arm64/sysreg: Improve PIR/POR helpers

We currently have one helper to set a PIRx_ELx's permission field to
a given value, PIRx_ELx_PERM(), and another helper to extract a
permission field from POR_ELx, POR_ELx_IDX(). The naming is pretty
confusing - it isn't clear at all that "_PERM" corresponds to a
setter and "_IDX" to a getter.

This patch aims at improving the situation by using the same
suffixes as FIELD_PREP()/FIELD_GET(), which we have already adopted
for SYS_FIELD_{PREP,GET}():

* PIRx_ELx_PERM_PREP(), POR_ELx_PERM_PREP() create a register value
  where the permission field for a given index is set to a given value.

* POR_ELx_PERM_GET() extracts the permission field from a given
  register value for a given index.

These helpers are not implemented using FIELD_PREP()/FIELD_GET()
because the mask may not be constant, and they need to be usable in
assembly. They are all defined in asm/sysreg.h, as one would expect
for basic sysreg-related helpers.

Finally the new POR_ELx_PERM_* macros are used for existing
calculations in signal.c and mmu.c.

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Link: https://lore.kernel.org/r/20250219164029.2309119-2-kevin.brodsky@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
index a95f1f7..7830d03 100644 (file)
--- a/arch/arm64/include/asm/pgtable-prot.h
+++ b/arch/arm64/include/asm/pgtable-prot.h
@@ -169,25 +169,25 @@ static inline bool __pure lpa2_is_enabled(void)
 #define PAGE_GCS_RO    __pgprot(_PAGE_GCS_RO)
 
 #define PIE_E0 ( \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_GCS),           PIE_GCS)  | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_GCS_RO),        PIE_R)   | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_EXECONLY),      PIE_X_O) | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_READONLY_EXEC), PIE_RX_O)  | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_SHARED_EXEC),   PIE_RWX_O) | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_READONLY),      PIE_R_O)   | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_SHARED),        PIE_RW_O))
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_GCS),           PIE_GCS)  | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_GCS_RO),        PIE_R)   | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_EXECONLY),      PIE_X_O) | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_READONLY_EXEC), PIE_RX_O)  | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_SHARED_EXEC),   PIE_RWX_O) | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_READONLY),      PIE_R_O)   | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_SHARED),        PIE_RW_O))
 
 #define PIE_E1 ( \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_GCS),           PIE_NONE_O) | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_GCS_RO),        PIE_NONE_O) | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_EXECONLY),      PIE_NONE_O) | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_READONLY_EXEC), PIE_R)      | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_SHARED_EXEC),   PIE_RW)     | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_READONLY),      PIE_R)      | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_SHARED),        PIE_RW)     | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_KERNEL_ROX),    PIE_RX)     | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_KERNEL_EXEC),   PIE_RWX)    | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_KERNEL_RO),     PIE_R)      | \
-       PIRx_ELx_PERM(pte_pi_index(_PAGE_KERNEL),        PIE_RW))
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_GCS),           PIE_NONE_O) | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_GCS_RO),        PIE_NONE_O) | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_EXECONLY),      PIE_NONE_O) | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_READONLY_EXEC), PIE_R)      | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_SHARED_EXEC),   PIE_RW)     | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_READONLY),      PIE_R)      | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_SHARED),        PIE_RW)     | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_KERNEL_ROX),    PIE_RX)     | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_KERNEL_EXEC),   PIE_RWX)    | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_KERNEL_RO),     PIE_R)      | \
+       PIRx_ELx_PERM_PREP(pte_pi_index(_PAGE_KERNEL),        PIE_RW))
 
 #endif /* __ASM_PGTABLE_PROT_H */

diff --git a/arch/arm64/include/asm/por.h b/arch/arm64/include/asm/por.h
index e06e9f4..e6bf00b 100644 (file)
--- a/arch/arm64/include/asm/por.h
+++ b/arch/arm64/include/asm/por.h
@@ -6,26 +6,25 @@
 #ifndef _ASM_ARM64_POR_H
 #define _ASM_ARM64_POR_H
 
