ptrace: introduce PTRACE_SET_SYSCALL_INFO API

This function is 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]>

Acked-by Helge Deller <[email protected]> # parisc

Reviewed-by Maciej W. Rozycki <[email protected]> # mips

arch/riscv/include/asm/syscall.h +0 -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]));

Hi Dmitry,

[dropping majority of folks since this seems irrelevant to them]

Quoted 12 lines · Dmitry V. Levin

This function is 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]>

Acked-by Helge Deller <[email protected]> # parisc

Reviewed-by Maciej W. Rozycki <[email protected]> # mips

...

Quoted 6 lines

arch/riscv/include/asm/syscall.h +0 -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]));

arch/riscv/include/asm/syscall.h static inline void syscall_get_arguments(struct task_struct *task, · line 76

Quoted 10 lines

arch/riscv/include/asm/syscall.h +8 -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));
+}

This upsets the compiletime fortify checks, as I see a warning after syscall_set_arguments() starts being used in kernel/ptrace.c later in the series.

  $ make -skj"$(nproc)" ARCH=riscv CROSS_COMPILE=riscv64-linux- allmodconfig kernel/ptrace.o
  In file included from include/linux/string.h:392,
                   from include/linux/bitmap.h:13,
                   from include/linux/cpumask.h:12,
                   from arch/riscv/include/asm/processor.h:55,
                   from include/linux/sched.h:13,
                   from kernel/ptrace.c:13:
  In function 'fortify_memcpy_chk',
      inlined from 'syscall_set_arguments.isra' at arch/riscv/include/asm/syscall.h:82:2:
  include/linux/fortify-string.h:571:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
    571 |                         __write_overflow_field(p_size_field, size);
        |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  cc1: all warnings being treated as errors

The compiler knows the size of the destination and the size to be copied so it knows there will be an (intentional) overwrite here. struct_group() would normally work but I think this structure already has a struct_group() around some of the members that would be needed. I build tested eliminating the memcpy() altogether, which would appear to work, but I am not sure if there is a better solution, hence just the report.

Cheers,
Nathan

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

index a5281cdf2b10..70ec19dc8506 100644
@@ -78,8 +78,11 @@ static inline void syscall_set_arguments(struct task_struct *task,
                                         const unsigned long *args)

Quoted 14 lines · Nathan Chancellor

Review

Quoted 8 lines · Dmitry V. Levin

(quoted diff) +8 -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));
+}

This upsets the compiletime fortify checks, as I see a warning after syscall_set_arguments() starts being used in kernel/ptrace.c later in the series.

Quoted 13 lines

  $ make -skj"$(nproc)" ARCH=riscv CROSS_COMPILE=riscv64-linux- allmodconfig kernel/ptrace.o
  In file included from include/linux/string.h:392,
                   from include/linux/bitmap.h:13,
                   from include/linux/cpumask.h:12,
                   from arch/riscv/include/asm/processor.h:55,
                   from include/linux/sched.h:13,
                   from kernel/ptrace.c:13:
  In function 'fortify_memcpy_chk',
      inlined from 'syscall_set_arguments.isra' at arch/riscv/include/asm/syscall.h:82:2:
  include/linux/fortify-string.h:571:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
    571 |                         __write_overflow_field(p_size_field, size);
        |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  cc1: all warnings being treated as errors

I certainly tested the series on riscv64, but somehow I haven't seen this compiler diagnostics before.

Quoted 14 lines

arch/riscv/include/asm/syscall.h +4 -2

index a5281cdf2b10..70ec19dc8506 100644
@@ -78,8 +78,11 @@ static inline void syscall_set_arguments(struct task_struct *task,
                                         const unsigned long *args)
 {
        regs->orig_a0 = args[0];
-       args++;
-       memcpy(&regs->a1, args, 5 * sizeof(regs->a1));
+       regs->a1 = args[1];
+       regs->a2 = args[2];
+       regs->a3 = args[3];
+       regs->a4 = args[4];

arch/riscv/include/asm/syscall.h static inline void syscall_set_arguments(struct task_struct *task, · line 86

Quoted 2 lines

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

+       regs->a5 = args[5];
 }

I don't mind eliminating the memcpy() altogether, but I'd like to note that syscall_set_arguments() is an exact mirror of syscall_get_arguments(), so if the intentional overwrite in syscall_set_arguments() is not acceptable, then the intentional overread in syscall_get_arguments() shouldn't be acceptable either.

