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lib: sbi: sbi_hart: track firmware PMP entries for SmePMP

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Add fw_smepmp_ids bitmap to track PMP entries that protect firmware
regions. Allow us to preserve these critical entries across domain
transitions and check inconsistent firmware entry allocation.

Also add sbi_hart_smepmp_is_fw_region() helper function to query
whether a given SmePMP entry protects firmware regions.

Signed-off-by: Yu-Chien Peter Lin <peter.lin@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20251008084444.3525615-8-peter.lin@sifive.com
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Yu-Chien Peter Lin
2025-10-08 16:44:43 +08:00
committed by Anup Patel
parent 631efeeb49
commit b210376fe2
2 changed files with 30 additions and 0 deletions
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1
include/sbi/sbi_hart.h
View File

@ -146,6 +146,7 @@ unsigned int sbi_hart_pmp_count(struct sbi_scratch *scratch);
unsigned int sbi_hart_pmp_log2gran(struct sbi_scratch *scratch);
unsigned int sbi_hart_pmp_addrbits(struct sbi_scratch *scratch);
unsigned int sbi_hart_mhpm_bits(struct sbi_scratch *scratch);
bool sbi_hart_smepmp_is_fw_region(unsigned int pmp_idx);
int sbi_hart_pmp_configure(struct sbi_scratch *scratch);
int sbi_hart_map_saddr(unsigned long base, unsigned long size);
int sbi_hart_unmap_saddr(void);

29
lib/sbi/sbi_hart.c
View File

@ -30,6 +30,8 @@ extern void __sbi_expected_trap_hext(void);
void (*sbi_hart_expected_trap)(void) = &__sbi_expected_trap;
static unsigned long hart_features_offset;
static DECLARE_BITMAP(fw_smepmp_ids, PMP_COUNT);
static bool fw_smepmp_ids_inited;
static void mstatus_init(struct sbi_scratch *scratch)
{
@ -301,6 +303,14 @@ unsigned int sbi_hart_mhpm_bits(struct sbi_scratch *scratch)
return hfeatures->mhpm_bits;
}
bool sbi_hart_smepmp_is_fw_region(unsigned int pmp_idx)
{
if (!fw_smepmp_ids_inited)
return false;
return bitmap_test(fw_smepmp_ids, pmp_idx) ? true : false;
}
static void sbi_hart_smepmp_set(struct sbi_scratch *scratch,
struct sbi_domain *dom,
struct sbi_domain_memregion *reg,
@ -366,12 +376,31 @@ static int sbi_hart_smepmp_configure(struct sbi_scratch *scratch,
continue;
}
/*
* Track firmware PMP entries to preserve them during
* domain switches. Under SmePMP, M-mode requires
* explicit PMP entries to access firmware code/data.
* These entries must remain enabled across domain
* context switches to prevent M-mode access faults.
*/
if (SBI_DOMAIN_MEMREGION_IS_FIRMWARE(reg->flags)) {
if (fw_smepmp_ids_inited) {
/* Check inconsistent firmware region */
if (!sbi_hart_smepmp_is_fw_region(pmp_idx))
return SBI_EINVAL;
} else {
bitmap_set(fw_smepmp_ids, pmp_idx, 1);
}
}
pmp_flags = sbi_domain_get_smepmp_flags(reg);
sbi_hart_smepmp_set(scratch, dom, reg, pmp_idx++, pmp_flags,
pmp_log2gran, pmp_addr_max);
}
fw_smepmp_ids_inited = true;
/* Set the MML to enforce new encoding */
csr_set(CSR_MSECCFG, MSECCFG_MML);