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The get_stack_info() functionality is needed in the entry code for the
#VC exception handler. Provide a version of it in the .text.noinstr
section which can be called safely from there.
Signed-off-by: Joerg Roedel <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
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Both #DB itself, as all other IST users (NMI, #MC) now clear DR7 on
entry. Combined with not allowing breakpoints on entry/noinstr/NOKPROBE
text and no single step (EFLAGS.TF) inside the #DB handler should guarantee
no nested #DB.
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
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The replacement of <asm/pgrable.h> with <linux/pgtable.h> made the include
of the latter in the middle of asm includes. Fix this up with the aid of
the below script and manual adjustments here and there.
import sys
import re
if len(sys.argv) is not 3:
print "USAGE: %s <file> <header>" % (sys.argv[0])
sys.exit(1)
hdr_to_move="#include <linux/%s>" % sys.argv[2]
moved = False
in_hdrs = False
with open(sys.argv[1], "r") as f:
lines = f.readlines()
for _line in lines:
line = _line.rstrip('
')
if line == hdr_to_move:
continue
if line.startswith("#include <linux/"):
in_hdrs = True
elif not moved and in_hdrs:
moved = True
print hdr_to_move
print line
Signed-off-by: Mike Rapoport <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Cain <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Chris Zankel <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Greentime Hu <[email protected]>
Cc: Greg Ungerer <[email protected]>
Cc: Guan Xuetao <[email protected]>
Cc: Guo Ren <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Ley Foon Tan <[email protected]>
Cc: Mark Salter <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Max Filippov <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Michal Simek <[email protected]>
Cc: Nick Hu <[email protected]>
Cc: Paul Walmsley <[email protected]>
Cc: Richard Weinberger <[email protected]>
Cc: Rich Felker <[email protected]>
Cc: Russell King <[email protected]>
Cc: Stafford Horne <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Vincent Chen <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Yoshinori Sato <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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The include/linux/pgtable.h is going to be the home of generic page table
manipulation functions.
Start with moving asm-generic/pgtable.h to include/linux/pgtable.h and
make the latter include asm/pgtable.h.
Signed-off-by: Mike Rapoport <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Cain <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Chris Zankel <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Greentime Hu <[email protected]>
Cc: Greg Ungerer <[email protected]>
Cc: Guan Xuetao <[email protected]>
Cc: Guo Ren <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Ley Foon Tan <[email protected]>
Cc: Mark Salter <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Max Filippov <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Michal Simek <[email protected]>
Cc: Nick Hu <[email protected]>
Cc: Paul Walmsley <[email protected]>
Cc: Richard Weinberger <[email protected]>
Cc: Rich Felker <[email protected]>
Cc: Russell King <[email protected]>
Cc: Stafford Horne <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Vincent Chen <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Yoshinori Sato <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>
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Make the doublefault exception handler unconditional on 32-bit. Yes,
it is important to be able to catch #DF exceptions instead of silent
reboots. Yes, the code size increase is worth every byte. And one less
CONFIG symbol is just the cherry on top.
No functional changes.
Signed-off-by: Borislav Petkov <[email protected]>
Acked-by: Andy Lutomirski <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
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There are three problems with the current layout of the doublefault
stack and TSS. First, the TSS is only cacheline-aligned, which is
not enough -- if the hardware portion of the TSS (struct x86_hw_tss)
crosses a page boundary, horrible things happen [0]. Second, the
stack and TSS are global, so simultaneous double faults on different
CPUs will cause massive corruption. Third, the whole mechanism
won't work if user CR3 is loaded, resulting in a triple fault [1].
Let the doublefault stack and TSS share a page (which prevents the
TSS from spanning a page boundary), make it percpu, and move it into
cpu_entry_area. Teach the stack dump code about the doublefault
stack.
