From: Juergen Gross <jgross@suse.com>
To: xen-devel@lists.xenproject.org, x86@kernel.org,
linux-kernel@vger.kernel.org
Cc: Juergen Gross <jgross@suse.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: [PATCH v3 07/15] x86/alternative: support "not feature" and ALTERNATIVE_TERNARY
Date: Thu, 17 Dec 2020 10:31:25 +0100 [thread overview]
Message-ID: <20201217093133.1507-8-jgross@suse.com> (raw)
In-Reply-To: <20201217093133.1507-1-jgross@suse.com>
Instead of only supporting to modify instructions when a specific
feature is set, support doing so for the case a feature is not set.
As today a feature is specified using a 16 bit quantity and the highest
feature number in use is around 600, using a negated feature number for
specifying the inverted case seems to be appropriate.
ALTERNATIVE "default_instr", "patched_instr", ~FEATURE_NR
will start with "default_instr" and patch that with "patched_instr" in
case FEATURE_NR is not set.
Using that add ALTERNATIVE_TERNARY:
ALTERNATIVE_TERNARY "default_instr", FEATURE_NR,
"feature_on_instr", "feature_off_instr"
which will start with "default_instr" and at patch time will, depending
on FEATURE_NR being set or not, patch that with either
"feature_on_instr" or "feature_off_instr".
Signed-off-by: Juergen Gross <jgross@suse.com>
---
V3:
- new patch
---
arch/x86/include/asm/alternative-asm.h | 3 +++
arch/x86/include/asm/alternative.h | 7 +++++++
arch/x86/kernel/alternative.c | 17 ++++++++++++-----
3 files changed, 22 insertions(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/alternative-asm.h b/arch/x86/include/asm/alternative-asm.h
index 464034db299f..b6989995fddf 100644
--- a/arch/x86/include/asm/alternative-asm.h
+++ b/arch/x86/include/asm/alternative-asm.h
@@ -109,6 +109,9 @@
.popsection
.endm
+#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2) \
+ ALTERNATIVE_2 oldinstr, newinstr1, feature, newinstr2, ~(feature)
+
#endif /* __ASSEMBLY__ */
#endif /* _ASM_X86_ALTERNATIVE_ASM_H */
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 13adca37c99a..a0f8f33609aa 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -59,6 +59,7 @@ struct alt_instr {
s32 instr_offset; /* original instruction */
s32 repl_offset; /* offset to replacement instruction */
u16 cpuid; /* cpuid bit set for replacement */
+#define ALT_INSTR_CPUID_INV 0x8000 /* patch if ~cpuid bit is NOT set */
u8 instrlen; /* length of original instruction */
u8 replacementlen; /* length of new instruction */
u8 padlen; /* length of build-time padding */
@@ -175,6 +176,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
".popsection\n"
+#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2) \
+ ALTERNATIVE_2(oldinstr, newinstr1, feature, newinstr2, ~(feature))
+
#define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \
OLDINSTR_3(oldinsn, 1, 2, 3) \
".pushsection .altinstructions,\"a\"\n" \
@@ -206,6 +210,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
+#define alternative_ternary(oldinstr, feature, newinstr1, newinstr2) \
+ asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2) ::: "memory")
+
/*
* Alternative inline assembly with input.