-#define POR_BITS_PER_PKEY              4
-#define POR_ELx_IDX(por_elx, idx)      (((por_elx) >> ((idx) * POR_BITS_PER_PKEY)) & 0xf)
+#include <asm/sysreg.h>
 
 static inline bool por_elx_allows_read(u64 por, u8 pkey)
 {
-       u8 perm = POR_ELx_IDX(por, pkey);
+       u8 perm = POR_ELx_PERM_GET(pkey, por);
 
        return perm & POE_R;
 }
 
 static inline bool por_elx_allows_write(u64 por, u8 pkey)
 {
-       u8 perm = POR_ELx_IDX(por, pkey);
+       u8 perm = POR_ELx_PERM_GET(pkey, por);
 
        return perm & POE_W;
 }
 
 static inline bool por_elx_allows_exec(u64 por, u8 pkey)
 {
-       u8 perm = POR_ELx_IDX(por, pkey);
+       u8 perm = POR_ELx_PERM_GET(pkey, por);
 
        return perm & POE_X;
 }

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 05ea522..c9ce4ce 100644 (file)
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -1062,8 +1062,11 @@
 #define PIE_RX         UL(0xa)
 #define PIE_RW         UL(0xc)
 #define PIE_RWX                UL(0xe)
+#define PIE_MASK       UL(0xf)
 
-#define PIRx_ELx_PERM(idx, perm)       ((perm) << ((idx) * 4))
+#define PIRx_ELx_BITS_PER_IDX          4
+#define PIRx_ELx_PERM_SHIFT(idx)       ((idx) * PIRx_ELx_BITS_PER_IDX)
+#define PIRx_ELx_PERM_PREP(idx, perm)  (((perm) & PIE_MASK) << PIRx_ELx_PERM_SHIFT(idx))
 
 /*
  * Permission Overlay Extension (POE) permission encodings.
@@ -1078,6 +1081,11 @@
 #define POE_RXW                UL(0x7)
 #define POE_MASK       UL(0xf)
 
+#define POR_ELx_BITS_PER_IDX           4
+#define POR_ELx_PERM_SHIFT(idx)                ((idx) * POR_ELx_BITS_PER_IDX)
+#define POR_ELx_PERM_GET(idx, reg)     (((reg) >> POR_ELx_PERM_SHIFT(idx)) & POE_MASK)
+#define POR_ELx_PERM_PREP(idx, perm)   (((perm) & POE_MASK) << POR_ELx_PERM_SHIFT(idx))
+
 /* Initial value for Permission Overlay Extension for EL0 */
 #define POR_EL0_INIT   POE_RXW
 

diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 99ea26d..bf62262 100644 (file)
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -91,7 +91,7 @@ static void save_reset_user_access_state(struct user_access_state *ua_state)
                u64 por_enable_all = 0;
 
                for (int pkey = 0; pkey < arch_max_pkey(); pkey++)
-                       por_enable_all |= POE_RXW << (pkey * POR_BITS_PER_PKEY);
+                       por_enable_all |= POR_ELx_PERM_PREP(pkey, POE_RXW);
 
                ua_state->por_el0 = read_sysreg_s(SYS_POR_EL0);
                write_sysreg_s(por_enable_all, SYS_POR_EL0);

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index b4df5bc..69a83a7 100644 (file)
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1557,7 +1557,6 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, unsigned long i
 {
        u64 new_por = POE_RXW;
        u64 old_por;
-       u64 pkey_shift;
 
        if (!system_supports_poe())
                return -ENOSPC;
@@ -1582,12 +1581,11 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, unsigned long i
                new_por &= ~POE_X;
 
        /* Shift the bits in to the correct place in POR for pkey: */
-       pkey_shift = pkey * POR_BITS_PER_PKEY;
-       new_por <<= pkey_shift;
+       new_por = POR_ELx_PERM_PREP(pkey, new_por);
 
        /* Get old POR and mask off any old bits in place: */
        old_por = read_sysreg_s(SYS_POR_EL0);
-       old_por &= ~(POE_MASK << pkey_shift);
+       old_por &= ~(POE_MASK << POR_ELx_PERM_SHIFT(pkey));
 
        /* Write old part along with new part: */
        write_sysreg_s(old_por | new_por, SYS_POR_EL0);