[0] Real hardware will read past the end of the page onto the next
*physical* page if a task switch happens. Virtual machines may
have any number of bugs, and I would consider it reasonable for
a VM to summarily kill the guest if it tries to task-switch to
a page-spanning TSS.
[1] Real hardware triple faults. At least some VMs seem to hang.
I'm not sure what's going on.
Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Linus Torvalds <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 iopl updates from Ingo Molnar:
"This implements a nice simplification of the iopl and ioperm code that
Thomas Gleixner discovered: we can implement the IO privilege features
of the iopl system call by using the IO permission bitmap in
permissive mode, while trapping CLI/STI/POPF/PUSHF uses in user-space
if they change the interrupt flag.
This implements that feature, with testing facilities and related
cleanups"
[ "Simplification" may be an over-statement. The main goal is to avoid
the cli/sti of iopl by effectively implementing the IO port access
parts of iopl in terms of ioperm.
This may end up not workign well in case people actually depend on
cli/sti being available, or if there are mixed uses of iopl and
ioperm. We will see.. - Linus ]
* 'x86-iopl-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits)
x86/ioperm: Fix use of deprecated config option
x86/entry/32: Clarify register saving in __switch_to_asm()
selftests/x86/iopl: Extend test to cover IOPL emulation
x86/ioperm: Extend IOPL config to control ioperm() as well
x86/iopl: Remove legacy IOPL option
x86/iopl: Restrict iopl() permission scope
x86/iopl: Fixup misleading comment
selftests/x86/ioperm: Extend testing so the shared bitmap is exercised
x86/ioperm: Share I/O bitmap if identical
x86/ioperm: Remove bitmap if all permissions dropped
x86/ioperm: Move TSS bitmap update to exit to user work
x86/ioperm: Add bitmap sequence number
x86/ioperm: Move iobitmap data into a struct
x86/tss: Move I/O bitmap data into a seperate struct
x86/io: Speedup schedule out of I/O bitmap user
x86/ioperm: Avoid bitmap allocation if no permissions are set
x86/ioperm: Simplify first ioperm() invocation logic
x86/iopl: Cleanup include maze
x86/tss: Fix and move VMX BUILD_BUG_ON()
x86/cpu: Unify cpu_init()
...
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the CPU_ENTRY_AREA_PAGES assert precise
When two recent commits that increased the size of the 'struct cpu_entry_area'
were merged in -tip, the 32-bit defconfig build started failing on the following
build time assert:
./include/linux/compiler.h:391:38: error: call to ‘__compiletime_assert_189’ declared with attribute error: BUILD_BUG_ON failed: CPU_ENTRY_AREA_PAGES * PAGE_SIZE < CPU_ENTRY_AREA_MAP_SIZE
arch/x86/mm/cpu_entry_area.c:189:2: note: in expansion of macro ‘BUILD_BUG_ON’
In function ‘setup_cpu_entry_area_ptes’,
Which corresponds to the following build time assert:
BUILD_BUG_ON(CPU_ENTRY_AREA_PAGES * PAGE_SIZE < CPU_ENTRY_AREA_MAP_SIZE);
The purpose of this assert is to sanity check the fixed-value definition of
CPU_ENTRY_AREA_PAGES arch/x86/include/asm/pgtable_32_types.h:
#define CPU_ENTRY_AREA_PAGES (NR_CPUS * 41)
The '41' is supposed to match sizeof(struct cpu_entry_area)/PAGE_SIZE, which value
we didn't want to define in such a low level header, because it would cause
dependency hell.
Every time the size of cpu_entry_area is changed, we have to adjust CPU_ENTRY_AREA_PAGES
accordingly - and this assert is checking that constraint.
But the assert is both imprecise and buggy, primarily because it doesn't
include the single readonly IDT page that is mapped at CPU_ENTRY_AREA_BASE
(which begins at a PMD boundary).
