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riscv: Implement indirect branch tracking prctls

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This patch adds a RISC-V implementation of the following prctls:
PR_SET_INDIR_BR_LP_STATUS, PR_GET_INDIR_BR_LP_STATUS and
PR_LOCK_INDIR_BR_LP_STATUS.

Reviewed-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Deepak Gupta <debug@rivosinc.com>
Tested-by: Andreas Korb <andreas.korb@aisec.fraunhofer.de>
Tested-by: Valentin Haudiquet <valentin.haudiquet@canonical.com>
Link: https://patch.msgid.link/20251112-v5_user_cfi_series-v23-14-b55691eacf4f@rivosinc.com
[pjw@kernel.org: clean up patch description]
Signed-off-by: Paul Walmsley <pjw@kernel.org>
This commit is contained in:
Deepak Gupta
2026-01-25 21:09:54 -07:00
committed by Paul Walmsley
parent 5ca243f6e3
commit 8a9e22d2ca
4 changed files with 102 additions and 0 deletions
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79
arch/riscv/kernel/usercfi.c
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@@ -72,6 +72,35 @@ void set_shstk_lock(struct task_struct *task)
task->thread_info.user_cfi_state.ubcfi_locked = 1;
}
bool is_indir_lp_enabled(struct task_struct *task)
{
return task->thread_info.user_cfi_state.ufcfi_en;
}
bool is_indir_lp_locked(struct task_struct *task)
{
return task->thread_info.user_cfi_state.ufcfi_locked;
}
void set_indir_lp_status(struct task_struct *task, bool enable)
{
if (!cpu_supports_indirect_br_lp_instr())
return;
task->thread_info.user_cfi_state.ufcfi_en = enable ? 1 : 0;
if (enable)
task->thread.envcfg |= ENVCFG_LPE;
else
task->thread.envcfg &= ~ENVCFG_LPE;
csr_write(CSR_ENVCFG, task->thread.envcfg);
}
void set_indir_lp_lock(struct task_struct *task)
{
task->thread_info.user_cfi_state.ufcfi_locked = 1;
}
/*
* If size is 0, then to be compatible with regular stack we want it to be as big as
* regular stack. Else PAGE_ALIGN it and return back
@@ -368,3 +397,53 @@ int arch_lock_shadow_stack_status(struct task_struct *task,
return 0;
}
int arch_get_indir_br_lp_status(struct task_struct *t, unsigned long __user *status)
{
unsigned long fcfi_status = 0;
if (!cpu_supports_indirect_br_lp_instr())
return -EINVAL;
/* indirect branch tracking is enabled on the task or not */
fcfi_status |= (is_indir_lp_enabled(t) ? PR_INDIR_BR_LP_ENABLE : 0);
return copy_to_user(status, &fcfi_status, sizeof(fcfi_status)) ? -EFAULT : 0;
}
int arch_set_indir_br_lp_status(struct task_struct *t, unsigned long status)
{
bool enable_indir_lp = false;
if (!cpu_supports_indirect_br_lp_instr())
return -EINVAL;
/* indirect branch tracking is locked and further can't be modified by user */
if (is_indir_lp_locked(t))
return -EINVAL;
/* Reject unknown flags */
if (status & ~PR_INDIR_BR_LP_ENABLE)
return -EINVAL;
enable_indir_lp = (status & PR_INDIR_BR_LP_ENABLE);
set_indir_lp_status(t, enable_indir_lp);
return 0;
}
int arch_lock_indir_br_lp_status(struct task_struct *task,
unsigned long arg)
{
/*
* If indirect branch tracking is not supported or not enabled on task,
* nothing to lock here
*/
if (!cpu_supports_indirect_br_lp_instr() ||
!is_indir_lp_enabled(task) || arg != 0)
return -EINVAL;
set_indir_lp_lock(task);
return 0;
}