diff options
| author | Dave Martin <Dave.Martin@arm.com> | 2020-03-16 16:50:45 +0000 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2020-03-16 17:19:48 +0000 |
| commit | 8ef8f360cf30be12382f89ff48a57fbbd9b31c14 (patch) | |
| tree | 6060caf0bfe50a4c370c86625b7325f6199b746a /Documentation/arm64 | |
| parent | 00e19ceec80b03a43f626f891fcc53e57919f1b3 (diff) | |
arm64: Basic Branch Target Identification support
This patch adds the bare minimum required to expose the ARMv8.5
Branch Target Identification feature to userspace.
By itself, this does _not_ automatically enable BTI for any initial
executable pages mapped by execve(). This will come later, but for
now it should be possible to enable BTI manually on those pages by
using mprotect() from within the target process.
Other arches already using the generic mman.h are already using
0x10 for arch-specific prot flags, so we use that for PROT_BTI
here.
For consistency, signal handler entry points in BTI guarded pages
are required to be annotated as such, just like any other function.
This blocks a relatively minor attack vector, but comforming
userspace will have the annotations anyway, so we may as well
enforce them.
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'Documentation/arm64')
| -rw-r--r-- | Documentation/arm64/cpu-feature-registers.rst | 2 | ||||
| -rw-r--r-- | Documentation/arm64/elf_hwcaps.rst | 5 |
2 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/arm64/cpu-feature-registers.rst b/Documentation/arm64/cpu-feature-registers.rst index 41937a8091aa..314fa5bc2655 100644 --- a/Documentation/arm64/cpu-feature-registers.rst +++ b/Documentation/arm64/cpu-feature-registers.rst @@ -176,6 +176,8 @@ infrastructure: +------------------------------+---------+---------+ | SSBS | [7-4] | y | +------------------------------+---------+---------+ + | BT | [3-0] | y | + +------------------------------+---------+---------+ 4) MIDR_EL1 - Main ID Register diff --git a/Documentation/arm64/elf_hwcaps.rst b/Documentation/arm64/elf_hwcaps.rst index 7dfb97dfe416..84a9fd2d41b4 100644 --- a/Documentation/arm64/elf_hwcaps.rst +++ b/Documentation/arm64/elf_hwcaps.rst @@ -236,6 +236,11 @@ HWCAP2_RNG Functionality implied by ID_AA64ISAR0_EL1.RNDR == 0b0001. +HWCAP2_BTI + + Functionality implied by ID_AA64PFR0_EL1.BT == 0b0001. + + 4. Unused AT_HWCAP bits ----------------------- |