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authorLinus Torvalds <torvalds@linux-foundation.org>2018-07-21 16:52:08 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-07-21 16:52:08 -0700
commitea75a2c715a4bf682c756d4754665fb3595f3531 (patch)
treeee2b4979e9c3b7b35dae23578264c1dfa2a55c72
parentMerge tag 'powerpc-4.18-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux (diff)
parentx86/asm/memcpy_mcsafe: Fix copy_to_user_mcsafe() exception handling (diff)
downloadlinux-dev-ea75a2c715a4bf682c756d4754665fb3595f3531.tar.xz
linux-dev-ea75a2c715a4bf682c756d4754665fb3595f3531.zip
Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core kernel fixes from Ingo Molnar: "This is mostly the copy_to_user_mcsafe() related fixes from Dan Williams, and an ORC fix for Clang" * 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/asm/memcpy_mcsafe: Fix copy_to_user_mcsafe() exception handling lib/iov_iter: Fix pipe handling in _copy_to_iter_mcsafe() lib/iov_iter: Document _copy_to_iter_flushcache() lib/iov_iter: Document _copy_to_iter_mcsafe() objtool: Use '.strtab' if '.shstrtab' doesn't exist, to support ORC tables on Clang
-rw-r--r--arch/x86/Kconfig2
-rw-r--r--arch/x86/include/asm/uaccess_64.h7
-rw-r--r--lib/iov_iter.c77
-rw-r--r--tools/objtool/elf.c6
4 files changed, 84 insertions, 8 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f1dbb4ee19d7..887d3a7bb646 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -63,7 +63,7 @@ config X86
select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_REFCOUNT
select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64
- select ARCH_HAS_UACCESS_MCSAFE if X86_64
+ select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE
select ARCH_HAS_SET_MEMORY
select ARCH_HAS_SG_CHAIN
select ARCH_HAS_STRICT_KERNEL_RWX
diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index 62acb613114b..a9d637bc301d 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -52,7 +52,12 @@ copy_to_user_mcsafe(void *to, const void *from, unsigned len)
unsigned long ret;
__uaccess_begin();
- ret = memcpy_mcsafe(to, from, len);
+ /*
+ * Note, __memcpy_mcsafe() is explicitly used since it can
+ * handle exceptions / faults. memcpy_mcsafe() may fall back to
+ * memcpy() which lacks this handling.
+ */
+ ret = __memcpy_mcsafe(to, from, len);
__uaccess_end();
return ret;
}
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 7e43cd54c84c..8be175df3075 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -596,15 +596,70 @@ static unsigned long memcpy_mcsafe_to_page(struct page *page, size_t offset,
return ret;
}
+static size_t copy_pipe_to_iter_mcsafe(const void *addr, size_t bytes,
+ struct iov_iter *i)
+{
+ struct pipe_inode_info *pipe = i->pipe;
+ size_t n, off, xfer = 0;
+ int idx;
+
+ if (!sanity(i))
+ return 0;
+
+ bytes = n = push_pipe(i, bytes, &idx, &off);
+ if (unlikely(!n))
+ return 0;
+ for ( ; n; idx = next_idx(idx, pipe), off = 0) {
+ size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
+ unsigned long rem;
+
+ rem = memcpy_mcsafe_to_page(pipe->bufs[idx].page, off, addr,
+ chunk);
+ i->idx = idx;
+ i->iov_offset = off + chunk - rem;
+ xfer += chunk - rem;
+ if (rem)
+ break;
+ n -= chunk;
+ addr += chunk;
+ }
+ i->count -= xfer;
+ return xfer;
+}
+
+/**
+ * _copy_to_iter_mcsafe - copy to user with source-read error exception handling
+ * @addr: source kernel address
+ * @bytes: total transfer length
+ * @iter: destination iterator
+ *
+ * The pmem driver arranges for filesystem-dax to use this facility via
+ * dax_copy_to_iter() for protecting read/write to persistent memory.
+ * Unless / until an architecture can guarantee identical performance
+ * between _copy_to_iter_mcsafe() and _copy_to_iter() it would be a
+ * performance regression to switch more users to the mcsafe version.
+ *
+ * Otherwise, the main differences between this and typical _copy_to_iter().
+ *
+ * * Typical tail/residue handling after a fault retries the copy
+ * byte-by-byte until the fault happens again. Re-triggering machine
+ * checks is potentially fatal so the implementation uses source
+ * alignment and poison alignment assumptions to avoid re-triggering
+ * hardware exceptions.
+ *
+ * * ITER_KVEC, ITER_PIPE, and ITER_BVEC can return short copies.
+ * Compare to copy_to_iter() where only ITER_IOVEC attempts might return
+ * a short copy.
+ *
+ * See MCSAFE_TEST for self-test.
+ */
size_t _copy_to_iter_mcsafe(const void *addr, size_t bytes, struct iov_iter *i)
{
const char *from = addr;
unsigned long rem, curr_addr, s_addr = (unsigned long) addr;
- if (unlikely(i->type & ITER_PIPE)) {
- WARN_ON(1);
- return 0;
- }
+ if (unlikely(i->type & ITER_PIPE))
+ return copy_pipe_to_iter_mcsafe(addr, bytes, i);
if (iter_is_iovec(i))
might_fault();
iterate_and_advance(i, bytes, v,
@@ -701,6 +756,20 @@ size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
EXPORT_SYMBOL(_copy_from_iter_nocache);
#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
+/**
+ * _copy_from_iter_flushcache - write destination through cpu cache
+ * @addr: destination kernel address
+ * @bytes: total transfer length
+ * @iter: source iterator
+ *
+ * The pmem driver arranges for filesystem-dax to use this facility via
+ * dax_copy_from_iter() for ensuring that writes to persistent memory
+ * are flushed through the CPU cache. It is differentiated from
+ * _copy_from_iter_nocache() in that guarantees all data is flushed for
+ * all iterator types. The _copy_from_iter_nocache() only attempts to
+ * bypass the cache for the ITER_IOVEC case, and on some archs may use
+ * instructions that strand dirty-data in the cache.
+ */
size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
{
char *to = addr;
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 0d1acb704f64..7ec85d567598 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -519,10 +519,12 @@ struct section *elf_create_section(struct elf *elf, const char *name,
sec->sh.sh_flags = SHF_ALLOC;
- /* Add section name to .shstrtab */
+ /* Add section name to .shstrtab (or .strtab for Clang) */
shstrtab = find_section_by_name(elf, ".shstrtab");
+ if (!shstrtab)
+ shstrtab = find_section_by_name(elf, ".strtab");
if (!shstrtab) {
- WARN("can't find .shstrtab section");
+ WARN("can't find .shstrtab or .strtab section");
return NULL;
}