[PATCH v7 12/33] arm64: idreg-override: Use relative references to filter routines
Ard Biesheuvel
ardb at kernel.org
Fri Nov 11 09:11:40 PST 2022
To avoid statically initialized pointer variables, which need runtime
relocation and therefore prevent this code from being used before
relocations have been processed, tweak the static declarations so that
relative references are used instead. This means we will be doing the
job of the compiler and calculate where exactly the relocation needs to
point, so add some asserts to ensure we notice when we get it wrong.
Signed-off-by: Ard Biesheuvel <ardb at kernel.org>
---
arch/arm64/kernel/idreg-override.c | 63 +++++++++++++-------
1 file changed, 41 insertions(+), 22 deletions(-)
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index f8ae7f6d0d9b4fd0..01eed0eaba7c1cdd 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -15,8 +15,8 @@
#include <asm/cpufeature.h>
#include <asm/setup.h>
-#define FTR_DESC_NAME_LEN 20
-#define FTR_DESC_FIELD_LEN 10
+#define FTR_DESC_NAME_LEN 20 // must remain multiple of 4
+#define FTR_DESC_FIELD_LEN 10 // must remain multiple of 4 +/- 2
#define FTR_ALIAS_NAME_LEN 30
#define FTR_ALIAS_OPTION_LEN 116
@@ -26,16 +26,20 @@ struct ftr_set_desc {
s32 override_offset; // must remain first
char name[FTR_DESC_NAME_LEN];
struct {
+ s32 filter_offset; // must remain first
char name[FTR_DESC_FIELD_LEN];
u8 shift;
u8 width;
- bool (*filter)(u64 val);
} fields[];
};
static_assert(offsetof(struct ftr_set_desc, override_offset) == 0);
+static_assert(offsetof(struct ftr_set_desc, fields[0].filter_offset) ==
+ 4 + FTR_DESC_NAME_LEN);
+static_assert(offsetof(struct ftr_set_desc, fields[1].filter_offset) ==
+ 4 + FTR_DESC_NAME_LEN + 4 + FTR_DESC_FIELD_LEN + 2);
-#define FIELD(n, s, f) { .name = n, .shift = s, .width = 4, .filter = f }
+#define FIELD(n, s) { .name = n, .shift = s, .width = 4 }
#define DEFINE_OVERRIDE(__idx, __id, __name, __ovr, ...) \
asmlinkage const struct ftr_set_desc __initconst __id = { \
@@ -46,7 +50,12 @@ static_assert(offsetof(struct ftr_set_desc, override_offset) == 0);
".reloc " #__id ", R_AARCH64_PREL32, " #__ovr "; " \
".reloc regs + (4 * " #__idx "), R_AARCH64_PREL32, " #__id)
-static bool __init mmfr1_vh_filter(u64 val)
+#define DEFINE_OVERRIDE_FILTER(__id, __idx, __filter) \
+ asm(".reloc " #__id " + 4 + " __stringify(FTR_DESC_NAME_LEN) \
+ " + " #__idx " * (4 + " __stringify(FTR_DESC_FIELD_LEN) " + 2)," \
+ "R_AARCH64_PREL32, " #__filter)
+
+asmlinkage bool __init mmfr1_vh_filter(u64 val)
{
/*
* If we ever reach this point while running VHE, we're
@@ -59,10 +68,11 @@ static bool __init mmfr1_vh_filter(u64 val)
}
DEFINE_OVERRIDE(0, mmfr1, "id_aa64mmfr1", id_aa64mmfr1_override,
- FIELD("vh", ID_AA64MMFR1_EL1_VH_SHIFT, mmfr1_vh_filter),
+ FIELD("vh", ID_AA64MMFR1_EL1_VH_SHIFT),
{});
+DEFINE_OVERRIDE_FILTER(mmfr1, 0, mmfr1_vh_filter);
-static bool __init pfr0_sve_filter(u64 val)
+asmlinkage bool __init pfr0_sve_filter(u64 val)
{
/*
* Disabling SVE also means disabling all the features that
