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lib: sbi: call platform load/store emulators

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sbi_load/store_access_handler now tries to call platform emulators
if defined. Otherwise, redirects the fault. If the platform code
returns failure, this means the H/S/U has accessed the emulated
devices in an unexpected manner, which is very likely caused by
buggy code in H/S/U. We redirect the fault, so lower privileged
level can get notified, and act accordingly. (E.g., oops in Linux)

We let the handler truly fail if the trap was originated from M mode.
In this case, something must be very wrong and we should just fail.

Signed-off-by: Bo Gan <ganboing@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Bo Gan
2024-03-05 18:35:40 -08:00
committed by Anup Patel
parent ddf3b649f1
commit 81e3ba77a6
2 changed files with 80 additions and 2 deletions
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37
lib/sbi/sbi_trap_ldst.c
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@@ -15,6 +15,7 @@
#include <sbi/sbi_pmu.h>
#include <sbi/sbi_trap.h>
#include <sbi/sbi_unpriv.h>
#include <sbi/sbi_platform.h>
/**
* Load emulator callback:
@@ -319,14 +320,46 @@ int sbi_misaligned_store_handler(struct sbi_trap_regs *regs,
sbi_misaligned_st_emulator);
}
static int sbi_ld_access_emulator(int rlen, union sbi_ldst_data *out_val,
struct sbi_trap_regs *regs,
const struct sbi_trap_info *orig_trap)
{
/* If fault came from M mode, just fail */
if (((regs->mstatus & MSTATUS_MPP) >> MSTATUS_MPP_SHIFT) == PRV_M)
return SBI_EINVAL;
/* If platform emulator failed, we redirect instead of fail */
if (sbi_platform_emulate_load(sbi_platform_thishart_ptr(), rlen,
orig_trap->tval, out_val))
return sbi_trap_redirect(regs, orig_trap);
return rlen;
}
int sbi_load_access_handler(struct sbi_trap_regs *regs,
const struct sbi_trap_info *orig_trap)
{
return sbi_trap_redirect(regs, orig_trap);
return sbi_trap_emulate_load(regs, orig_trap, sbi_ld_access_emulator);
}
static int sbi_st_access_emulator(int wlen, union sbi_ldst_data in_val,
struct sbi_trap_regs *regs,
const struct sbi_trap_info *orig_trap)
{
/* If fault came from M mode, just fail */
if (((regs->mstatus & MSTATUS_MPP) >> MSTATUS_MPP_SHIFT) == PRV_M)
return SBI_EINVAL;
/* If platform emulator failed, we redirect instead of fail */
if (sbi_platform_emulate_store(sbi_platform_thishart_ptr(), wlen,
orig_trap->tval, in_val))
return sbi_trap_redirect(regs, orig_trap);
return wlen;
}
int sbi_store_access_handler(struct sbi_trap_regs *regs,
const struct sbi_trap_info *orig_trap)
{
return sbi_trap_redirect(regs, orig_trap);
return sbi_trap_emulate_store(regs, orig_trap, sbi_st_access_emulator);
}