This bug was hidden by the fact that by accident CPU_ENTRY_AREA_PAGES is defined
too large upstream (v5.4-rc8):
#define CPU_ENTRY_AREA_PAGES (NR_CPUS * 40)
While 'struct cpu_entry_area' is 155648 bytes, or 38 pages. So we had two extra
pages, which hid the bug.
The following commit (not yet upstream) increased the size to 40 pages:
x86/iopl: ("Restrict iopl() permission scope")
... but increased CPU_ENTRY_AREA_PAGES only 41 - i.e. shortening the gap
to just 1 extra page.
Then another not-yet-upstream commit changed the size again:
880a98c33996: ("x86/cpu_entry_area: Add guard page for entry stack on 32bit")
Which increased the cpu_entry_area size from 38 to 39 pages, but
didn't change CPU_ENTRY_AREA_PAGES (kept it at 40). This worked
fine, because we still had a page left from the accidental 'reserve'.
But when these two commits were merged into the same tree, the
combined size of cpu_entry_area grew from 38 to 40 pages, while
CPU_ENTRY_AREA_PAGES finally caught up to 40 as well.
Which is fine in terms of functionality, but the assert broke:
BUILD_BUG_ON(CPU_ENTRY_AREA_PAGES * PAGE_SIZE < CPU_ENTRY_AREA_MAP_SIZE);
because CPU_ENTRY_AREA_MAP_SIZE is the total size of the area,
which is 1 page larger due to the IDT page.
To fix all this, change the assert to two precise asserts:
BUILD_BUG_ON((CPU_ENTRY_AREA_PAGES+1)*PAGE_SIZE != CPU_ENTRY_AREA_MAP_SIZE);
BUILD_BUG_ON(CPU_ENTRY_AREA_TOTAL_SIZE != CPU_ENTRY_AREA_MAP_SIZE);
This takes the IDT page into account, and also connects the size-based
define of CPU_ENTRY_AREA_TOTAL_SIZE with the address-subtraction based
define of CPU_ENTRY_AREA_MAP_SIZE.
Also clean up some of the names which made it rather confusing:
- 'CPU_ENTRY_AREA_TOT_SIZE' wasn't actually the 'total' size of
the cpu-entry-area, but the per-cpu array size, so rename this
to CPU_ENTRY_AREA_ARRAY_SIZE.
- Introduce CPU_ENTRY_AREA_TOTAL_SIZE that _is_ the total mapping
size, with the IDT included.
- Add comments where '+1' denotes the IDT mapping - it wasn't
obvious and took me about 3 hours to decode...
Finally, because this particular commit is actually applied after
this patch:
880a98c33996: ("x86/cpu_entry_area: Add guard page for entry stack on 32bit")
Fix the CPU_ENTRY_AREA_PAGES value from 40 pages to the correct 39 pages.
All future commits that change cpu_entry_area will have to adjust
this value precisely.
As a side note, we should probably attempt to remove CPU_ENTRY_AREA_PAGES
and derive its value directly from the structure, without causing
header hell - but that is an adventure for another day! :-)
Fixes: 880a98c33996: ("x86/cpu_entry_area: Add guard page for entry stack on 32bit")
Cc: Thomas Gleixner <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>
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The BUILD_BUG_ON(IO_BITMAP_OFFSET - 1 == 0x67) in the VMX code is bogus in
two aspects:
1) This wants to be in generic x86 code simply to catch issues even when
VMX is disabled in Kconfig.
2) The IO_BITMAP_OFFSET is not the right thing to check because it makes
asssumptions about the layout of tss_struct. Nothing requires that the
I/O bitmap is placed right after x86_tss, which is the hardware mandated
tss structure. It pointlessly makes restrictions on the struct
tss_struct layout.
The proper thing to check is:
- Offset of x86_tss in tss_struct is 0
- Size of x86_tss == 0x68
Move it to the other build time TSS checks and make it do the right thing.
