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Revert "riscv: Reset pmm when PR_TAGGED_ADDR_ENABLE is not set"

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This reverts commit 3033b2b1e3.

The reverted patch is userspace-visible behavior change, not a bug fix.
The two variables here (pmm and pmlen) control two independent features:
pmm is the _hardware_ pointer masking mode that applies while executing
in userspace. pmlen is the shift amount that the _kernel_ uses when
untagging addresses; PMLEN_0 means no untagging occurs, so the kernel
does not accept tagged addresses in syscall arguments.

It is valid (as documented and tested by the self test) to enable
pointer masking without enabling the tagged address ABI. This separation
is necessary to allow userspace to create an execution environment
similar to what the kernel supports on arm64 by default, where TBI is
enabled but the tagged address ABI is not. (On arm64, there is no
equivalent to PR_PMLEN_MASK because TBI is always enabled.)

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Link: https://patch.msgid.link/20260820014551.1979772-1-samuel.holland@sifive.com
Cc: stable@vger.kernel.org
Fixes: 3033b2b1e3 ("riscv: Reset pmm when PR_TAGGED_ADDR_ENABLE is not set")
Signed-off-by: Paul Walmsley <pjw@kernel.org>
This commit is contained in:
Samuel Holland 2026-08-31 19:11:23 -06:00 committed by Paul Walmsley
parent 8718e5a309
commit 2d2184ac90
1 changed files with 1 additions and 3 deletions
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4
arch/riscv/kernel/process.c
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@ -349,10 +349,8 @@ long set_tagged_addr_ctrl(struct task_struct *task, unsigned long arg)
if (arg & PR_TAGGED_ADDR_ENABLE && (tagged_addr_disabled || !pmlen))
return -EINVAL;
if (!(arg & PR_TAGGED_ADDR_ENABLE)) {
if (!(arg & PR_TAGGED_ADDR_ENABLE))
pmlen = PMLEN_0;
pmm = ENVCFG_PMM_PMLEN_0;
}
if (mmap_write_lock_killable(mm))
return -EINTR;