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b5325b2a27
Give userspace a way to instruct the kernel to install a pidfd into the usermode helper process. This makes coredump handling a lot more reliable for userspace. In parallel with this commit we already have systemd adding support for this in [1]. We create a pidfs file for the coredumping process when we process the corename pattern. When the usermode helper process is forked we then install the pidfs file as file descriptor three into the usermode helpers file descriptor table so it's available to the exec'd program. Since usermode helpers are either children of the system_unbound_wq workqueue or kthreadd we know that the file descriptor table is empty and can thus always use three as the file descriptor number. Note, that we'll install a pidfd for the thread-group leader even if a subthread is calling do_coredump(). We know that task linkage hasn't been removed due to delay_group_leader() and even if this @current isn't the actual thread-group leader we know that the thread-group leader cannot be reaped until @current has exited. Link: https://github.com/systemd/systemd/pull/37125 [1] Link: https://lore.kernel.org/20250414-work-coredump-v2-3-685bf231f828@kernel.org Tested-by: Luca Boccassi <luca.boccassi@gmail.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Christian Brauner <brauner@kernel.org>
80 lines
2.2 KiB
C
80 lines
2.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_COREDUMP_H
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#define _LINUX_COREDUMP_H
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#include <linux/types.h>
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#include <linux/mm.h>
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#include <linux/fs.h>
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#include <asm/siginfo.h>
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#ifdef CONFIG_COREDUMP
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struct core_vma_metadata {
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unsigned long start, end;
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unsigned long flags;
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unsigned long dump_size;
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unsigned long pgoff;
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struct file *file;
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};
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struct coredump_params {
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const kernel_siginfo_t *siginfo;
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struct file *file;
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unsigned long limit;
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unsigned long mm_flags;
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int cpu;
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loff_t written;
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loff_t pos;
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loff_t to_skip;
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int vma_count;
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size_t vma_data_size;
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struct core_vma_metadata *vma_meta;
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struct pid *pid;
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};
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extern unsigned int core_file_note_size_limit;
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/*
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* These are the only things you should do on a core-file: use only these
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* functions to write out all the necessary info.
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*/
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extern void dump_skip_to(struct coredump_params *cprm, unsigned long to);
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extern void dump_skip(struct coredump_params *cprm, size_t nr);
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extern int dump_emit(struct coredump_params *cprm, const void *addr, int nr);
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extern int dump_align(struct coredump_params *cprm, int align);
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int dump_user_range(struct coredump_params *cprm, unsigned long start,
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unsigned long len);
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extern void do_coredump(const kernel_siginfo_t *siginfo);
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/*
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* Logging for the coredump code, ratelimited.
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* The TGID and comm fields are added to the message.
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*/
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#define __COREDUMP_PRINTK(Level, Format, ...) \
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do { \
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char comm[TASK_COMM_LEN]; \
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/* This will always be NUL terminated. */ \
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memcpy(comm, current->comm, sizeof(comm)); \
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printk_ratelimited(Level "coredump: %d(%*pE): " Format "\n", \
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task_tgid_vnr(current), (int)strlen(comm), comm, ##__VA_ARGS__); \
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} while (0) \
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#define coredump_report(fmt, ...) __COREDUMP_PRINTK(KERN_INFO, fmt, ##__VA_ARGS__)
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#define coredump_report_failure(fmt, ...) __COREDUMP_PRINTK(KERN_WARNING, fmt, ##__VA_ARGS__)
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#else
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static inline void do_coredump(const kernel_siginfo_t *siginfo) {}
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#define coredump_report(...)
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#define coredump_report_failure(...)
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#endif
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#if defined(CONFIG_COREDUMP) && defined(CONFIG_SYSCTL)
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extern void validate_coredump_safety(void);
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#else
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static inline void validate_coredump_safety(void) {}
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#endif
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#endif /* _LINUX_COREDUMP_H */
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