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linprocfs: Skip printing of the guard page in the /proc/self/maps

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To calculate the base (lowest addressable) address of the stack of the
initial thread glibc parses /proc/self/maps.
In fact, the base address is calculated as 'to' value of stack entry of the
/proc/self/maps - stack size limit (if the stack grows down).
The base address should fit in between preceding entry and stack entry of
the /proc/self/maps.
In FreeBSD, since 19bd0d9 (Implement address space guards), we actually
have two mappings for the stack region. The first one is the no-access
mapping for the region the stack can grow into (guard page), and the
second - initial stack region with size sgrowsiz.
The first mapping confuses Glibc, in the end which is improperly
calculate stack size and the base address.

PR:			253337
Reviewed by:		kib
Differential revision:	https://reviews.freebsd.org/D35537
MFC after:		2 week
This commit is contained in:
Dmitry Chagin 2022-06-22 14:49:40 +03:00
parent 4d496ab44a
commit ef1976ccf5
1 changed files with 7 additions and 1 deletions
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8
sys/compat/linprocfs/linprocfs.c
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@ -1307,7 +1307,13 @@ linprocfs_doprocmaps(PFS_FILL_ARGS)
VM_MAP_ENTRY_FOREACH(entry, map) {
name = "";
freename = NULL;
if (entry->eflags & MAP_ENTRY_IS_SUB_MAP)
/*
* Skip printing of the guard page of the stack region, as
* it confuses glibc pthread_getattr_np() method, where both
* the base address and size of the stack of the initial thread
* are calculated.
*/
if ((entry->eflags & (MAP_ENTRY_IS_SUB_MAP | MAP_ENTRY_GUARD)) != 0)
continue;
e_prot = entry->protection;
e_start = entry->start;