get_mempolicy

Implemented in Antinomie 0.7.0 · Syscall list

Synopsis

long get_mempolicy(int *policy, unsigned long *nmask, unsigned long maxnode, unsigned long addr, unsigned long flags);


Number (x86-64)	239
ABI	common
Kernel entry point	`sys_get_mempolicy`

This is the raw kernel prototype from the pinned Linux 6.12.94 schema, not the libc wrapper.

Description

Reads the NUMA memory policy of a thread or of an address.

Arguments

Name	Type	Meaning
`policy` (arg0)	`int *`	Scheduling or memory policy.
`nmask` (arg1)	`unsigned long *`	Pointer to a node mask.
`maxnode` (arg2)	`unsigned long`	Number of bits in a node mask.
`addr` (arg3)	`unsigned long`	Memory or socket address, depending on the call.
`flags` (arg4)	`unsigned long`	Option flags that change the behavior of the call.

Return value

On success: 0.

In an Antinomie trace the Return column and the ret filter field show the raw kernel return value. On failure that is the negative errno, for example -2 for ENOENT, not the -1 plus errno that the libc wrapper gives. syscall.errno holds the positive errno and syscall.success is false.

Common errors

Raw return	Name	Meaning
`-14`	`EFAULT`	A pointer argument points outside the accessible address space.
`-22`	`EINVAL`	An argument is invalid.

Man page

get_mempolicy(2) on man7.org

Captured by Antinomie

Coverage mark: Implemented. Every pointer argument has a capture rule in the pinned kernel patch and none of them records a “no decoder”, “address only” or “not observed” gap on any code path. Individual values can still be incomplete on a particular call; see the capture statuses.

Every call is recorded as an Entry record (the six argument words and the pointees copied at entry) and an Exit record (the return value and the pointees copied at exit).

Arguments

Argument	When	How	Recorded field key	Condition
`policy` (arg0)	Entry	the pointer itself, as a raw word	`args.0`, `args.raw[0]`
↳ pointee	Exit	`int` policy	`arg0.policy`	result is 0 and the pointer is not NULL
`nmask` (arg1)	Entry	the pointer itself, as a raw word	`args.1`, `args.raw[1]`
↳ pointee	Exit	node mask, bits from `maxnode` (arg2) - 1	`arg1.node_mask`	result is 0
`maxnode` (arg2)	Entry	raw scalar word	`args.2`, `args.maxnode`
`addr` (arg3)	Entry	raw scalar word	`args.3`, `args.addr`
`flags` (arg4)	Entry	raw scalar word; Syscall Trace also decodes it into flag names (`mempolicy_get` group), listing unknown bits separately	`args.4`, `args.flags`

Filter fields

Result: ret, syscall.errno, syscall.success, syscall.duration_ns.
Argument words: args.policy (arg0), args.nmask (arg1), args.maxnode (arg2), args.addr (arg3), args.flags (arg4); args.0 to args.5 by position.
Structure wait_status behind policy (arg0): args.policy.<member> for value.
Structure unsigned_long[] behind nmask (arg1): args.nmask.<member> for value.

See Syscall Trace filter for the full syntax.

For what the capture statuses mean, see Capture statuses. For what is never recorded, see Known gaps.