From: Catalin Marinas <catalin.marinas@arm.com>
To: Szabolcs Nagy <szabolcs.nagy@arm.com>
Cc: "Mark Brown" <broonie@kernel.org>,
"Will Deacon" <will@kernel.org>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"Paul Elliott" <paul.elliott@arm.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Yu-cheng Yu" <yu-cheng.yu@intel.com>,
"Amit Kachhap" <amit.kachhap@arm.com>,
"Vincenzo Frascino" <vincenzo.frascino@arm.com>,
"Marc Zyngier" <maz@kernel.org>,
"Eugene Syromiatnikov" <esyr@redhat.com>,
"H . J . Lu " <hjl.tools@gmail.com>,
"Andrew Jones" <drjones@redhat.com>,
"Kees Cook" <keescook@chromium.org>,
"Arnd Bergmann" <arnd@arndb.de>, "Jann Horn" <jannh@google.com>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Kristina Martšenko" <kristina.martsenko@arm.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Florian Weimer" <fweimer@redhat.com>,
"Sudakshina Das" <sudi.das@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
linux-fsdevel@vger.kernel.org, nd@arm.com
Subject: Re: [PATCH v10 00/13] arm64: Branch Target Identification support
Date: Mon, 23 Mar 2020 12:21:44 +0000 [thread overview]
Message-ID: <20200323122143.GB4892@mbp> (raw)
In-Reply-To: <20200320173945.GC27072@arm.com>
On Fri, Mar 20, 2020 at 05:39:46PM +0000, Szabolcs Nagy wrote:
> The 03/16/2020 16:50, Mark Brown wrote:
> > This patch series implements support for ARMv8.5-A Branch Target
> > Identification (BTI), which is a control flow integrity protection
> > feature introduced as part of the ARMv8.5-A extensions.
>
> i was playing with this and it seems the kernel does not add
> PROT_BTI to non-static executables (i.e. there is an interpreter).
>
> i thought any elf that the kernel maps would get PROT_BTI from the
> kernel. (i want to remove the mprotect in glibc when not necessary)
I haven't followed the early discussions but I think this makes sense.
> i tested by linking a hello world exe with -Wl,-z,force-bti (and
> verified that the property note is there) and expected it to crash
> (with SIGILL) when the dynamic linker jumps to _start in the exe,
> but it executed without errors (if i do the mprotect in glibc then
> i get SIGILL as expected).
>
> is this deliberate? does the kernel map static exe and dynamic
> linked exe differently?
I think the logic is in patch 5:
+int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state,
+ bool has_interp, bool is_interp)
+{
+ if (is_interp != has_interp)
+ return prot;
+
+ if (!(state->flags & ARM64_ELF_BTI))
+ return prot;
+
+ if (prot & PROT_EXEC)
+ prot |= PROT_BTI;
+
+ return prot;
+}
At a quick look, for dynamic binaries we have has_interp == true and
is_interp == false. I don't know why but, either way, the above code
needs a comment with some justification.
--
Catalin
next prev parent reply other threads:[~2020-03-23 12:21 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-16 16:50 [PATCH v10 00/13] arm64: Branch Target Identification support Mark Brown
2020-03-16 16:50 ` [PATCH v10 01/13] ELF: UAPI and Kconfig additions for ELF program properties Mark Brown
2020-03-16 16:50 ` [PATCH v10 02/13] ELF: Add ELF program property parsing support Mark Brown
2020-03-16 16:50 ` [PATCH v10 03/13] arm64: Basic Branch Target Identification support Mark Brown
2020-03-16 16:50 ` [PATCH v10 04/13] elf: Allow arch to tweak initial mmap prot flags Mark Brown
2020-03-16 16:50 ` [PATCH v10 05/13] arm64: elf: Enable BTI at exec based on ELF program properties Mark Brown
2020-03-16 16:50 ` [PATCH v10 06/13] arm64: BTI: Decode BYTPE bits when printing PSTATE Mark Brown
2020-03-16 16:50 ` [PATCH v10 07/13] arm64: unify native/compat instruction skipping Mark Brown
2020-03-16 16:50 ` [PATCH v10 08/13] arm64: traps: Shuffle code to eliminate forward declarations Mark Brown
2020-03-16 16:50 ` [PATCH v10 09/13] arm64: BTI: Reset BTYPE when skipping emulated instructions Mark Brown
2020-03-16 16:50 ` [PATCH v10 10/13] KVM: " Mark Brown
2020-03-16 16:50 ` [PATCH v10 11/13] arm64: mm: Display guarded pages in ptdump Mark Brown
2020-03-16 16:50 ` [PATCH v10 12/13] mm: smaps: Report arm64 guarded pages in smaps Mark Brown
2020-03-16 16:50 ` [PATCH v10 13/13] arm64: BTI: Add Kconfig entry for userspace BTI Mark Brown
2020-03-17 18:49 ` [PATCH v10 00/13] arm64: Branch Target Identification support Catalin Marinas
2020-03-20 17:39 ` Szabolcs Nagy
2020-03-23 12:21 ` Catalin Marinas [this message]
2020-03-23 13:24 ` Mark Brown
2020-03-23 13:57 ` Mark Rutland
2020-03-23 14:39 ` Catalin Marinas
2020-03-23 14:55 ` Mark Rutland
2020-03-23 15:32 ` Mark Brown
2020-03-24 15:43 ` Szabolcs Nagy
2020-03-23 15:02 ` Mark Rutland
2020-04-22 15:44 ` Mark Brown
2020-04-22 16:29 ` Catalin Marinas
2020-04-28 13:28 ` Will Deacon
2020-04-28 15:12 ` Mark Brown
2020-04-28 15:18 ` Will Deacon
2020-04-28 15:58 ` Mark Brown
2020-04-28 16:01 ` Will Deacon
2020-04-30 21:26 ` Will Deacon
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