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Revision 55b6f763d8bcb5546997933105d66d3e6b080e6a authored by Johannes Berg on 05 February 2021, 02:32:28 UTC, committed by Linus Torvalds on 05 February 2021, 19:03:47 UTC 
init/gcov: allow CONFIG_CONSTRUCTORS on UML to fix module gcov
 
On ARCH=um, loading a module doesn't result in its constructors getting
called, which breaks module gcov since the debugfs files are never
registered.  On the other hand, in-kernel constructors have already been
called by the dynamic linker, so we can't call them again.

Get out of this conundrum by allowing CONFIG_CONSTRUCTORS to be
selected, but avoiding the in-kernel constructor calls.

Also remove the "if !UML" from GCOV selecting CONSTRUCTORS now, since we
really do want CONSTRUCTORS, just not kernel binary ones.

Link: https://lkml.kernel.org/r/20210120172041.c246a2cac2fb.I1358f584b76f1898373adfed77f4462c8705b736@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Raw File
min_addr.c 
// SPDX-License-Identifier: GPL-2.0
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/security.h>
#include <linux/sysctl.h>

/* amount of vm to protect from userspace access by both DAC and the LSM*/
unsigned long mmap_min_addr;
/* amount of vm to protect from userspace using CAP_SYS_RAWIO (DAC) */
unsigned long dac_mmap_min_addr = CONFIG_DEFAULT_MMAP_MIN_ADDR;
/* amount of vm to protect from userspace using the LSM = CONFIG_LSM_MMAP_MIN_ADDR */

/*
 * Update mmap_min_addr = max(dac_mmap_min_addr, CONFIG_LSM_MMAP_MIN_ADDR)
 */
static void update_mmap_min_addr(void)
{
#ifdef CONFIG_LSM_MMAP_MIN_ADDR
	if (dac_mmap_min_addr > CONFIG_LSM_MMAP_MIN_ADDR)
		mmap_min_addr = dac_mmap_min_addr;
	else
		mmap_min_addr = CONFIG_LSM_MMAP_MIN_ADDR;
#else
	mmap_min_addr = dac_mmap_min_addr;
#endif
}

/*
 * sysctl handler which just sets dac_mmap_min_addr = the new value and then
 * calls update_mmap_min_addr() so non MAP_FIXED hints get rounded properly
 */
int mmap_min_addr_handler(struct ctl_table *table, int write,
			  void *buffer, size_t *lenp, loff_t *ppos)
{
	int ret;

	if (write && !capable(CAP_SYS_RAWIO))
		return -EPERM;

	ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);

	update_mmap_min_addr();

	return ret;
}

static int __init init_mmap_min_addr(void)
{
	update_mmap_min_addr();

	return 0;
}
pure_initcall(init_mmap_min_addr);
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