*
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 8d778e46725d..0a904fb2678b 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -388,21 +388,28 @@ void __init_or_module noinline apply_alternatives(struct alt_instr *start,
*/
for (a = start; a < end; a++) {
int insn_buff_sz = 0;
+ u16 feature;
+ bool not_feature;
instr = (u8 *)&a->instr_offset + a->instr_offset;
replacement = (u8 *)&a->repl_offset + a->repl_offset;
+ feature = a->cpuid;
+ not_feature = feature & ALT_INSTR_CPUID_INV;
+ if (not_feature)
+ feature = ~feature;
BUG_ON(a->instrlen > sizeof(insn_buff));
- BUG_ON(a->cpuid >= (NCAPINTS + NBUGINTS) * 32);
- if (!boot_cpu_has(a->cpuid)) {
+ BUG_ON(feature >= (NCAPINTS + NBUGINTS) * 32);
+ if (!!boot_cpu_has(feature) == not_feature) {
if (a->padlen > 1)
optimize_nops(a, instr);
continue;
}
- DPRINTK("feat: %d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d), pad: %d",
- a->cpuid >> 5,
- a->cpuid & 0x1f,
+ DPRINTK("feat: %s%d*32+%d, old: (%pS (%px) len: %d), repl: (%px, len: %d), pad: %d",
+ not_feature ? "~" : "",
+ feature >> 5,
+ feature & 0x1f,
instr, instr, a->instrlen,
replacement, a->replacementlen, a->padlen);
--
2.26.2
next prev parent reply other threads:[~2020-12-17 9:32 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-17 9:31 [PATCH v3 00/15] x86: major paravirt cleanup Juergen Gross
2020-12-17 9:31 ` [PATCH v3 01/15] x86/xen: use specific Xen pv interrupt entry for MCE Juergen Gross
2020-12-17 9:31 ` [PATCH v3 02/15] x86/xen: use specific Xen pv interrupt entry for DF Juergen Gross
2020-12-17 9:31 ` [PATCH v3 03/15] x86/pv: switch SWAPGS to ALTERNATIVE Juergen Gross
2020-12-17 9:31 ` [PATCH v3 04/15] x86/xen: drop USERGS_SYSRET64 paravirt call Juergen Gross
2020-12-17 9:31 ` [PATCH v3 05/15] x86: rework arch_local_irq_restore() to not use popf Juergen Gross
2020-12-17 9:31 ` [PATCH v3 06/15] x86/paravirt: switch time pvops functions to use static_call() Juergen Gross
2020-12-17 17:31 ` Michael Kelley
2021-01-06 10:41 ` Borislav Petkov
2021-01-19 11:36 ` Jürgen Groß
2021-01-06 10:03 ` Borislav Petkov
2021-01-19 11:33 ` Jürgen Groß
2020-12-17 9:31 ` Juergen Gross [this message]
2021-01-07 19:08 ` [PATCH v3 07/15] x86/alternative: support "not feature" and ALTERNATIVE_TERNARY Borislav Petkov
2021-01-19 11:35 ` Jürgen Groß
2021-01-19 12:06 ` Borislav Petkov
2021-01-19 12:12 ` Jürgen Groß
2020-12-17 9:31 ` [PATCH v3 08/15] x86: add new features for paravirt patching Juergen Gross
2020-12-17 13:12 ` kernel test robot
2021-01-14 18:30 ` Borislav Petkov
2021-01-14 18:40 ` Borislav Petkov
2020-12-17 9:31 ` [PATCH v3 09/15] x86/paravirt: remove no longer needed 32-bit pvops cruft Juergen Gross
2020-12-17 9:31 ` [PATCH v3 10/15] x86/paravirt: simplify paravirt macros Juergen Gross
2020-12-17 16:46 ` kernel test robot
2020-12-17 9:31 ` [PATCH v3 11/15] x86/paravirt: switch iret pvops to ALTERNATIVE Juergen Gross
2020-12-17 9:31 ` [PATCH v3 12/15] objtool: Alternatives vs ORC, the hard way Juergen Gross
2020-12-17 9:31 ` [PATCH v3 13/15] x86/paravirt: add new macros PVOP_ALT* supporting pvops in ALTERNATIVEs Juergen Gross
2020-12-17 9:31 ` [PATCH v3 14/15] x86/paravirt: switch functions with custom code to ALTERNATIVE Juergen Gross
2020-12-17 16:42 ` kernel test robot
2020-12-17 9:31 ` [PATCH v3 15/15] x86/paravirt: have only one paravirt patch function Juergen Gross
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