(CONFIG_SPARC64) && defined(CONFIG_COMPAT)

arch/um/include/asm/syscall-generic.h +14 -0

index 172b74143c4b..2984feb9d576 100644
@@ -62,6 +62,20 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	*args   = UPT_SYSCALL_ARG6(r);
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+	struct uml_pt_regs *r = &regs->regs;
+
+	UPT_SYSCALL_ARG1(r) = *args++;
+	UPT_SYSCALL_ARG2(r) = *args++;
+	UPT_SYSCALL_ARG3(r) = *args++;
+	UPT_SYSCALL_ARG4(r) = *args++;
+	UPT_SYSCALL_ARG5(r) = *args++;
+	UPT_SYSCALL_ARG6(r) = *args;
+}
+
  /* See arch/x86/um/asm/syscall.h for syscall_get_arch() definition. */
 
  #endif	/* __UM_SYSCALL_GENERIC_H */

arch/x86/include/asm/syscall.h +36 -0

index 7c488ff0c764..b9c249dd9e3d 100644
@@ -90,6 +90,18 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	args[5] = regs->bp;
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+	regs->bx = args[0];
+	regs->cx = args[1];
+	regs->dx = args[2];
+	regs->si = args[3];
+	regs->di = args[4];
+	regs->bp = args[5];
+}
+
  static inline int syscall_get_arch(struct task_struct *task)
  {
  	return AUDIT_ARCH_I386;

@@ -121,6 +133,30 @@ static inline void syscall_get_arguments(struct task_struct *task,
  	}
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+# ifdef CONFIG_IA32_EMULATION
+	if (task->thread_info.status & TS_COMPAT) {
+		regs->bx = *args++;
+		regs->cx = *args++;
+		regs->dx = *args++;
+		regs->si = *args++;
+		regs->di = *args++;
+		regs->bp = *args;
+	} else
+# endif
+	{
+		regs->di = *args++;
+		regs->si = *args++;
+		regs->dx = *args++;
+		regs->r10 = *args++;
+		regs->r8 = *args++;
+		regs->r9 = *args;
+	}
+}
+
  static inline int syscall_get_arch(struct task_struct *task)
  {
  	/* x32 tasks should be considered AUDIT_ARCH_X86_64. */

arch/xtensa/include/asm/syscall.h +11 -0

index 5ee974bf8330..f9a671cbf933 100644
@@ -68,6 +68,17 @@ static inline void syscall_get_arguments(struct task_struct *task,
  		args[i] = regs->areg[reg[i]];
  }
 
+static inline void syscall_set_arguments(struct task_struct *task,
+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+	static const unsigned int reg[] = XTENSA_SYSCALL_ARGUMENT_REGS;
+	unsigned int i;
+
+	for (i = 0; i < 6; ++i)
+		regs->areg[reg[i]] = args[i];
+}
+
  asmlinkage long xtensa_rt_sigreturn(void);
  asmlinkage long xtensa_shmat(int, char __user *, int);
  asmlinkage long xtensa_fadvise64_64(int, int,

include/asm-generic/syscall.h +16 -0

index 5a80fe728dc8..0f7b9a493de7 100644
@@ -117,6 +117,22 @@ void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
  void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
  			   unsigned long *args);
 
+/**
+ * syscall_set_arguments - change system call parameter value
+ * @task:	task of interest, must be in system call entry tracing
+ * @regs:	task_pt_regs() of @task
+ * @args:	array of argument values to store
+ *
+ * Changes 6 arguments to the system call.
+ * The first argument gets value @args[0], and so on.
+ *
+ * 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_arguments(struct task_struct *task, struct pt_regs *regs,
+			   const unsigned long *args);
+
  /**
   * syscall_get_arch - return the AUDIT_ARCH for the current system call
   * @task:	task of interest, must be blocked

Le 28/01/2025 à 10:16, Dmitry V. Levin a écrit :

Quoted 2 lines

These functions are going to be needed on all HAVE_ARCH_TRACEHOOK architectures to implement PTRACE_SET_SYSCALL_INFO API.

