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| author |   Peter Zijlstra <peterz@infradead.org> | 2022-06-14 23:15:48 +0200 |
|---|---|---|
| committer |   Borislav Petkov <bp@suse.de> | 2022-06-27 10:33:59 +0200 |
| commit | a149180fbcf336e97ce4eb2cdc13672727feb94d (patch) | |
| tree | 465e0b2ebf7a147d686abed224a732907c475c1b /arch/x86/entry | |
| parent | objtool: Treat .text.__x86.* as noinstr (diff) | |
| download | linux-dev-a149180fbcf336e97ce4eb2cdc13672727feb94d.tar.xz linux-dev-a149180fbcf336e97ce4eb2cdc13672727feb94d.zip | |
x86: Add magic AMD return-thunk
Note: needs to be in a section distinct from Retpolines such that the
Retpoline RET substitution cannot possibly use immediate jumps.
ORC unwinding for zen_untrain_ret() and __x86_return_thunk() is a
little tricky but works due to the fact that zen_untrain_ret() doesn't
have any stack ops and as such will emit a single ORC entry at the
start (+0x3f).
Meanwhile, unwinding an IP, including the __x86_return_thunk() one
(+0x40) will search for the largest ORC entry smaller or equal to the
IP, these will find the one ORC entry (+0x3f) and all works.
[ Alexandre: SVM part. ]
[ bp: Build fix, massages. ]
Suggested-by: Andrew Cooper <Andrew.Cooper3@citrix.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Diffstat (limited to 'arch/x86/entry')
| -rw-r--r-- | arch/x86/entry/entry_64.S | 6 | ||||
| -rw-r--r-- | arch/x86/entry/entry_64_compat.S | 4 |
2 files changed, 10 insertions, 0 deletions
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 9f5d6a4f293e..1f4b18c8909b 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -96,6 +96,7 @@ SYM_CODE_START(entry_SYSCALL_64) SYM_INNER_LABEL(entry_SYSCALL_64_safe_stack, SYM_L_GLOBAL) ANNOTATE_NOENDBR + UNTRAIN_RET /* Construct struct pt_regs on stack */ pushq $__USER_DS /* pt_regs->ss */ @@ -717,6 +718,7 @@ native_irq_return_ldt: pushq %rdi /* Stash user RDI */ swapgs /* to kernel GS */ SWITCH_TO_KERNEL_CR3 scratch_reg=%rdi /* to kernel CR3 */ + UNTRAIN_RET movq PER_CPU_VAR(espfix_waddr), %rdi movq %rax, (0*8)(%rdi) /* user RAX */ @@ -911,6 +913,7 @@ SYM_CODE_START_LOCAL(paranoid_entry) * be retrieved from a kernel internal table. */ SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg=%rax save_reg=%r14 + UNTRAIN_RET /* * Handling GSBASE depends on the availability of FSGSBASE. @@ -1020,6 +1023,7 @@ SYM_CODE_START_LOCAL(error_entry) FENCE_SWAPGS_USER_ENTRY /* We have user CR3. Change to kernel CR3. */ SWITCH_TO_KERNEL_CR3 scratch_reg=%rax + UNTRAIN_RET leaq 8(%rsp), %rdi /* arg0 = pt_regs pointer */ .Lerror_entry_from_usermode_after_swapgs: @@ -1072,6 +1076,7 @@ SYM_CODE_START_LOCAL(error_entry) swapgs FENCE_SWAPGS_USER_ENTRY SWITCH_TO_KERNEL_CR3 scratch_reg=%rax + UNTRAIN_RET /* * Pretend that the exception came from user mode: set up pt_regs @@ -1167,6 +1172,7 @@ SYM_CODE_START(asm_exc_nmi) movq %rsp, %rdx movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp UNWIND_HINT_IRET_REGS base=%rdx offset=8 + UNTRAIN_RET pushq 5*8(%rdx) /* pt_regs->ss */ pushq 4*8(%rdx) /* pt_regs->rsp */ pushq 3*8(%rdx) /* pt_regs->flags */ diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index d1052742ad0c..03d74c5153fb 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -14,6 +14,7 @@ #include <asm/irqflags.h> #include <asm/asm.h> #include <asm/smap.h> +#include <asm/nospec-branch.h> #include <linux/linkage.h> #include <linux/err.h> @@ -72,6 +73,7 @@ SYM_CODE_START(entry_SYSENTER_compat) pushq $__USER32_CS /* pt_regs->cs */ pushq $0 /* pt_regs->ip = 0 (placeholder) */ SYM_INNER_LABEL(entry_SYSENTER_compat_after_hwframe, SYM_L_GLOBAL) + UNTRAIN_RET /* * User tracing code (ptrace or signal handlers) might assume that @@ -190,6 +192,7 @@ SYM_CODE_START(entry_SYSCALL_compat) SYM_INNER_LABEL(entry_SYSCALL_compat_safe_stack, SYM_L_GLOBAL) ANNOTATE_NOENDBR + UNTRAIN_RET /* Construct struct pt_regs on stack */ pushq $__USER32_DS /* pt_regs->ss */ @@ -332,6 +335,7 @@ SYM_CODE_START(entry_INT80_compat) pushq 0*8(%rax) /* regs->orig_ax */ .Lint80_keep_stack: + UNTRAIN_RET PUSH_AND_CLEAR_REGS rax=$-ENOSYS UNWIND_HINT_REGS |