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Paolo Bonzini <[email protected]>
Acked-by: Andy Lutomirski <[email protected]>
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The debug IST stack is actually two separate debug stacks to handle #DB
recursion. This is required because the CPU starts always at top of stack
on exception entry, which means on #DB recursion the second #DB would
overwrite the stack of the first.
The low level entry code therefore adjusts the top of stack on entry so a
secondary #DB starts from a different stack page. But the stack pages are
adjacent without a guard page between them.
Split the debug stack into 3 stacks which are separated by guard pages. The
3rd stack is never mapped into the cpu_entry_area and is only there to
catch triple #DB nesting:
--- top of DB_stack <- Initial stack
--- end of DB_stack
guard page
--- top of DB1_stack <- Top of stack after entering first #DB
--- end of DB1_stack
guard page
--- top of DB2_stack <- Top of stack after entering second #DB
--- end of DB2_stack
guard page
If DB2 would not act as the final guard hole, a second #DB would point the
top of #DB stack to the stack below #DB1 which would be valid and not catch
the not so desired triple nesting.
The backing store does not allocate any memory for DB2 and its guard page
as it is not going to be mapped into the cpu_entry_area.
- Adjust the low level entry code so it adjusts top of #DB with the offset
between the stacks instead of exception stack size.
- Make the dumpstack code aware of the new stacks.
- Adjust the in_debug_stack() implementation and move it into the NMI code
where it belongs. As this is NMI hotpath code, it just checks the full
area between top of DB_stack and bottom of DB1_stack without checking
for the guard page. That's correct because the NMI cannot hit a
stackpointer pointing to the guard page between DB and DB1 stack. Even
if it would, then the NMI operation still is unaffected, but the resume
of the debug exception on the topmost DB stack will crash by touching
the guard page.
[ bp: Make exception_stack_names static const char * const ]
Suggested-by: Andy Lutomirski <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Sean Christopherson <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: "Chang S. Bae" <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Dominik Brodowski <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: [email protected]
Cc: Masahiro Yamada <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Qian Cai <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
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Store a pointer to the per cpu entry area exception stack mappings to allow
fast retrieval.
Required for converting various places from using the shadow IST array to
directly doing address calculations on the actual mapping address.
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
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To allow guard pages between the IST stacks each stack needs to be
mapped individually.
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
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At the moment everything assumes a full linear mapping of the various
exception stacks. Adding guard pages to the cpu entry area mapping of the
exception stacks will break that assumption.
As a preparatory step convert both the real storage and the effective
mapping in the cpu entry area from character arrays to structures.
To ensure that both arrays have the same ordering and the same size of the
individual stacks fill the members with a macro. The guard size is the only
difference between the two resulting structures. For now both have guard
size 0 until the preparation of all usage sites is done.
Provide a couple of helper macros which are used in the following
conversions.
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Sean Christopherson <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: "Chang S. Bae" <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Dominik Brodowski <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
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No point in retrieving the entry area pointer over and over. Do it once
and use unsigned int for 'cpu' everywhere.
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Sean Christopherson <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
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WARNING: vmlinux.o(.text.unlikely+0x498d): Section mismatch in reference
from the function percpu_setup_debug_store() to the function
.init.text:cea_map_percpu_pages()
Signed-off-by: Sergey Senozhatsky <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: "H . Peter Anvin" <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
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The SYSCALL64 trampoline has a couple of nice properties:
- The usual sequence of SWAPGS followed by two GS-relative accesses to
set up RSP is somewhat slow because the GS-relative accesses need
to wait for SWAPGS to finish. The trampoline approach allows
RIP-relative accesses to set up RSP, which avoids the stall.
- The trampoline avoids any percpu access before CR3 is set up,
which means that no percpu memory needs to be mapped in the user
page tables. This prevents using Meltdown to read any percpu memory
outside the cpu_entry_area and prevents using timing leaks
to directly locate the percpu areas.
The downsides of using a trampoline may outweigh the upsides, however.