The subject is misleading. syscall_set_return_value() already exists on most architectures and was not addressed by commit 7962c2eddbfe.

Maybe it would be better to handle syscall_set_return_value() in a separate commit.

These functions are going to be needed on all HAVE_ARCH_TRACEHOOK architectures to implement PTRACE_SET_SYSCALL_INFO API.

This partially reverts commit 7962c2eddbfe ("arch: remove unused function syscall_set_arguments()") by reusing some of old syscall_set_arguments() implementations.

Signed-off-by Dmitry V. Levin <[email protected]>

Tested-by Charlie Jenkins <[email protected]>

Reviewed-by Charlie Jenkins <[email protected]>

---
 arch/arc/include/asm/syscall.h        | 14 +++++++++++
 arch/arm/include/asm/syscall.h        | 13 ++++++++++
 arch/arm64/include/asm/syscall.h      | 13 ++++++++++
 arch/csky/include/asm/syscall.h       | 13 ++++++++++
 arch/hexagon/include/asm/syscall.h    | 14 +++++++++++
 arch/loongarch/include/asm/syscall.h  |  8 ++++++
 arch/mips/include/asm/syscall.h       | 32 ++++++++++++++++++++++++
 arch/nios2/include/asm/syscall.h      | 11 ++++++++
 arch/openrisc/include/asm/syscall.h   |  7 ++++++
 arch/parisc/include/asm/syscall.h     | 12 +++++++++
 arch/powerpc/include/asm/syscall.h    | 10 ++++++++
 arch/riscv/include/asm/syscall.h      |  9 +++++++
 arch/s390/include/asm/syscall.h       | 12 +++++++++
 arch/sh/include/asm/syscall_32.h      | 12 +++++++++
 arch/sparc/include/asm/syscall.h      | 10 ++++++++
 arch/um/include/asm/syscall-generic.h | 14 +++++++++++
 arch/x86/include/asm/syscall.h        | 36 +++++++++++++++++++++++++++
 arch/xtensa/include/asm/syscall.h     | 11 ++++++++
 include/asm-generic/syscall.h         | 16 ++++++++++++
 19 files changed, 267 insertions(+)

arch/s390/include/asm/syscall.h +1 -0

index 27e3d804b311..b3dd883699e7 100644
@@ -78,6 +78,18 @@ static inline void syscall_get_arguments(struct task_struct *task,
 	args[0] = regs->orig_gpr2 & mask;
 }
 
+static inline void syscall_set_arguments(struct task_struct *task,

Quoted 41 lines · Dmitry V. Levin

These functions are going to be needed on all HAVE_ARCH_TRACEHOOK architectures to implement PTRACE_SET_SYSCALL_INFO API.

This partially reverts commit 7962c2eddbfe ("arch: remove unused function syscall_set_arguments()") by reusing some of old syscall_set_arguments() implementations.

Signed-off-by Dmitry V. Levin <[email protected]>

Tested-by Charlie Jenkins <[email protected]>

Reviewed-by Charlie Jenkins <[email protected]>

---
 arch/arc/include/asm/syscall.h        | 14 +++++++++++
 arch/arm/include/asm/syscall.h        | 13 ++++++++++
 arch/arm64/include/asm/syscall.h      | 13 ++++++++++
 arch/csky/include/asm/syscall.h       | 13 ++++++++++
 arch/hexagon/include/asm/syscall.h    | 14 +++++++++++
 arch/loongarch/include/asm/syscall.h  |  8 ++++++
 arch/mips/include/asm/syscall.h       | 32 ++++++++++++++++++++++++
 arch/nios2/include/asm/syscall.h      | 11 ++++++++
 arch/openrisc/include/asm/syscall.h   |  7 ++++++
 arch/parisc/include/asm/syscall.h     | 12 +++++++++
 arch/powerpc/include/asm/syscall.h    | 10 ++++++++
 arch/riscv/include/asm/syscall.h      |  9 +++++++
 arch/s390/include/asm/syscall.h       | 12 +++++++++
 arch/sh/include/asm/syscall_32.h      | 12 +++++++++
 arch/sparc/include/asm/syscall.h      | 10 ++++++++
 arch/um/include/asm/syscall-generic.h | 14 +++++++++++
 arch/x86/include/asm/syscall.h        | 36 +++++++++++++++++++++++++++
 arch/xtensa/include/asm/syscall.h     | 11 ++++++++
 include/asm-generic/syscall.h         | 16 ++++++++++++
 19 files changed, 267 insertions(+)

