Re: [PATCH] Core dump file control

From: Michael Sinz (msinz@wgate.com)
Date: Thu Feb 14 2002 - 12:53:24 EST

Michael Sinz wrote:
>
> I have, for a long time, wished that Linux had a way to specify where
> core dumps are stored and what the name of the core dump is. Now that
> I have been building large linux clusters with many diskless nodes,
> this need has become even more important.

[...]

This patch is the one for Linux 2.5.4 (albeit not as heavily tested) 

-- 
Michael Sinz ---- Worldgate Communications ---- msinz@wgate.com
A master's secrets are only as good as
	the master's ability to explain them to others.

diff -urP linux-2.5.4/fs/exec.c linux-2.5.4-patch/fs/exec.c --- linux-2.5.4/fs/exec.c Sun Feb 10 20:50:15 2002 +++ linux-2.5.4-patch/fs/exec.c Thu Feb 14 12:45:00 2002 @@ -35,6 +35,7 @@ #include <linux/highmem.h> #include <linux/spinlock.h> #include <linux/personality.h> +#include <linux/utsname.h> #include <linux/binfmts.h> #define __NO_VERSION__ #include <linux/module.h> @@ -49,6 +50,12 @@ int core_uses_pid; +/* The format string for the core file name... + We default to "core" such that past behavior + remains unchanged. The 64 character limit is + arbitrary but must match the sysctl table. */ +char core_name_format[64] = {"core"}; + static struct linux_binfmt *formats; static rwlock_t binfmt_lock = RW_LOCK_UNLOCKED; @@ -934,14 +941,37 @@ __MOD_DEC_USE_COUNT(old->module); } +/* This is the maximum expanded core file name. We use + a reasonable number here since we use the stack to + do the expansion. However, the number should be big + enough to handle a reasonable command name plus PID + and/or UID in addition to the file name part that + is in the core_name_format string. */ +#define MAX_CORE_NAME (160) + int do_coredump(long signr, struct pt_regs * regs) { struct linux_binfmt * binfmt; - char corename[6+sizeof(current->comm)+10]; struct file * file; struct inode * inode; int retval = 0; + int fmt_i; + int name_n; + int addPID; + char *cname; + + /* The +11 is here to simplify the code path. What + we do is always check that we are less than MAX + but there are times when we also need to append + a number (such as the PID or UID). Rather than + using another temporary buffer, we provide for + enough extra space such that those numbers can + be added in one gulp even if we are just under + the MAX_CORE_NAME. Reduction in complexity of + the code path means a more reliable implementation. */ + char corename[MAX_CORE_NAME + 1 + 11]; + lock_kernel(); binfmt = current->binfmt; if (!binfmt || !binfmt->core_dump) @@ -952,10 +982,92 @@ if (current->rlim[RLIMIT_CORE].rlim_cur < binfmt->min_coredump) goto fail; - memcpy(corename,"core.", 5); - corename[4] = '\0'; - if (core_uses_pid || atomic_read(&current->mm->mm_users) != 1) - sprintf(&corename[4], ".%d", current->pid); + /* Set this to true if we are going to add the PID. If the PID + already is added in the format we will end up clearing this. + The purpose is to provide for the old behavior of adding the + PID to the core file name but to not add it if it already + was included via the file name format pattern. */ + addPID = (core_uses_pid || atomic_read(&current->mm->mm_users) != 1); + + /* Build the core file name as needed from the format string */ + for (fmt_i=0, name_n=0; + name_n < MAX_CORE_NAME && core_name_format[fmt_i]; + fmt_i++) + { + switch (core_name_format[fmt_i]) + { + case '%': /* A format character */ + fmt_i++; + switch (core_name_format[fmt_i]) + { + case '%': /* The way we get this character */ + corename[name_n++] = '%'; + break; + + case 'N': /* Process name */ + cname=current->comm; + + /* Only copy as much as will fit within the + MAX_CORE_NAME */ + while (*cname && (name_n < MAX_CORE_NAME)) + { + if (*cname != '/') + corename[name_n++] = *cname; + cname++; + } + break; + + case 'H': /* Node name */ + cname=system_utsname.nodename; + + /* Only copy as much as will fit within the + MAX_CORE_NAME */ + while (*cname && (name_n < MAX_CORE_NAME)) + { + if (*cname != '/') + corename[name_n++] = *cname; + cname++; + } + break; + + case 'P': /* Process PID */ + /* Since we are adding it here, don't append */ + addPID=0; + + /* We don't need to pre-check that the number + fits since we added a padding of 11 + characters to the end of the string buffer + just so that we don't need to do an extra + check */ + name_n += sprintf(&corename[name_n],"%d",current->pid); + break; + + case 'U': /* UID of the process */ + /* We don't need to pre-check that the number + fits since we added a padding of 11 + characters to the end of the string buffer + just so that we don't need to do an extra + check */ + name_n += sprintf(&corename[name_n],"%d",current->uid); + break; + } + break; + + default: /* Anything else just pass along */ + corename[name_n++] = core_name_format[fmt_i]; + } + } + + /* If we still want to append the PID and there is room, do so */ + /* This is to preserve current behavior */ + if (addPID && (name_n < MAX_CORE_NAME)) + { + name_n += sprintf(&corename[name_n],".%d",current->pid); + } + + /* And make sure to null terminate the string */ + corename[name_n]='\0'; + file = filp_open(corename, O_CREAT | 2 | O_NOFOLLOW, 0600); if (IS_ERR(file)) goto fail; diff -urP linux-2.5.4/include/linux/sysctl.h linux-2.5.4-patch/include/linux/sysctl.h --- linux-2.5.4/include/linux/sysctl.h Sun Feb 10 20:50:07 2002 +++ linux-2.5.4-patch/include/linux/sysctl.h Thu Feb 14 12:43:52 2002 @@ -124,6 +124,7 @@ KERN_CORE_USES_PID=52, /* int: use core or core.%pid */ KERN_TAINTED=53, /* int: various kernel tainted flags */ KERN_CADPID=54, /* int: PID of the process to notify on CAD */ + KERN_CORE_NAME_FORMAT=55, /* string: core file name format string */ }; diff -urP linux-2.5.4/kernel/sysctl.c linux-2.5.4-patch/kernel/sysctl.c --- linux-2.5.4/kernel/sysctl.c Sun Feb 10 20:50:09 2002 +++ linux-2.5.4-patch/kernel/sysctl.c Thu Feb 14 12:43:52 2002 @@ -50,6 +50,7 @@ extern int max_queued_signals; extern int sysrq_enabled; extern int core_uses_pid; +extern char core_name_format[]; extern int cad_pid; /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */ @@ -172,6 +173,8 @@ 0644, NULL, &proc_dointvec}, {KERN_CORE_USES_PID, "core_uses_pid", &core_uses_pid, sizeof(int), 0644, NULL, &proc_dointvec}, + {KERN_CORE_NAME_FORMAT, "core_name_format", core_name_format, 64, + 0644, NULL, &proc_doutsstring, &sysctl_string}, {KERN_TAINTED, "tainted", &tainted, sizeof(int), 0644, NULL, &proc_dointvec}, {KERN_CAP_BSET, "cap-bound", &cap_bset, sizeof(kernel_cap_t),

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This archive was generated by hypermail 2b29 : Fri Feb 15 2002 - 21:01:03 EST