| Message ID | 20250217091034.GD18175@strace.io (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | ptrace: introduce PTRACE_SET_SYSCALL_INFO API | expand |
On Mon, 17 Feb 2025, Dmitry V. Levin wrote: > diff --git a/arch/mips/include/asm/syscall.h b/arch/mips/include/asm/syscall.h > index ea050b23d428..b956b015641c 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. That label is called `trace_a_syscall' in arch/mips/kernel/scall64-o32.S instead. To bring some order and avoid an inaccuracy here should the odd one be matched to the other three? > + * > + * 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) > { Otherwise: Reviewed-by: Maciej W. Rozycki <macro@orcam.me.uk> for this part, thank you! Maciej
On Wed, Feb 19, 2025 at 05:16:05PM +0000, Maciej W. Rozycki wrote: > On Mon, 17 Feb 2025, Dmitry V. Levin wrote: > > > diff --git a/arch/mips/include/asm/syscall.h b/arch/mips/include/asm/syscall.h > > index ea050b23d428..b956b015641c 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. > > That label is called `trace_a_syscall' in arch/mips/kernel/scall64-o32.S > instead. To bring some order and avoid an inaccuracy here should the odd > one be matched to the other three? Apparently, there are two instances of syscall_trace_entry(), one n32_syscall_trace_entry(), one trace_a_syscall(), and each of them is calling syscall_trace_enter(), not to be confused with syscall_trace_entry(): scall32-o32.S-syscall_trace_entry: scall32-o32.S- SAVE_STATIC scall32-o32.S- move a0, sp scall32-o32.S- scall32-o32.S: jal syscall_trace_enter scall32-o32.S- scall32-o32.S- bltz v0, 1f # seccomp failed? Skip syscall scall32-o32.S- scall32-o32.S- RESTORE_STATIC scall32-o32.S- lw v0, PT_R2(sp) # Restore syscall (maybe modified) -- scall64-n32.S-n32_syscall_trace_entry: scall64-n32.S- SAVE_STATIC scall64-n32.S- move a0, sp scall64-n32.S: jal syscall_trace_enter scall64-n32.S- scall64-n32.S- bltz v0, 1f # seccomp failed? Skip syscall scall64-n32.S- scall64-n32.S- RESTORE_STATIC scall64-n32.S- ld v0, PT_R2(sp) # Restore syscall (maybe modified) -- scall64-n64.S-syscall_trace_entry: scall64-n64.S- SAVE_STATIC scall64-n64.S- move a0, sp scall64-n64.S: jal syscall_trace_enter scall64-n64.S- scall64-n64.S- bltz v0, 1f # seccomp failed? Skip syscall scall64-n64.S- scall64-n64.S- RESTORE_STATIC scall64-n64.S- ld v0, PT_R2(sp) # Restore syscall (maybe modified) -- scall64-o32.S-trace_a_syscall: scall64-o32.S- SAVE_STATIC scall64-o32.S- sd a4, PT_R8(sp) # Save argument registers scall64-o32.S- sd a5, PT_R9(sp) scall64-o32.S- sd a6, PT_R10(sp) scall64-o32.S- sd a7, PT_R11(sp) # For indirect syscalls scall64-o32.S- scall64-o32.S- move a0, sp scall64-o32.S: jal syscall_trace_enter scall64-o32.S- scall64-o32.S- bltz v0, 1f # seccomp failed? Skip syscall scall64-o32.S- scall64-o32.S- RESTORE_STATIC scall64-o32.S- ld v0, PT_R2(sp) # Restore syscall (maybe modified) I'd change the wording of my comment rather than try to disentangle this. After all, the most important here is that the new syscall number is loaded from regs[2] right after the syscall_trace_enter() invocation. Would you be OK with the following wording: /* * New syscall number has to be assigned to regs[2] because it is * loaded from there unconditionally after syscall_trace_enter() * invocation. * * Consequently, if the syscall was indirect and nr != __NR_syscall, * then after this assignment the syscall will cease to be indirect. */ ?
On Wed, 19 Feb 2025, Dmitry V. Levin wrote: > > That label is called `trace_a_syscall' in arch/mips/kernel/scall64-o32.S > > instead. To bring some order and avoid an inaccuracy here should the odd > > one be matched to the other three? > > Apparently, there are two instances of syscall_trace_entry(), one > n32_syscall_trace_entry(), one trace_a_syscall(), and each of them > is calling syscall_trace_enter(), not to be confused with > syscall_trace_entry(): Oh dear! > I'd change the wording of my comment rather than try to disentangle this. > After all, the most important here is that the new syscall number is > loaded from regs[2] right after the syscall_trace_enter() invocation. Right. > Would you be OK with the following wording: > /* > * New syscall number has to be assigned to regs[2] because it is > * loaded from there unconditionally after syscall_trace_enter() > * invocation. May I suggest "[...] after return from syscall_trace_enter() invocation." instead? Minor reformatting might be required for better visual alignment though. Maciej
On Wed, Feb 19, 2025 at 07:20:33PM +0000, Maciej W. Rozycki wrote: > On Wed, 19 Feb 2025, Dmitry V. Levin wrote: [...] > > Would you be OK with the following wording: > > /* > > * New syscall number has to be assigned to regs[2] because it is > > * loaded from there unconditionally after syscall_trace_enter() > > * invocation. > > May I suggest "[...] after return from syscall_trace_enter() invocation." > instead? Minor reformatting might be required for better visual alignment > though. Like this: /* * New syscall number has to be assigned to regs[2] because * it is loaded from there unconditionally after return from * syscall_trace_enter() invocation. * * Consequently, if the syscall was indirect and nr != __NR_syscall, * then after this assignment the syscall will cease to be indirect. */ ?
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 ea050b23d428..b956b015641c 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 0e3296a32e6a..db6ca55564ff 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 292b412f4e9a..c5a3ad53beec 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