arch/s390/include/asm/syscall.h +1 -0

index 27e3d804b311..b3dd883699e7 100644
@@ -78,6 +78,18 @@ static inline void syscall_get_arguments(struct task_struct *task,
 	args[0] = regs->orig_gpr2 & mask;
 }
 
+static inline void syscall_set_arguments(struct task_struct *task,

arch/s390/include/asm/syscall.h static inline void syscall_get_arguments(struct task_struct *task, · line 91

Quoted 10 lines

arch/s390/include/asm/syscall.h +10 -0

+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+	unsigned int n = 6;
+
+	while (n-- > 0)
+		if (n > 0)
+			regs->gprs[2 + n] = args[n];
+	regs->orig_gpr2 = args[0];
+}

Could that be changed to something like:

for (int n = 1; n < 6; n++)

        regs->gprs[2 + n] = args[n];

regs->orig_gpr2 = args[0];

I think this is way easier to parse.

Quoted 60 lines · Sven Schnelle

Quoted 41 lines · Dmitry V. Levin

These functions are going to be needed on all HAVE_ARCH_TRACEHOOK architectures to implement PTRACE_SET_SYSCALL_INFO API.

This partially reverts commit 7962c2eddbfe ("arch: remove unused function syscall_set_arguments()") by reusing some of old syscall_set_arguments() implementations.

Signed-off-by Dmitry V. Levin <[email protected]>

Tested-by Charlie Jenkins <[email protected]>

Reviewed-by Charlie Jenkins <[email protected]>

---
 arch/arc/include/asm/syscall.h        | 14 +++++++++++
 arch/arm/include/asm/syscall.h        | 13 ++++++++++
 arch/arm64/include/asm/syscall.h      | 13 ++++++++++
 arch/csky/include/asm/syscall.h       | 13 ++++++++++
 arch/hexagon/include/asm/syscall.h    | 14 +++++++++++
 arch/loongarch/include/asm/syscall.h  |  8 ++++++
 arch/mips/include/asm/syscall.h       | 32 ++++++++++++++++++++++++
 arch/nios2/include/asm/syscall.h      | 11 ++++++++
 arch/openrisc/include/asm/syscall.h   |  7 ++++++
 arch/parisc/include/asm/syscall.h     | 12 +++++++++
 arch/powerpc/include/asm/syscall.h    | 10 ++++++++
 arch/riscv/include/asm/syscall.h      |  9 +++++++
 arch/s390/include/asm/syscall.h       | 12 +++++++++
 arch/sh/include/asm/syscall_32.h      | 12 +++++++++
 arch/sparc/include/asm/syscall.h      | 10 ++++++++
 arch/um/include/asm/syscall-generic.h | 14 +++++++++++
 arch/x86/include/asm/syscall.h        | 36 +++++++++++++++++++++++++++
 arch/xtensa/include/asm/syscall.h     | 11 ++++++++
 include/asm-generic/syscall.h         | 16 ++++++++++++
 19 files changed, 267 insertions(+)

arch/s390/include/asm/syscall.h +1 -0

index 27e3d804b311..b3dd883699e7 100644
@@ -78,6 +78,18 @@ static inline void syscall_get_arguments(struct task_struct *task,
 	args[0] = regs->orig_gpr2 & mask;
 }
 
+static inline void syscall_set_arguments(struct task_struct *task,

arch/s390/include/asm/syscall.h static inline void syscall_get_arguments(struct task_struct *task, · line 91

Quoted 10 lines

arch/s390/include/asm/syscall.h +10 -0

+					 struct pt_regs *regs,
+					 const unsigned long *args)
+{
+	unsigned int n = 6;
+
+	while (n-- > 0)
+		if (n > 0)
+			regs->gprs[2 + n] = args[n];
+	regs->orig_gpr2 = args[0];
+}

Could that be changed to something like:

for (int n = 1; n < 6; n++)

        regs->gprs[2 + n] = args[n];

regs->orig_gpr2 = args[0];

Quoted 1 line

I think this is way easier to parse.

