From 6d77d3b43ad84a48b502f02dc618e7c36737bdfe Mon Sep 17 00:00:00 2001 From: Simon Ser Date: Mon, 9 Jul 2018 11:17:22 -0500 Subject: objtool: Use '.strtab' if '.shstrtab' doesn't exist, to support ORC tables on Clang Clang puts its section header names in the '.strtab' section instead of '.shstrtab', which causes objtool to fail with a "can't find .shstrtab section" warning when attempting to write ORC metadata to an object file. If '.shstrtab' doesn't exist, use '.strtab' instead. Signed-off-by: Simon Ser Signed-off-by: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/d1c1c3fe55872be433da7bc5e1860538506229ba.1531153015.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- tools/objtool/elf.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) 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; } -- cgit v1.2.3 From bf3eeb9b5f2a1a05b3a68c6d82112babd58d6a39 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Sun, 8 Jul 2018 13:46:02 -0700 Subject: lib/iov_iter: Document _copy_to_iter_mcsafe() Add some theory of operation documentation to _copy_to_iter_mcsafe(). Reported-by: Al Viro Signed-off-by: Dan Williams Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Tony Luck Link: http://lkml.kernel.org/r/153108276256.37979.1689794213845539316.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Ingo Molnar --- lib/iov_iter.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 7e43cd54c84c..94fa361be7bb 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -596,6 +596,32 @@ static unsigned long memcpy_mcsafe_to_page(struct page *page, size_t offset, return ret; } +/** + * _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; -- cgit v1.2.3 From abd08d7d245397bcbded8c6c29ff79a36b3875b0 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Sun, 8 Jul 2018 13:46:07 -0700 Subject: lib/iov_iter: Document _copy_to_iter_flushcache() Add some theory of operation documentation to _copy_to_iter_flushcache(). Reported-by: Al Viro Signed-off-by: Dan Williams Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Tony Luck Link: http://lkml.kernel.org/r/153108276767.37979.9462477994086841699.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Ingo Molnar --- lib/iov_iter.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 94fa361be7bb..09fb73ad9d54 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -727,6 +727,20 @@ 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; -- cgit v1.2.3 From ca146f6f091e47b3fd18d6a7e76ec0297d202e0f Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Sun, 8 Jul 2018 13:46:12 -0700 Subject: lib/iov_iter: Fix pipe handling in _copy_to_iter_mcsafe() By mistake the ITER_PIPE early-exit / warning from copy_from_iter() was cargo-culted in _copy_to_iter_mcsafe() rather than a machine-check-safe version of copy_to_iter_pipe(). Implement copy_pipe_to_iter_mcsafe() being careful to return the indication of short copies due to a CPU exception. Without this regression-fix all splice reads to dax-mode files fail. Reported-by: Ross Zwisler Tested-by: Ross Zwisler Signed-off-by: Dan Williams Acked-by: Al Viro Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Tony Luck Fixes: 8780356ef630 ("x86/asm/memcpy_mcsafe: Define copy_to_iter_mcsafe()") Link: http://lkml.kernel.org/r/153108277278.37979.3327916996902264102.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Ingo Molnar --- lib/iov_iter.c | 37 +++++++++++++++++++++++++++++++++---- 1 file changed, 33 insertions(+), 4 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 09fb73ad9d54..8be175df3075 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -596,6 +596,37 @@ 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 @@ -627,10 +658,8 @@ 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, -- cgit v1.2.3 From 092b31aa2048cf7561a39697974adcd147fbb27b Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Sun, 8 Jul 2018 13:46:17 -0700 Subject: x86/asm/memcpy_mcsafe: Fix copy_to_user_mcsafe() exception handling All copy_to_user() implementations need to be prepared to handle faults accessing userspace. The __memcpy_mcsafe() implementation handles both mmu-faults on the user destination and machine-check-exceptions on the source buffer. However, the memcpy_mcsafe() wrapper may silently fallback to memcpy() depending on build options and cpu-capabilities. Force copy_to_user_mcsafe() to always use __memcpy_mcsafe() when available, and otherwise disable all of the copy_to_user_mcsafe() infrastructure when __memcpy_mcsafe() is not available, i.e. CONFIG_X86_MCE=n. This fixes crashes of the form: run fstests generic/323 at 2018-07-02 12:46:23 BUG: unable to handle kernel paging request at 00007f0d50001000 RIP: 0010:__memcpy+0x12/0x20 [..] Call Trace: copyout_mcsafe+0x3a/0x50 _copy_to_iter_mcsafe+0xa1/0x4a0 ? dax_alive+0x30/0x50 dax_iomap_actor+0x1f9/0x280 ? dax_iomap_rw+0x100/0x100 iomap_apply+0xba/0x130 ? dax_iomap_rw+0x100/0x100 dax_iomap_rw+0x95/0x100 ? dax_iomap_rw+0x100/0x100 xfs_file_dax_read+0x7b/0x1d0 [xfs] xfs_file_read_iter+0xa7/0xc0 [xfs] aio_read+0x11c/0x1a0 Reported-by: Ross Zwisler Tested-by: Ross Zwisler Signed-off-by: Dan Williams Cc: Al Viro Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Tony Luck Fixes: 8780356ef630 ("x86/asm/memcpy_mcsafe: Define copy_to_iter_mcsafe()") Link: http://lkml.kernel.org/r/153108277790.37979.1486841789275803399.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Ingo Molnar --- arch/x86/Kconfig | 2 +- arch/x86/include/asm/uaccess_64.h | 7 ++++++- 2 files changed, 7 insertions(+), 2 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; } -- cgit v1.2.3