@@ -78,10 +88,11 @@ static bool __init pfr0_sve_filter(u64 val)
}
DEFINE_OVERRIDE(1, pfr0, "id_aa64pfr0", id_aa64pfr0_override,
- FIELD("sve", ID_AA64PFR0_EL1_SVE_SHIFT, pfr0_sve_filter),
+ FIELD("sve", ID_AA64PFR0_EL1_SVE_SHIFT),
{});
+DEFINE_OVERRIDE_FILTER(pfr0, 0, pfr0_sve_filter);
-static bool __init pfr1_sme_filter(u64 val)
+asmlinkage bool __init pfr1_sme_filter(u64 val)
{
/*
* Similarly to SVE, disabling SME also means disabling all
@@ -97,30 +108,31 @@ static bool __init pfr1_sme_filter(u64 val)
}
DEFINE_OVERRIDE(2, pfr1, "id_aa64pfr1", id_aa64pfr1_override,
- FIELD("bt", ID_AA64PFR1_EL1_BT_SHIFT, NULL ),
- FIELD("mte", ID_AA64PFR1_EL1_MTE_SHIFT, NULL),
- FIELD("sme", ID_AA64PFR1_EL1_SME_SHIFT, pfr1_sme_filter),
+ FIELD("bt", ID_AA64PFR1_EL1_BT_SHIFT ),
+ FIELD("mte", ID_AA64PFR1_EL1_MTE_SHIFT),
+ FIELD("sme", ID_AA64PFR1_EL1_SME_SHIFT),
{});
+DEFINE_OVERRIDE_FILTER(pfr1, 2, pfr1_sme_filter);
DEFINE_OVERRIDE(3, isar1, "id_aa64isar1", id_aa64isar1_override,
- FIELD("gpi", ID_AA64ISAR1_EL1_GPI_SHIFT, NULL),
- FIELD("gpa", ID_AA64ISAR1_EL1_GPA_SHIFT, NULL),
- FIELD("api", ID_AA64ISAR1_EL1_API_SHIFT, NULL),
- FIELD("apa", ID_AA64ISAR1_EL1_APA_SHIFT, NULL),
+ FIELD("gpi", ID_AA64ISAR1_EL1_GPI_SHIFT),
+ FIELD("gpa", ID_AA64ISAR1_EL1_GPA_SHIFT),
+ FIELD("api", ID_AA64ISAR1_EL1_API_SHIFT),
+ FIELD("apa", ID_AA64ISAR1_EL1_APA_SHIFT),
{});
DEFINE_OVERRIDE(4, isar2, "id_aa64isar2", id_aa64isar2_override,
- FIELD("gpa3", ID_AA64ISAR2_EL1_GPA3_SHIFT, NULL),
- FIELD("apa3", ID_AA64ISAR2_EL1_APA3_SHIFT, NULL),
+ FIELD("gpa3", ID_AA64ISAR2_EL1_GPA3_SHIFT),
+ FIELD("apa3", ID_AA64ISAR2_EL1_APA3_SHIFT),
{});
DEFINE_OVERRIDE(5, smfr0, "id_aa64smfr0", id_aa64smfr0_override,
/* FA64 is a one bit field... :-/ */
- { "fa64", ID_AA64SMFR0_EL1_FA64_SHIFT, 1, },
+ { 0, "fa64", ID_AA64SMFR0_EL1_FA64_SHIFT, 1, },
{});
DEFINE_OVERRIDE(6, sw_features, "arm64_sw", arm64_sw_feature_override,
- FIELD("nokaslr", ARM64_SW_FEATURE_OVERRIDE_NOKASLR, NULL),
+ FIELD("nokaslr", ARM64_SW_FEATURE_OVERRIDE_NOKASLR),
{});
/*
@@ -169,6 +181,13 @@ static int __init find_field(const char *cmdline,
return kstrtou64(cmdline + len, 0, v);
}
+static const void * __init get_filter(const struct ftr_set_desc *reg, int idx)
+{
+ const s32 *offset = ®->fields[idx].filter_offset;
+
+ return *offset ? offset_to_ptr(offset) : NULL;
+}
+
static void __init match_options(const char *cmdline)
{
int i;
@@ -181,6 +200,7 @@ static void __init match_options(const char *cmdline)
u64 shift = reg->fields[f].shift;
u64 width = reg->fields[f].width ?: 4;
u64 mask = GENMASK_ULL(shift + width - 1, shift);
+ bool (*filter)(u64) = get_filter(reg, f);
u64 v;
if (find_field(cmdline, reg, f, &v))
@@ -191,8 +211,7 @@ static void __init match_options(const char *cmdline)
* it by setting the value to the all-ones while
* clearing the mask... Yes, this is fragile.
*/
- if (reg->fields[f].filter &&
- !reg->fields[f].filter(v)) {
+ if (filter && !filter(v)) {
reg_override(i)->val |= mask;
reg_override(i)->mask &= ~mask;
continue;
--
2.35.1
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