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arm64: vdso: Map the vDSO text with guarded pages when built for BTI 

The kernel is responsible for mapping the vDSO into userspace processes,
including mapping the text section as executable. Handle the mapping of
the vDSO for BTI similarly, mapping the text section as guarded pages so
the BTI annotations in the vDSO become effective when they are present.

This will mean that we can have BTI active for the vDSO in processes that
do not otherwise support BTI. This should not be an issue for any expected
use of the vDSO.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20200506195138.22086-12-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Mark Brown 2020-05-06 20:51:38 +01:00 committed by Will Deacon
parent 5e02a1887f
commit bf740a905f
1 changed files with 5 additions and 1 deletions
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6
arch/arm64/kernel/vdso.c
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@ -142,6 +142,7 @@ static int __setup_additional_pages(enum arch_vdso_type arch_index,
int uses_interp)
{
unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
unsigned long gp_flags = 0;
void *ret;
vdso_text_len = vdso_lookup[arch_index].vdso_pages << PAGE_SHIFT;
@ -160,10 +161,13 @@ static int __setup_additional_pages(enum arch_vdso_type arch_index,
if (IS_ERR(ret))
goto up_fail;
if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
gp_flags = VM_ARM64_BTI;
vdso_base += PAGE_SIZE;
mm->context.vdso = (void *)vdso_base;
ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
VM_READ|VM_EXEC|
VM_READ|VM_EXEC|gp_flags|
VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
vdso_lookup[arch_index].cm);
if (IS_ERR(ret))