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FROMGIT: arm64/fpsimd: signal: Consistently read FPSIMD context

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For historical reasons, restore_sve_fpsimd_context() has an open-coded
copy of the logic from read_fpsimd_context(), which is used to either
restore an FPSIMD-only context, or to merge FPSIMD state into an
SVE state when restoring an SVE+FPSIMD context. The logic is *almost*
identical.

Refactor the logic to avoid duplication and make this clearer.

This comes with two functional changes that I do not believe will be
problematic in practice:

* The user_fpsimd_state::size field will be checked in all restore paths
  that consume it user_fpsimd_state. The kernel always populates this
  field when delivering a signal, and so this should contain the
  expected value unless it has been corrupted.

* If a read of user_fpsimd_state fails, we will return early without
  modifying TIF_SVE, the saved SVCR, or the save fp_type. This will
  leave the task in a consistent state, without potentially resurrecting
  stale FPSIMD state. A read of user_fpsimd_state should never fail
  unless the structure has been corrupted or the stack has been
  unmapped.

Suggested-by: Will Deacon <will@kernel.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20250508132644.1395904-5-mark.rutland@arm.com
[will: Ensure read_fpsimd_context() returns negative error code or zero]
Signed-off-by: Will Deacon <will@kernel.org>
(cherry picked from commit be625d803c3bbfa9652697eb57589fe6f2f24b89
 https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git
 for-next/sme-fixes)
Bug: 393087661
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: Idf13bb79dbb3dfe64c237badb8b6eabb02fa2361
This commit is contained in:
Mark Rutland
2025-05-08 14:26:24 +01:00
committed by Will Deacon
parent bed5006f4a
commit b2853208b1
1 changed files with 29 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

57
arch/arm64/kernel/signal.c
View File

@@ -264,30 +264,40 @@ static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
return err ? -EFAULT : 0;
}
static int restore_fpsimd_context(struct user_ctxs *user)
static int read_fpsimd_context(struct user_fpsimd_state *fpsimd,
struct user_ctxs *user)
{
struct user_fpsimd_state fpsimd;
int err = 0;
int err;
/* check the size information */
if (user->fpsimd_size != sizeof(struct fpsimd_context))
return -EINVAL;
/* copy the FP and status/control registers */
err = __copy_from_user(fpsimd.vregs, &(user->fpsimd->vregs),
sizeof(fpsimd.vregs));
__get_user_error(fpsimd.fpsr, &(user->fpsimd->fpsr), err);
__get_user_error(fpsimd.fpcr, &(user->fpsimd->fpcr), err);
err = __copy_from_user(fpsimd->vregs, &(user->fpsimd->vregs),
sizeof(fpsimd->vregs));
__get_user_error(fpsimd->fpsr, &(user->fpsimd->fpsr), err);
__get_user_error(fpsimd->fpcr, &(user->fpsimd->fpcr), err);
return err ? -EFAULT : 0;
}
static int restore_fpsimd_context(struct user_ctxs *user)
{
struct user_fpsimd_state fpsimd;
int err;
err = read_fpsimd_context(&fpsimd, user);
if (err)
return err;
clear_thread_flag(TIF_SVE);
current->thread.svcr &= ~SVCR_SM_MASK;
current->thread.fp_type = FP_STATE_FPSIMD;
/* load the hardware registers from the fpsimd_state structure */
if (!err)
fpsimd_update_current_state(&fpsimd);
return err ? -EFAULT : 0;
fpsimd_update_current_state(&fpsimd);
return 0;
}
static int preserve_fpmr_context(struct fpmr_context __user *ctx)
@@ -427,12 +437,8 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
* consistency and robustness, reject restoring streaming SVE state
* without an SVE payload.
*/
if (!sm && user->sve_size == sizeof(*user->sve)) {
clear_thread_flag(TIF_SVE);
current->thread.svcr &= ~SVCR_SM_MASK;
current->thread.fp_type = FP_STATE_FPSIMD;
goto fpsimd_only;
}
if (!sm && user->sve_size == sizeof(*user->sve))
return restore_fpsimd_context(user);
vq = sve_vq_from_vl(vl);
@@ -458,19 +464,14 @@ static int restore_sve_fpsimd_context(struct user_ctxs *user)
set_thread_flag(TIF_SVE);
current->thread.fp_type = FP_STATE_SVE;
fpsimd_only:
/* copy the FP and status/control registers */
/* restore_sigframe() already checked that user->fpsimd != NULL. */
err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs,
sizeof(fpsimd.vregs));
__get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err);
__get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err);
err = read_fpsimd_context(&fpsimd, user);
if (err)
return err;
/* load the hardware registers from the fpsimd_state structure */
if (!err)
fpsimd_update_current_state(&fpsimd);
/* Merge the FPSIMD registers into the SVE state */
fpsimd_update_current_state(&fpsimd);
return err ? -EFAULT : 0;
return 0;
}
#else /* ! CONFIG_ARM64_SVE */