Date: Wed, 16 Apr 2025 15:30:59 +0100 From: Jessica Clarke <jrtc27@freebsd.org> To: =?utf-8?Q?Bojan_Novkovi=C4=87?= <bnovkov@FreeBSD.org> Cc: "src-committers@freebsd.org" <src-committers@FreeBSD.org>, "dev-commits-src-all@freebsd.org" <dev-commits-src-all@FreeBSD.org>, "dev-commits-src-main@freebsd.org" <dev-commits-src-main@FreeBSD.org> Subject: Re: git: f1e18f331923 - main - riscv: Exclude OpenSBI memory regions when booting with EFI Message-ID: <6F9CE6EB-8A7E-48D1-BDE5-AB7D930EC1DE@freebsd.org> In-Reply-To: <202504161421.53GELphv059586@gitrepo.freebsd.org> References: <202504161421.53GELphv059586@gitrepo.freebsd.org>
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On 16 Apr 2025, at 15:21, Bojan Novkovi=C4=87 <bnovkov@FreeBSD.org> = wrote: >=20 > The branch main has been updated by bnovkov: >=20 > URL: = https://cgit.FreeBSD.org/src/commit/?id=3Df1e18f331923041980149fef46cdb273= 6e61debb >=20 > commit f1e18f331923041980149fef46cdb2736e61debb > Author: Bojan Novkovi=C4=87 <bnovkov@FreeBSD.org> > AuthorDate: 2025-04-15 16:28:05 +0000 > Commit: Bojan Novkovi=C4=87 <bnovkov@FreeBSD.org> > CommitDate: 2025-04-16 14:20:13 +0000 >=20 > riscv: Exclude OpenSBI memory regions when booting with EFI >=20 > OpenSBI uses the first PMP entry to prevent buggy supervisor > software from overwriting the firmware [1]. However, this > region may not be properly marked as reserved in the EFI map, = leading > to an access violation exception whenever the kernel > attempts to write to a page from that region. >=20 > Fix this by preemptively excluding first EFI memory map entry > if it is marked as "BootServicesData". >=20 > [1] https://github.com/riscv-non-isa/riscv-sbi-doc/pull/37 >=20 > Reported by: tuexen > Tested by: tuexen > Fixes: a2e2178402af > Reviewed by: imp, jrtc27 No I didn=E2=80=99t, I left a comment saying I didn=E2=80=99t like the = concept. > Differential Revision: https://reviews.freebsd.org/D49839 > --- > sys/riscv/riscv/machdep.c | 32 ++++++++++++++++++++++++++++++-- > 1 file changed, 30 insertions(+), 2 deletions(-) >=20 > diff --git a/sys/riscv/riscv/machdep.c b/sys/riscv/riscv/machdep.c > index 516dbde5ffaa..f253bc9a853b 100644 > --- a/sys/riscv/riscv/machdep.c > +++ b/sys/riscv/riscv/machdep.c > @@ -541,6 +541,22 @@ fdt_physmem_exclude_region_cb(const struct = mem_region *mr, void *arg __unused) > } > #endif >=20 > +static void > +efi_exclude_sbi_pmp_cb(struct efi_md *p, void *argp) > +{ > + bool *first =3D (bool *)argp; > + > + if (!*first) > + return; > + > + *first =3D false; > + if (p->md_type =3D=3D EFI_MD_TYPE_BS_DATA) { > + physmem_exclude_region(p->md_phys, > + min(p->md_pages * EFI_PAGE_SIZE, L2_SIZE), > + EXFLAG_NOALLOC); Doesn=E2=80=99t this need EXFLAG_NODUMP like the FDT case? Jess > + } > +} > + > void > initriscv(struct riscv_bootparams *rvbp) > { > @@ -548,6 +564,7 @@ initriscv(struct riscv_bootparams *rvbp) > struct pcpu *pcpup; > vm_offset_t lastaddr; > vm_size_t kernlen; > + bool first; > char *env; >=20 > TSRAW(&thread0, TS_ENTER, __func__, NULL); > @@ -577,11 +594,22 @@ initriscv(struct riscv_bootparams *rvbp) > if (efihdr !=3D NULL) { > efi_map_add_entries(efihdr); > efi_map_exclude_entries(efihdr); > + > + /* > + * OpenSBI uses the first PMP entry to prevent buggy supervisor > + * software from overwriting the firmware. However, this > + * region may not be properly marked as reserved, leading > + * to an access violation exception whenever the kernel > + * attempts to write to a page from that region. > + * > + * Fix this by excluding first EFI memory map entry > + * if it is marked as "BootServicesData". > + */ > + first =3D true; > + efi_map_foreach_entry(efihdr, efi_exclude_sbi_pmp_cb, &first); > } > #ifdef FDT > else { > - bool first; > - > /* Exclude reserved memory specified by the device tree. */ > fdt_foreach_reserved_mem(fdt_physmem_exclude_region_cb, NULL); >=20
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