Re: [PATCH v2 3/7] syscall.h: add syscall_set_arguments() and syscall_set_return_value()

H. Peter Anvin
2025-01-17T01:03:52Z

I link the concept of this patchset, but *please* make it clear in the
comments that this does not solve the issue of 64-bit kernel arguments
on 32-bit systems being ABI specific.

This isn't unique to this patch in any way; the only way to handle it is
by keeping track of each ABI.

On 1/15/25 18:20, Charlie Jenkins wrote:
> On Mon, Jan 13, 2025 at 07:11:40PM +0200, Dmitry V. Levin wrote:
>> 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 <ldv@strace.io>
>> ---
>>
>> Note that I'm not a MIPS expert, I just added mips_set_syscall_arg() by
>> looking at mips_get_syscall_arg() and the result passes tests in qemu on
>> mips O32, mips64 O32, mips64 N32, and mips64 N64.
>>
>> 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(+)
>>
>> diff --git a/arch/arc/include/asm/syscall.h b/arch/arc/include/asm/syscall.h
>> index 9709256e31c8..89c1e1736356 100644
>> --- a/arch/arc/include/asm/syscall.h
>> +++ b/arch/arc/include/asm/syscall.h
>> @@ -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)
>> {
>> diff --git a/arch/arm/include/asm/syscall.h b/arch/arm/include/asm/syscall.h
>> index fe4326d938c1..21927fa0ae2b 100644
>> --- a/arch/arm/include/asm/syscall.h
>> +++ b/arch/arm/include/asm/syscall.h
>> @@ -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. */
>> diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
>> index ab8e14b96f68..76020b66286b 100644
>> --- a/arch/arm64/include/asm/syscall.h
>> +++ b/arch/arm64/include/asm/syscall.h
>> @@ -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.
>> diff --git a/arch/csky/include/asm/syscall.h b/arch/csky/include/asm/syscall.h
>> index 0de5734950bf..30403f7a0487 100644
>> --- a/arch/csky/include/asm/syscall.h
>> +++ b/arch/csky/include/asm/syscall.h
>> @@ -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)
>> {
>> diff --git a/arch/hexagon/include/asm/syscall.h b/arch/hexagon/include/asm/syscall.h
>> index f6e454f18038..1024a6548d78 100644
>> --- a/arch/hexagon/include/asm/syscall.h
>> +++ b/arch/hexagon/include/asm/syscall.h
>> @@ -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;
>> diff --git a/arch/loongarch/include/asm/syscall.h b/arch/loongarch/include/asm/syscall.h
>> index e286dc58476e..ff415b3c0a8e 100644
>> --- a/arch/loongarch/include/asm/syscall.h
>> +++ b/arch/loongarch/include/asm/syscall.h
>> @@ -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;
>> diff --git a/arch/mips/include/asm/syscall.h b/arch/mips/include/asm/syscall.h
>> index 2f85f2d8f754..3163d1506fae 100644
>> --- a/arch/mips/include/asm/syscall.h
>> +++ b/arch/mips/include/asm/syscall.h
>> @@ -76,6 +76,23 @@ 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)
>> {
>> @@ -122,6 +139,21 @@ 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[];
>> diff --git a/arch/nios2/include/asm/syscall.h b/arch/nios2/include/asm/syscall.h
>> index fff52205fb65..526449edd768 100644
>> --- a/arch/nios2/include/asm/syscall.h
>> +++ b/arch/nios2/include/asm/syscall.h
>> @@ -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;
>> diff --git a/arch/openrisc/include/asm/syscall.h b/arch/openrisc/include/asm/syscall.h
>> index 903ed882bdec..e6383be2a195 100644
>> --- a/arch/openrisc/include/asm/syscall.h
>> +++ b/arch/openrisc/include/asm/syscall.h
>> @@ -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;
>> diff --git a/arch/parisc/include/asm/syscall.h b/arch/parisc/include/asm/syscall.h
>> index 00b127a5e09b..b146d0ae4c77 100644
>> --- a/arch/parisc/include/asm/syscall.h
>> +++ b/arch/parisc/include/asm/syscall.h
>> @@ -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)
>> {
>> diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
>> index 422d7735ace6..521f279e6b33 100644
>> --- a/arch/powerpc/include/asm/syscall.h
>> +++ b/arch/powerpc/include/asm/syscall.h
>> @@ -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))
>> diff --git a/arch/riscv/include/asm/syscall.h b/arch/riscv/include/asm/syscall.h
>> index 121fff429dce..8d389ba995c8 100644
>> --- a/arch/riscv/include/asm/syscall.h
>> +++ b/arch/riscv/include/asm/syscall.h
>> @@ -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));
>> +}
>
> Looks good for riscv.
>
> Tested-by: Charlie Jenkins <charlie@rivosinc.com>
> Reviewed-by: Charlie Jenkins <charlie@rivosinc.com
>
>> +
>> static inline int syscall_get_arch(struct task_struct *task)
>> {
>> #ifdef CONFIG_64BIT
>> diff --git a/arch/s390/include/asm/syscall.h b/arch/s390/include/asm/syscall.h
>> index 27e3d804b311..b3dd883699e7 100644
>> --- a/arch/s390/include/asm/syscall.h
>> +++ b/arch/s390/include/asm/syscall.h
>> @@ -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
>> diff --git a/arch/sh/include/asm/syscall_32.h b/arch/sh/include/asm/syscall_32.h
>> index d87738eebe30..cb51a7528384 100644
>> --- a/arch/sh/include/asm/syscall_32.h
>> +++ b/arch/sh/include/asm/syscall_32.h
>> @@ -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;
>> diff --git a/arch/sparc/include/asm/syscall.h b/arch/sparc/include/asm/syscall.h
>> index 20c109ac8cc9..62a5a78804c4 100644
>> --- a/arch/sparc/include/asm/syscall.h
>> +++ b/arch/sparc/include/asm/syscall.h
>> @@ -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)
>> diff --git a/arch/um/include/asm/syscall-generic.h b/arch/um/include/asm/syscall-generic.h
>> index 172b74143c4b..2984feb9d576 100644
>> --- a/arch/um/include/asm/syscall-generic.h
>> +++ b/arch/um/include/asm/syscall-generic.h
>> @@ -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 */
>> diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
>> index 7c488ff0c764..b9c249dd9e3d 100644
>> --- a/arch/x86/include/asm/syscall.h
>> +++ b/arch/x86/include/asm/syscall.h
>> @@ -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. */
>> diff --git a/arch/xtensa/include/asm/syscall.h b/arch/xtensa/include/asm/syscall.h
>> index 5ee974bf8330..f9a671cbf933 100644
>> --- a/arch/xtensa/include/asm/syscall.h
>> +++ b/arch/xtensa/include/asm/syscall.h
>> @@ -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,
>> diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h
>> index 5a80fe728dc8..0f7b9a493de7 100644
>> --- a/include/asm-generic/syscall.h
>> +++ b/include/asm-generic/syscall.h
>> @@ -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
>> --
>> ldv