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authorThomas Gleixner <tglx@linutronix.de>2021-09-08 15:29:18 +0200
committerBorislav Petkov <bp@suse.de>2021-09-13 17:51:47 +0200
commit46d28947d9876fc0f8f93d3c69813ef6e9852595 (patch)
treed0b4e31b2261fb5ba4fce3d9f7dae12a7139dfd8 /arch/x86/net
parent083b32d6f4fa26abaf585721abeee73c92ea5376 (diff)
x86/extable: Rework the exception table mechanics
The exception table entries contain the instruction address, the fixup address and the handler address. All addresses are relative. Storing the handler address has a few downsides: 1) Most handlers need to be exported 2) Handlers can be defined everywhere and there is no overview about the handler types 3) MCE needs to check the handler type to decide whether an in kernel #MC can be recovered. The functionality of the handler itself is not in any way special, but for these checks there need to be separate functions which in the worst case have to be exported. Some of these 'recoverable' exception fixups are pretty obscure and just reuse some other handler to spare code. That obfuscates e.g. the #MC safe copy functions. Cleaning that up would require more handlers and exports Rework the exception fixup mechanics by storing a fixup type number instead of the handler address and invoke the proper handler for each fixup type. Also teach the extable sort to leave the type field alone. This makes most handlers static except for special cases like the MCE MSR fixup and the BPF fixup. This allows to add more types for cleaning up the obscure places without adding more handler code and exports. There is a marginal code size reduction for a production config and it removes _eight_ exported symbols. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Alexei Starovoitov <ast@kernel.org> Link: https://lkml.kernel.org/r/20210908132525.211958725@linutronix.de
Diffstat (limited to 'arch/x86/net')
-rw-r--r--arch/x86/net/bpf_jit_comp.c11
1 files changed, 2 insertions, 9 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 0fe6aacef3db..703dc6eaf4c7 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -827,9 +827,7 @@ static int emit_atomic(u8 **pprog, u8 atomic_op,
return 0;
}
-static bool ex_handler_bpf(const struct exception_table_entry *x,
- struct pt_regs *regs, int trapnr,
- unsigned long error_code, unsigned long fault_addr)
+bool ex_handler_bpf(const struct exception_table_entry *x, struct pt_regs *regs)
{
u32 reg = x->fixup >> 8;
@@ -1313,12 +1311,7 @@ st: if (is_imm8(insn->off))
}
ex->insn = delta;
- delta = (u8 *)ex_handler_bpf - (u8 *)&ex->handler;
- if (!is_simm32(delta)) {
- pr_err("extable->handler doesn't fit into 32-bit\n");
- return -EFAULT;
- }
- ex->handler = delta;
+ ex->type = EX_TYPE_BPF;
if (dst_reg > BPF_REG_9) {
pr_err("verifier error\n");