[PATCH v2 6/8] lib: sbi: Add support for Smepmp
Himanshu Chauhan
hchauhan at ventanamicro.com
Thu Jul 6 03:49:26 PDT 2023
- If Smepmp is enabled, the access flags of an entry are determined based on
truth table defined in Smepmp.
- First PMP entry (index 0) is reserved.
- Existing boot PMP entries start from index 1.
- Since enabling Smepmp revokes the access privileges of the M-mode software
on S/U-mode region, first PMP entry is used to map/unmap the shared memory
between M and S/U-mode. This allows a temporary access window for the M-mode
software to read/write to S/U-mode memory region.
Signed-off-by: Himanshu Chauhan <hchauhan at ventanamicro.com>
---
include/sbi/sbi_hart.h | 15 +++++
lib/sbi/sbi_domain.c | 14 +++--
lib/sbi/sbi_hart.c | 132 +++++++++++++++++++++++++++++++++++------
lib/sbi/sbi_init.c | 22 ++++---
4 files changed, 151 insertions(+), 32 deletions(-)
diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
index 9957565..fb5bb59 100644
--- a/include/sbi/sbi_hart.h
+++ b/include/sbi/sbi_hart.h
@@ -43,6 +43,21 @@ enum sbi_hart_extensions {
SBI_HART_EXT_MAX,
};
+/*
+ * Smepmp enforces access boundaries between M-mode and
+ * S/U-mode. When it is enabled, the PMPs are programmed
+ * such that M-mode doesn't have access to S/U-mode memory.
+ *
+ * To give M-mode R/W access to the shared memory between M and
+ * S/U-mode, first entry is reserved. It is disabled at boot.
+ * When shared memory access is required, the physical address
+ * should be programmed into the first PMP entry with R/W
+ * permissions to the M-mode. Once the work is done, it should be
+ * unmapped. sbi_hart_map_saddr/sbi_hart_unmap_saddr function
+ * pair should be used to map/unmap the shared memory.
+ */
+#define SBI_SMEPMP_RESV_ENTRY 0
+
struct sbi_hart_features {
bool detected;
int priv_version;
diff --git a/lib/sbi/sbi_domain.c b/lib/sbi/sbi_domain.c
index 38a5902..acd0f74 100644
--- a/lib/sbi/sbi_domain.c
+++ b/lib/sbi/sbi_domain.c
@@ -772,11 +772,17 @@ int sbi_domain_init(struct sbi_scratch *scratch, u32 cold_hartid)
root.fw_region_inited = true;
- /* Root domain allow everything memory region */
+ /*
+ * Allow SU RWX on rest of the memory region. Since pmp entries
+ * have implicit priority on index, previous entries will
+ * deny access to SU on M-mode region. Also, M-mode will not
+ * have access to SU region while previous entries will allow
+ * access to M-mode regions.
+ */
sbi_domain_memregion_init(0, ~0UL,
- (SBI_DOMAIN_MEMREGION_READABLE |
- SBI_DOMAIN_MEMREGION_WRITEABLE |
- SBI_DOMAIN_MEMREGION_EXECUTABLE),
+ (SBI_DOMAIN_MEMREGION_SU_READABLE |
+ SBI_DOMAIN_MEMREGION_SU_WRITABLE |
+ SBI_DOMAIN_MEMREGION_SU_EXECUTABLE),
&root_memregs[root_memregs_count++]);
/* Root domain memory region end */
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 7b9d5dc..5d91718 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -284,11 +284,75 @@ unsigned int sbi_hart_mhpm_bits(struct sbi_scratch *scratch)
return hfeatures->mhpm_bits;
}
+/*
+ * Returns Smepmp flags for a given domain and region based on permissions.
