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[wasm] Enable PKU usage on patched kernels

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The 5.4 and 5.10 kernels received a patch for PKRU handling, which
landed in 5.4.182 and 5.10.103.
See "x86/fpu: Correct pkru/xstate inconsistency" by Brian Geffon
<bgeffon@google.com>:
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.4.182
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.10.103

R=jkummerow@chromium.org

Bug: v8:11974
Change-Id: Ie2d4840f9fbd902a0988c94c50ab450485d9117c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3506991
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79405}
This commit is contained in:
Clemens Backes 2022-03-07 13:45:39 +01:00 committed by V8 LUCI CQ
parent 53f20f3db7
commit 0215c53789
1 changed files with 15 additions and 7 deletions
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22
src/wasm/memory-protection-key.cc
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@ -66,18 +66,26 @@ void InitializeMemoryProtectionKeySupport() {
// Flip {pkey_initialized} (in debug mode) and check the new value.
DCHECK_EQ(true, pkey_initialized = !pkey_initialized);
#if defined(V8_OS_LINUX) && defined(V8_HOST_ARCH_X64)
// PKU is broken on Linux kernels before 5.13 (see
// PKU was broken on Linux kernels before 5.13 (see
// https://lore.kernel.org/all/20210623121456.399107624@linutronix.de/).
// Thus check the kernel version we are running on, and bail out if it's
// not at least 5.13.
// A fix is also included in the 5.4.182 and 5.10.103 versions ("x86/fpu:
// Correct pkru/xstate inconsistency" by Brian Geffon <bgeffon@google.com>).
// Thus check the kernel version we are running on, and bail out if does not
// contain the fix.
struct utsname uname_buffer;
CHECK_EQ(0, uname(&uname_buffer));
int major, minor;
int kernel, major, minor;
// Conservatively return if the release does not match the format we expect.
if (sscanf(uname_buffer.release, "%d.%d.", &major, &minor) != 2) return;
if (major < 5 || (major == 5 && minor < 13)) return;
if (sscanf(uname_buffer.release, "%d.%d.%d", &kernel, &major, &minor) != 3) {
return;
}
bool kernel_has_pkru_fix =
kernel > 5 || (kernel == 5 && major >= 13) || // anything >= 5.13
(kernel == 5 && major == 4 && minor >= 182) || // 5.4 >= 5.4.182
(kernel == 5 && major == 10 && minor >= 103); // 5.10 >= 5.10.103
if (!kernel_has_pkru_fix) return;
// Try to to find the pkey functions in glibc.
// Try to find the pkey functions in glibc.
void* pkey_alloc_ptr = dlsym(RTLD_DEFAULT, "pkey_alloc");
if (!pkey_alloc_ptr) return;