It adds an extra non-contiguous I$ cache line to system calls, and it
forces an indirect jump to transfer control back to the normal kernel
text after CR3 is set up. The latter is because x86 lacks a 64-bit
direct jump instruction that could jump from the trampoline to the entry
text. With retpolines enabled, the indirect jump is extremely slow.
Change the code to map the percpu TSS into the user page tables to allow
the non-trampoline SYSCALL64 path to work under PTI. This does not add a
new direct information leak, since the TSS is readable by Meltdown from the
cpu_entry_area alias regardless. It does allow a timing attack to locate
the percpu area, but KASLR is more or less a lost cause against local
attack on CPUs vulnerable to Meltdown regardless. As far as I'm concerned,
on current hardware, KASLR is only useful to mitigate remote attacks that
try to attack the kernel without first gaining RCE against a vulnerable
user process.
On Skylake, with CONFIG_RETPOLINE=y and KPTI on, this reduces syscall
overhead from ~237ns to ~228ns.
There is a possible alternative approach: Move the trampoline within 2G of
the entry text and make a separate copy for each CPU. This would allow a
direct jump to rejoin the normal entry path. There are pro's and con's for
this approach:
+ It avoids a pipeline stall
- It executes from an extra page and read from another extra page during
the syscall. The latter is because it needs to use a relative
addressing mode to find sp1 -- it's the same *cacheline*, but accessed
using an alias, so it's an extra TLB entry.
- Slightly more memory. This would be one page per CPU for a simple
implementation and 64-ish bytes per CPU or one page per node for a more
complex implementation.
- More code complexity.
The current approach is chosen for simplicity and because the alternative
does not provide a significant benefit, which makes it worth.
[ tglx: Added the alternative discussion to the changelog ]
Signed-off-by: Andy Lutomirski <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Borislav Petkov <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lkml.kernel.org/r/8c7c6e483612c3e4e10ca89495dc160b1aa66878.1536015544.git.luto@kernel.org
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Without program headers for PTI entry trampoline pages, the trampoline
virtual addresses do not map to anything.
Example before:
sudo gdb --quiet vmlinux /proc/kcore
Reading symbols from vmlinux...done.
[New process 1]
Core was generated by `BOOT_IMAGE=/boot/vmlinuz-4.16.0 root=UUID=a6096b83-b763-4101-807e-f33daff63233'.
#0 0x0000000000000000 in irq_stack_union ()
(gdb) x /21ib 0xfffffe0000006000
0xfffffe0000006000: Cannot access memory at address 0xfffffe0000006000
(gdb) quit
After:
sudo gdb --quiet vmlinux /proc/kcore
[sudo] password for ahunter:
Reading symbols from vmlinux...done.
[New process 1]
Core was generated by `BOOT_IMAGE=/boot/vmlinuz-4.16.0-fix-4-00005-gd6e65a8b4072 root=UUID=a6096b83-b7'.
#0 0x0000000000000000 in irq_stack_union ()
(gdb) x /21ib 0xfffffe0000006000
0xfffffe0000006000: swapgs
0xfffffe0000006003: mov %rsp,-0x3e12(%rip) # 0xfffffe00000021f8
0xfffffe000000600a: xchg %ax,%ax
0xfffffe000000600c: mov %cr3,%rsp
0xfffffe000000600f: bts $0x3f,%rsp
0xfffffe0000006014: and $0xffffffffffffe7ff,%rsp
0xfffffe000000601b: mov %rsp,%cr3
0xfffffe000000601e: mov -0x3019(%rip),%rsp # 0xfffffe000000300c
0xfffffe0000006025: pushq $0x2b
0xfffffe0000006027: pushq -0x3e35(%rip) # 0xfffffe00000021f8
0xfffffe000000602d: push %r11
0xfffffe000000602f: pushq $0x33
0xfffffe0000006031: push %rcx
0xfffffe0000006032: push %rdi
0xfffffe0000006033: mov $0xffffffff91a00010,%rdi
0xfffffe000000603a: callq 0xfffffe0000006046
0xfffffe000000603f: pause
0xfffffe0000006041: lfence
0xfffffe0000006044: jmp 0xfffffe000000603f
0xfffffe0000006046: mov %rdi,(%rsp)
0xfffffe000000604a: retq
(gdb) quit
In addition, entry trampolines all map to the same page. Represent that
by giving the corresponding program headers in kcore the same offset.
