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um: further clean up user_syms

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Make some cleanups, add and fix some comments and document
here that we shouldn't export (libc) symbols for "_user.c"
code, rather such should work like hostfs does now.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Johannes Berg 2023-02-10 22:05:10 +01:00 committed by Richard Weinberger
parent 6d708d1a0d
commit 5d90cf6dcc
1 changed files with 16 additions and 15 deletions
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31
arch/um/os-Linux/user_syms.c
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@ -3,35 +3,36 @@
#include <linux/types.h>
#include <linux/module.h>
/* Some of this are builtin function (some are not but could in the future),
* so I *must* declare good prototypes for them and then EXPORT them.
* The kernel code uses the macro defined by include/linux/string.h,
* so I undef macros; the userspace code does not include that and I
* add an EXPORT for the glibc one.
/*
* This file exports some critical string functions and compiler
* built-in functions (where calls are emitted by the compiler
* itself that we cannot avoid even in kernel code) to modules.
*
* "_user.c" code that previously used exports here such as hostfs
* really should be considered part of the 'hypervisor' and define
* its own API boundary like hostfs does now; don't add exports to
* this file for such cases.
*/
#undef strlen
#undef strstr
#undef memcpy
#undef memset
extern size_t strlen(const char *);
extern void *memmove(void *, const void *, size_t);
extern void *memset(void *, int, size_t);
/* If it's not defined, the export is included in lib/string.c.*/
#ifdef __HAVE_ARCH_STRSTR
#undef strstr
EXPORT_SYMBOL(strstr);
#endif
#ifndef __x86_64__
#undef memcpy
extern void *memcpy(void *, const void *, size_t);
EXPORT_SYMBOL(memcpy);
extern void *memmove(void *, const void *, size_t);
EXPORT_SYMBOL(memmove);
#undef memset
extern void *memset(void *, int, size_t);
EXPORT_SYMBOL(memset);
#endif
#ifdef CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA
/* needed for __access_ok() */
EXPORT_SYMBOL(vsyscall_ehdr);
EXPORT_SYMBOL(vsyscall_end);
#endif
@ -44,6 +45,6 @@ extern long __guard __attribute__((weak));
EXPORT_SYMBOL(__guard);
#ifdef _FORTIFY_SOURCE
extern int __sprintf_chk(char *str, int flag, size_t strlen, const char *format);
extern int __sprintf_chk(char *str, int flag, size_t len, const char *format);
EXPORT_SYMBOL(__sprintf_chk);
#endif