diff options
Diffstat (limited to 'usr/src/uts/common/io/mem.c')
| -rw-r--r-- | usr/src/uts/common/io/mem.c | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/usr/src/uts/common/io/mem.c b/usr/src/uts/common/io/mem.c index 7a703c5750..c0173a6f42 100644 --- a/usr/src/uts/common/io/mem.c +++ b/usr/src/uts/common/io/mem.c @@ -24,6 +24,10 @@ */ /* + * Copyright (c) 2015, Joyent, Inc. All rights reserved. + */ + +/* * Memory special file */ @@ -95,6 +99,49 @@ static int mm_kstat_snapshot(kstat_t *ksp, void *buf, int rw); static int mm_read_mem_name(intptr_t data, mem_name_t *mem_name); +#define MM_KMEMLOG_NENTRIES 64 + +static int mm_kmemlogent; +static mm_logentry_t mm_kmemlog[MM_KMEMLOG_NENTRIES]; + +/* + * On kmem/allmem writes, we log information that might be useful in the event + * that a write is errant (that is, due to operator error) and induces a later + * problem. Note that (in particular) in the event of such operator-induced + * corruption, a search over the kernel address space for the corrupted + * address will yield the ring buffer entry that recorded the write. And + * should it seem baroque or otherwise unnecessary, yes, we need this kind of + * auditing facility and yes, we learned that the hard way: disturbingly, + * there exist recommendations for "tuning" the system that involve writing to + * kernel memory addresses via the kernel debugger, and -- as we discovered -- + * these can easily be applied incorrectly or unsafely, yielding an entirely + * undebuggable "can't happen" kind of panic. + */ +static void +mm_logkmem(struct uio *uio) +{ + mm_logentry_t *ent; + proc_t *p = curthread->t_procp; + + mutex_enter(&mm_lock); + + ent = &mm_kmemlog[mm_kmemlogent++]; + + if (mm_kmemlogent == MM_KMEMLOG_NENTRIES) + mm_kmemlogent = 0; + + ent->mle_vaddr = (uintptr_t)uio->uio_loffset; + ent->mle_len = uio->uio_resid; + gethrestime(&ent->mle_hrestime); + ent->mle_hrtime = gethrtime(); + ent->mle_pid = p->p_pidp->pid_id; + + (void) strncpy(ent->mle_psargs, + p->p_user.u_psargs, sizeof (ent->mle_psargs)); + + mutex_exit(&mm_lock); +} + /*ARGSUSED1*/ static int mm_attach(dev_info_t *devi, ddi_attach_cmd_t cmd) @@ -354,6 +401,9 @@ mmrw(dev_t dev, struct uio *uio, enum uio_rw rw, cred_t *cred) if ((error = plat_mem_do_mmio(uio, rw)) != ENOTSUP) break; + if (rw == UIO_WRITE) + mm_logkmem(uio); + /* * If vaddr does not map a valid page, as_pagelock() * will return failure. Hence we can't check the |