+ */
+unsigned int sbi_hart_get_smepmp_flags(struct sbi_scratch *scratch,
+ struct sbi_domain *dom,
+ struct sbi_domain_memregion *reg)
+{
+ unsigned int pmp_flags = 0;
+
+ if (SBI_DOMAIN_MEMREGION_IS_SHARED(reg->flags)) {
+ /* Read only for both M and SU modes */
+ if (SBI_DOMAIN_MEMREGION_IS_SUR_MR(reg->flags))
+ pmp_flags = (PMP_R | PMP_W | PMP_X);
+
+ /* Execute for SU but Read/Execute for M mode */
+ else if (SBI_DOMAIN_MEMREGION_IS_SUX_MRX(reg->flags))
+ /* locked region */
+ pmp_flags = (PMP_L | PMP_W | PMP_X);
+
+ /* Execute only for both M and SU modes */
+ else if (SBI_DOMAIN_MEMREGION_IS_SUX_MX(reg->flags))
+ pmp_flags = (PMP_L | PMP_W);
+
+ /* Read/Write for both M and SU modes */
+ else if (SBI_DOMAIN_MEMREGION_IS_SURW_MRW(reg->flags))
+ pmp_flags = (PMP_W | PMP_X);
+
+ /* Read only for SU mode but Read/Write for M mode */
+ else if (SBI_DOMAIN_MEMREGION_IS_SUR_MRW(reg->flags))
+ pmp_flags = (PMP_W);
+ } else if (SBI_DOMAIN_MEMREGION_M_ONLY_ACCESS(reg->flags)) {
+ /*
+ * When smepmp is supported and used, M region cannot have RWX
+ * permissions on any region.
+ */
+ if ((reg->flags & SBI_DOMAIN_MEMREGION_M_ACCESS_MASK)
+ == SBI_DOMAIN_MEMREGION_M_RWX) {
+ sbi_printf("%s: M-mode only regions cannot have"
+ "RWX permissions\n", __func__);
+ return 0;
+ }
+
+ /* M-mode only access regions are always locked */
+ pmp_flags |= PMP_L;
+
+ if (reg->flags & SBI_DOMAIN_MEMREGION_M_READABLE)
+ pmp_flags |= PMP_R;
+ if (reg->flags & SBI_DOMAIN_MEMREGION_M_WRITABLE)
+ pmp_flags |= PMP_W;
+ if (reg->flags & SBI_DOMAIN_MEMREGION_M_EXECUTABLE)
+ pmp_flags |= PMP_X;
+ } else if (SBI_DOMAIN_MEMREGION_SU_ONLY_ACCESS(reg->flags)) {
+ if (reg->flags & SBI_DOMAIN_MEMREGION_SU_READABLE)
+ pmp_flags |= PMP_R;
+ if (reg->flags & SBI_DOMAIN_MEMREGION_SU_WRITABLE)
+ pmp_flags |= PMP_W;
+ if (reg->flags & SBI_DOMAIN_MEMREGION_SU_EXECUTABLE)
+ pmp_flags |= PMP_X;
+ }
+
+ return pmp_flags;
+}
+
int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
{
struct sbi_domain_memregion *reg;
struct sbi_domain *dom = sbi_domain_thishart_ptr();
- unsigned int pmp_idx = 0, pmp_flags, pmp_bits, pmp_gran_log2;
+ unsigned int pmp_idx = 0;
+ unsigned int pmp_flags, pmp_bits, pmp_gran_log2;
unsigned int pmp_count = sbi_hart_pmp_count(scratch);
unsigned long pmp_addr = 0, pmp_addr_max = 0;
@@ -299,36 +363,66 @@ int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
pmp_bits = sbi_hart_pmp_addrbits(scratch) - 1;
pmp_addr_max = (1UL << pmp_bits) | ((1UL << pmp_bits) - 1);
+ if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SMEPMP)) {
+ /* Reserve first entry for dynamic shared mappings */
+ pmp_idx = SBI_SMEPMP_RESV_ENTRY + 1;
+
+ /*
+ * Set the RLB now so that, we can write to entries
+ * even if some entries are locked.
+ */
+ csr_write(CSR_MSECCFG, MSECCFG_RLB);
+
+ /* Disable the reserved entry */
+ pmp_disable(SBI_SMEPMP_RESV_ENTRY);
+ }
+
sbi_domain_for_each_memregion(dom, reg) {
if (pmp_count <= pmp_idx)
break;
pmp_flags = 0;
- /*
- * If permissions are to be enforced for all modes on this
- * region, the lock bit should be set.
