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authorPeter Zijlstra <peterz@infradead.org>2022-09-15 13:11:28 +0200
committerPeter Zijlstra <peterz@infradead.org>2022-10-17 16:41:15 +0200
commit3b6c1747da48ff40ab746b0e860cffe83619f5c5 (patch)
treeb9de2a7bca8cbf4df6d9e5020e292dc266ceaa8a /arch/x86/include/asm/nospec-branch.h
parentx86/retbleed: Add SKL return thunk (diff)
downloadlinux-3b6c1747da48ff40ab746b0e860cffe83619f5c5.tar.xz
linux-3b6c1747da48ff40ab746b0e860cffe83619f5c5.zip
x86/retpoline: Add SKL retthunk retpolines
Ensure that retpolines do the proper call accounting so that the return accounting works correctly. Specifically; retpolines are used to replace both 'jmp *%reg' and 'call *%reg', however these two cases do not have the same accounting requirements. Therefore split things up and provide two different retpoline arrays for SKL. The 'jmp *%reg' case needs no accounting, the __x86_indirect_jump_thunk_array[] covers this. The retpoline is changed to not use the return thunk; it's a simple call;ret construct. [ strictly speaking it should do: andq $(~0x1f), PER_CPU_VAR(__x86_call_depth) but we can argue this can be covered by the fuzz we already have in the accounting depth (12) vs the RSB depth (16) ] The 'call *%reg' case does need accounting, the __x86_indirect_call_thunk_array[] covers this. Again, this retpoline avoids the use of the return-thunk, in this case to avoid double accounting. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/r/20220915111147.996634749@infradead.org
Diffstat (limited to 'arch/x86/include/asm/nospec-branch.h')
-rw-r--r--arch/x86/include/asm/nospec-branch.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index d4be826a2282..06ba7caa0cad 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -301,6 +301,8 @@
typedef u8 retpoline_thunk_t[RETPOLINE_THUNK_SIZE];
extern retpoline_thunk_t __x86_indirect_thunk_array[];
+extern retpoline_thunk_t __x86_indirect_call_thunk_array[];
+extern retpoline_thunk_t __x86_indirect_jump_thunk_array[];
extern void __x86_return_thunk(void);
extern void zen_untrain_ret(void);
@@ -330,6 +332,16 @@ static inline void x86_set_skl_return_thunk(void) {}
#include <asm/GEN-for-each-reg.h>
#undef GEN
+#define GEN(reg) \
+ extern retpoline_thunk_t __x86_indirect_call_thunk_ ## reg;
+#include <asm/GEN-for-each-reg.h>
+#undef GEN
+
+#define GEN(reg) \
+ extern retpoline_thunk_t __x86_indirect_jump_thunk_ ## reg;
+#include <asm/GEN-for-each-reg.h>
+#undef GEN
+
#ifdef CONFIG_X86_64
/*