Quoted 29 lines · Dmitry V. Levin

Quoted 14 lines · Nathan Chancellor

Review

Quoted 8 lines · Dmitry V. Levin

(quoted diff) +8 -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));
+}

This upsets the compiletime fortify checks, as I see a warning after syscall_set_arguments() starts being used in kernel/ptrace.c later in the series.

Quoted 13 lines

  $ make -skj"$(nproc)" ARCH=riscv CROSS_COMPILE=riscv64-linux- allmodconfig kernel/ptrace.o
  In file included from include/linux/string.h:392,
                   from include/linux/bitmap.h:13,
                   from include/linux/cpumask.h:12,
                   from arch/riscv/include/asm/processor.h:55,
                   from include/linux/sched.h:13,
                   from kernel/ptrace.c:13:
  In function 'fortify_memcpy_chk',
      inlined from 'syscall_set_arguments.isra' at arch/riscv/include/asm/syscall.h:82:2:
  include/linux/fortify-string.h:571:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
    571 |                         __write_overflow_field(p_size_field, size);
        |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  cc1: all warnings being treated as errors

Quoted 2 lines

I certainly tested the series on riscv64, but somehow I haven't seen this compiler diagnostics before.

Maybe CONFIG_FORTIFY_SOURCE was not enabled? This comes from the kernel's fortified memcpy checking function, fortify_memcpy_chk(), not necessarily the compiler itself.

Quoted 14 lines

Quoted 14 lines

arch/riscv/include/asm/syscall.h +4 -2

index a5281cdf2b10..70ec19dc8506 100644
@@ -78,8 +78,11 @@ static inline void syscall_set_arguments(struct task_struct *task,
                                         const unsigned long *args)
 {
        regs->orig_a0 = args[0];
-       args++;
-       memcpy(&regs->a1, args, 5 * sizeof(regs->a1));
+       regs->a1 = args[1];
+       regs->a2 = args[2];
+       regs->a3 = args[3];
+       regs->a4 = args[4];

Quoted 8 lines

arch/riscv/include/asm/syscall.h static inline void syscall_set_arguments(struct task_struct *task, · line 89

Quoted 2 lines

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

+       regs->a5 = args[5];
 }

I don't mind eliminating the memcpy() altogether, but I'd like to note that syscall_set_arguments() is an exact mirror of syscall_get_arguments(), so if the intentional overwrite in syscall_set_arguments() is not acceptable, then the intentional overread in syscall_get_arguments() shouldn't be acceptable either.

Yes, I noticed the symmetry too but I was only looking at it from the overwrite perspective, not the overread one. That reminded me to double check what fortify_memcpy_chk() actually checks for and I remembered that the overread version of this warning is hidden under W=1 (I guess because it happens more frequently).

  $ make -skj"$(nproc)" ARCH=riscv CROSS_COMPILE=riscv64-linux- W=1 allmodconfig kernel/ptrace.o
  In file included from include/linux/string.h:392,
                   from include/linux/bitmap.h:13,
                   from include/linux/cpumask.h:12,
                   from arch/riscv/include/asm/processor.h:55,
                   from include/linux/sched.h:13,
                   from kernel/ptrace.c:13:
  In function 'fortify_memcpy_chk',
      inlined from 'syscall_get_arguments.isra' at arch/riscv/include/asm/syscall.h:73:2:
  include/linux/fortify-string.h:580:25: error: call to '__read_overflow2_field' declared with attribute warning: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Werror=attribute-warning]
    580 |                         __read_overflow2_field(q_size_field, size);
        |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  cc1: all warnings being treated as errors

So memcpy() should indeed be eliminated from both, which obviously clears up the warnings.