I don't mind changing syscall_set_arguments() this way, but it just mirrors syscall_get_arguments(), so I think it would be better if these two functions were written in the same style. Would you like to change syscall_get_arguments() as well?

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 <[email protected]>

Tested-by Charlie Jenkins <[email protected]>

Reviewed-by Charlie Jenkins <[email protected]>

---
  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(+)

arch/arm64/include/asm/syscall.h +16 -0

index 76020b66286b..712daa90e643 100644
@@ -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,

arch/powerpc/include/asm/syscall.h +0 -0

index 521f279e6b33..7505dcfed247 100644
@@ -39,6 +39,16 @@ static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
  		return -1;

arch/powerpc/include/asm/syscall.h +2 -0

+}
+
  static inline void syscall_rollback(struct task_struct *task,
  				    struct pt_regs *regs)
  {

Le 28/01/2025 à 10:16, Dmitry V. Levin a écrit :

Quoted 71 lines

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 <[email protected]>

Tested-by Charlie Jenkins <[email protected]>

Reviewed-by Charlie Jenkins <[email protected]>

---
  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(+)

arch/arm64/include/asm/syscall.h +16 -0

index 76020b66286b..712daa90e643 100644
@@ -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,

arch/powerpc/include/asm/syscall.h +0 -0

index 521f279e6b33..7505dcfed247 100644
@@ -39,6 +39,16 @@ static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
  		return -1;
  }
 

arch/powerpc/include/asm/syscall.h static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs) · line 49

Quoted 8 lines

arch/powerpc/include/asm/syscall.h +8 -0

+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;

Doesn't the same as for ARM64 apply here as well ?

PTRACE_SET_SYSCALL_INFO is a generic ptrace API that complements PTRACE_GET_SYSCALL_INFO by letting the ptracer modify details of system calls the tracee is blocked in.

This API allows ptracers to obtain and modify system call details in a straightforward and architecture-agnostic way.

Current implementation supports changing only those bits of system call information that are used by strace, namely, syscall number, syscall arguments, and syscall return value.

Support of changing additional details returned by PTRACE_GET_SYSCALL_INFO, such as instruction pointer and stack pointer, could be added later if needed, by using struct ptrace_syscall_info.flags to specify the additional details that should be set. Currently, "flags", "reserved", and "seccomp.reserved2" fields of struct ptrace_syscall_info must be initialized with zeroes; "arch", "instruction_pointer", and "stack_pointer" fields are ignored.

PTRACE_SET_SYSCALL_INFO currently supports only PTRACE_SYSCALL_INFO_ENTRY, PTRACE_SYSCALL_INFO_EXIT, and PTRACE_SYSCALL_INFO_SECCOMP operations. Other operations could be added later if needed.

Ideally, PTRACE_SET_SYSCALL_INFO should have been introduced along with PTRACE_GET_SYSCALL_INFO, but it didn't happen. The last straw that convinced me to implement PTRACE_SET_SYSCALL_INFO was apparent failure to provide an API of changing the first system call argument on riscv architecture.

ptrace(2) man page:

long ptrace(enum __ptrace_request request, pid_t pid, void *addr, void *data);
...
PTRACE_SET_SYSCALL_INFO
Modify information about the system call that caused the stop. The "data" argument is a pointer to struct ptrace_syscall_info that specifies the system call information to be set.
The "addr" argument should be set to sizeof(struct ptrace_syscall_info)).