- */
- if (reg->flags & SBI_DOMAIN_MEMREGION_ENF_PERMISSIONS)
- pmp_flags |= PMP_L;
-
- if (reg->flags & SBI_DOMAIN_MEMREGION_SU_READABLE)
- pmp_flags |= PMP_R;
- if (reg->flags & SBI_DOMAIN_MEMREGION_SU_WRITABLE)
- pmp_flags |= PMP_W;
- if (reg->flags & SBI_DOMAIN_MEMREGION_SU_EXECUTABLE)
- pmp_flags |= PMP_X;
+ if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SMEPMP)) {
+ pmp_flags = sbi_hart_get_smepmp_flags(scratch, dom, reg);
+
+ if (pmp_flags == 0)
+ return 0;
+ } else {
+ /*
+ * If permissions are to be enforced for all modes on
+ * this region, the lock bit should be set.
+ */
+ if (reg->flags & SBI_DOMAIN_MEMREGION_ENF_PERMISSIONS)
+ pmp_flags |= PMP_L;
+
+ if (reg->flags & SBI_DOMAIN_MEMREGION_SU_READABLE)
+ pmp_flags |= PMP_R;
+ if (reg->flags & SBI_DOMAIN_MEMREGION_SU_WRITABLE)
+ pmp_flags |= PMP_W;
+ if (reg->flags & SBI_DOMAIN_MEMREGION_SU_EXECUTABLE)
+ pmp_flags |= PMP_X;
+ }
pmp_addr = reg->base >> PMP_SHIFT;
- if (pmp_gran_log2 <= reg->order && pmp_addr < pmp_addr_max)
+ if (pmp_gran_log2 <= reg->order && pmp_addr < pmp_addr_max) {
pmp_set(pmp_idx++, pmp_flags, reg->base, reg->order);
- else {
- sbi_printf("Can not configure pmp for domain %s", dom->name);
- sbi_printf(" because memory region address %lx or size %lx is not in range\n",
- reg->base, reg->order);
+ } else {
+ sbi_printf("Can not configure pmp for domain %s because"
+ " memory region address 0x%lx or size 0x%lx "
+ "is not in range.\n", dom->name, reg->base,
+ reg->order);
}
}
+ if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SMEPMP)) {
+ /*
+ * All entries are programmed. Enable MML bit.
+ * Keep the RLB bit so that dynamic mappings can be done.
+ */
+ csr_write(CSR_MSECCFG, (MSECCFG_RLB | MSECCFG_MML));
+ }
+
/*
* As per section 3.7.2 of privileged specification v1.12,
* virtual address translations can be speculatively performed
diff --git a/lib/sbi/sbi_init.c b/lib/sbi/sbi_init.c
index 423e6d8..5e1f439 100644
--- a/lib/sbi/sbi_init.c
+++ b/lib/sbi/sbi_init.c
@@ -356,13 +356,6 @@ static void __noreturn init_coldboot(struct sbi_scratch *scratch, u32 hartid)
sbi_hart_hang();
}
- rc = sbi_hart_pmp_configure(scratch);
- if (rc) {
- sbi_printf("%s: PMP configure failed (error %d)\n",
- __func__, rc);
- sbi_hart_hang();
- }
-
/*
* Note: Platform final initialization should be after finalizing
* domains so that it sees correct domain assignment and PMP
@@ -392,6 +385,17 @@ static void __noreturn init_coldboot(struct sbi_scratch *scratch, u32 hartid)
sbi_boot_print_hart(scratch, hartid);
+ /*
+ * Configure PMP at last because if SMEPMP is detected,
+ * M-mode access to the S/U space will be rescinded.
+ */
+ rc = sbi_hart_pmp_configure(scratch);
+ if (rc) {
+ sbi_printf("%s: PMP configure failed (error %d)\n",
+ __func__, rc);
+ sbi_hart_hang();
+ }
+
wake_coldboot_harts(scratch, hartid);
count = sbi_scratch_offset_ptr(scratch, init_count_offset);
@@ -445,11 +449,11 @@ static void __noreturn init_warm_startup(struct sbi_scratch *scratch,
if (rc)
sbi_hart_hang();
- rc = sbi_hart_pmp_configure(scratch);
+ rc = sbi_platform_final_init(plat, false);
if (rc)
sbi_hart_hang();
- rc = sbi_platform_final_init(plat, false);
+ rc = sbi_hart_pmp_configure(scratch);
if (rc)
sbi_hart_hang();
--
2.34.1
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