diff options
| author | Alexander Potapenko <glider@google.com> | 2018-05-09 11:18:22 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-05-14 11:14:30 +0200 |
| commit | 4a09f0210c8b1221aae8afda8bd3a603fece0986 (patch) | |
| tree | caf78773f04aa44afa5a4eba51056a7e247a1b23 /arch/x86/kernel/head64.c | |
| parent | 4fe875e4bd3cae85ae6f6eaf77f63fabe613b66e (diff) | |
| download | linux-4a09f0210c8b1221aae8afda8bd3a603fece0986.tar.bz2 | |
x86/boot/64/clang: Use fixup_pointer() to access '__supported_pte_mask'
Clang builds with defconfig started crashing after the following
commit:
fb43d6cb91ef ("x86/mm: Do not auto-massage page protections")
This was caused by introducing a new global access in __startup_64().
Code in __startup_64() can be relocated during execution, but the compiler
doesn't have to generate PC-relative relocations when accessing globals
from that function. Clang actually does not generate them, which leads
to boot-time crashes. To work around this problem, every global pointer
must be adjusted using fixup_pointer().
Signed-off-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: dvyukov@google.com
Cc: kirill.shutemov@linux.intel.com
Cc: linux-mm@kvack.org
Cc: md@google.com
Cc: mka@chromium.org
Fixes: fb43d6cb91ef ("x86/mm: Do not auto-massage page protections")
Link: http://lkml.kernel.org/r/20180509091822.191810-1-glider@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/head64.c')
| -rw-r--r-- | arch/x86/kernel/head64.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 0c408f8c4ed4..2d29e47c056e 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -104,6 +104,12 @@ static bool __head check_la57_support(unsigned long physaddr) } #endif +/* Code in __startup_64() can be relocated during execution, but the compiler + * doesn't have to generate PC-relative relocations when accessing globals from + * that function. Clang actually does not generate them, which leads to + * boot-time crashes. To work around this problem, every global pointer must + * be adjusted using fixup_pointer(). + */ unsigned long __head __startup_64(unsigned long physaddr, struct boot_params *bp) { @@ -113,6 +119,7 @@ unsigned long __head __startup_64(unsigned long physaddr, p4dval_t *p4d; pudval_t *pud; pmdval_t *pmd, pmd_entry; + pteval_t *mask_ptr; bool la57; int i; unsigned int *next_pgt_ptr; @@ -196,7 +203,8 @@ unsigned long __head __startup_64(unsigned long physaddr, pmd_entry = __PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL; /* Filter out unsupported __PAGE_KERNEL_* bits: */ - pmd_entry &= __supported_pte_mask; + mask_ptr = fixup_pointer(&__supported_pte_mask, physaddr); + pmd_entry &= *mask_ptr; pmd_entry += sme_get_me_mask(); pmd_entry += physaddr; |