This has the benefit that, when perf tools uses /proc/kcore as a source
for kernel object code, samples from different CPU trampolines are
aggregated together. Note, such aggregation is normal for profiling
i.e. people want to profile the object code, not every different virtual
address the object code might be mapped to (across different processes
for example).
Notes by PeterZ:
This also adds the KCORE_REMAP functionality.
Signed-off-by: Adrian Hunter <[email protected]>
Acked-by: Andi Kleen <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
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Currently, the addresses of PTI entry trampolines are not exported to
user space. Kernel profiling tools need these addresses to identify the
kernel code, so add a symbol and address for each CPU's PTI entry
trampoline.
Signed-off-by: Alexander Shishkin <[email protected]>
Acked-by: Andi Kleen <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
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The entry/exit text and cpu_entry_area are mapped into userspace and
the kernel. But, they are not _PAGE_GLOBAL. This creates unnecessary
TLB misses.
Add the _PAGE_GLOBAL flag for these areas.
Signed-off-by: Dave Hansen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arjan van de Ven <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Nadav Amit <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
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The separation of the cpu_entry_area from the fixmap missed the fact that
on 32bit non-PAE kernels the cpu_entry_area mapping might not be covered in
initial_page_table by the previous synchronizations.
This results in suspend/resume failures because 32bit utilizes initial page
table for resume. The absence of the cpu_entry_area mapping results in a
triple fault, aka. insta reboot.
With PAE enabled this works by chance because the PGD entry which covers
the fixmap and other parts incindentally provides the cpu_entry_area
mapping as well.
Synchronize the initial page table after setting up the cpu entry
area. Instead of adding yet another copy of the same code, move it to a
function and invoke it from the various places.
It needs to be investigated if the existing calls in setup_arch() and
setup_per_cpu_areas() can be replaced by the later invocation from
setup_cpu_entry_areas(), but that's beyond the scope of this fix.
Fixes: 92a0f81d8957 ("x86/cpu_entry_area: Move it out of the fixmap")
Reported-by: Woody Suwalski <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Woody Suwalski <[email protected]>
Cc: William Grant <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
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The Intel PEBS/BTS debug store is a design trainwreck as it expects virtual
addresses which must be visible in any execution context.
So it is required to make these mappings visible to user space when kernel
page table isolation is active.
Provide enough room for the buffer mappings in the cpu_entry_area so the
buffers are available in the user space visible page tables.
At the point where the kernel side entry area is populated there is no
buffer available yet, but the kernel PMD must be populated. To achieve this
set the entries for these buffers to non present.
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Laight <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: Eduardo Valentin <[email protected]>
Cc: Greg KH <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>
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The loop which populates the CPU entry area PMDs can wrap around on 32bit
machines when the number of CPUs is small.
It worked wonderful for NR_CPUS=64 for whatever reason and the moron who
wrote that code did not bother to test it with !SMP.
Check for the wraparound to fix it.
Fixes: 92a0f81d8957 ("x86/cpu_entry_area: Move it out of the fixmap")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Thomas "Feels stupid" Gleixner <[email protected]>
Tested-by: Borislav Petkov <[email protected]>
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Put the cpu_entry_area into a separate P4D entry. The fixmap gets too big
and 0-day already hit a case where the fixmap PTEs were cleared by
cleanup_highmap().
Aside of that the fixmap API is a pain as it's all backwards.
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>
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Separate the cpu_entry_area code out of cpu/common.c and the fixmap.
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
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