Link https://lore.kernel.org/all/[email protected]/ open here

Signed-off-by Dmitry V. Levin <[email protected]>

Reviewed-by Alexey Gladkov <[email protected]>

Reviewed-by Charlie Jenkins <[email protected]>

Tested-by Charlie Jenkins <[email protected]>

---
  include/uapi/linux/ptrace.h |   7 ++-
  kernel/ptrace.c             | 121 +++++++++++++++++++++++++++++++++++-
  2 files changed, 126 insertions(+), 2 deletions(-)

include/uapi/linux/ptrace.h +6 -1

index 72c038fc71d0..5f8ef6156752 100644
@@ -74,6 +74,7 @@ struct seccomp_metadata {
  };
 
  #define PTRACE_GET_SYSCALL_INFO		0x420e
+#define PTRACE_SET_SYSCALL_INFO		0x4212
  #define PTRACE_SYSCALL_INFO_NONE	0
  #define PTRACE_SYSCALL_INFO_ENTRY	1
  #define PTRACE_SYSCALL_INFO_EXIT	2

@@ -81,7 +82,8 @@ struct seccomp_metadata {
 
  struct ptrace_syscall_info {
  	__u8 op;	/* PTRACE_SYSCALL_INFO_* */
-	__u8 pad[3];
+	__u8 reserved;
+	__u16 flags;
  	__u32 arch;
  	__u64 instruction_pointer;
  	__u64 stack_pointer;

@@ -98,6 +100,7 @@ struct ptrace_syscall_info {
  			__u64 nr;
  			__u64 args[6];
  			__u32 ret_data;
+			__u32 reserved2;
  		} seccomp;
  	};
  };

@@ -142,6 +145,8 @@ struct ptrace_sud_config {
  	__u64 len;
  };
 
+/* 0x4212 is PTRACE_SET_SYSCALL_INFO */
+
  /*
   * These values are stored in task->ptrace_message
   * by ptrace_stop to describe the current syscall-stop.

kernel/ptrace.c +120 -1

index 22e7d74cf4cd..b9c1949186bf 100644
@@ -944,7 +944,10 @@ ptrace_get_syscall_info_seccomp(struct task_struct *child, struct pt_regs *regs,
  	ptrace_get_syscall_info_entry(child, regs, info);
  	info->seccomp.ret_data = child->ptrace_message;
 
-	/* ret_data is the last field in struct ptrace_syscall_info.seccomp */
+	/*
+	 * ret_data is the last non-reserved field
+	 * in struct ptrace_syscall_info.seccomp
+	 */
  	return offsetofend(struct ptrace_syscall_info, seccomp.ret_data);
  }
 