Cheers,
Nathan

arch/riscv/include/asm/syscall.h +5 -2

index a5281cdf2b10..34313387f977 100644
@@ -69,8 +69,11 @@ static inline void syscall_get_arguments(struct task_struct *task,
 					 unsigned long *args)
 {
 	args[0] = regs->orig_a0;
-	args++;
-	memcpy(args, &regs->a1, 5 * sizeof(args[0]));
+	args[1] = regs->a1;
+	args[2] = regs->a2;
+	args[3] = regs->a3;
+	args[4] = regs->a4;
+	args[5] = regs->a5;
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,

@@ -78,8 +81,11 @@ static inline void syscall_set_arguments(struct task_struct *task,
 					 const unsigned long *args)
 {
 	regs->orig_a0 = args[0];

Quoted 31 lines · Nathan Chancellor

arch/riscv/include/asm/syscall.h +10 -4

index a5281cdf2b10..34313387f977 100644
@@ -69,8 +69,11 @@ static inline void syscall_get_arguments(struct task_struct *task,
 					 unsigned long *args)
 {
 	args[0] = regs->orig_a0;
-	args++;
-	memcpy(args, &regs->a1, 5 * sizeof(args[0]));
+	args[1] = regs->a1;
+	args[2] = regs->a2;
+	args[3] = regs->a3;
+	args[4] = regs->a4;
+	args[5] = regs->a5;
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,

@@ -78,8 +81,11 @@ static inline void syscall_set_arguments(struct task_struct *task,
 					 const unsigned long *args)
 {
 	regs->orig_a0 = args[0];
-	args++;
-	memcpy(&regs->a1, args, 5 * sizeof(regs->a1));
+	regs->a1 = args[1];
+	regs->a2 = args[2];
+	regs->a3 = args[3];
+	regs->a4 = args[4];
+	regs->a5 = args[5];
 }
 

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

Quoted 1 line

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

 static inline int syscall_get_arch(struct task_struct *task)

Looks good, thanks. How do we proceed from this point?

Quoted 32 lines · Dmitry V. Levin

Quoted 31 lines · Nathan Chancellor

arch/riscv/include/asm/syscall.h +10 -4

index a5281cdf2b10..34313387f977 100644
@@ -69,8 +69,11 @@ static inline void syscall_get_arguments(struct task_struct *task,
 					 unsigned long *args)
 {
 	args[0] = regs->orig_a0;
-	args++;
-	memcpy(args, &regs->a1, 5 * sizeof(args[0]));
+	args[1] = regs->a1;
+	args[2] = regs->a2;
+	args[3] = regs->a3;
+	args[4] = regs->a4;
+	args[5] = regs->a5;
 }
 
 static inline void syscall_set_arguments(struct task_struct *task,

@@ -78,8 +81,11 @@ static inline void syscall_set_arguments(struct task_struct *task,
 					 const unsigned long *args)
 {
 	regs->orig_a0 = args[0];
-	args++;
-	memcpy(&regs->a1, args, 5 * sizeof(regs->a1));
+	regs->a1 = args[1];
+	regs->a2 = args[2];
+	regs->a3 = args[3];
+	regs->a4 = args[4];
+	regs->a5 = args[5];
 }
 

Quoted 3 lines

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

Quoted 1 line

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

 static inline int syscall_get_arch(struct task_struct *task)

Looks good, thanks. How do we proceed from this point?

I can send a standalone patch for syscall_get_arguments() since that is an issue present before your series then Andrew could fold in the same change for syscall_set_arguments() into your change that introduces it so there is no bisect problem?

Hi Dmitry,

[dropping majority of folks since this seems irrelevant to them]

Quoted 12 lines · Dmitry V. Levin

This function is 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]>

Acked-by Helge Deller <[email protected]> # parisc

Reviewed-by Maciej W. Rozycki <[email protected]> # mips

...

Quoted 6 lines

arch/riscv/include/asm/syscall.h +0 -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]));

arch/riscv/include/asm/syscall.h static inline void syscall_get_arguments(struct task_struct *task, · line 76

Quoted 10 lines

arch/riscv/include/asm/syscall.h +8 -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));
+}

This upsets the compiletime fortify checks, as I see a warning after syscall_set_arguments() starts being used in kernel/ptrace.c later in the series.

