From: Paul Walmsley <pjw@kernel.org>
To: Deepak Gupta <debug@rivosinc.com>, Andy Chiu <andybnac@gmail.com>
Cc: "Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
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"Vlastimil Babka" <vbabka@suse.cz>,
"Lorenzo Stoakes" <lorenzo.stoakes@oracle.com>,
"Paul Walmsley" <paul.walmsley@sifive.com>,
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Subject: Re: [PATCH v22 17/28] riscv/signal: save and restore of shadow stack for signal
Date: Fri, 31 Oct 2025 14:07:32 -0600 (MDT) [thread overview]
Message-ID: <a8f469b8-5750-dfec-2390-09bad4515f99@kernel.org> (raw)
In-Reply-To: <20251023-v5_user_cfi_series-v22-17-1935270f7636@rivosinc.com>
On Thu, 23 Oct 2025, Deepak Gupta via B4 Relay wrote:
> From: Deepak Gupta <debug@rivosinc.com>
>
> Save shadow stack pointer in sigcontext structure while delivering signal.
> Restore shadow stack pointer from sigcontext on sigreturn.
>
> As part of save operation, kernel uses `ssamoswap` to save snapshot of
> current shadow stack on shadow stack itself (can be called as a save
> token). During restore on sigreturn, kernel retrieves token from top of
> shadow stack and validates it. This allows that user mode can't arbitrary
> pivot to any shadow stack address without having a token and thus provide
> strong security assurance between signaly delivery and sigreturn window.
>
> Use ABI compatible way of saving/restoring shadow stack pointer into
> signal stack. This follows what Vector extension, where extra registers
> are placed in a form of extension header + extension body in the stack.
> The extension header indicates the size of the extra architectural
> states plus the size of header itself, and a magic identifier of the
> extension. Then, the extensions body contains the new architectural
> states in the form defined by uapi.
>
> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
> Signed-off-by: Deepak Gupta <debug@rivosinc.com>
This patch causes some 'checkpatch.pl --strict' messages:
CHECK: Comparison to NULL could be written "!saved_shstk_ptr"
#271: FILE: arch/riscv/kernel/usercfi.c:186:
+ if (saved_shstk_ptr == NULL)
CHECK: Lines should not end with a '('
#300: FILE: arch/riscv/kernel/usercfi.c:215:
+ pr_info_ratelimited(
I've fixed them up here in the event that v22 goes in, but please do the
same on your side in case a new version is needed.
- Paul
next prev parent reply other threads:[~2025-10-31 20:07 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-23 16:51 [PATCH v22 00/28] riscv control-flow integrity for usermode Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 01/28] mm: VM_SHADOW_STACK definition for riscv Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 02/28] dt-bindings: riscv: zicfilp and zicfiss in dt-bindings (extensions.yaml) Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 03/28] riscv: zicfiss / zicfilp enumeration Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 04/28] riscv: zicfiss / zicfilp extension csr and bit definitions Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 05/28] riscv: usercfi state for task and save/restore of CSR_SSP on trap entry/exit Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 06/28] riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 07/28] riscv/mm: manufacture shadow stack pte Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 08/28] riscv/mm: teach pte_mkwrite to manufacture shadow stack PTEs Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 09/28] riscv/mm: write protect and shadow stack Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 10/28] riscv/mm: Implement map_shadow_stack() syscall Deepak Gupta via B4 Relay
2025-10-31 19:48 ` Paul Walmsley
2025-11-02 23:51 ` Maciej W. Rozycki
2025-10-23 16:51 ` [PATCH v22 11/28] riscv/shstk: If needed allocate a new shadow stack on clone Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 12/28] riscv: Implements arch agnostic shadow stack prctls Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 13/28] prctl: arch-agnostic prctl for indirect branch tracking Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 14/28] riscv: Implements arch agnostic indirect branch tracking prctls Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 15/28] riscv/traps: Introduce software check exception and uprobe handling Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 16/28] riscv: signal: abstract header saving for setup_sigcontext Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 17/28] riscv/signal: save and restore of shadow stack for signal Deepak Gupta via B4 Relay
2025-10-31 20:07 ` Paul Walmsley [this message]
2025-10-31 22:10 ` Randy Dunlap
2025-11-04 7:52 ` Paul Walmsley
2025-10-23 16:51 ` [PATCH v22 18/28] riscv/kernel: update __show_regs to print shadow stack register Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 19/28] riscv/ptrace: riscv cfi status and state via ptrace and in core files Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 20/28] riscv/hwprobe: zicfilp / zicfiss enumeration in hwprobe Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 21/28] riscv: kernel command line option to opt out of user cfi Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 22/28] riscv: enable kernel access to shadow stack memory via FWFT sbi call Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 23/28] arch/riscv: compile vdso with landing pad and shadow stack note Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 24/28] arch/riscv: dual vdso creation logic and select vdso based on hw Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 25/28] riscv: create a config for shadow stack and landing pad instr support Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 26/28] riscv: Documentation for landing pad / indirect branch tracking Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 27/28] riscv: Documentation for shadow stack on riscv Deepak Gupta via B4 Relay
2025-10-23 16:51 ` [PATCH v22 28/28] kselftest/riscv: kselftest for user mode cfi Deepak Gupta via B4 Relay
2025-10-23 23:20 ` [PATCH v22 00/28] riscv control-flow integrity for usermode Deepak Gupta
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