@@ -1016,6 +1019,118 @@ ptrace_get_syscall_info(struct task_struct *child, unsigned long user_size,
  	write_size = min(actual_size, user_size);
  	return copy_to_user(datavp, &info, write_size) ? -EFAULT : actual_size;
  }
+
+static int
+ptrace_set_syscall_info_entry(struct task_struct *child, struct pt_regs *regs,
+			      struct ptrace_syscall_info *info)
+{
+	unsigned long args[ARRAY_SIZE(info->entry.args)];
+	int nr = info->entry.nr;
+	int i;
+
+	/*
+	 * Check that the syscall number specified in info->entry.nr
+	 * is either a value of type "int" or a sign-extended value
+	 * of type "int".
+	 */
+	if (nr != info->entry.nr)
+		return -ERANGE;
+
+	for (i = 0; i < ARRAY_SIZE(args); i++) {
+		args[i] = info->entry.args[i];
+		/*
+		 * Check that the syscall argument specified in
+		 * info->entry.args[i] is either a value of type
+		 * "unsigned long" or a sign-extended value of type "long".
+		 */
+		if (args[i] != info->entry.args[i])
+			return -ERANGE;
+	}
+
+	syscall_set_nr(child, regs, nr);
+	/*
+	 * If the syscall number is set to -1, setting syscall arguments is not
+	 * just pointless, it would also clobber the syscall return value on
+	 * those architectures that share the same register both for the first
+	 * argument of syscall and its return value.
+	 */
+	if (nr != -1)
+		syscall_set_arguments(child, regs, args);
+
+	return 0;
+}
+
+static int
+ptrace_set_syscall_info_seccomp(struct task_struct *child, struct pt_regs *regs,
+				struct ptrace_syscall_info *info)
+{
+	/*
+	 * info->entry is currently a subset of info->seccomp,
+	 * info->seccomp.ret_data is currently ignored.
+	 */
+	return ptrace_set_syscall_info_entry(child, regs, info);
+}
+
+static int
+ptrace_set_syscall_info_exit(struct task_struct *child, struct pt_regs *regs,
+			     struct ptrace_syscall_info *info)
+{
+	long rval = info->exit.rval;
+
+	/*
+	 * Check that the return value specified in info->exit.rval
+	 * is either a value of type "long" or a sign-extended value
+	 * of type "long".
+	 */
+	if (rval != info->exit.rval)
+		return -ERANGE;
+
+	if (info->exit.is_error)
+		syscall_set_return_value(child, regs, rval, 0);
+	else
+		syscall_set_return_value(child, regs, 0, rval);
+
+	return 0;
+}
+
+static int
+ptrace_set_syscall_info(struct task_struct *child, unsigned long user_size,
+			const void __user *datavp)
+{
+	struct pt_regs *regs = task_pt_regs(child);
+	struct ptrace_syscall_info info;
+
+	if (user_size < sizeof(info))
+		return -EINVAL;
+
+	/*
+	 * The compatibility is tracked by info.op and info.flags: if user-space
+	 * does not instruct us to use unknown extra bits from future versions
+	 * of ptrace_syscall_info, we are not going to read them either.
+	 */
+	if (copy_from_user(&info, datavp, sizeof(info)))
+		return -EFAULT;
+
+	/* Reserved for future use. */
+	if (info.flags || info.reserved || info.seccomp.reserved2)
+		return -EINVAL;
+
+	/* Changing the type of the system call stop is not supported yet. */
+	if (ptrace_get_syscall_info_op(child) != info.op)
+		return -EINVAL;
+
+	switch (info.op) {
+	case PTRACE_SYSCALL_INFO_ENTRY:
+		return ptrace_set_syscall_info_entry(child, regs, &info);
+	case PTRACE_SYSCALL_INFO_EXIT:
+		return ptrace_set_syscall_info_exit(child, regs, &info);
+	case PTRACE_SYSCALL_INFO_SECCOMP:
+		return ptrace_set_syscall_info_seccomp(child, regs, &info);
+	default:
+		/* Other types of system call stops are not supported yet. */
+		return -EINVAL;
+	}
+}
  #endif /* CONFIG_HAVE_ARCH_TRACEHOOK */
 
  int ptrace_request(struct task_struct *child, long request,

@@ -1234,6 +1349,10 @@ int ptrace_request(struct task_struct *child, long request,
  	case PTRACE_GET_SYSCALL_INFO:
  		ret = ptrace_get_syscall_info(child, addr, datavp);
  		break;
+
+	case PTRACE_SET_SYSCALL_INFO:
+		ret = ptrace_set_syscall_info(child, addr, datavp);
+		break;
  #endif
 
  	case PTRACE_SECCOMP_GET_FILTER:

Le 28/01/2025 à 10:16, Dmitry V. Levin a écrit :

Quoted 7 lines

PTRACE_SET_SYSCALL_INFO is a generic ptrace API that complements PTRACE_GET_SYSCALL_INFO by letting the ptracer modify details of system calls the tracee is blocked in.

This API allows ptracers to obtain and modify system call details in a straightforward and architecture-agnostic way.

Quoted 3 lines

Current implementation supports changing only those bits of system call information that are used by strace, namely, syscall number, syscall arguments, and syscall return value.

How do you handle changes related to syscalls that call force_successful_syscall_return() ?

* ptrace: Add explicit padding to the end of struct ptrace_syscall_info, simplify obtaining of user ptrace_syscall_info,
do not introduce PTRACE_SYSCALL_INFO_SIZE_VER0
* ptrace: Change the return type of ptrace_set_syscall_info_* functions from "unsigned long" to "int"
* ptrace: Add -ERANGE check to ptrace_set_syscall_info_exit, add comments to -ERANGE checks
* ptrace: Update comments about supported syscall stops
* selftests: Extend set_syscall_info test, fix for mips n32