  $ make -skj"$(nproc)" ARCH=riscv CROSS_COMPILE=riscv64-linux- allmodconfig kernel/ptrace.o
  In file included from include/linux/string.h:392,
                   from include/linux/bitmap.h:13,
                   from include/linux/cpumask.h:12,
                   from arch/riscv/include/asm/processor.h:55,
                   from include/linux/sched.h:13,
                   from kernel/ptrace.c:13:
  In function 'fortify_memcpy_chk',
      inlined from 'syscall_set_arguments.isra' at arch/riscv/include/asm/syscall.h:82:2:
  include/linux/fortify-string.h:571:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
    571 |                         __write_overflow_field(p_size_field, size);
        |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  cc1: all warnings being treated as errors

The compiler knows the size of the destination and the size to be copied so it knows there will be an (intentional) overwrite here. struct_group() would normally work but I think this structure already has a struct_group() around some of the members that would be needed. I build tested eliminating the memcpy() altogether, which would appear to work, but I am not sure if there is a better solution, hence just the report.

Cheers,
Nathan

arch/riscv/include/asm/syscall.h +5 -2

index a5281cdf2b10..70ec19dc8506 100644
@@ -78,8 +78,11 @@ static inline void syscall_set_arguments(struct task_struct *task,
                                         const unsigned long *args)
 {
        regs->orig_a0 = args[0];
-       args++;
-       memcpy(&regs->a1, args, 5 * sizeof(regs->a1));
+       regs->a1 = args[1];
+       regs->a2 = args[2];
+       regs->a3 = args[3];
+       regs->a4 = args[4];
+       regs->a5 = args[5];
 }
 
 static inline int syscall_get_arch(struct task_struct *task)

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, providing a consistent way of manipulating the system call number and arguments across architectures.

As in case of PTRACE_GET_SYSCALL_INFO, PTRACE_SET_SYSCALL_INFO also does not aim to address numerous architecture-specific system call ABI peculiarities, like differences in the number of system call arguments for such system calls as pread64 and preadv.

The current implementation supports changing only those bits of system call information that are used by strace system call tampering, 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" and "reserved" fields of struct ptrace_syscall_info must be initialized with zeroes; "arch", "instruction_pointer", and "stack_pointer" fields are currently 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 [1].

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)).

[1] https://lore.kernel.org/all/[email protected]/

Notes:
v7:
* csky: Fix typo in comment
* mips: syscall_set_arguments: Remove mips_syscall_is_indirect check
* mips: syscall_set_nr: Reword comment
* mips: Add Reviewed-by
* v6: https://lore.kernel.org/all/[email protected]/

v6:
* mips: Submit mips_get_syscall_arg() o32 fix via mips tree to get it merged into v6.14-rc3
* Rebase to v6.14-rc3
* v5: https://lore.kernel.org/all/[email protected]/

v5:
* ptrace: Extend the commit message to say that the new API does not aim to address numerous architecture-specific syscall ABI peculiarities
* selftests: Add a workaround for s390 16-bit syscall numbers
* parisc: Add Acked-by
* v4: https://lore.kernel.org/all/[email protected]/

v4:
* Split out syscall_set_return_value() for hexagon into a separate patch
* s390: Change the style of syscall_set_arguments() implementation as requested
* ptrace: Add Reviewed-by
* v3: https://lore.kernel.org/all/[email protected]/

v3:
* powerpc: Submit syscall_set_return_value() fix for "sc" case separately
* mips: Do not introduce erroneous argument truncation on mips n32, add a detailed description to the commit message of the mips_get_syscall_arg() change
* 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
* riscv: Add Tested-by and Reviewed-by

v2:
* Add patch to fix syscall_set_return_value() on powerpc
* Add patch to fix mips_get_syscall_arg() on mips
* Add syscall_set_return_value() implementation on hexagon
* Add syscall_set_return_value() invocation to syscall_set_nr() on arm and arm64.
* Fix syscall_set_nr() and mips_set_syscall_arg() on mips
* Add a comment to syscall_set_nr() on arc, powerpc, s390, sh, and sparc
* Remove redundant ptrace_syscall_info.op assignments in ptrace_get_syscall_info_*
* Minor style tweaks in ptrace_get_syscall_info_op()
* Remove syscall_set_return_value() invocation from ptrace_set_syscall_info_entry()
* Skip syscall_set_arguments() invocation in case of syscall number -1 in ptrace_set_syscall_info_entry()
* Split ptrace_syscall_info.reserved into ptrace_syscall_info.reserved and ptrace_syscall_info.flags
* Use __kernel_ulong_t instead of unsigned long in set_syscall_info test

Dmitry V. Levin (6):
hexagon: add syscall_set_return_value()
syscall.h: add syscall_set_arguments()
syscall.h: introduce syscall_set_nr()
ptrace_get_syscall_info: factor out ptrace_get_syscall_info_op
ptrace: introduce PTRACE_SET_SYSCALL_INFO request selftests/ptrace: add a test case for PTRACE_SET_SYSCALL_INFO

 arch/arc/include/asm/syscall.h                |  25 +
 arch/arm/include/asm/syscall.h                |  37 ++
 arch/arm64/include/asm/syscall.h              |  29 +
 arch/csky/include/asm/syscall.h               |  13 +
 arch/hexagon/include/asm/syscall.h            |  21 +
 arch/loongarch/include/asm/syscall.h          |  15 +
 arch/m68k/include/asm/syscall.h               |   7 +
 arch/microblaze/include/asm/syscall.h         |   7 +
 arch/mips/include/asm/syscall.h               |  43 ++
 arch/nios2/include/asm/syscall.h              |  16 +
 arch/openrisc/include/asm/syscall.h           |  13 +
 arch/parisc/include/asm/syscall.h             |  19 +
 arch/powerpc/include/asm/syscall.h            |  20 +
 arch/riscv/include/asm/syscall.h              |  16 +
 arch/s390/include/asm/syscall.h               |  21 +
 arch/sh/include/asm/syscall_32.h              |  24 +
 arch/sparc/include/asm/syscall.h              |  22 +
 arch/um/include/asm/syscall-generic.h         |  19 +
 arch/x86/include/asm/syscall.h                |  43 ++
 arch/xtensa/include/asm/syscall.h             |  18 +
 include/asm-generic/syscall.h                 |  30 +
 include/uapi/linux/ptrace.h                   |   7 +-
 kernel/ptrace.c                               | 179 +++++-
 tools/testing/selftests/ptrace/Makefile       |   2 +-
 .../selftests/ptrace/set_syscall_info.c       | 519 ++++++++++++++++++
 25 files changed, 1138 insertions(+), 27 deletions(-)
 create mode 100644 tools/testing/selftests/ptrace/set_syscall_info.c

base-commit: 7eb172143d5508b4da468ed59ee857c6e5e01da6

Andrew, could you take this patchset into your tree, please?

It has been under review for almost two months, the last reply was two weeks ago, and by now all activity seems to be over. The ptrace maintainer approved the ptrace-related patches of this patchset more than a month ago. Admittedly, most of architecture maintainers ignored the architecture-specific patches from this series, but this is expected, so I don't think it's worth waiting for their reaction any longer.

v7: https://lore.kernel.org/all/[email protected]/

[trimmed Cc list to save people from irrelevant ping messages.]

Quoted 148 lines · Dmitry V. Levin

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, providing a consistent way of manipulating the system call number and arguments across architectures.

As in case of PTRACE_GET_SYSCALL_INFO, PTRACE_SET_SYSCALL_INFO also does not aim to address numerous architecture-specific system call ABI peculiarities, like differences in the number of system call arguments for such system calls as pread64 and preadv.

The current implementation supports changing only those bits of system call information that are used by strace system call tampering, 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" and "reserved" fields of struct ptrace_syscall_info must be initialized with zeroes; "arch", "instruction_pointer", and "stack_pointer" fields are currently 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 [1].

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)).

[1] https://lore.kernel.org/all/[email protected]/

Notes:
v7:
* csky: Fix typo in comment
* mips: syscall_set_arguments: Remove mips_syscall_is_indirect check
* mips: syscall_set_nr: Reword comment
* mips: Add Reviewed-by
* v6: https://lore.kernel.org/all/[email protected]/

v6:
* mips: Submit mips_get_syscall_arg() o32 fix via mips tree to get it merged into v6.14-rc3
* Rebase to v6.14-rc3
* v5: https://lore.kernel.org/all/[email protected]/

v5:
* ptrace: Extend the commit message to say that the new API does not aim to address numerous architecture-specific syscall ABI peculiarities
* selftests: Add a workaround for s390 16-bit syscall numbers
* parisc: Add Acked-by
* v4: https://lore.kernel.org/all/[email protected]/

v4:
* Split out syscall_set_return_value() for hexagon into a separate patch
* s390: Change the style of syscall_set_arguments() implementation as requested
* ptrace: Add Reviewed-by
* v3: https://lore.kernel.org/all/[email protected]/

v3:
* powerpc: Submit syscall_set_return_value() fix for "sc" case separately
* mips: Do not introduce erroneous argument truncation on mips n32, add a detailed description to the commit message of the mips_get_syscall_arg() change
* 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
* riscv: Add Tested-by and Reviewed-by

v2:
* Add patch to fix syscall_set_return_value() on powerpc
* Add patch to fix mips_get_syscall_arg() on mips
* Add syscall_set_return_value() implementation on hexagon
* Add syscall_set_return_value() invocation to syscall_set_nr() on arm and arm64.
* Fix syscall_set_nr() and mips_set_syscall_arg() on mips
* Add a comment to syscall_set_nr() on arc, powerpc, s390, sh, and sparc
* Remove redundant ptrace_syscall_info.op assignments in ptrace_get_syscall_info_*
* Minor style tweaks in ptrace_get_syscall_info_op()
* Remove syscall_set_return_value() invocation from ptrace_set_syscall_info_entry()
* Skip syscall_set_arguments() invocation in case of syscall number -1 in ptrace_set_syscall_info_entry()
* Split ptrace_syscall_info.reserved into ptrace_syscall_info.reserved and ptrace_syscall_info.flags
* Use __kernel_ulong_t instead of unsigned long in set_syscall_info test

Dmitry V. Levin (6):
hexagon: add syscall_set_return_value()
syscall.h: add syscall_set_arguments()
syscall.h: introduce syscall_set_nr()
ptrace_get_syscall_info: factor out ptrace_get_syscall_info_op
ptrace: introduce PTRACE_SET_SYSCALL_INFO request selftests/ptrace: add a test case for PTRACE_SET_SYSCALL_INFO

 arch/arc/include/asm/syscall.h                |  25 +
 arch/arm/include/asm/syscall.h                |  37 ++
 arch/arm64/include/asm/syscall.h              |  29 +
 arch/csky/include/asm/syscall.h               |  13 +
 arch/hexagon/include/asm/syscall.h            |  21 +
 arch/loongarch/include/asm/syscall.h          |  15 +
 arch/m68k/include/asm/syscall.h               |   7 +
 arch/microblaze/include/asm/syscall.h         |   7 +
 arch/mips/include/asm/syscall.h               |  43 ++
 arch/nios2/include/asm/syscall.h              |  16 +
 arch/openrisc/include/asm/syscall.h           |  13 +
 arch/parisc/include/asm/syscall.h             |  19 +
 arch/powerpc/include/asm/syscall.h            |  20 +
 arch/riscv/include/asm/syscall.h              |  16 +
 arch/s390/include/asm/syscall.h               |  21 +
 arch/sh/include/asm/syscall_32.h              |  24 +
 arch/sparc/include/asm/syscall.h              |  22 +
 arch/um/include/asm/syscall-generic.h         |  19 +
 arch/x86/include/asm/syscall.h                |  43 ++
 arch/xtensa/include/asm/syscall.h             |  18 +
 include/asm-generic/syscall.h                 |  30 +
 include/uapi/linux/ptrace.h                   |   7 +-
 kernel/ptrace.c                               | 179 +++++-
 tools/testing/selftests/ptrace/Makefile       |   2 +-
 .../selftests/ptrace/set_syscall_info.c       | 519 ++++++++++++++++++
 25 files changed, 1138 insertions(+), 27 deletions(-)
 create mode 100644 tools/testing/selftests/ptrace/set_syscall_info.c

base-commit: 7eb172143d5508b4da468ed59ee857c6e5e01da6

Signature · 1 line

ldv

Quoted 9 lines · Dmitry V. Levin

Andrew, could you take this patchset into your tree, please?

It has been under review for almost two months, the last reply was two weeks ago, and by now all activity seems to be over. The ptrace maintainer approved the ptrace-related patches of this patchset more than a month ago. Admittedly, most of architecture maintainers ignored the architecture-specific patches from this series, but this is expected, so I don't think it's worth waiting for their reaction any longer.

Quoted 1 line

v7: https://lore.kernel.org/all/[email protected]/

Andrew, could you take this patchset into your tree, please?

Nothing has changed since v7, so I have nothing new to add to the text written above.